Abstract

SNMP is currently most widely used network management tool when managing a large scale networks. However, there are many limitations while using SNMP which will be discussed in this paper. To overcome SNMP weaknesses, this research paper will introduce Web services based network management tools to give a contrast between them. Web services also can be implemented as an additional layer stay on top of SNMP.

1.   Introduction

1.1 SNMP
In the early of 1990, Internet has grown rapidly every year in the area of IP Networks, and how to manage those networks. SNMP (Simple Network Management Protocol) which works alike Manager and Agent mechanism is the current dominant network management tool. The advantage of SNMP is mainly due to its simplicity. However users have found out its limitations such as inefficient in configuration management operations, application development complexity and lack of scalability in large scale networks. A better technology has to be introduced in order to replace or enhanced the current technology.

SNMP design is based on MIB (Management Information Bases), it contains objects identifiers which organized hierarchically. MIB will be accessed by different protocol such as SNMP. Complete MIB is a list of characteristics of the specific device [5]. Devices can be a router, server, switch, computer, printers and any hardware that’s need to be monitored. An agent will be installed as a software module which resides in the device. Agent will provide required management information which is in SNMP protocol format. A manager is the main component in a network management system; it can be considering as client in a client and server architecture. Manager control management operations, applications and traps from different agents [5].

1.2 XML
In 1998, the World Wide Web Consortium (XML) has standardized a markup language called Extensible Markup Language (XML). In term of flexibility, because XML documents such as Document Type Definition DTD and XML can be transferred to the internet, it is easer to manage compared to SNMP. The development cost of XML can be low because it comes with many free APIs which can be used for accessing different types of XML data. The structure of XML is simple, where XML documents store all the data and XEL (Extensible Style Sheet) will

be used to create query to retrieve the relevant data. XML is able to transfer large amount of data with only one single XML document [3].

All of these advantages mentioned above were able to solve the problem of scalability and efficiency of the current management system using SNMP management systems. Most of the current hardware devices have SNMP agent installed on them, therefore a gateway to communicate between SNMP and XML need to be installed to allow communication between them [3]. XML is highly scalable in bulk data processing; therefore it is suitable for bulk configuration management such as network management.

2. Scalability and Efficiency of SNMP

While the SNMP simplicity may be good in managing network systems but the increasing of internet or network systems caused the SNMP management system failed to process all the tasks quick enough to maintain the performance of efficiency in a long term basis. Management data increase when the Internet and agent required managing increased [2]. The increase of agent means the increase of IP Routing table, TCP connection table, accounting table and others. The current SNMP management cannot process these tasks efficiency with a few reasons such as the increase of network overhead. Network overhead is a network management traffic that generate on top of user client. It will obviously affect the client network speed when a large overhead traffic increases continuously due to the increasing of required data management. Latency in network management should be keep in the minimum level, the increase of latency will greatly reduce the whole network performance by using SNMP because the time to recover a problem may be increase when the network size increased. SNMP does not using a distributing processing mechanism while processing its task, thus increase the cost of hardware resources such as processor and memory. SNMP also limits the flexibility of management level due to the centralized mechanism. Data from all clients are gathered into one segment point. The scalability and efficiency of SNMP communication protocols can be improved by using XML network management tool [2].

3. XML

3.1 Introduction
XML is simple yet powerful enough because it is using HTTP structure. Data are stored in a XML document which can be exchanged easily over the internet. XML works differently compared to HTML, XML separates data and expression, thus information can be expressed in different methods. XML document is able to define data structures by using Data Type Definition in an XML document. XML also fully accessible by any programs that support Document Object Model structure either for storing or retrieving data [2].

In network management system, XML is good in transferring network data which will be processed by network management tools. Data can be modelled with the modelling function provided in XML function, which mean that SNMP data structure can be

read by XML easily. XML then transfer the retrieved data via HTTP mechanism which is already standardize in World Wide Web. In terms of compatibility, XML can transfer data between any software and hardware that support HTTP. It is easy and low cost when developing XML because XML comes with standard free APIs and development tools. During data transmitting, XML data only required one document to store all the information. This obviously solved the scalability and efficiency of SNMP network management system [2].

3.2 XML in Network Management
Most agents used in the current industry uses EWS (embedded web server) to communicate with their device. In this research criterion, XML will be implemented to retrieve information from devices through the agent which has embedded web server in order to pass data between XML and devices. The figure below shows the step by step on how the manager is able to manage a device within agent and device by using XML translation.

In example (A), a manager request a data from agent and the agent reply with a message with a list of managers back to the manager. In example (B), manager tries to control agent and tell the agent to add a new user into the system. Manager Operation=“Add” used to give an operation action called Add, while “<UserName>James</UserName>”is the new user that need to be added into the system. Example (C) shows that agent can communicate to manager when there is a fault alarm such as device’s cooling fan failed to work properly. The manager client will receive “<FanStatus>Fail<FanStatus>” and translate the information to the manager and seek for instruction to solve the problem. Each action A, B and C are similar in methods where sender using either POST or GET method to retrieve data and “HTTP/1.1 200 OK” to reply with the status “OK”.

3.3 Reasons for using HTTP medium
There are a lot of benefits by using web-based network monitoring. Manager can connect to the system at any browser enabled computer around the world. No additional cost is required for accessing into the network management system. Previously, SNMP tools required user to install software in order to use it. Different software vendor may come with different licensing prices. Installing software on new machine often required new license which increase the management cost. Furthermore, HTML browser works perfectly with XML technology without any conflict [4].

4. Gateways

4.1 Introduction
Trap, Set and Get are common function in SNMP communication methods. They work similar to the methods of XML. By using XML as a communication level, it can solve the limitations of SNMP network management system. Because SNMP is already widely used in current network system, it is very hard to replace every system into XML based network management system. In order to solve the limitations, a gateway needs to be implemented for XML to communicate between SNMP based agents and XML based manager. In [2], a gateway was introduced that relays data between SNMP based agent and XML based manager. XML based manager will pass the data with XML document over HTTP; while SNMP based agent will pass their data via SNMP protocol. The proposed gateway will convert all the data and relaying the XML and SNMP protocols [2].

4.2 SNMP – XML Translation Algorithm
Before any conversions it is important keep the data and structure of the original form correctly. Each line of SNMP data will be converted into XML element. Any clauses will be converted into XML element’s attribute. In figure 2 shows an example of how each node will be converted in XML format [2].

Syntax analyser will read the SNMP and check for errors. It will also remove any unwanted data such as comments and definitions. When error occurs, it will return an error message to the user. Every successful generated table will contains a list of nodes with object. Object will be classified into different classes. XML Schema will generate XML schema documents from the node table. In this scenario study, the author uses JAVA programming language to implement the SNMP – XML translator [2].

5. Web Services

5.1 Introduction on WS
XML is a high level semantics system that works great in bulk processing. Some devices vendor such as CISCO, they have already built-in XML capabilities into their system which accelerate the development using XML mechanism. In some cases, XML is usually build in a distributed behavior where allows remote communications between manager and agent. Web Services is a distributed object technologies that works together with XML technology. WS has become one of the proposed network management tools because of a number of benefits. Web Services is a W3C standardized technology which greatly reduces the complexity during implementing process. Open standards technology often comes with free associate tools to help accelerate the development process [1].

Programming language tools that support Web Services such as JAVA, Microsoft .Net, C++ and others obviously increase the potential of Web Services portability. Web Services network management system can be easily integrated in different platforms which developed in different languages [1].

5.2 Web Services Implementation
The easier way to implement a Web Services management system is illustrate in figure 3.

In figure 3, Web Services was implemented on top of SNMP enabled devices. The XML / SOAP interface receive commands from Manager, and then transmute it over the IP Networks. Embedded SOAP engine will transfer command into SNMP commands such as GET, SET or TRAP which mentioned in section 4 [1].

5.3 Advantages
Recently, XML based network management system has solved the limitation of SNMP network management in term of operations. XML have higher level semantics compared to SNMP, thus is it more efficient in processing bulk configuration. XML also can handle complex management data due to the easy to generate data structure. Again, XML is a standard from W3C technology and they come with different supporting tools such as XSLT which can transform XML document into different queried output. In terms of security, internet browser has increase the security level in recent years. Browser now supports sophisticated checks on security files and security in scripting language [4].

6. Conclusion
Web-based network management system will become more popular and more efficient in the coming years. XML technology was getting better everyday; APIs are provided for free which greatly reduce implementation cost. When using web-based as a communication tool, security is very important as internet is open to the public. Good security systems such as Virtual Private Networks need to be implemented in order to provide a secure communication tunnel between client and server.

However, web-based monitoring applications may increase the efficiency of current SNMP systems but it will not completely replace the whole SNMP system anytime soon because most of the devices in the market now are building for SNMP protocol. Only new and limited devices come with build in XML mechanism. Before that, the current approach will only be implemented on top of SNMP enabled devices. Gateways translator as mentioned above are required to allow communication between XML and SNMP devices.

References
[1] John, S., Dimitris, A. (2007), “Web services-based network management: approaches and the WSNET system”, John Wiley & Sons, Inc. USA, Vol. 17, Iss.1, PP 33-50

[2] Jeong, H. Y., Hong, T. J., James, W. H. (2003), “Development of SNMP-XML translator and gateway for XML-based integrated network management”, John Wiley & Sons, Inc. USA, Vol.13, Iss.4, PP.259-276

[3] Shaik, S., Mohammed, H. S. (2006), “Distributed XML-based network management using JPVM”, John Wiley & Sons, Inc. USA, Vol.16, Iss.4, PP.263-277

[4] Ron, D. J. (1999), “Why web-based network monitoring? Leveraging the platform”, John Wiley & Sons, Inc. USA, Vol.9, Iss.3, PP.175-183

[5] Wikipedia, “Simple network management Protocol” 2007; http://en.wikipedia.org/wiki/SNMP

1. Introduction

1.1 General Information
Bloggs Information System wants to expand their product range and its presence in the market; they need to build a new call centre to handle all the sales-related calls. However due to the limited floor space in the company’s main office building, they will have to build the new call centre in a different building. The new building will be located on a leased warehouse which is 3 kilometres away from the Company’s main office building. By accident, the warehouse is located within line of sight to the Company’s main building. Geographically, the main office building has a direct sight on the roof of the warehouse if a two-metre mast is installed on either one of the building’s roof.

1.2 Specifications of Call Centre
Call centre is a growing business that large business organisations are looking on them as a main communication method with their customers. Call centre may help company to improve efficiency on their services. However it is a challenging task to build a call centre, there are many different areas of specification that need to be achieved in order to provide a good and efficient customer service call centre. The greatest challenge would be to provide accurate information to customer in a given time slot. Different tool may need to be implemented in order to gather and record the right solutions for further uses. Customer usually expects an instant answer, call centre operators need to be well-trained to handle any kind of situations [3].

Apart from the accuracy of information that needs to be provided, the system communications of the call centre need to be well designed as well. There are many design problems that need to be solved in order to develop a flawless call centre.

The calls centre is located line of sight from a 3 kilometres distance from the Company’s main building. Therefore it is possible to use wireless communication between the two buildings. Call centre will be equipped with personal computers, all computers will be using VoIP communications and capable for user database inquiries. Communication between database and personal computer will be telnet based, thus it will not create significant data load on the networks. User database traffic will be no more than 1 Megabit per second at most in a high peak situation. The complete design will be focused on the call centre performance, to create an efficient call centre. User workloads will be calculated in order to find out how many operators will be required in peak and off-peak time.

The advantages of VoIP are definitely cost saving. In some cases VoIP is consider as free phone calls. VoIP service providers usually offer call charges which is significantly lower than normal PSTN phone calls. It is easier for a company to manage the networks as only one type of network traffic need to be handling instead of separated by data and voice networks. In terms of scalability, VoIP is very easy to add or remove individual node within the networks.

2. Design Solutions

2.1 Erlang Formulas
To calculate the traffic measurement in the call centre system, Erlang formulas will be used in the calculations. The calculation steps will try to sort out the number of agents required during peak or off-peak daily working hours. The calculations will be based on each working hour. In order to calculate the estimated agents required per hour, the following information have to be gathered:

• Number of calls received per hour, this will be calculated by Erlang formulas.

• Number of operators, 100 of operators will be operated in this scenario.

• Average call durations

• Average allowed wait time of each calls, also known as the average wrap up time where the unavailable time for an operator after finish a call and before answering the next incoming call.

Based on the Erlang formulas, an average of 515 calls can be handle by 100 operators and with an average waiting time per call of 2 seconds, 90% of calls to require no more than 5 seconds of waiting time, an average holding time of 10 minutes. Therefore, in a peak hour condition, an average of 500 to 600 of calls can be handled by 100 operators.

2.2 VoIP Traffic
The amount of bandwidth carried over a network includes the calculations of Codec, IP header, transmission medium and silence suppression. Codec usually declare the total amount of voice data per millisecond (ms). IP header usually has fixed packets which is 40 octets per packet. Transmission medium such as TCP/IP will add its own communication headers which need to be considered as well. Some codec has the silence suppression technology which can reduce the total bandwidth required by 50%. It reduces the data when it detects silence situations [5].

The use of codec is mainly to convert conversation waveform into digital form. 20 ms is a common time to generate a frame of data. Different codec may have different conversion time such as codec G.723.1 required 30 ms while codec G.729a only need 10 ms to do the job. Size of a frame is calculated by the number of bits produced per second and the transmission period. For example, Codec G.711 generating at rate of 20 ms, which generates 50 frames per second will transmits 64,000 bps. Each frame is equal to 64,000 divide by 50 frames which is 1,280 bits per frame transmitted.

IP header is the combinations of IP, UDP and RTP packets. The packets generated by codec are wrapped by IP header. Figure 1.0 below shows an example of IP header.

Figure 1.0 IP Header and Voice Data [5].

RTP contain 12 octets which control the timing of orders of the frame. UDP is around 8 octets which routes the data to the correct port of destination. IP function is to deliver the data to the destination host, sums up of 20 octets by it selves. There will be 40 octets need to be added into the codec per 20 ms which is 160 + 40 = 200 octets equivalent of 1600 bits being sent 50 times per second, which is 80 kbps.

TCP/IP Ethernet packet starts with 8 octets followed by a header of 14 octets which uses to define the source and destination of MAC address followed by a 4 octets CRC. Packets gap will be separated by 12 octets which results an additional total of 8 + 14 + 4 + 12 = 38 octets to be included in the total codec bandwidth.

Consider the new centre will be operates by 100 operators. Therefore each VoIP Codec G.711 of (200 octets + 38 octets) * 50 = 95.2 kbps multiply by 100 operators is equal to 9.52 Mbps. The call centre will be using a total of 9.52 Mbps bandwidth during peak hours. 9.52 Mbps will only cover the VoIP bandwidth and will not cover any others bandwidth such as database access or internet surfing.

Other types of codec also have been calculated at 100 operators during peak time and shows in figure 2.0 below:

Figure 2.0 Table of Codec comparisons [2]
2.3 Router Capacity
To get the best sound available, the VoIP G.711 codec will be choosing for the call centre. 9.52 Mbps of VoIP usage will be the peak time where 100 lines operated at the same time. The given bandwidth for database access during is 1 Mbps. So the total bandwidth usage for the call centre is the summation of 9.52 Mbps plus 1 Mbps, which sum up a total of 10.52 Mbps. The required router capacity will be 10.52 Mbps at least.

2.4 Suitable Routers
NetVanta 7100 from ADTRAN

Most of the enterprise level routers support from 100 to 1000 of operators, which is overwhelming for a 100 operators only call centre. NetVanta 7100 routers support up to 50 operators. Therefore, by using two NetVanta 7100 routers, 100 operators can be accommodated without any problems. This router coverage both IP telephony and data networking which is suitable for call centre to handle calls and database queries. QoS is also included in the system in order to maintain voice quality [6].

Figure 3.0 Picture of NetVanta 7100

This single chassis will be able to do all the required work such as IP PBX, gateway, voicemail, full-featured IP router, firewall, VPN, 24-port Ethernet switch with two Gigabit uplinks and two expansion slots for future upgrades. The installations for this router is simple because its reduced the amount of extra hardware required to operate [6].

Cisco 3825 Integrated Services Router

This router support up to 168 IP phones, which is suitable for the call centre to operates 100 calls simultaneous. The Cisco 3825 provides concurrent services such as security and voice. Its also support different modules to best suite operation needs.

In term of security features, Cisco 3825 provides on-board encryption and support up to 2000 VPN tunnels. This router supports both analogue and digital voice call support and with optional of voice mail support as well.

Figure 4.0 Picture of Cisco 3825

2.5 Microwave Link
Wireless link is often the solution to eliminate the required of wired, due to long distance required long cable work which is troublesome. However, many circumstances need to be applied in order to create a successful microwave link. Distance is the main are to determine the required power budget for the link based on the frequency strength gains from antenna, transmitter and receiver.

The connection between the office main building and the call centre will be using a microwave link connection. Microwave receiver and transmitter will be installed on both roofs of the two buildings. Even the frequency is enough for the distance of 3 Kilometers, there are many other propagation losses while transmitting the date. Latency will be an issue when transmitting wirelessly for a long distance. For example, in a worse case condition, a rain rate of 150 mm/hr and fog density of 200 g/m3 may be occurring. These signal lose need to be calculated and minus the total output frequency. If the result is greater than the receiver power, then the wireless network will be working properly in a bad condition.

In many situations, packet may be lost due to interferences, two widely used techniques are “discard and resend” and “forward error control” model. In “discard and resend” model, corrupted packet will be resend with a new packet. While “forward error control” model transmitting redundant packets so each data can be reconstitute corrupted bits themselves [8].

Wireless link basically is a link of antenna, receiver and transmitter. They are based on the required frequency and drop rates of the communication link. While transmitting, the transmitter will modulate radio-frequency power through an antenna; the power will then pass through an open environment and reach the receiver antenna. The receiver will then demodulate the frequency data. Frequency / wavelength link is the best choice for the scenario. 3 Kilometers is still considering close and may only caused cause very low data packet loss [8].

Suitable hardware can be found in the tabular information page. Choice of antenna, receiver and transmitter are based on the frequency around 5 to 10 GHz. This is suitable for the call centre traffic usage.

References and Bibliography

[1] T. Howard (2006), “Call Centre Design”, CRM Today, http://www.crm2day.com/library/EpFEkuAlpFBgOQuVcz.php

[2] Erlang (2006), “Call Centre Staffing and Trunk Design”, Westbay Engineers Limited, http://www.erlang.com/calldesign.html

[3] Step Two (2002) “Knowledge Management for Call Centres”, Step Two Designs Pty Ltd, pp.1-7, http://www.steptwo.com.au/ papers/kmc_callcentre/pdf/KMC_CallCentre.pdf

[4] (2004), “VoIP Terms and Definitions”, Patton Electronics Company, http://www.patton.com/manuals/VoIP_Glossary.pdf

[5] (2005) “VoIP bandwidth Calculations”, Newports, http://www.newport-networks.com/ whitepapers/voip-bandwidth1.html

[6] Adtran (2006) “The NetVanta 7000 Series”, https://www.adtran.com/adtranpx/Doc/0/P8DRSVBSTIUKH6 BDM6LVV91473/EN698c%20NetVanta%207100%20ICP.pdf

[7] Cisco (2006), “Deliver Integrated Services to Branch Offices and SMB“, http://www.cisco.com/en/US/products/ps5855/index.html

[8] Monash (2006) “Error rate and impact; RF Propagation in Wireless and Cellular Networks”, http://www.csse.monash.edu.au/courseware/ cse4884/SLIDES/CSE-4884-13-14.pdf

1. Introduction

Wireless hospital ward is trialing the use of wireless and healthcare mobility applications in the convenient way for patient care. This project is currently running by the Monash Medical Centre’s neurology ward in Melbourne. PDA and others devices such as laptop and tablet PC will be used in this system to obtain patient history reports and display information such as X-ray [1].

This project main aim is to speed up the work flow of patient information and to reduce the inaccurate data being stored in the database. This system will allow doctors and nurses to retrieve update information at any places such as patient bedside [1].

Security will be the main concern as everything is processed electronically and wirelessly. Security expert need to ensure the system is as secure as possible before running this system in hospital. The system will be using multiple WLAN connections due to the flexible of this protocol compared to others [1].

2. Thread Modeling Part 1

2.1 Security Objective
Confidentially, Integrity and Availability will be considered when outlining the security objectives for Wireless Hospital Ward system. Confidentially will identified the ways to protecting against unauthorized and information enclosure. Integrity is to prevent any unauthorized data has been changed and Availability will mainly concern the availability of backup system when the main system is down due to attack by hackers or other reasons [2].

Security Objectives:
a) Stop unauthorized person to retrieve or modified patient’s data.
b) Prevent unauthorized person to obtain access username and password.
c) Meets industrial standards level on availability when system down.

2.2 Application Overview

2.2.1 End to end deployment scenario

Figure 1.0 above shows the Wireless Hospital Ward System Components [3]. The main components are:
a) The Patients’ Record Manager (PRM)
b) The Workflow Manager (WM) and the Personal Organizer (PO)
c) The Legacy System Interface (LSI)

2.2.2 Identify Roles

2.2.3 Identify Technologies

Devices:

• PDA
• Laptop or Tablet PC

Operating System:

• Microsoft Windows

Network Equipments:

• Wi-Fi access point
• Local area networks

Databases:

• Oracle

2.2.4 Identify Application Security Mechanisms

• Input and data validation
• Authentication
• Authorization
• Configure workflow
• Confidential patient’s data
• Session and html cookie control
• Data encryption
• Data backup
• Users logging
• Firewall

2.3 Application Decomposition

2.3.1 Identify Trust Boundaries
• Firewall will be the first trust boundary. IT filters authorized data out of the unauthorized data to your data server.
• PRM and WF database. Database can sometimes include in the trust boundaries. Network protocols act as a firewall to the database. This will control the database being exposed to the public.
• When doctors or nurses need to login to the system, they need to enter their username and password. The server will then check their login details and process the authentication. This is a trust boundary.
• The boundary between different hospitals to share information.

2.3.2 Identify Data Flows

1. User login and the server will authenticate the login details. If true, it will then assign a session to the user and allowed to connect to the system.
2. User will be able to retrieve or update the patient’s database.
3. Finalized data will be saved to the legacy system.

2.3.3 Identify Entry Points
There are different entry points in the Wireless Hospital Ward system. For example the administrator login page, unauthorized person may break through this level and enter the system directly. System should be able to detect and block the connection which is not connected normally from the level 1 interface.

2.3.4 Identify Exit Points
A user sending a client’s data back to the server, the data will first reach the Wi-Fi access point routers and then routes to the appropriate server. It is important that there are no hijacked access points between different exit points.

3. Thread Modeling Part 2

3.1 Identify Threats
There are two basic approaches that can be use to identify threats and attacks:
1. Start with common threats and attacks
In this approach, we can start with a group of common threats and then apply the list to our Hospital Ward system. During testing phase, we will eliminate some of the threats if it was not appropriate [2].

2. Use a question-driven approach
This can be done by using STRIDE model to ask a question that related to the system. This approach is concentrated on how a attacker break into the system [2].
There are multiple tier and layer in the Wireless Hospital Ward system. The security areas that this system usually will be mistaken are the connection between devices and access point. Data encryption is a must in this area as access point can be broke in quite easily sometimes. Therefore if all the data is encrypted, no one else can read the data.

3.2 Common Threats

3.3 Wireless Hospital Ward Security Frame [2]

Authentication
• Attacker may use a key generator to spoof identity
• Attacker may be able to enter to the system by using spoof identity
• If an attacker hack into system directory, all password file might be stolen
• Attacker can bypass the session time by getting new session key

Authorization
• Attacker can steal the username and password and login to the system
• If the attacker bypass security and enter to the main system, he can adjust user permission level and break in the entire systems.

Input and Data Validation
• Attacker may record the network traffic and create fake data packets
• Attacker may sending fake data packet to the server

Configuration Management
• Attacker can gain access to configuration file by break in to the system directory
• Attacker can break into system directory by using a stolen username and password

Sensitive Data
• Sensitive data such as patient’s privacy should be store in a safe area
• Sensitive data will be pass across networks when doctors or nurses retrieve and updating the patient’s details
• Attacker could read the sensitive data by logging into the system or capture all the network traffic
Session Management
• Attacker could hijacked user’s session by using a tool such as “tap” to take over existing login sessions of the system
• Attacker will be able to get into the system without any login details if the previous user has already login.

Cryptography
• To crack an encryption the attacker will required to have a decryption key
• Attacker can get the decryption keys by hack into the system
Parameter Manipulation:
• Attacker can manipulate parameters to influence security on SQL server

Exception Management
• How could an attacker crash the application?
• How could an attacker gain useful exception details?

Auditing and Logging
• Attacker could cover his or her tracks by deleting the logging file
• By checking the login date, time and location. We can prove that whether the person is attacker or legitimate user

3.4 Use Cases Diagram

3.5 Data Flows Diagram

In level 1, security remain the main issue as these are the main path that usually used by attackers. D1 to D3 which should installed with appropriate firewall and remains trust boundaries.

3.6 Threats by Using Attack Trees
The use of attack tree can helps identified other threat possibilities. Attack tree analyzed deeper path compared to other thread diagrams. There are 2 normal way an attacker could break into the system by using the authentication and networks vulnerabilities. Figure 5.0 below is an attack tree shows the possible threats carried on by an attacker once they break into the system.

Threat no: 1 Attacker obtains login details

1.1 Spoofing access details
1.1.1 Login to patient’s directory and retrieve data
1.2 Access to network and monitoring traffic packets
1.2.1 Read important network information
1.2.2 Spamming network traffic causing system crashed

3.7 System Vulnerabilities

List of References:

[1] Kristyn Maslog-Levis, “Monash neurology ward trials wireless,” Jan 2005; http://www.necbs.com.au/mediacoverage/2005/ wardtrialswireless.htm

[2] J.D. Meier, A. Mackman, B. Wastell, “Thread Modelling Web Application,” May 2005; http://msdn.microsoft.com/library/default.asp? url=/library/en-us/dnpag2/html/tmwatemplatesample.asp.

[3] “Wireless Hospital Ward,” Practicalwork.doc provided by unit website.

[4] CACI, “Computer Security Threats,” http://www.caci.com/business/ia/ threats.html

1. Network Security

1.1 General Information

The reason to have a good security system in a network can be classified to three main reasons, Confidentiality, Integrity and Availability. Confidentiality means the protection of personal private information, no others should be able to view or access the locked information unless they have the right access. Having an Integrity security is to ensure the quality of the data originality, no unauthorized user able to make any changes to the data. Availability is to ensure the authorised user was able to access the data without any problem (Knipp, Browne, Weaver, Baumrucker, Chaffin, Caesr, Osipov, Danielyan, 2002, pp2-3).

1.2 Encapsulation

A normal network contains different kind of datagram, which is transmitted everywhere. To help the network understand each datagram that passes through the networks, encapsulation system technique is needed to help the datagram to be delivered to the right places.

What the encapsulation do is place the IP datagram inside a frame, and the entire data followed by the IP datagram will be placed in the same frame as well.

Figure 1 below shows the concept:

By default, the receiver will not know whether the incoming frame contains IP datagram or any other data. This will be discussed by sender and receiver, then they can set up a standard to recognize those incoming frame. As usual, an encapsulated frame should also carry destination IP.

When a frame is reached its destination, it will be discarded and the IP datagram will be removed from the frame. If the data needs to be transferred to another destination, a new encapsulation method can be different from previous standard and all these depended on the new destination (Douglas, 1997, pp.278-281)

1.3 Encryption

Encryption is a method to create secure environment while transferring data within internet network. One of the encryption systems is cryptosystem, the concept is whereby the sender encrypts his message with a key and sends to the receiver then the receiver will use his key to decrypt the message and confirm whether the message is sent by the right person. This system is not good enough compared to other systems because it is using only one key for encrypting and decrypting. If one of the keys is broken, then the entire message can be decrypted.

A better and more secure system is Diffie-Hellman encryption. This system was started in 1976. Users able to use the same secret but without exchange the secret itself, hence lower the chance of getting the secret key being exposing. DH algorithm is both of the users exchange their public key then encrypt with their own private key and created a shared secret key. User will then encrypt the message with shared secret key and send to the receiver, the receiver will use the shared secret key, which he has created to decrypt the message. This method will ensure both users’ private key will not expose to anyone (Fowler, 2005, Lecture Note).

1.4 Authentication

Authentication is a method use to block unauthenticated person or system to access on some networks or systems. Only users or systems with the logon password or right can be able to access the system. However, there should be a balance between authentication and users. The over use of authentication will cause problems for users as well.

The commonly use is Challenge Handshake Authentication Protocol (CHAP). CHAP will ask for the revalidate password to check whether the right person is using the system or not. CHAP generate key within domain or host, clients then need to use the key to encrypt the username/password in order to use the system.

There is one common problem in authentication which is the password length, short password which is very easy being break by brute force algorithm. However, long password may require the user to write down the password and the risk for being exposed is higher compared to short password (Fowler, 2005, Lecture Note).

2.0 Network Topology

2.1 General Information

There are many ways of creating a VPN depending the size and area needed. Different topologies can be implemented by a different protocol.

2.2 Host-to-Host

Host-to-host secure connection can be done by using IPsec. This kind of network can be easily done by just installing IPsec in both of the host. A host-to-host connection can be a desktop or workstation that wants to create a private network to secure transferring file or data. Figure 3 below shows the idea of a host-to-host network.

To create this network, a unique name for the IPsec to identify the 2 host is required. Both of the IP address also needed when making change to the configuration file. 2 PC will need to have their encryption key and exchange the key using shared authentication key when establishing the connection. (IPsec Host-to-Host Configuration https://www.redhat.com/docs/manuals/enterprise/RHEL-3-Manual/ security-guide/s1-ipsec-host2host.html, 2005)

2.3 Host-to-Network
The host-to-network network is the less complicated version of the network-to-network version. Most of the structure is the same as network-to-network system which using a host connecting to a large network. This is useful for people working at home that require secure connection to the company networks.

2.4 Network-to-Network
When creating a connection between two networks, its mean the connection between two subnets will be connected with VPN tunnel. A network-to-network connection required IPsec routers to be installed in both of the subnets in order to route the every single host pc. This network usually used by two companies that want to link their network together at a lower cost. VPN is much cheaper compared to rent a leased line that cost few hundreds thousands per year. (IPsec Network-to-Network Configuration https://www.redhat.com/docs/manuals/enterprise/RHEL-3-Manual/ security-guide/s1-ipsec-net2net.html, 2005)

Figure 4 shows the IPsec making connection through a tunnel via the internet.

Conclusion
In conclusion, virtual private network has provided a secure network to the network industry. VPN was able to reduce the cost to setup a network in a long distance by using internet. By writing this report, getting more and more understand to the VPN on implementation and configuration. The information is all about the general structure, the security systems, and the different topology of VPN. This will help to understand the whole main idea about the Virtual Private Network

List of reference

Douglas, C. (1997), Computer networks and internets, Prentice Hall, pp.278-281

Fowler, D. (2005), Authentication and Authorisation, Lecture Note

Fowler, D. (2005), Encryption, Lecture Note

IPsec Host-to-Host Configuration https://www.redhat.com/docs/manuals/enterprise/RHEL-3-Manual/ security-guide/s1-ipsec-host2host.html, 2005 [Accessed: 30/08/05]

IPsec Network-to-Network Configuration https://www.redhat.com/docs/manuals/enterprise/RHEL-3-Manual/ security-guide/s1-ipsec-net2net.html, 2005 [accessed: 30/08/05]

Knipp, E., Browne, B., Weaver, W., Baumrucker, C. T., Chaffin, L., Caesr, J., Osipov, V., Danielyan, E. (2002), Managing Cisco Network Security, (2th edn), Callisma, pp2-3

Linux VPN Fundamentals http://www.informit.com/articles/article.asp?p=25946&rl=1, 2005 [Accessed: 31/08/05]

Microsoft’s monopoly is damaging the software market. Nowadays, there are many kinds of open source software available in the market. The amount of open source software is increasing day by day. The Microsoft domination of the software market is actually causing a lot of problems to people because it is damaging the software competition with other software companies. Monopoly means control over a product is held by only one group of people. Monopolizing the whole software market actually does not bring any benefits for Microsoft, because they do not have any competition for them to improve themselves.

Open source software is developing as a rival to Microsoft. Bear in mind that open source does not mean just access to the source code. In order to classify whether the software is up to the open source standard, it must fulfill a certain number of criteria. There are a few criteria that need to be fulfilled such as free redistribution, which means that a developer cannot make a profit from the modified version of the software. It must be free and open to others as well. All the programs must come with the source code, so that everyone will be able to access the code. The license of open source must not discriminate against any person or groups; therefore, people should be able to use the program in any area they want (Open Source Initiative, 2005, p.1).
Open source could be better than the Microsoft monopoly in many aspects such as reliability, security, functionality and other ways as well. Every individual or organization and programmers able to make use of the source code because the source code is free and available on the Internet, they are able to download and improve it according to their needs. It is also more reliable compared to Microsoft’s dominant products. With Microsoft, users are not allowed to view or modifying the source code. In fact, there is no source code available anyway. Source code is the programming code of a program, open source software will include a complete and compiled coding while Microsoft only selling their software but without any source code. This is a huge contrast compared with open source software that can be accessed anytime with no cost.

Generally, in terms of security and functionality, software from Microsoft has a higher risk of being hacked compared to open source software. For example, a worm called Bofra had infected a lot of Internet Explorer users in 2004. It is not a file or attachment but just a link to a web page; once a user clicked on the link their PC will be infected (The Australian, 2004, p.C07). There are many reasons why this phenomenon could happen in the modern technology world. If Microsoft does not monopolize the software market, giving chances to open source, these problems could be reduced. More people are working on open source programs compared to Microsoft products; therefore, the functionality of open source software could be competitive with Microsoft software. Open source could become dominant development system in the world if some of the areas had been improved. Sometimes, the features within open source software are more useful, because the software is modified to suite personal need (Ferguson, 2005, p.64).

Microsoft’s monopoly has been in place since the release of the first version of the Windows operating system. An operating system is a program that helps to run the computer hardware and software systems. It is the core of a computer system. Microsoft has never admitted that they are actually monopolizing the software market, but some of the facts and measurement have been proved that Microsoft has indeed monopolized the software market in the world (Khan, Islam and Ahmed, 2005, p.130). Statistics shows that more than 90% of computers use Microsoft Windows Operating Systems in the world. Microsoft products such as Windows, Office, and Servers have become the industry standard, and control the current market (Khan, Islam and Ahmed, 2005, p.130).

The problems of Microsoft’s monopolization can be potentially huge, because it may not only affect other software companies competitive ability, but also limit the choices of consumers. Glover (2005, p.1) stated that Microsoft does not reveal how Windows actually works; this can obviously limit the ability of software developers to create competitive software to compete with Microsoft’s products such as the Office series. In the author’s experience this would allows Microsoft to dominate software markets without competition. Recently, the European Union wanted to fine Microsoft 500 million because they want Microsoft to make two major changes: first, they want Microsoft to remove Windows Media Player (WMP) as bundled software for the Windows OS. WMP is a program that allows users to play most kinds of media such as CD, VCD and DVD. The bundling of this program damages competition between others who produce similar software, companies such as Real Networks, who produce Real Player; the second reason is Microsoft does not share enough information about how Windows work with other software manufacturers (Microsoft hit by record EU fine, 2004, p.1).

The main concerns about Microsoft’s monopoly are security, reliability and functionality. Logically, if there is no competition then there will be no improvement. Thayer (2005, pp.76-77) indicates that Microsoft’s products have created several security issues which have been critical for industry or home users. For example, Internet Explorer (IE) is a program that is used to browse the Internet website. The author also stated that IE has been vulnerable to hackers or viruses for such a long time before it gets fixed until the CERT (Computer Emergency Response Team) warned people to stop using IE. This vulnerability means it is possible to be attacked by something else, or it is not safe in certain kinds of situations. The competitor of IE is the open source program, Mozilla Firefox that works in a similar way to IE, but it has less security and stability problems compared to IE. Because the source is open, problems may be fixed very quickly by anybody. It has been developed under the open source community; thus it is completely free and seems to have better functionality. In term of overall performance, many people say that Firefox is better than IE; for example, Thayer (2005, pp.76-77) argued that users should be using Firefox for Internet surfing and use the IE for intranets. An intranet is a network within an organization which has no connection from outside. Since IE is recommended for use only on intranets, it has serious security problems for use on the normal Internet. There are many cases in which hackers were able to steal credit card or banking information from IE but not from the Firefox browser (Thayer, 2005, pp.76-77).

Again, this shows the effectiveness of open source programs compared to Microsoft’s products. At least the problems on Firefox get fixed quickly rather than being ignored as in IE. Firefox works so well because of the huge support from the open source community. The source is open to public, and anyone can change and modify the program and make improvements. When problems have been identified, millions of programmers will work for a solution and problems get fixed in few days or even few hours. For IE, the programming code is not accessible to the public, so only the employee in Microsoft will be able to look for a solution. Therefore, it takes longer to fix the error and will mean the problems will exist for a longer period. From the example given above, it is obvious that open source software could be better than Microsoft’s products. Generally speaking, for security purposes, we should use Firefox because of its lower vulnerability compared to Microsoft Internet Explorer.

The future of open source will be bright, because more people are switching from Microsoft Windows Server to Linux. Linux is not an acronym, but the first version of Linux’s core which was originally written by Ken Thompson called UNIX. It is an operating system that developed under the GNU General Public License, therefore the source code is available for everybody. It is free to use and modify, provided your modified version is also open to the public (About the Linux operating system, 2005, p.1). Linux is widely used to serve as a server for many purposes, such as web hosting and database serving. Ferguson (2005, p.64) says that companies such as IBM have contributed lots of money to support open source software. Ferguson continues to report that in company revenue trends, statistics shows that Linux has grown significantly from year 2002 to 2004. There is no extra cost to run a Linux server for a business; however, the Microsoft’s Windows Server comes at an expensive cost.

The benefits of using open source software over Microsoft are immense; nonetheless, open source is not perfect. There are still many problems which exist in certain areas, such as money, coding and maintenance. Money is important for the open source community to pay for the daily development expenses. Development will have to be stopped if the community runs out of money or materials. For the open source coding structure, people often just copy and paste the source code into a particular system. When modifying the program, it will be difficult to understand the code because part of the structure might be different. One of the main problems of open source software is the lack of maintenance or updates, because all the programmers are working as volunteer. They only work part-time or in their spare time; therefore, user support on open source programs is often limited.

In conclusion, Microsoft’s monopolization does not bring any benefits to software markets. In other words, it would only restrict markets in terms of business value. Since it brings more problems to software markets compared to open source software, this would result in higher demand for open source software. Users will know the differences clearly between open source and Microsoft’s products, thus giving open source the opportunity for it to grow faster. Open source software would have better expansion in the future, depending on the users and mostly programmers or software engineers. Since open source software can provide more services to software developers, developers can use the entire source code to enhance the features of the particular software. Open source software is free but users will need to pay in order to get Microsoft’s software license. In term of consumer value, therefore, most people should pay more attention to open source software. Furthermore, open source can provide better security and functionality compared to Microsoft’s products.

List of References

About the Linux operating system (2005) (URL: http://www.linux.org/info/index. html) [Accessed: 22 June 2005]

Alper, J. (1998), From Army of hackers, an upstart operating system, Science, Vol.282, pp.1976-1979

Boulanger, A. (2005), Open-source versus proprietary software: Is one more reliable and secure than the other?, IBM Systems Journal, Vol.44, pp.239-249

Ferguson, C. (2005), How Linux could overthrow Microsoft, Technology Review, Vol. 108, p.64

Galli, P. (2005), Why Unix can’t win, eWeek, Vol.22, pp.18

Glover, T. (2005), Gates caves in to EU on monopoly, Knight Ridder Tribune Business News, Jan 30, 2005, p.1

Khan, S., Islam, F. & Ahmed, S. M. (2004), Is Microsoft a monopoly, American Business Review, Vol.22, pp.130-135

Meza, P. (2005), Putting Open Source to work, Optimize, Vol.4, pp.77-79

Microsoft hit by record EU fine (2004) (URL: http://www.cnn.com/2004/BUSINE SS/06/08/eu.microsoft.app eal/index.html) [Accessed: 19 June 2005]

Open Source Initiative (OSI) (2005) (URL: http://www.opensource.org/docs/defin ition_plain.php) [Accessed: 12 June 2005]

Salvator, D. (2005), Giving Microsoft the boot, ExtreamTech.com, Part 1, p.1

Serious flaw in internet Explorer (2004), The Australian, 30 November 2004, p.C07

Thayer, R. (2005), Should IE stay or should IE go?, Network World, Vol.22, pp.76-77

2. State of the art

YouTube choose Adobe Flash as a tool to broadcast their media because compressed flash based videos are much smaller than the usual one. This will be the state of the art of sharing videos with flash compressed format compared to the old day’s video sharing technology which required a very fast internet connection. Why YouTube is so famous? Because Chad and Hurley designed it so that everyone can post everything they like in minutes. This is something like a TV station which people can publish everything they like. Members can post comment their comment on videos or setting up their own site on YouTube [4].

3. Advantages

Flash was developed and used for multimedia purposes. With the new flash version 6 to 8 the capability of video steaming, new format called FLV has been build to broadcast flash video. FLV separates stream able content and the flash movie into two file. The flash movie will act like a video player and load the stream able content into it and run the video. A FLV file contains at most one audio and video stream only. Audio supported a variety of sound format such as MP3, ADPCM as well as uncompressed sound. Previous flash version only supports Sorenson H.263 video codec as a standard. But the latest flash technology allows a new video format called “Screen Video”, which is a simple screen capturing video format [6].

Flash video eliminated the need of forcing clients to use anything they don’t like, for example some users may prefer QuickTime than RealPlayer. The main reason is none of the video player in the market has 100% compatibility to all video formats. This is where Flash has huge advantages over other video players. FLV videos often only can be played in specially constructed FLV players. Therefore even if user capture the video file is it very hard to re-playing the video.

Flash multimedia often supports by most browsers and the flash player is free to download. All the conversion is done by the YouTube, users do not need to worry about the conversion methods. Users can upload all types of compression format videos to YouTube and it will do the job and converting them into flash based video in about 5 minute’s time. By using flash, it’s eliminated the required of video decoder to view any kind of compressed video format. YouTube also make sharing videos become so easy compared to the old time where user has to find a host to host their video and often it is not free.

4. Disadvantages

There are disadvantages for using flash as a broadcast media such as video frame rate and sound quality. Video compressed by YouTube Flash engine often low frame rate, unless the source file is in a very good quality of compression. When video is uploaded to YouTube, they actually decode the video into raw video and then re-encode into flash format video. Video frame size will be scaled to 320 x 240 and frame rate in around 25 to 30 fps. Total video rate will be somewhere around 200 kbps. For the audio compression, stereo audio will be reduced to mono and re-encoded in a lower bit rate [2]. All these re-encoding steps are the wait time for an average of 5 minutes for each video to be completed and published to YouTube community.

200 kbps video quality is considered very low compared to DVD and DV compression. DVD has a video rate of 8 mbps and DV have around 25 mbps. There is no way YouTube compression can be compared to DVD or DV format. Video quality is more than 10 times greater than YouTube compression [2]. Normally if video was recorded out door, most scenes will have lots of fine-grained detail object which usually will be throwing away during compression thus the video quality often in poor quality. In order to compress a good quality video, less movement and motion and indoor environment will greatly increase the video quality output by YouTube. Even if we have to take video outdoors, the use of tripod can greatly reduce video information rate and will still look good in a low bit rates flash video [2].

5. Impact in the next 5 years

Big companies such as Google and Microsoft’s MSN have launched video services on their sites. But none of them come close to YouTube popularity. The success of YouTube has drowned the attention of mainstream media. Marketers such as advertiser are already interested in looking for ways to invest in YouTube technology. Lucian James, president of Agenda Inc., a brand marketing firm says that “It comes at a perfect time when brands are looking beyond the 30 seconds commercial and are looking for new ways to connect to their audience” [3]. This shows that the impact to TV industry where advertiser may try to put their advertisement on YouTube while still getting the same amount of viewers compared to TV.

The strength of YouTube is the ability of connect audience across the world. 16 millions US users attracted in July came from 63.4 Million total unique worldwide users. Which mean YouTube is the best promotional device in US such as delivering advertisement to younger audiences. With the popularity of global visitors, the different in brand borders such as US and Chinese will no longer exist in 5 to 10 years time. Delivery methods will be global in the future and programs will work in multiple countries.

Some major companies such as Nike Inc, has used YouTube to broadcast a clip of soccer star Ronaldinho showing off with a new pair of shoes. About million of users watched the clip and giving their comments. Satellite TV service like BSkyB, the distributor of The Simpsons posted their live action animation shows intro to promote in Britain. Music Company such as Matador Records also starts marketing several bands on YouTube by specifically creating video contest to attract bands all over the world [3].

Other than the impact on entertainment, the effect of posting educational purposed video can be obtain a good result as well. For example, the White House is distributing government produced anti-drug videos on YouTube. The video features 30 seconds advertisement of “a teenager running from a snaring dog and bemoaning pressure from his friends to smoke marijuana” [5]. This video was previously published on TV and now the government put them on YouTube. The government linked its video with the search tags “war on drugs”, “peer-pressure”, “marijuana”, “weed”, “ONDCP” and “420” which often the keywords for drugs. Few thousands of YouTube users had watched some of the government’s videos and it is completely free compared to TV broadcasting. Again, this shows that the usefulness of flash based videos not only for entertainment purposed but also for educational purpose [5].

Even though the size of a flash en-coded video is smaller then the usual video, the size still stays in around few megabytes. The impact to internet service provider may be effected by this technology, because everyone is watching video online compared to the old days which the majority of internet user only use the internet to check mails. Internet service provider may need to invest and increase their broadband speed and adjust their packages. The popularity of videos sharing may also increase the speed of internet technology development due to the demand of internet users.

6. Copyrighted problem

YouTube seems to look very good in the future, but the freedom that’s YouTube provided may resulted a downfall in the future. Most of the users have been posting copyrighted video, without the required legal approval from authors. These videos including clips from the TV prime-time shows, Hollywood movies, Olympics games and music videos. Major companies such as NBC and CBS have taken actions to YouTube. YouTube solved these problems by taking down all the requested video from their host. However, YouTube usually do not take any actions on copyrighted videos unless they have been warned or action has been taken by the video original authors [4]. Nonetheless, there are still tons of copyrighted videos on YouTube because some authors may not have the ability to take any action on them.

7. Conclusion

The future of video sharing is very hard to be predictable; will it be the next NBC or the next Napster? YouTube might become a new era of web multimedia and benefits everyone users all over the world. New technology has to be implemented in order to detect copyrighted videos and preventing them from being published to the internet. This will be a hard decision for them because if the removed all copyrighted material which is often good and fun clips, YouTube may lost most of the visitors that they having now. They have invested about $3.5 million on it, it is doubt that how they can earn their own money in five years time while dealing with all the pirated content. However, if copyrighted problem can be solved then no doubt YouTube technology will be the key success on introducing new technique to web multimedia technology.

References

1. Wiki, “YouTube” 2006; http://en.wikipedia.org/wiki/YouTube

2. J. Thompson and J. K. Tumlinson, “Making Movies” 2006; http://blogs.chron.com/makingmovies/archives/2006/04/ youtube_and_the.html

3. S. K. Goo, “Five Months After Its Debut, YouTube Is a Star” 2006; http://www.washingtonpost.com/wp-dyn/content/article/2006/04/30/ AR2006043001040.html

4. H. Green, “YouTube way beyong home videos” 2006; http://www.businessweek.com/magazine/content/06_15/b3979093.htm

5. CNN, “White House uploads anti-drug videos to YouTube” 2006, http://www.cnn.com/2006/TECH/internet/09/19/youtube.drug.policy.ap/ index.html?section=cnn_tech

6. K. Rechert, “Video and Audio Streaming with Flash and Open Source Tools” 2005, http://klaus.geekserver.net/flash/streaming.html

Distributed Database Systems (Advanced Topics in Distributed Systems)

Nested Transaction

In the mid 80’s, all record-keeping required database application. The users started by using the traditional record-keeping application, and then advanced to more complex applications such as Office Information System or Computer Aided Design. Information plays an important role in this sophisticated world. Without this information, we cannot know what is happening in or outside our country. Information is very important as a mean of communication in the business world. Since information is so vital to everyone, the only way to keep the information secure is by using record keeping. Record keeping can be done using applications; most people will use database applications because it will enhance the efficiency of their work.

There are two main types of database systems, centralized systems and decentralized systems; also known as distributed systems. The main advantage for centralized systems is the quality control. This is so as the database will only work within a system and it is also easily maintained by a small group of people. However, the centralized system is not a cost effective system due to the duplication of data. The storage cost for the centralized system will be high compared to a distributed system. The source of distributed systems will always be online because all the systems will not be offline at the same time. A good distributed system can reduce the duplication of data as well, thus reducing the cost for storage media within the network. The only disadvantage of the distributed system is the difficulty of keeping the database up-to-date, because the data can be located all over the world (Centralized versus distributed database systems, 1997, pg.54).

Nowadays, most of the people use nested transaction model, this model is used to satisfy the requirement of advanced database applications. What is nested transaction model? This model was originally introduced to increase transaction reliability in the distributed system. Transactions in advanced database application are considered long and complex. However, conventional flat transaction model cannot support all requirements in advanced applications. As a result, the basic nested transaction model has been extended and several new models have been added as well. So, the nested transaction model and its extensions are currently being used in most of the advanced database systems. A nested transaction is a hierarchy of sub transactions, whereby each sub transaction may consist of other sub transactions. A nested transaction can be defined as a collection of sub transactions that are combined together to form one atomic unit for execution (Hassanein, El-Sharkawi, 2000, pg.4).

A transaction is a series of processes executing on a database to perform any kind of calculation. Each of the transactions has to terminate at the end of process. There are only two possibilities for a transaction result, a failure or a success. When a transaction has failed, it needs to rollback or perform with any other action depending on how the system is designed. If the transaction is successful, it will be saved and will continue on to the next transaction. Transactions such as a flat transaction were widely used in current DBMS system. But the technology changes from time to time and requires very complex transaction calculation. The traditional flat transaction will not be powerful enough to handle all these new queries. In this stage, nested transaction is introduced to handle all the problems (Alkhatib, Labban, 2002, pg.95).

The concept of nested transactions is much more complicated than other systems. Therefore, it is impossible to avoid every single possible occurrence of the error. When an error occurs, we should have a fine transaction recovering system in the nested transactions. There are a few common failures that may happen in nested transaction such as transaction failure, node failure, system failure and media failure. Transaction failure often happens in large DBMS when the transaction program could not be saved correctly due to deadlock. If this problem happens in a small transaction, only a short amount of time is needed to recover the error or recovering during the same execution time when the transaction is executed. For a large transaction error, it may require a longer time to completely do a rollback-and-recover process for the lost transaction. Another type of failure is node failure, that is, one of the single systems not functioning. This kind of failure should only affect that particular failed process and thus reducing the problem area as much as possible. System failure means that the entire computer system crashed for some reason and needs to be rebooted. This case is similar to node failure, which can be handled without affecting other running processes in a distributed environment. Media failure refers to a disk or any other storage failure and thus the process needs to be recovered or rollback to the last known backup (Haerder and Rothermel, 1987, pp.239-248).

There are two main types of algorithms when dealing with recovery in a nested transaction. First algorithm is UNDO, or called recovering without save points. UNDO will wipe out all the remaining transactions and processes to the beginning, and do the transaction from the start. The second algorithm is recovering using save points. The main difference compared to the first algorithm is that it will add save points to the UNDO list. It allows for partial rollback which reduces the loss of work effort compared to the first algorithm. Each algorithm has two types or interfaces which are single call interfaces and conversational interfaces. In a single call interface, a successful transaction recovery will require the complete removal of the entire transaction made. However, this will affect all its relation either in process or saved data. When a transaction failure happens, the parent of that transaction will receive a message called ‘aborted’ rather than ‘committed’. After understanding the failure and error message, a new transaction should be created to recover the failed transaction (Haerder and Rothermel, 1987, pp.239-248).

In conversational interface, they have a better parent and child control system. When a transaction is being made between grandparent, parent and child, it makes sure no error or wrong information is passed to the grandparent level. If any transaction error occurs between transaction and child level, it may only need to rollback and recover within that transaction rather than rolling back the whole system (Haerder and Rothermel, 1987, pp.239-248).

The second recovery system uses save points for tracking the recovering point in the transaction. Save points is actually an upgrade or better add-on for UNDO. It allows failed transaction to be recovered at any stage which is needed, thus creating a greater flexibility for recovering in nested transaction. Save points are also known as restart points, when the transaction failed, it will try to locate the best stage and restart the transaction recovering procedure (Haerder and Rothermel, 1987, pp.239-248).

There are many well known transaction models in the world. A majority of them is the flat transaction model, which is a modification of basic transaction. Flat transaction is a collection of ACID properties which are Atomicity, Consistency, Isolation and Durability. Atomicity is a process to make sure all the transaction processes are in a single unit. Consistency is to control every single execution when transactions are being concurrently executed. The function of Isolation is to isolate each transaction to prevent them from reading the same database at the same time. Durability is to make sure everything is saved properly to reduce the risk of data loss (Bertino, Catania, Ferrari, 2001, pp.321-370).

The main problem of flat transaction is that there is no way to stop the transaction halfway. If the transaction is being forced to stop or abort, the whole transaction will be cancelled and restarted from the beginning. The following example will show the limitation of flat transaction. Mr. A is in Melbourne and wish to travel to Sandakan, a small town in Malaysia. There is no direct flight from Melbourne to Sandakan. Therefore Mr. A should fly to Singapore or Kuala Lumpur, then transit to Kota Kinabalu. The travel agent will start making the transaction and book the ticket from Melbourne to Kuala Lumpur and Kuala Lumpur to Kota Kinabalu. Soon, he finds out that there is no way to travel from Kota Kinabalu to Sandakan, but there is an available flight from Brunei to Sandakan. So what the travel agent needs to do is to change the route from Kuala Lumpur to Kota Kinabalu with Kuala Lumpur to Brunei and then Brunei to Sandakan. In a flat transaction model, the agent has to either rollback or cancels all the operations that were incorrect. However, both operations will require a massive rollback that will destroy all the previous efforts that have been made; these methods will be costly if the transaction is much longer than this given example (Bertino, Catania, Ferrari, 2001, pp.321-370).

The best method for this example is using a selective rollback, rather than throwing away all the previously-made transaction. By using selective rollback, it is possible to just cancel the flight from Kuala Lumpur to Kota Kinabalu and replace it with a flight from Kuala Lumpur to Brunei. To improve the function of a flat transaction, a new or good extension has to be implemented into the transaction system. One of the more popular and powerful system is the use of nested transaction. The characteristics of nested transaction as discussed before; has a different level that controls each single layer of transaction. Each transaction can be rollback individually without affecting the whole transaction itself (Bertino, Catania, Ferrari, 2001, pp.321-370).

There are three rules of nested transaction: commit rule, rollback rule and visibility rule. Bear in mind that there are parent and children layer in a nested transaction system. Parent will not commit until all its children or sub transactions are committed or aborted. Rollback rule in nested transaction are much more flexible compared to a normal transaction system. Parent level transaction will still be able to be processed even when the child level is having problems. Parent level can carry on by just issuing a new process to replace that aborted sub-transaction. However, if the parent level transaction is aborted, all the sub transactions should be terminated and rollback. All the processes made within sub transactions are visible to parent level whether their execution is completed or aborted (Bertino, Catania, Ferrari, 2001, pp.321-370).

To prevent any lost updates or uncommitted dependency problems, locking is a kind of concurrency control mechanism that can solve the entire problem. The basic algorithm is such that it will lock the object of the database to prevent the transaction to make any changes with it. By doing so, the working transaction will be able to continue its task until some stages that it wish to stop. Thus, the locked data will remain safe throughout the whole process. There are two types of locks: exclusive locks and shared locks. If transaction A uses the exclusive lock method to lock data, the other transaction that tries to access the data will not be immediately granted the access (Date, 2004, pp.465-479).

However, the shared lock mechanism functions differently. Transaction B will be able to access the data, but will also lock the data with the shared lock method. All these methods are able to solve most concurrency problems. Nonetheless, this method is not perfect – it has a problem called deadlock. The reason for using locking is to prevent different transactions accessing the same data and causing problems. But when two transactions are in a locked state, none of them will be able to read each other. This is known as a deadlock. When this problem happens, Date (2004, pp.465-479) claims that a good system will be able to detect it, but some other systems might require a timeout mechanism to detect a deadlock. This may not be accurate because sometimes a delay lock may not be an error but a human delay. When someone execute a transaction, he may use a long period to collect information from the customer. The system might consider this as a deadlock and do a rollback, thus this will cause some inconvenience for the staff and customer. When a deadlock has been detected, one of the transactions should be rolled back and the lock released, so that both transactions will resume normal execution (Date, 2004, pp.465-479).

Security is an important criterion to be focused on when dealing with nested transaction in a multilevel environment. All sub transaction has the same security level with the single nested transaction. A transaction does not have written permission; it cannot create any low-level sub transactions. A transaction does not allow creating any high-level sub transactions as well; otherwise it will lose all the advantages in a nested transactions environment. Basically, data access is based on two rules, L (d) <= L (T) and L (T) = L (d). These two formulas are based on two transactions d and T. L (d) <= L (T) show that the security level of T is greater than transaction d, therefore T can only be able to read the data. For L (T) = L (d), transaction T security level is equal to transaction d, it will then allow the transaction T to write the data. From these rules we understand that a lower level transaction cannot process any writing command to any transaction level on a higher level (Bertino, Catania, Ferrari, 2001, pp.321-370).

Most of the commercial DBMS systems are using 2PL protocol (Bertino, Catania, Ferrari, 2001, pp.321-370). The algorithm for this protocol is when a transaction is trying to read or write a particular data, it will first perform a lock on that data. They are read lock and write lock, read lock is applied when a transaction is reading the data and write lock being applied when trying to write the data. In an interactive manner, when a data does not have any lock on it, any transaction can apply a read-or-write lock on it. When the data has a write lock on it, no transaction is able to do a read or write lock on it. However multiple transactions can have read lock on the same data but not write lock. A write lock will only be applicable when the data is totally free with any lock. Otherwise, they need to wait until the transaction, that holds the lock, releases it. Within this 2PL protocol, transactions will need to go through two steps when locking and releasing a lock, which are growing phase and shrinking phase. To ensure the serializability for the transaction, no other lock can be held by a transaction after entering a shrinking phase. Bertino, Catania, Ferrari (2001, pp.321-370) mention that 2PL is not a good protocol for the current execution of nested transactions because of the bad timing channels in a multilevel environment. However, a better protocol called Bertino et al uses save points which is more secure for timing channels (Bertino, Catania, Ferrari, 2001, pp.321-370).

A new lock called signal lock is introduced in order to avoid the timing channels. In 2PL protocol, a transaction needs to apply a read lock when reading a data. But in Bertino et al protocol, the transaction can read the data without applying any locks. Signal lock is acquired by a transaction when it wants to access a lower security level data. A nested transaction is similar to a normal transaction method, which uses read, signal and write lock before accessing any data. The significant difference compared to normal transaction is that there is no shrinking process within the nested transaction. Nested transaction is too complicated to apply shrinking process. Therefore, when a process is done any lock will be automatically released to the upper level in a nested transaction rather than releasing the lock itself by using the shrinking phase as discussed before in 2PL transaction (Bertino, Catania, Ferrari, 2001, pp.321-370).

Locking rules for a nested transaction is significantly different compared to a normal transaction. If transaction A wants to apply a write lock to data B, the data must not have any lock held by other transactions. This is similar to non-nested transaction; however, nested transaction has a special rule. When all the transactions that hold either read or write lock on the data B are under the same tree of transaction A, A will still be able to apply a write or read lock on data A. Signal lock will only be applied if data A does not hold any write locks. When a transaction is complete, its parent will keep all the locks that have made by the transaction. If the transaction is aborted, all the locks will be released and will not have any relation with their parents. The reason for all the above rules is to prevent any delay of the data read by lower level transaction. Signal lock will not be blocked by any lower level transaction to lock a data. High-level transaction will have to wait if the data is locked by a write lock. This is to ensure that the high level transaction is reading the most updated version of the data (Bertino, Catania, Ferrari, 2001, pp.321-370).

The benefits of using nested transaction over flat transaction are immense; nonetheless, nested transaction is not perfect. There are still many problems which exist in certain areas, such as the complexity of coding structure. It is very complicated to implement a nested transaction system. A company might need to spend a very high cost to upgrade their system to a nested transaction system. Deadlock still happens in a nested transaction environment just that nested transaction is able to solve the problem flawlessly.

In conclusion, nested transaction model can bring many advantages to their users. Why do users still need to use the traditional transaction instead of using nested transaction model for making transaction and record keeping? Living in this sophisticated world, everyone must focus on nested transaction model in order to get the best out of database application. Nested transaction model has been introduced for a long time; it has been use in many large scale DBMS systems. Therefore, the use of nested transaction will bring more benefits to the transaction systems compared to normal flat transaction systems.

List of References

Alkhatib, G., Labban, R. S. (2002), “Transaction management in distributed database systems”, Journal of Information Systems Education, Vol.13, pg.95

Bertino, E., Catania, B., Ferrari, E. (2001), “A nested transaction model for multilevel secure database management systems”, ACM Transactions on Information and System Security (TISSEC), Vol.4, pp.321-370

“Centralized versus distributed database systems” (1997), Bioscience, Vol.47, pg.54

Date, C. J. (2004), An introduction to Database Systems, (8th edn), Pearson/Addison Wesley

Haerder, T., Rothermel, K. (1987), “Concepts for Transaction Recovery in Nested Transactions”, ACM SIGMOD, pp.239-248

Hassanein, H. S., El-Sharkawi, M. E. (2000), “Performance modeling of nested transactions in database systems”, IBM Centre for Advanced Studies Conference, pg.4

Energy-Efficient mobile computing approaches

1. Introduction

1.1 General Information
Mobile or wireless devices have become important tools for the modern world. For example GSM mobile, ad hoc networks and sensor networks are good examples of modern wireless networks. However the current battery technology couldn’t catch up with the implementation of mobile wireless technology. Mobile devices are always stuck with the limitation of battery life. Therefore a good protocol has to be implemented to overcome this matter. In mobile devices, the main consumption of battery power is used by the circuit board of the device. Then the second consumption is used for transmitting and receiving the total traffic. The third consumption will be the output of the devices [1].

Capacity of battery is usually based on the size of the battery itself. Obviously, the bigger the battery, the longer the battery will last. Big-sized battery is not the solution for mobile devices, as mobility required small, light and portable batteries. Devices that operated on AA size batteries should focus on the battery issues. The battery life should last at least 2 to 3 hours before the next recharge cycle. Battery experts make a prediction that battery technology will only improve 10 to 30% in the next 5 to 10 years [3].

Currently new mobiles devices are all designed in a downsizing manner that can fit in our palm such as Pocket PC and PDA Palm. In the future, if battery power problem can be solved, they all can establish a reliable distributed network that can serve people well. The demand of portable file system keeps increasing as more people wants to access their file on the move. To achieve that, battery power problem has to be solved to provide a reliable and constant connection to the networks. Unreliable battery power will cause disconnection and poor network latency performance such as limited bandwidth, because the device’s wireless interface may need to be turned off to recover or conserve its battery energy [3].

To reduce energy consumption in mobile networks is a crucial and an important task. Hardware has been improving in recent years for the aim of achieving low energy consumption standard. However due to the slow improvement of battery technology, others area of possibility of energy consumption method has to be made in order to cooperate in conserving energy. Due to the limitation of hardware design, energy consumption has to be done in protocol design. A protocol that uses schedule mechanism will allow the wireless interface enough time to turn off, thus allowing the battery cells to regenerate its energy.

2. Infrastructure and Ad-hoc networks

2.1 Infrastructure Network
There are two normal wireless architectures being used in our current wireless network system. They are infrastructure and ad-hoc networks. Infrastructure networks are often connected to a base station such as desktop or server that is installed with different wired adapters. They work as a router to connect the device to other devices wirelessly through different channels [2]. Those channels can be FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access) or CDMA (Code Division Multiple Access) which are also widely used in phone networks. All the server or host know how to communicate with each other on different channels, thus they will act as the last route for mobile devices. An example of infrastructure network can be seen in Figure 1.

2.2 Ad-hoc Network
Ad-hoc networks are a multi-connection network of mobile devices itself without the need of a server to route the communication channel. This type of network will be completely devoid of wires, all connections are made with wireless. An idea of Ad-hoc networks is shown in figure 2. All wireless devices communicate with each other rather than connecting to a server first. This method is a good temporary network environment especially for military needs. All the devices must be able to exchange topology information in order to route the networks successfully [2].

3. Power Consumptions

3.1 General Information
Software or applications in mobile devices do not interact with the wireless network directly, in fact they communicate with the protocol software and then the protocol software interact with the hardware to communicate with the networks. Efficient energy research has been done around the physical layer because people believe that the power consumption of a device is mainly by the system hardware itself [2]. There are many researches that tend to increase the battery life by increasing the battery size but bear with the limitation that we cannot have a bulky battery in our mobile devices such as cell phone or PDA. Battery technology has not been improving much for over 30 years, unlike other part of computer system such as CPU, the technology keep changing every year. The usual way to reduce battery consumption is to reduce the processing speed and hard disk spinning speed [2]. All these ways are able to reduce the battery consumption significantly but more ways should be considered to improve the battery life. One of the ways would be the refinement of the current protocol layers.

A basic wireless communication devices required receiving, transmitting and standby mode. Transmitting required the most power consumption and the least for standby mode [2]. For example, power consumption for Proxim RangeLAN2 2.4GHz PCMCIA card needs 1.5Wolt for transmitting, 0.75Wolt when receiving and 0.01Wolt while idle [2]. Therefore, the way to reduce energy consumption would be the implementation of new energy savings protocol to reduce the transmitting power.

4. Energy-efficient protocol

4.1 General Information
Before we can start discussing the way of implementing an energy-efficient protocol, we need to understand what the characteristics of current wireless protocol are. For IEEE 802.11 wireless mechanism, the receiver is turned on at all times to receive every packet and check for the required packets. This mechanism will waste lots of battery energy as it keeps on monitoring all the packets. Solution can be made if they schedule the transmission time; receiver will switch off until the transmission time started. The other way is the receiver will assume that it does no need to receive any more packets and it will turn off the receiver [2]. To established a complete connection, device have to switch from transmit to receive mode and vice-versa, that will cost a lot of time and wastage of energy. This can be solved by allocating contiguous transmitting slots so that it can transmit or receiving in a longer time before each mode switching [2].

4.2 IEEE 802.11 Protocol
Three widely used protocol named IEEE 802.11, EC-MAC and PAMAS protocol are all designed with the idea of energy savings but not efficient enough for today’s mobile technology. IEEE 802.11 protocol basically was designed based on CSMA/CA (Collision Sense Multiple Access / Collision Avoidance). IEEE 802.11 uses a transmission channel to transmit packet. Mobile will capture the channel and transmit all data if the channel is not busy [2]. If the channel is busy, it will enter into the “off” state again. This protocol conserves power by switching the mobile to sleep mode and informing the station of this action. When there is data that needs to be sent to the sleeping mobile, the station will send a small buffered packet on air and wait for the mobile to wake up and receive it [2]. This method can conserve some energy but may result in high latency for the wireless network. Even though the IEEE 802.11 protocol can conserve energy, but energy efficient was not the main issue when designing this protocol compared to EC-MAC protocol [2].

4.3 EC-MAC Protocol
EC-MAC (Energy Conserving – Medium Access Control) protocol was designed based on energy-efficient as a main goal [2]. The EC-MAC protocol usage in infrastructure network is as mentioned before; where a base station routes the entire mobile client. Basically it uses reservation and scheduling methods to conserve energy [2]. EC-MAC protocol uses a frame with multiple data slots to transmit its data.

Every time EC-MAC transfers the frame, it will include a Frame Synchronization Message (FSM) at the beginning followed by request or update, new user, scheduled message and data phase [2]. In request or update phase, mobile will send a request of establishment of queues which has been set in the FSM. Collision is avoided by letting the base station control the order of reservation transmission within this phase. The new user phase will allow new user to register to the network. In schedules message phase, it will broadcast the slot permission for the transmitting data. Downlink and uplink are both used to store the data that needs to be transmitted [2].

EC-MAC protocol can reduce energy consumption because its uses a centralized scheduler as mentioned before [2]. This can avoid lots of collisions in a wireless environment. With the scheduler system, client mobile will not be required to keep scanning the whole channel for packets. Centralized scheduler will also provide contiguous slot allocations for each mobile device, this reduce the transmission mode changes that increases energy consumption. It can also assign appropriate priority to each client mobile based on their battery power level [2].

4.4 PAMAS Protocol
PAMAS protocol is similar with EC-MAC protocol that they both are designed as a main idea to conserve energy. PAMAS is designed mainly for ad-hoc network with the modification of MACA protocol. In PAMAS protocol, if a mobile wants to send a packet to the receiver mobile, it first send a RTS (request to send) signal to the receiver and wait for CTS (clear to send) signal [2]. If the receiver rejects the request, the sender will enter into “off” mode. The mobile that is receiving packets will send a “busy” signal to the channel to block further incoming request. Power conservation will be achieved by turning off the wireless receiver when they are not sending or receiving packets. With the busy signal, other will not be able to request RTS signal and thus conserve energy [2]. The main idea of using RTS and CTS is to determine when to turn off the wireless device to save energy. Simulation of analysis shows that around 10 to 70% of energy can be conserved with this protocol in the topology [2].

5. Battery Technology

5.1 General Information
It is important to understand how a battery works before we can discuss what the ways to utilize battery efficiency are. A battery consists of many cells that arranged in an array. Each cell contain anode and cathode which separated by electrolyte. Electric current is generated by the chemical reaction from the anode/cathode – electrolyte interface. As the use of current is increased, the cell voltage will be decreased and this is called “rate capacity effect” [1]. When the materials such as electrodes and electrolytes used to generate power is decreased, the cells voltage will significant drop down to an unusable level. Therefore the amount of electric that can be generated by a battery is based on the amount of electrodes and electrolytes the battery have [1].

Normal way of battery energy drain is by using a constant energy drain method. Using constant discharge method will drain battery life much faster because materials used in battery cells will not gain enough time to get compensation for the depletion. Even though there improvements have been made in battery technology, constant discharge will still only receive 10-30% power from a full charge battery [1]. The only way to solve this problem is using discharge pulsed. The idea is to allow the battery cells enough time to rest and regenerate for enough active materials to produce energy. By using discharge pulsed method, the energy delivered by a battery will be greater [1]. Therefore by using a battery discharge shaping method, it is obvious that it can increase the energy of battery efficiency.

5.2 Stochastic Emulation
A battery recovery model has been introduced in [1]. This model designed so that it uses a stochastic process to emulate the discharge of a battery. The model assumed that time scale is divided into time slots and one discharge pulsed represent by one time slot. This method was tested by the function of number of discharge per time slot that can be emulated by changing the value of number of discharge pulsed [1]. This model proves that energy can be increased if the number of discharge pulses is decreased per time slot, because the time of recovery of each slot is increased. It’s also shows that the more discharge pulses it have, the weaker the battery life would be.

5.3 Scheduling Scheme
Another approach was introduced in [1] is that the used of smart scheduling algorithm with discharge shaping. Battery will be divided into parallel of cells that can be selected specifically by the algorithm. Scheduling scheme will detect and choose the fully charged cell to drain energy. When the cell energy drop down to a specific threshold, it then switch to the next cell and continue the discharge process. This method will allow all the cells enough time to recover their battery life. The scheduler will always choose the battery cell that has the best state of charge [1]. When the energy of each cell drops down to a threshold, it will be removed from the active cell and allowed time for recovery. If none of the cells are available when the discharge arrives, the discharge process will be buffered and waits for the next available cell. By using this scheduler scheme, battery will be able to produce its maximum energy even with a continuous discharge requests.

6. Energy-efficient Protocols Design (Network Layer)

6.1 General Information
Network layer is used for routing packets in both infrastructure and ad-hoc network. However, the function of energy efficiency will not apply in infrastructure network because base station will do the routing job for all the client mobiles. But energy consumption plays an important role in ad-hoc network. As mentioned before, ad-hoc networks are a multi connection of mobile devices itself without the need of a server to route the communication channel. Ad-hoc networks are complicated because it required updating the network topology details every time [1]. Figure 4 represent an example of a small ad-hoc network, if A wants to communicate with C, the network should choose the shortest route which is through A, E and destination D. But it will continuous drain the mobile E’s battery life and will be forced to turn off. In the end it will cause F could not connect to the entire networks. Therefore, a good routing algorithm should be designed so that the route of A to D should not always use route E but using the route of B and C [1].

6.2 Unicast Traffic
There are two types of methods to achieve the above approach which are Unicast traffic and Broadcast traffic. Unicast traffic tends to conserve energy by choosing the cost effective routes rather than the shortest path [1]. This is to ensure that all the mobiles can stay alive as long as possible. Although packets that are transmitting through a longer path might logically drain more battery life, but it can actually conserve energy in some way. For example E may be a congested node, going through B and C will reduce the frequent changes of mode in E [1]. People argued that by choosing a longer path may result in high latency networks. But this is not often true because shortest path usually will be the highly congested path; therefore by using the longer path can actually have the same or better performance of short path routing [1].

6.3 Broadcast Traffic
Broadcast traffic simply broadcast packet to all the nodes, each mobile will receive the packet once and then turn off if they know theirs neighbors has already received the packet. Only the intermediate nodes will be required to retransmit the packet to next destination. The traditional broadcast way of broadcasting is simply flooding algorithm because it keeps sending the packet to all mobiles until it reaches the destination [1]. Therefore it is not suitable for wireless network as mobile devices will consume lots of energy if they keep on broadcasting the same packet.

Networks can be divided into different sets of trees. When a mobile want to broadcast a packet, it can choose the tree that have most power energy available. One of the way is to ensure that the packet arrive at as many new nodes as possible in order to expand the connection area. A packet that in a specific tree can travel to a different tree if the energy allows, priority will be given to a tree that generally have more energy power and more nodes available [1].

7. Application Layer

7.1 Video encoding and Proxies
Apart from the refinement of protocol layers, energy consumption reduction can be done in application layer as well. Advanced tools such as Power Monitor and PowerScope can help software developer to develop energy conserving applications. A report shows that 46% of energy reduction by a video player application by using the information and advantages provided by PowerScope [1]. Another way of conserving energy and bandwidth is to use proxies. It helps reduce the processing power of application such as browser and streaming software. Proxies can control the streaming content such as blocking the video and only allows the sound to be streamed to the mobile devices [1]. Proxies are usually installed at the base station that is located closest to the mobiles.

7.2 Multimedia Processing
Multimedia processing is deemed to be the highest energy-consuming task in mobile networks. Video processing and transmission often takes up a lot of energy and bandwidth due to the high data packet of video format. Therefore video encoding and decoding plays a main role in wireless mobile networks. There are two main methods to reduce the bits in video streaming. First, video can be encoded to a lower bit by using encoder such as DIVX then send to the receiver, the challenge is that the reduction of quality should be kept minimal. Receiver should also make sure that they have the appropriate decoder to play the video correctly. By reducing the video file size, transmission of the transmitter will be reduced thus reduces the energy consumption by the wireless interface. Secondly, remove selected bit from the network interface card. This can be achieved if the network card is sensitive to battery energy power status, it can then remove unwanted or unimportant packet during the video streaming transmission.

8. Conclusion
As conclusion, mobile wireless technology is changing and improving everyday. The main issue will be the battery technology that hasn’t been improved very much for the last 5 to 10 years. It can be deduced from the researches above, the longer the idle time of the transmitter, the longer the battery life that can be saved due to the nature of battery structure. The design of good energy-efficient mechanism is not only limited to protocol design, many other areas can be improved at different layers. Low power consumption protocols remain one of the main important tasks for the wireless technology’s researchers and communities. Designers must focus on designing energy-efficient protocol within the physical layer and application layer. A balanced must be achieved between delay and battery life, latency should be kept as low as possible while keeping a good battery life.

List of References

[1] Carla, F. C., Pavan, N., Vikram, S. (2002), “Energy-Efficient Communication Protocols”, ACM, New Orleans, Louisiana, USA, pp. 824-829

[2] Christine, E. J., Krishna, M. S., Prathima, A., Jyh, C. C. (2001), “A Survey of Energy Efficient Network Protocols for Wireless Networks”, Wireless Networks, Kluwer Academic Publishers, Netherlands, Vol. 7, pp.343-358

[3] Jun, C., Kian, L. T. (1999), “Energy-efficient selective cache invalidation”, Wireles Networks, J.C. Baltzer AG, Science Publishers, Vol. 5, pp.489-502

[4] Kian, L. T. (2001), “Organization of Invalidation Reports for Energy-Efficient Cache Invalidation in Mobile Environments”, Mobile Networks and Applications, Kluwer Academic Publishers, Netherlands, Vol. 6, pp.270-290