WAN Service
The Frame Relay service provides for a cost-efficient way to transmit intermittent data between the LAN Network or between two endpoints of a WAN. The Frame Relay service uses Virtual Circuits, which are logical paths between source and destination, for data transmission (Protocols.com, 2009). In the lines below a justification is given for choosing Frame Relay Service over X.25 and ATM.
Reasons for Choosing Frame Relay over X.25 Networks
Frame Relay provides an attractive alternative to X.25 when it comes to transmitting data over current WAN networks. The first reason for choosing Frame Relay over X.25 is that X.25 was designed for transportation of data over high error rate links Frame Relay, on the other hand, takes advantage of the improved reliability of the communication lines and the increased error handling capability of end devices and does away with several services present in X.25 network including the time-consuming error handling service, hence it offers speeds which are up to 20 times faster than X.25 Networks (Data Connect Enterprise, 2009). The second reason is that Frame Relay is a Layer 2 Network while X.25 is a layer three network which also makes Frame Relay faster and thus preferable (Solution. pro, 2009). The round trip delay time of X.25 networks is also much higher than Frame Relay and only allows for static bandwidth allocation, contrary to Frame Relay networks which permit the dynamic allocation of the bandwidth (Wang, 2002 p.37). X.25 circuits, however, offer an advantage over Frame Relay, as they do allow for their initiation and termination from user terminals in contrast to Frame Relay circuits which can only be set up at the time of installation. This advantage, however, is not very useful in WAN configuration ( Data Comm for Business, 2009) and we have chosen to give less weight to it thus preferring Frame Relay over X.25.
Reasons for Choosing Frame Relay over Asynchronous Transfer Mode (ATM) Networks
Asynchronous Transfer Mode or ATM standard was released after X.25 and Frame Relay and offers several advantages and some major disadvantages over Frame Relay. ATM has been designed to handle data as well as video and voice traffic in real-time, which can occur at the same time (TechFAQ, 2009). The First advantage of ATM is that it can emulate direct circuits between source and destination and can guarantee bandwidth for connections, a feature that lacks in frame relay, and one of the main reasons for choosing ATM over Frame Relay. ATM also allows for flexible bandwidth allocation which can go from few megabytes up to gigabytes (Exforsys Inc., 2009). However, ATM does have a disadvantage because of its large header size, which is about 10% of the basic unit of ATM transport, a Cell. Although both offer similar features such as burst rate features, congestion avoidance techniques, and traffic shaping strategies (TechFAQ, 2009), ATM networks are not able to compete with Frame Relay, despite added advantages, when it comes to implementation on WANs. The biggest reason for this is WANs are usually characterized by high-speed data transfers Committed Information Rate (CIR) and Excessive Information Rate (EIR) hence ATM networks do not offer much advantage over Frame Relay on WANs. Another thing that was considered when comparison was done between ATM and Frame Relay was that since ATM is a newer technology and offers much more than Frame Relay in other features, the equipment which is used to deploy them is very expensive as compare to Frame Relay (Greene, 2007). This was an important factor in our decision as Frame Relay is much more cost-effective to implement here than ATM.
References
Data Comm for Business. (2009). Frame Relay: An Overview. Web.
Data Connect Enterprise. (2009). Frame Relay and X.25. Web.
Exforsys Inc. (2009). Asynchronous Transfer Mode (ATM) Switching. Web.
Greene, T. (2007). Frame Relay vs ATM.
Protocols.com. (2009). Frame Relay.
Solution.pro. (2009). Configuring Frame-Relay on Cisco 2520/2522 Router.
TechFAQ. (2009). Understanding Frame Relay.
TechFAQ. (2009). What is ATM? We
Wang, H. (2002). Pocket Mobile Broadband Handbook. McGraw-Hill Professional.