Using Frame Relay

Frame Relay - past present and future

frame relay began it's life as a "high speed" interconnection technology and was first marketed as  "the WAN for the LANs". It has come a long way and became the be-all and end-all of networking for many users ( a role that many attribute now to ATM).
Frame relay is being used increasingly for transport of traditional; highly bursty LAN interconnection and for constant bit rate data types such as voice and video.
In addition many high profile networks are adopting frame relay not only as the network interface but as a backbone switching technology.
The main reason for this wide adoption is the simplicity and ubiquity of frame relay which assures low cost.

The following  are some of the issues which the Frame Relay Forum is dealing with now or about to deal with in the near future.

Frame Relay fragmentation: frame relay handles frames of varying lengths. The size but especially the range of possible frame sizes makes the performance of frame relay variable. The more uniform the distribution of frames, the more possible it becomes to predict performances and if the frames are also short, better performances (ATM like), can be achieved. The solution is to provide network based segmentation and reassembly of incoming frames. A frame of any size can be presented to the network for transport. At the edge of the network it can be modified. if the frame is larger than the maximum transfer unit length, it is parsed into two or more shorter frames which are then transmitted through the network, reassembled at the destination and forwarded. In this scenario there is no risk that a single large frame will monopolize the network devices and the performance is more predictable and therefore may be utilized by a wider range of applications.

 
Multilink Frame Relay at the UNI: The majority of frame relay UNI's are 64 kbit/second, however there are still a growing number of sites that require connection at bandwidth greater than 1.5 mbit/second of T1 or 2 mbit/second of E1.  The reason for that is that many 64 kbit/second connections from remote sites are aggregated into a host. The solution to this problem is multilink frame relay UNI's. These are super T1/E1-rate UNI built in increments of T1/E1 that use inverse multiplexing technology to preserve timing and bit alignment and to give the appearance of n*T1 or n*E1 aggregate. Multilink frame relay UNI can be built in increments up a the point that a full T3/E3 is cheaper.
the benefits are :  a multilink UNI is treated as a single UNI connection and it will continue to function even if one or more of the T1/E1 on the UNI fail.

Frame Relay and Multimedia Applications:

multimedia networks are designed to  carry a mixture of information types. Although Frame Relay was intended to carry bursty frame-type data, it recently shows the ability to carry other types of information simultaneously as a part of a multimedia application.

Traditional and bursty data: traditional data includes all forms of computer data that have been carried by leased lines. In many cases it means bursty data and in many other cases it means traffic that is carried by circuits since delay sensitivity and delay variation must be minimized.
As frame relay achieves higher speeds, the delay that will cause  problems for circuit type data will not be a problem and frame relay will find wider utilization.
Increasingly  frame relay users will move traditional leased line connections over to frame relay, and the carriers and service providers will be positioned to handle this type of traffic.

Voice: this is and will continue to be an important traffic type for frame relay. The idea of which network (telephony, frame relay, internet, etc.) carries voice becomes a question of availability, cost and utilization level of the network. Much of the research and development done on internet and intranet voice has direct applicability to frame relay and both areas will continue to flourish.

Image:  Since  images are actually very large files, image application on frame relay networks will benefit from standardized frame fragmentation. with no fragmentation a large frame could monopolize resources and cause delays for other applications. Therefore, in many cases image applications use separate dedicated leased lines or other transport capability besides frame relay service.
improving  image compression technologies together with fragmentation will make image application perform better.

Video:  video is known to be a difficult application for frame relay due to the real time, delay sensitive,  constant bit rate nature of current video transmission techniques. The appearance of real time video compression and use of other technologies has given the video applications (accept the highest bandwidth ones) a  bursty aspect and has improved their sensitivity to delay.
From a transmission point of view, video can be divided into 3 categories:

• High bandwidth  broadcast quality or near broadcast quality real time video- not a very good application.
• real time or near real time video that can be compressed or modified to require a smaller amount of bandwidth. As a result of variations in compression it exhibits a bursty traffic profile and may be multiplexed with other information. This type of video has great promise for use on frame relay and there are  a number of products that use this method.
• Stored video -  in this method  video "clips" are being compressed,  stored and played back across the  network many times. the method  doesn't necessarily require the most powerful compression tool available on the market ( there are many innovative  video compression algorithms but most of them are not usable for real time because they take too much time to perform the compression  )  since the data/image  stored is not needed immediately.

 
Multimedia:   since it is a mixture of information types, multimedia takes into account  all of the information transport issues. The multimedia  nature of the communication enriches it's information content, therefore we will be seeing more multimedia applications using frame relay.