frame relay explained

Frame relay is a packet-switching telecommunication service designed for interconnecting enterprise LANs. Being a student of networking, it is important that you know about all the emerging WAN technologies. To stay up-to-date with emerging and developing technologies, you may know the following alternate options available for WAN connectivity.

• Frame Relay
• Broadband DSL
• Broadband cable modem
• GigaMAN
• VPN
• MPLS

WAN technologies are constantly developing to keep pace with the network demands of today and those of tomorrow. Each network administrator wants to offer the best quality, low-cost WAN network services for their companies. So, it should be your aim to gather information about these alternate WAN options to intelligently discuss the future goals of your network with your business manager and other network administrators.

Frame Relay is a layer2 non-broadcast multiaccess (NBMA) WAN technology. It allows for a single serial interface on the router to connect multiple remote sites with the help of permanent virtual circuits (PVCs) or switched virtual circuits (SVCs).

Frame Relay uses X.25 protocol across Integrated Services Digital Network (ISDN) interfaces as well as with other network interfaces. Network providers apply Frame Relay to support voice and data traffic between LANs over a WAN.

Each end-user gets a leased line, to a Frame Relay node. The Frame Relay deals with the transmission over a repeatedly changing path transparent to all end users. Frame relay is also the solution to permit the communications between multiple sites using a single access circuit to the provider. The figure below illustrates the Frame relay network.

Basically, Frame Relay is a low-cost WAN protocol as compared to committed leased lines. Equipment configuration in a Frame Relay network is very simple and easy. Frame Relay connections are contained customer premise equipment (CPE) routers or Data Communication Equipment (DCE) i.e. switches and modems.

PVCs have dedicated connection without having to pay for a full-time leased line, but the service provider can monitor each frame travels to its destination and can charge based on usage. PVCs can bring both voice and data traffic between a source and destination, and support data rates up to 4 Mb/s, with some providers offering higher data speed.

A customer can select a level of service quality, for example, they can prioritize some traffic and can make some traffic less important. Frame relay create switched virtual circuit (SVCs) when data is available for sending and then close these SVCs when there is no more data available for sending.

Data-link Connection Identifier (DLCI)

Data-link connection identifier (DLCI) is used to uniquely identify the frame relay PVCs. PVC and DLCI both are responsible for bidirectional communication from DTE to another device. DLCI may be the router configured with frame relay or provided by the service provider in both cases, the endpoints are configured as DLCI number to identify uniquely. DLCI number is necessary on both sides of the frame relay as the source and destination.

Frame Relay Devices

It is used, Data Terminal Equipment (DTE) and Data Circuit terminating Equipment (DCE) for data transmission. this is usually the customer’s side equipment and can include routers, bridges, and personal computers. DCEs are service provider side equipment providing switching and associated services.

Advantages and Disadvantages

At the presence of broadband services such as DSL and cable modem, Ethernet WAN, VPN, and MPLS, Frame Relay is no famous solution for accessing the WAN. But, there is still the importance of the Frame Relay for connectivity to the WAN. Frame Relay provides better bandwidth, reliability, and resiliency than private or leased lines.

Advantages

• Cost Savings: Cost saving is the first advantage of Frame Relay over other WAN technologies. It offers a low cost of physical local loops over a private line network as the frame uses a virtual circuit (VCs) for each new connection
• Higher circuit utilization: FrameRelay uses a physical circuit by statistically multiplexing multiple PVCs over a single physical circuit, that increased circuit utilization.
• Higher network availability: FrameRelay network switches support automatic routing of PVC around in case of failure, which improves network availability.
• Extended Technology Life Duration: Back-word compatibility is another advantage of Frame Relay that make possible communication with older technologies such as X.25 and forward compatible with newer technologies like ATM and MPLs
• Networks Overhead: FrameRelay network overhead is less due to the incorporation of a congestion control mechanism.
• Protocol Independence: FrameRelay allows a frame size of 9000 bytes which is enough for all the frame types therefore it supports a wide variety of application transports and meets the throughput requirements.
• Performance: FrameRelay services offer higher speed with lower delay as compared to X.25
• Security: FrameRelay provides a secure connection because it is difficult to break into PVCs between the sites.

Disadvantages

• The FrameRelay does not provide flow control and error control. This should be taken care of by upper-layer protocols.
• The FrameRelay provides a 44.736 Mbps data rate which is not enough for protocols with higher data rates
• It creates varying delays for different users, therefore it is not suitable to send sensitive data like real-time voice or video.
• Not suitable for sending delay-sensitive data such as real; time voice or video or teleconferencing.
• It is more expensive compare to internet service.
• It involves data overhead and processing overhead with every packet.