What is Frame Relay & Its Benifits

What is Frame Relay & Its Benifits

This chapter is on What is Frame Relay & Its Benifits. Frame Relay is an alternative to dedicated WAN leased lines, which are more expensive. This section describes the benefits of Frame Relay. Frame Relay is a high performance WAN protocol that works on the physical and data link layers of the OSI reference model. While more modern services such as broadband and metropolitan Ethernet reduced the need for Frame Relay in many locations, Frame Relay is still a viable option in many sites around the world.

FRAME RELAY TECHNOLOGY

Leased lines provide permanent dedicated capacity and are widely used to build WAN networks. They are the traditional connection of preference, but have a number of disadvantages.
A disadvantage is that customers pay for leased lines with a fixed capacity . However, WAN traffic usually varies, and some of the capacity remains unused. In addition, each terminal needs an individual physical interface on the router, which increases equipment costs. In general, any change in the leased line requires that the staff of the service provider visit the site.
Frame Relay is a high performance WAN protocol that works on the physical and data link layers of the OSI reference model. Unlike leased lines, Frame Relay only requires a single access circuit to the Frame Relay service provider to communicate with other sites connected to the same provider. The capacity between two sites may vary.
Eric Scace, a Sprint International engineer, invented Frame Relay as a simpler version of the X.25 protocol for use through the integrated services digital network (ISDN) interfaces. Currently, it is also used in other types of network interfaces. When Sprint implemented Frame Relay in its public network, it used StrataCom switches. The acquisition of StrataCom by Cisco in 1996 marked its entry into the market of service providers.

FRAME RELAY USEs

Network service providers implement Frame Relay to support voice and data traffic between LAN networks through a WAN. Each end user obtains a private line, or a leased line, to a Frame Relay node.
The Frame Relay network handles transmission through a frequently changing route, transparent to all end users. As shown in Image, Frame Relay provides a solution to allow communications between several sites through a single access circuit to the provider.

Historically, Frame Relay was widely used as a WAN protocol because it was economical compared to dedicated leased lines. In addition, configuring the user's equipment in a Frame Relay network is very simple.
Frame Relay connections are created by configuring the routers or other devices on the client's local computer (CPE) so that they communicate with a Frame Relay switch from a service provider. The service provider configures the Frame Relay switch, which minimizes the configuration tasks of the end user.

BENEFITS OF FRAME RELAY WAN TECHNOLOGY

With the advent of broadband services such as DSL and cable modem, Ethernet WAN, VPN and multi-protocol tag switching (MPLS), Frame Relay became a less suitable solution to access the WAN. However, there are still sites in the world that rely on Frame Relay to get connectivity to the WAN.
Frame Relay provides more bandwidth, reliability and resistance than private or leased lines.
Using an example of a large business network helps illustrate the benefits of using a Frame Relay WAN . In the example shown in Image, the SPAN Engineering company has five campuses throughout North America. Like most organizations, SPAN has various bandwidth requirements.

The first thing to keep in mind is the bandwidth requirement of each site . When working in the head office, connecting Chicago to New York requires a maximum speed of 256 kb / s. Three other sites need a maximum speed of 48 kb / s to connect to the central office, while the connection between the New York and Dallas branches requires only 12 kb / s.

REQUIREMENTS OF THE DEDICATED LINE

Through the leased lines, each of the SPAN sites is connected through a switch in the central office (CO) of the local telephone company through the local loop, and then through the entire network.
The Chicago and New York sites use a dedicated T1 line (equivalent to 24 DS0 channels) to connect to the switch, while other sites use ISDN connections (56 kb / s), as shown in Image 3.

Because the Dallas site connects to New York and Chicago, it has two locally leased lines. Network service providers provide SPAN with a DS0 between the respective COs, except for the largest pipeline that connects Chicago and New York, and has four DS0s.
The DS0 have different prices according to the region and are generally offered at a fixed price. These lines are really dedicated, since the network service provider reserves that line for SPAN exclusive use. There is no sharing, and SPAN pays for the end-to-end circuit, regardless of how much bandwidth it uses.

DISADVANTAGES OF DEDICATED LINES

A dedicated line provides few practical opportunities to establish a one-to-many connection without obtaining more lines from the network service provider. In the example, almost all communication must flow through the company's headquarters, simply to reduce the cost of additional lines.

• After a more detailed analysis of the bandwidth requirements for each site, it is verified that there is a lack of efficiency:
• Of the 24 DS0 channels available on the T1 connection, the Chicago site uses only seven. Some service providers offer fractional T1 connections in increments of 64 kb / s, but this requires a specialized device called a “multiplexer” at the client end to channel the signals. In this case, SPAN opted for the full T1 service.
• Similarly, the New York site uses only five of its 24 available DS0s.
• Because Dallas must connect to Chicago and New York, there are two lines that connect to each site through the CO.

The leased line design also limits flexibility. Unless the circuits are already installed, connecting new sites usually requires new circuit installations, and implementing it takes a long time. From the point of view of network reliability, imagine the additional costs in money and the complexity of adding redundant replacement circuits.

PROFITABILITY AND FLEXIBILITY OF FRAME RELAY

The SPAN Frame Relay network uses permanent virtual circuits (PVC), as shown in following image.

A PVC is the logical path along a source Frame Relay link, through the network and along a Frame Relay termination link to its final destination. Compare this to the physical path that a dedicated connection uses.
In a network with access through Frame Relay, a PVC defines the route between two terminals exclusively. The concept of virtual circuits (VC) is discussed in more detail later in this section.
SPAN Frame Relay solution provides flexibility and profitability.

FRAME RELAY PROFITABILITY

Frame Relay is a more profitable option for two reasons.

• First, with dedicated lines, customers pay for an end-to-end connection that includes the local loop and network link. With Frame Relay, customers only pay for the local loop and acquire the bandwidth of the network service provider.

The distance between the nodes is not important. In a dedicated line model, customers use dedicated lines provided in increments of 64 kb / s, and Frame Relay customers can define their virtual circuit needs with much greater granularity, often in increments as small as 4 kb / s.

• The second reason for the profitability of Frame Relay is that it shares bandwidth through a larger customer base. Generally, a network service provider can serve 40 or more clients of 56 kb / s through a T1 circuit.

The use of dedicated lines would require more CSU / DSU (one for each line), as well as more complicated routing and switching. Network service providers save because there is less equipment to acquire and maintain.

THE FLEXIBILITY OF FRAME RELAY

A virtual circuit provides considerable flexibility in network design. By analyzing the illustration, you can see that all SPAN offices connect to the Frame Relay cloud through their respective local loops. At the moment, what happens in the cloud is really not of interest.
The only thing that matters is that when any SPAN office wishes to communicate with any other SPAN office, all it has to do is connect to a virtual circuit that leads to the other office.
In Frame Relay, the end of each connection has a number to identify it called " data link connection identifier " (DLCI). Any station can connect to any other by simply indicating the address of that station and the DLCI number of the line to be used.
In a later section, you will learn that when Frame Relay is configured, all data from all configured DLCIs flow through the same router port. Imagine the same flexibility through dedicated lines. Not only is it difficult, but it also requires many more equipment.