What is Frame Relay?

Frame Relay is a network protocol based on packet switching technology offered by telephone companies and uses a high-performance and efficient link-oriented data link technology to send data over the public network.

What is Frame Relay?

Frame Relay Network

Frame Relay network is a network service specially designed to use and interconnect the needs of remote LAN networks.

This corporate network service allows different channels to share a single transmission line and increases the efficiency of networks thanks to its ability to transmit large volumes of traffic in short periods of time.

Frame Relay runs on layer 2 of the OSI model and transmits structured information in frames. It is also a transport service that can support multiple protocols and applications corresponding to various customer communication media.

Thanks to the multi-protocol structure of this network structure, the development of standards for voice transmission over the frame has also been achieved.

Although Frame Relay is a cost-effective technology for telecommunications companies to transmit data over long distances, the uses of this technology have decreased as companies move their applications to other IP-based solutions.

ATM technology differs significantly from Frame Relay and requires more expensive hardware using fixed-length packets instead of variable length packets.


Frame Relay reduces the complexity in the network and multiple virtual selections share the same access line. Provides direct switch between locations with latency in the network with improved performance and response time.

Network connections can be automatically redirected to another location when an error occurs. Network environment based QoS (Quality of Service) procedures can be used.

Pricing is not made based on the distance of corporate networks. Connections are defined by programs, and changes made to the network are faster and cheaper than other services.

It offers higher speed and performance thanks to the bandwidth efficiency of multiple virtual circuits sharing a single line port. Since this network technology is a reliable and high performance, it is an inexpensive method of sending data.

It is also ideal for users who need a medium or high-speed connection to keep data traffic between multiple and remote locations. It can be used easily on the Internet as it works on physical and data connection layers.

Frame Relay supports the data rates of standard T1 and T3 lines with individual connections up to 56 Kbps and also supports fiber connections up to 2.4 Gb/s.

It is more used as a data link layer technology to route IP datagrams from an IP router through the VC network with an encapsulation function.

It is also a more secure structure as it sends data over a private VC network rather than over the public Internet.

Virtual Circuits

   PVC (Permanent Virtual Circuits)

The PVC virtual circuit provides the same functionality as a leased line where a fixed route is established over the network to predetermined end nodes and is for permanent connections that are intended to be maintained for a long time even if data is not actively transferred.

PVC circuitry saves the bandwidth associated with setting up and disconnecting circuits if certain virtual circuits must always be available.

   SVC (Switched Virtual Circuits)

SVC virtual circuitry connects target nodes and is similar to telephone calls. A CIR (Minimum Committed Flow) is configured for each virtual circuit in each direction of communication.

This CIR configuration refers to the bandwidth guaranteed by the network in case of congestion or saturation of data traffic. Also, since it uses the statistical multiplexing system, the transmission rate can be up to the bandwidth service of the connection between the communication terminal equipment and the network node.

CIR refers to the minimum data rate that the connection should receive under stable conditions, and the difference between the bandwidth of the network link and the CIR is called EIR (Excess Burst).

SVC is dynamically adjusted and stops when the transmission is completed, and they are also used when the data transfer is irregular.

   DLCI (Data-Link Connection Identifier)

DLCI is a value that indicates a PVC or SVC, and DLCIs are important locally. In the extended LMI specification, DLCIs are important globally.

   CIR (Minimum Committed Flow)

CIR is the rate at which a Frame-Relay network accepts to transfer information under normal conditions and is the value measured in bits per second with an average minimum time increment.

   Reverse ARP (Reverse Address Resolution Protocol)

RARP is a method of creating dynamic paths in a network, and one device finds the network address of another device through a virtual circuit.

   LMI (Local Administration Interface)

LMI uses a message mechanism that verifies that the data has been transmitted. It transmits a multicast by sending its native DLCI and multicast DLCI to the network server.

It provides DLCIs with global addressing and a status mechanism that indicates the current state.

   FECN (Forward Explicit Congestion Notification)

FECN is the bit value set to notify the DTE receiving the frame that congestion has occurred on the path from the source to the destination.

   BECN (Backward Explicit Congestion Notification)

BECN is the bit value set on frames moving in the opposite direction of frames encountering a congested route. DTEs that receive frames with the preset BECN bit configure higher-level protocols to take the required flow control actions.

Network Devices

Frame Relay devices are divided into two groups:

1) DTE (Data Terminal Equipment)

It is the customer equipment that terminates the Frame Relay connection.

2) DCE (Data Circuit-Terminating Equipment)

The DCE device is the network equipment owned by the provider of the leased line.


Frame Relay, operating on the second layer of OSI, requiring control and retransmission services that carry highly useful information about the service control information in their frames. In short, there is no level 3 control header as with X.25 network technology.

With this network topology, it is ideal to configure wide area networks. Significant changes to the physical equipment level are not required, and changes in logical equipment at the link level are minimal.

It is sufficient for connecting local networks at medium and long distances and offers excellent performance up to 45 Mbps.

It is a suitable protocol for applications that exchange large volumes of data at high speeds and is particularly suitable for asynchronous data transfer.

Frame Relay networks can transmit voice and data traffic over a line at the same time. While performing this transfer, it uses the Data & Voice service that integrates data communications and voice communications.

This service is done through FRAD (Frame Relay Access Device) on the device installed and configured at the customer’s location.

Since it is an end-to-end service, it manages the customer network, but in the case of private lines, the management function is the customer’s responsibility.

It supports a frame size of 9000 bytes that accommodates and provides frames for all LANs.


It creates variable delays to different users by allowing variable-length frames and due to this variable delays, it is not suitable for sending latency-sensitive data such as real-time video or teleconferencing.

Differences Between Frame Relay and X.25

Frame Relay
Traffic Type
Resource Sharing
Error Detection
Error Recovery
It is suitable for high speed, low latency, heavy traffic handling, end-to-end management, and high connectivity between sites.
It is suitable for low and medium-speed operation and especially centralized networks where many points communicate with a central facility.
It runs on layer 2 of the OSI model.
It runs on layer 3 of the OSI model.
Error Rate
It manages the functionality of the network, error control, flow control, and user terminal equipment.
Because it is designed to work with analog circuits, it has a high rate of transmission errors, making it necessary for the network to use error correction mechanisms.
Speed ​​Limit
64 Kbps/45 Mbps
64 Kbps/2.400 bps
Network Management
By Consumer
By Provider

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