Frame Relay Protocol Architecture

Frame Relay Protocol Architecture

Figure shows the protocol architecture to support the frame-mode bearer service.
We need to consider two separate planes of operation,

(1) Control Plane (2) User Plane

CONTROL PLANE:

A Control plane is involved in the establishment and termination of logical connection. The control plane for frame is similar for CCS( common channel signaling) for circuit switching services. At data link layer LAPD is used to provide a reliable data link control services with error control and frame control between user and network.

USER PLANE:

A user plane is responsible for transfer of user data between subscriber.User plane protocol provides end-to-end functionality. For the actual transfer of information between end users, the user-plane protocol is
LAPF (Link Access Procedure for Frame-Mode Bearer Services), which is defined
in Q.922. Q.922 is an enhanced version of LAPD (Q.921). Only the core functions
of LAPF are used for frame relay:

• Frame delimiting, alignment, and transparency
• Frame multiplexing/demultiplexing using the address field
• 0 Inspection of the frame to ensure that it consists of an integral number of
• octets prior to zero-bit insertion or following zero-bit extraction
• Inspection of the frame to ensure that it is neither too long nor too short
• Detection of transmission errors
• Congestion control functions