Interworking between Frame Relay Bearer service(FRBS) and ATM: The following issues are to be taken into account to achieve interworking between FRBS and ATM. 1) Needs proper mapping of frame relaying loss priority and congestion control indications. 2) Requires procedures of negotiation for frame relaying frame size. 3) Able to provide message-mode unassured operation without flow control. 4) Able to transfer user data immediately upon the establishment of the connection using AAL parameter negotiation procedures.
Frame relay service and Cell relay service(ATM) can be compared quickly by using the following table.
Interworking Requirements:The following is the interworking arrangement between FRBS and B-ISDN Class C, message mode, non- assured operation. For Interworking in the C(Control) plane, Call Control mapping is provided in such a way that U(User)-plane connections are made and released in both interworking networks, with interconnection in the interworking function. C-Plane procedures must provide for the negotiation of U-Plane parameters like throughput, max. frame size etc. The mapping between frame relay and B-ISDN traffic descriptors are to be standardized. For Interworking in the U plane, there are two sets of service conditions for interworking the B-ISDN Class C services(message mode, unassured operation) and FRBS which are 1) B-ISDN directly supports FRBS and 2) B-ISDN supports Cell Relay Service (CRS) which can interwork with FRBS.
To know how IP can be supported over ATM, You can click here IP over ATM
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