Integrated Services Digital Network (ISDN); Digital Subscriber Signalling System No. One (DSS1) Protocol; Data Link Layer; Part 3: Frame Relay Protocol Specification
"This third part of ETS 300 402 specifies the frame structure@ elements of procedure@ format of fields and procedures for the proper operation of the Frame Relay layer 2 protocol as described in the service description ETS 300 399-1 [1]. NOTE 1: The Frame Relay protocol as defined in this ETS may be used with or without the elements of procedures of Link Access Procedure for Frame mode bearer services (LAPF) in CCITT Recommendation Q.922 [8]. LAPF as defined in CCITT Recommendation Q.922 [8] designates the link access procedures applicable to@ but not restricted to@ the Frame Relay service. The protocol specified in this ETS is a subset of LAPF; it is named ""Data Link Core protocol"" (DL-CORE) and it is used to support the Frame Relay service. It is intended to: - share the core functions of LAPF as defined in ITU-T Recommendation I.233 [5]; - be used on B- or D-channel or n ?? 64 kbit/s; and - operate on the D-channel simultaneously with the Link Access Procedure on the D-channel (LAPD) protocol as defined in ITU-T Recommendations Q.920 and Q.921 as modified by ETS 300 402-1 [2] and ETS 300 402-2 [3]. It assumes that data link identification is determined via group signalling or by prior agreement. NOTE 2: Group signalling is defined in appendix II of CCITT Recommendation Q.922 [8]. The functions of DL-CORE@ used to support the Frame Relay service@ are considered to be: - frame delimiting@ alignment and transparency; - frame multiplexing/demultiplexing using the address field; - 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 (but not recovery from) transmission errors; and - congestion control functions."