Multiprotocol Encapsulation over ATM Adaptation Layer 5 (RFC2684)
Original Publication Date: 1999-Sep-01
Included in the Prior Art Database: 2019-Feb-11
Internet Society Requests For Comment (RFCs)
D. Grossman: AUTHOR [+1]
This memo replaces RFC 1483. It describes two encapsulations methods for carrying network interconnect traffic over AAL type 5 over ATM. [STANDARDS-TRACK]
Network Working Group D. Grossman Request for Comments: 2684 Motorola, Inc. Obsoletes: 1483 J. Heinanen Category: Standards Track Telia September 1999
Multiprotocol Encapsulation over ATM Adaptation Layer 5
Status of this Memo
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
Copyright (C) The Internet Society (1999). All Rights Reserved.
This memo replaces RFC 1483. It describes two encapsulations methods for carrying network interconnect traffic over AAL type 5 over ATM. The first method allows multiplexing of multiple protocols over a single ATM virtual connection whereas the second method assumes that each protocol is carried over a separate ATM virtual connection.
This specification is intended to be used in implementations which use ATM networks to carry multiprotocol traffic among hosts, routers and bridges which are ATM end systems.
Asynchronous Transfer Mode (ATM) wide area, campus and local area networks are used to transport IP datagrams and other connectionless traffic between hosts, routers, bridges and other networking devices. This memo describes two methods for carrying connectionless routed and bridged Protocol Data Units (PDUs) over an ATM network. The "LLC Encapsulation" method allows multiplexing of multiple protocols over a single ATM virtual connection (VC). The protocol type of each PDU is identified by a prefixed IEEE 802.2 Logical Link Control (LLC) header. In the "VC Multiplexing" method, each ATM VC carries PDUs of exactly one protocol type. When multiple protocols need to be transported, there is a separate VC for each.
Grossman & Heinanen Standards Track [Page 1]
RFC 2684 Multiprotocol Over AALS September 1999
The unit of transport in ATM is a 53 octet fixed length PDU called a cell. A cell consists of a 5 octet header and a 48 byte payload. Variable length PDUs, including those addressed in this memo, must be segmented by the transmitter to fit into the 48 octet ATM cell payload, and reassembled by the receiver. This memo specifies the use of the ATM Adaptation Layer type 5 (AAL5), as defined in ITU-T Recommendation I.363.5  for this purpose. Variable length PDUs are carried in the Payload field of the AAL5 Common Part Convergence Sublayer (CPCS) PDU.
This memo only describes how routed and bridged PDUs are carried directly over the AAL5 CPCS, i.e., when the Service Specific Convergence Sublayer (SSCS) of AAL5 is absent. If Frame Relay Service Specific Convergence Sublayer (FR-SSCS), as defined in ITU-T Recommendation I.365.1 , is used over the CPCS, then routed and bridged PDUs are carried using the NLPID multiplexing method described in RFC 2427 . The RFC 2427 encaps...