Multiprotocol Encapsulation over ATM Adaptation Layer 5 (RFC2684)
Original Publication Date: 1999-Sep-01
Included in the Prior Art Database: 2000-Sep-13
Internet Society Requests For Comment (RFCs)
D. Grossman: AUTHOR [+2]
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.
Network Working Group D. Grossman
Request for Comments: 2684 Motorola, Inc.
Obsoletes: 1483 J. Heinanen
Category: Standards Track Telia
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.
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-SS...