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Multiprotocol Encapsulation over ATM Adaptation Layer 5 (RFC1483)

IP.com Disclosure Number: IPCOM000002311D
Original Publication Date: 1993-Jul-01
Included in the Prior Art Database: 2000-Sep-12
Document File: 13 page(s) / 33K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

Juha Heinanen: AUTHOR

Abstract

This memo describes two encapsulations methods for carrying network interconnect traffic over ATM AAL5. The first method allows multiplexing of multiple protocols over a single ATM virtual circuit whereas the second method assumes that each protocol is carried over a separate ATM virtual circuit.

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Network Working Group Juha Heinanen

Reguest for Comments: 1483 Telecom Finland

July 1993

Multiprotocol Encapsulation over ATM Adaptation Layer 5

Status of this Memo

This RFC specifies an IAB standards track protocol for the Internet

community, and requests discussion and suggestions for improvements.

Please refer to the current edition of the "IAB Official Protocol

Standards" for the standardization state and status of this protocol.

Distribution of this memo is unlimited.

Abstract

This memo describes two encapsulations methods for carrying network

interconnect traffic over ATM AAL5. The first method allows

multiplexing of multiple protocols over a single ATM virtual circuit

whereas the second method assumes that each protocol is carried over

a separate ATM virtual circuit.

1. Introduction

Asynchronous Transfer Mode (ATM) based networks are of increasing

interest for both local and wide area applications. This memo

describes two different methods for carrying connectionless network

interconnect traffic, routed and bridged Protocol Data Units (PDUs),

over an ATM network. The first method allows multiplexing of

multiple protocols over a single ATM virtual circuit. The protocol

of a carried PDU is identified by prefixing the PDU by an IEEE 802.2

Logical Link Control (LLC) header. This method is in the following

called "LLC Encapsulation" and a subset of it has been earlier

defined for SMDS [1]. The second method does higher-layer protocol

multiplexing implicitly by ATM Virtual Circuits (VCs). It is in the

following called "VC Based Multiplexing".

ATM is a cell based transfer mode that requires variable length user

information to be segmented and reassembled to/from short, fixed

length cells. This memo doesn't specify a new Segmentation And

Reassembly (SAR) method for bridged and routed PDUs. Instead, the

PDUs are carried in the Payload field of Common Part Convergence

Sublayer (CPCS) PDU of ATM Adaptation Layer type 5 (AAL5) [2].

Note that this memo only describes how routed and bridged PDUs are

carried directly over the CPCS of AAL5, i.e., when the Service

Specific Convergence Sublayer (SSCS) of AAL5 is empty. If Frame

Relay Service Specific Convergence Sublayer (FR-SSCS), as defined in

I.36x.1 [3], is used over the CPCS of AAL5, then routed and bridged

PDUs are carried using the NLPID multiplexing method described in RFC

1294 [4]. Appendix A (which is for information only) shows the

format of the FR-SSCS-PDU as well as how IP and CLNP PDUs are

encapsulated over FR-SSCS according to RFC 1294.

2. Selection of the Multiplexing Method

It is envisioned that VC Based Multiplexing will be dominant in

environments where dynamic creation of large numbers of ATM VCs is

fast and economical. These conditions are likely to first prevai...