PPP Over AAL5
RFC 2364

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Network Working Group                                           G. Gross
Request for Comments: 2364                           Lucent Technologies
Category: Standards Track                                      M. Kaycee
                                                                Paradyne
                                                                  A. Lin
                                                         Shasta Networks
                                                                A. Malis
                                                   Ascend Communications
                                                             J. Stephens
                                                          Cayman Systems
                                                               July 1998

                             PPP Over AAL5

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 Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

Abstract

   The Point-to-Point Protocol (PPP) [1] provides a standard method for
   transporting multi-protocol datagrams over point-to-point links.

   This document describes the use of ATM Adaptation Layer 5 (AAL5) for
   framing PPP encapsulated packets.

Applicability

   This specification is intended for those implementations which desire
   to use the facilities which are defined for PPP, such as the Link
   Control Protocol, Network-layer Control Protocols, authentication,
   and compression.  These capabilities require a point-to-point
   relationship between the peers, and are not designed for the multi-
   point relationships which are available in ATM and other multi-access
   environments.

Gross, et. al.              Standards Track                     [Page 1]
RFC 2364                     PPP Over AAL5                     July 1998

1. Introduction

   ATM AAL5 protocol is designed to provide virtual connections between
   end stations attached to the same network.  These connections offer a
   packet delivery service that includes error detection, but does not
   do error correction.

   Most existing implementations of PPP use ISO 3309 HDLC as a basis for
   their framing [3].

   When an ATM network is configured with point-to-point connections,
   PPP can use AAL5 as a framing mechanism.

2. Conventions

   The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
   SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
   document, are to be interpreted as described in [10].

3. AAL5 Layer Service Interface

   The PPP layer treats the underlying ATM AAL5 layer service as a bit-
   synchronous point-to-point link.  In this context, the PPP link
   corresponds to an ATM AAL5 virtual connection.  The virtual
   connection MUST be full-duplex, point to point, and it MAY be either
   dedicated (i.e. permanent, set up by provisioning) or switched (set
   up on demand).  In addition, the PPP/AAL5 service interface boundary
   MUST meet the following requirements:

        Interface Format - The PPP/AAL5 layer boundary presents an octet
        service interface to the AAL5 layer.  There is no provision for
        sub-octets to be supplied or accepted.

        Transmission Rate - The PPP layer does not impose any
        restrictions regarding transmission rate or the underlying ATM
        layer traffic descriptor parameters.

        Control Signals - The AAL5 layer MUST provide control signals to
        the PPP layer which indicate when the virtual connection link
        has become connected or disconnected.  These provide the "Up"
        and

        "Down" events to the LCP state machine [1] within the PPP layer.

Gross, et. al.              Standards Track                     [Page 2]
RFC 2364                     PPP Over AAL5                     July 1998

4. Multi-Protocol Encapsulation

   This specification uses the principles, terminology, and frame
   structure described in "Multiprotocol Encapsulation over ATM
   Adaptation Layer 5" [4].

   The purpose of this specification is not to document what is already
   standardized in [4], but to specify how the mechanisms described in
   [4] are to be used to map PPP onto an AAL5-based  ATM network.
   Section 1 within [4] defines the two mechanisms for identifying the
   Protocol Data Unit (PDU) payload field's protocol type: virtual
   circuit based multiplexing, and Logical Link Control (LLC)
   encapsulation.  In the former technique, the payload's protocol type
   is implicitly agreed to by the end points for each virtual circuit
   using provisioning or control plane procedures.  When using the LLC