Ascend Tunnel Management Protocol - ATMP
RFC 2107

Document Type RFC - Informational (February 1997; No errata)
Was draft-rfced-info-hamzeh (individual)
Last updated 2013-03-02
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Network Working Group                                          K. Hamzeh
Request for Comments: 2107                         Ascend Communications
Category: Informational                                    February 1997

                Ascend Tunnel Management Protocol - ATMP

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

IESG Note:

   This note documents a private protocol for tunnel management.  This
   protocol is NOT the product of an IETF working group nor is it a
   standards track document. There is ongoing effort in an IETF working
   group which could result in a standards track document which
   specifies a protocol which provides similar functionality.

Abstract

   This document specifies a generic tunnel management protocol that
   allows remote dial-in users to access their home network as if they
   were directly attached to the home network.  The user's client
   software uses an address contained in the home network address space
   for the remote access.  Packets to and from the home network are
   tunneled by the Network Access Server (NAS) to which the user
   connects and a Home Agent (HA) on the user's home network.  This
   allows for the support of access to Virtual Private Networks and also
   allows for the use of protocols other than IP to be carried over the
   tunnel.  An example of how the RADIUS (Remote Authentication Dial In
   User Service) can be used to provide the necessary configuration
   information to support this service is also provided.

1. Introduction

   The Ascend Tunnel Management Protocol (ATMP) is a protocol currently
   being used in Ascend Communication products to allow dial-in client
   software to obtain virtual presence on a user's home network from
   remote locations.  A user calls into a remote NAS but, instead of
   using an address belonging to a network directly supported by the
   NAS, the client software uses an address belonging to the user's
   "Home Network".  This address can be either provided by the client
   software or assigned from a pool of addresses from the Home Network
   address space.  In either case, this address belongs to the Home
   Network and therefore special routing considerations are required in

Hamzeh                       Informational                      [Page 1]
RFC 2107                          ATMP                     February 1997

   order to route packets to and from these clients.  A tunnel between
   the NAS and a special "Home Agent" (HA) located on the Home Network
   is used to carry data to and from the client.

   ATMP currently allows for both IP and IPX protocols to be tunneled
   between the NAS and the HA.  The protocol to be used, the HA to use,
   and other user specific information is provided by some configuration
   mechanism that is beyond the scope of this document.  Appendix A
   illustrates how RADIUS [5] is used to convey this information to the
   NAS.

   The determination of the Home Network address to be used can be
   accomplished in different ways.  It could, for example, be configured
   in the client and negotiated by IPCP (or IPXCP).  Alternatively, it
   could be defined to be an address specific to the given user ID, or
   it could be assigned from a pool of addresses provided by the Home
   Network for the purpose of remote dial-in access.  Again, how this
   address is assigned and how the NAS decides to invoke ATMP for a
   specific call is beyond the scope of this document.

1.1 Protocol Goals and Assumptions

   The ATMP protocol is implemented only by the NAS and HA.  No other
   systems need to be aware of ATMP.  All other systems communicate in
   the normal manner and are unaware that they may be communicating with
   remote clients.  The clients themselves are unaware of ATMP.  It is
   assumed that standard PPP [8] (or SLIP) clients are being used.

   Unlike the mobile-IP protocol [3], ATMP assumes that a single NAS
   will provide the physical connection to a remote client for the
   duration of the session.  The client will not switch between NASes
   expecting to keep the same IP address and all associated sessions
   active during these transitions.  A particular client can be
   registered with a given HA only once at any given time.
   Deregistration with a HA implies loss of all higher layer sessions
   for that client.

   IP multicasting is currently not provided by ATMP.

1.2 Terminology

   The terminology used in this document is similar to that used in
   mobile-IP.  As pointed out in the previous section, however, ATMP
   provides a subset of the functionality provided by mobile-IP and the
   meanings of the various terms used herein have been modified
   accordingly.

Hamzeh                       Informational                      [Page 2]
RFC 2107                          ATMP                     February 1997
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