RFC 2107 (rfc2107) - Page 2 of 21

Ascend Tunnel Management Protocol - ATMP

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