RFC 2107 (rfc2107) - Page 2 of 21
Ascend Tunnel Management Protocol - ATMP
Alternative Format: Original Text Document
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
