RFC 3374 (rfc3374) - Page 3 of 14

Problem Description: Reasons For Performing Context Transfers Between Nodes in an IP Access Network

RFC 3374           Context Transfer Problem Statement     September 2002


   exchanges.  If the host is required to re-establish those services by
   the same process as it uses to initially establish them, delay-
   sensitive real time traffic may be seriously impacted.

   An alternative is to transfer enough information on the context
   transfer-candidate service state, or context, to the new subnet so
   that the services can be re-established quickly, rather than require
   the mobile host to establish them from scratch.  The transfer of
   service context may be advantageous in minimizing the impact of host
   mobility on, for example, AAA, header compression, QoS, policy, and
   possibly sub-IP protocols and services such as PPP.  Context transfer
   at a minimum can be used to replicate the configuration information
   needed to establish the respective protocols and services.  In
   addition, it may also provide the capability to replicate state
   information, allowing stateful protocols and services at the new node
   to be activated along the new path with less delay and less signaling
   overhead.

   In this document, a case is made for why the Seamoby Working Group
   should investigate context transfer.

2.0 Reference Definitions

   Context

      The information on the current state of a service required to re-
      establish the service on a new subnet without having to perform
      the entire protocol exchange with the mobile host from scratch.

   Context Transfer

      The movement of context from one router or other network entity to
      another as a means of re-establishing specific services on a new
      subnet or collection of subnets.

   Context Transfer Candidate Service

      A service that is a candidate for context transfer.  In this
      document, only services that are concerned with the forwarding
      treatment of packets, such as QoS and security, or involve
      granting or denying the mobile host access to the network, such as
      AAA, are considered to be context transfer-candidate services.

3.0 Scope of the Context Transfer Problem

   The context transfer problem examined in this document is restricted
   to re-establishing services for a mobile host that are, in some
   sense, related to the forwarding treatment of the mobile host's



Kempf                        Informational