Mobile IPv6 specifies routing support to permit IP hosts using IPv6 to
move between IP subnetworks while maintaining session continuity. 
Mobile IPv6 supports transparency above the IP layer, including 
maintenance of active TCP connections and UDP port bindings.

To accomplish this, the mobile node notifies its home agent (and 
potentially also its correspondent nodes) of the current binding 
between its home address and its care of address. This binding allows 
a 
mobile node to maintain connectivity with the Internet as it moves 
between subnets.

Depending on what steps a mobile node must perform on a new subnet, the
lag between when the mobile node has layer 2 connectivity and when it
begins sending and receiving packets on the new link may be
substantial. A mobile node must first detect at layer 3 that its point
of attachment has changed, then it must perform configuration on the
new link, including router discovery and configuring a new care of
address. After that, the mobile node must perform binding updates with
the home address and any correspondent nodes. Since many layer 2
mobility technologies require that the mobile node drop its link
connectivity to the old subnet when moving, any packets between the
correspondent node and the mobile node sent or in-flight during this
time arrive at the old care of address, where they are dropped. Such
packet loss may have significant adverse effects.

The Mobile IP Working group had previously been developing two
technologies to address the issues of signaling overhead and handoff
latency/packet loss:

  - Hierarchical Mobile IPv6 mobility management (HMIPv6)

      HMIPv6 deals with reducing the amount and latency of signaling
      between a MN, its Home Agent and one or more correspondents by
      introducing the Mobility Anchor Point (MAP) (a special node
      located in the network visited by the mobile node). The MAP acts 
      somewhat like a local home agent for the visiting mobile node by
      limiting the amount of signaling required outside the MAP's 
      domain.

  - Fast Handovers for Mobile IPv6 (FMIPv6)

      FMIPv6 reduces packet loss by providing fast IP connectivity as
      soon as a new link is established. It does so by fixing up the
      routing during link configuration and binding update, so that
      packets delivered to the old care of address are forwarded to the
      new. In addition, FMIPv6 provides support for preconfiguration of
      link information (such as the subnet prefix) in the new subnet
      while the mobile node is still attached to the old subnet. This
      reduces the amount of preconfiguration time in the new subnet.

These two technologies can be used separately or together to reduce or
eliminate signaling overhead and packet loss due to handoff delays in
Mobile IPv6.

Scope of MIPSHOP:

The MIPSHOP Working Group will complete the FMIPv6 and HMIPv6 work
begun in the Mobile IP Working Group. Specifically, the WG will:

1) Complete the specification of HMIPv6 protocol.

2) Complete the specification of FMIPv6 protocol.

Because work (ongoing or originating) in other working groups may
suggest changes or alternative designs for HMIPv6 and FMIPv6, these
specifications will be advanced as Experimental RFCs until more
experience is obtained with IP mobility in IPv6.

3) Complete work on a set of requirements for "Localized Mobility
   Management (LMM)", whereby a Mobile Node is able to continue
   receiving packets in a new subnet before the corresponding changes
   in either the Home Agent or Correspondent Node binding. It is the
   intention that the requirements be consistent with the FMIPv6 and
   HMIPv6 protocols; in the event that there are inconsistencies, they
   will be documented.

4) Complete work on the applicability of FMIPv6 in the specific case
   of 802.11 networks for advancement as Informational RFC.

There are security issues that arise because of the highly dynamic
nature of the security relationships between, say, a mobile node and
its mobility anchor points, or between a mobile node and its access
routers in a fast handover scenario. The working group is not required
to provide solutions to all these issues before publishing its
experimental and informational protocols. The working group will
document the security requirements and the shortcomings of the
solutions in the corresponding protocol specifications. This will
provide valuable feedback to other groups or subsequent efforts.