Context Transfer, Handoff Candidate Discovery, and Dormant Mode Host Alerting

Document Charter Context Transfer, Handoff Candidate Discovery, and Dormant Mode Host Alerting WG (seamoby)
Title Context Transfer, Handoff Candidate Discovery, and Dormant Mode Host Alerting
Last updated 2004-10-04
State Approved
WG State Concluded
IESG Responsible AD (None)
Charter Edit AD (None)
Send notices to (None)


During the fast handoff discussions within the Mobile IP WG, a need for 
a new protocol was identified that would allow state information to be 
transferred between edge mobility devices. Examples of state 
that could be useful to transfer is AAA information, security context, 
QOS properties assigned to the user, Robust Header Compression 
information, etc.

Further, Standards Defining Organizations (SDOs) that work on wireless,
such as 3GPP, 3GPP2, IEEE and others, are hoping that the IETF will be 
able to provide a set of protocols that will enable them to provide 
real-time services over an IP infrastructure, and, along with Mobile
IP, SeaMoby is expected to provide such protocols. Furthermore, the 
protocols developed by the Seamoby Working Group must allow for 
real-time services to work with minimal disruption across heterogeneous 
wireless, and wired, technologies.

It is expected that SDOs working on wireless technologies will provide 
their input into the WG during the requirements gathering and protocol 
design phase.

In addition to Context Transfer, the working group has identified two 
more technologies that are important for use as tools for providing 
real-time services over IP wireless infrastructure:  Handoff Candidate 
Discovery and Dormant Mode Host Alerting (aka "IP paging"). Another 
technology, micro-mobility, in which routing occurs without the Mobile 
IP address change, was determined by WG discussions to require
research; it has been removed by the present rechartering and the topic 
has been addressed to the IRTF Routing Research Group. The present 
charter (revised from its original form) is to define and then possibly 
develop the three technologies.  The WG will ensure that its 
deliverables are compatible with the Mobile IP Working Group's mobility 
management technology.

Context Transfer

There are a large number of IP access networks that support mobility of 
hosts. For example, wireless Personal Area Networks (PANs) and LANs, 
satellite and cellular WANs. The nature of this roaming is such that 
communication path to the host changes frequently, and rapidly. In many 
situations, the chage of communications path includes a change in 
communications media between the host and access networking, including 
changes from a wireless to a wired connection and changes between 
wireless technologies even under common administration.

Although the protocol used to actively re-direct the IP packet flows 
during a change in a mobile's point of attachment is handled by the 
Mobile IP WG, there is a need for preserving the context of its active 
IP flows. The IP flow context that might be useful to transfer could 
include, but not be limited to security context, policy, QOS (diffserv 
or intserv as needed) header compression, and accounting/AAA 

The SeaMoby Working group will analyze the requirements and tradeoffs 
for the goal of transferring context information from a mobile's old 
access to the new access device. Depending on the results of the 
requirements analysis, the SeaMoby WG will develop a protocol (or start 
from an existing protocol such as Contract Net Protocol (CNP) or the 
IEEE's 802.11f) to transfer the context information for a session.

Handoff Candidate Discovery

Second, while the Mobile IP Working Group in particular is developing
protocols to provide "fast handoff" solutions, the mechanisms
currently under development assume that a set of candidates has
already been chosen and and that handoff should be initiated to all of
them. However, the selection of suitable candidates is not part of the
Mobile IP WG's overall scope.  The Seamoby Working Group has
documented that "seamless" handoffs can best be achieved by
considering multiple handoff candidates and selecting one or more of
them as targets for context transfer. This problem is within scope of
Seamoby. Specifically, Seamoby will define the work in a problem
statement, and if needed, will define the requirements and the
protocol for a handoff candidate discovery protocol, which could be
used with any mobility management protocol.

Dormant Mode Host Alerting

Third, the Working Group will define the requirements for Dormant Mode 
Host Alerting (DMHA) at the IP layer (also known as IP Paging) in 
networks, and a protocol will be developed to tackle this problem. DMHA 
is typically used in networks that support mobile devices that 
periodically enter dormant mode to reduce power consumption. DMHA 
network devices to track a mobile that has moved from its last point of 
attachment, while in dormant mode, allowing the mobile's packets to be 

All work produced by the Working Group will support both IPv4 and IPv6, 
will follow the congestion control principles in RFC2914 (BCP41), and 
will undergo a security review prior to WG last call. Protocols 
developed will be accompanied by MIBs.

The Working Group will coordinate closely with the aaa, mobileip, pilc, 
and rohc working groups.