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2.8.2 Context Transfer, Handoff Candidate Discovery, and Dormant Mode Host Alerting (seamoby)

NOTE: This charter is a snapshot of the 55th IETF Meeting in Altanta, Georgia USA. It may now be out-of-date.

Last Modifield: 08/14/2002

P. Calhoun <>
James Kempf <>
Transport Area Director(s):
Scott Bradner <>
A. Mankin <>
Transport Area Advisor:
A. Mankin <>
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Description of Working Group:
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 information 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 the 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 information.

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 enable 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 delivered.

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.

Goals and Milestones:
Done  Submit I-D on Layer 3 Paging Requirements & Needs assesment
Done  Submit revised charter to IESG with any changes needed especially with respect to the micro-mobility evaluation
Done  Submit I-D on Dormant Mode Host Alerting Requirements to IESG for consideration as Informational
Done  Submit Inter Access Point Context Transfer Problem Statement to IESG
JUL 01  Submit Handoff Candidate Discovery Problem Statement to IESG
SEP 01  Interim Meeting to review pending Inter Access Point Context Transfer and Handoff Candidate Discovery work
SEP 01  Candidate Mode Host Alerting Protocol Protocols are submitted, with accompanying comparison against requirements
OCT 01  Submit Inter Access Point Context Transfer Protocol Requirements to IESG for consideration as Informational
OCT 01  Submit Handoff Discovery Requirements I-D to IESG for consideration as Informational
NOV 01  Candidate Inter Access Point Context Transfer Protocols are submitted, with accompanying comparison against requirements
NOV 01  Candidate Handoff Discovery Protocols are submitted, with accompanying comparison against requirements
JAN 02  Dormant Mode Host Alerting Protocol to IESG for consideration as a Proposed Standard
FEB 02  Inter Access Point Context Transfer Protocol to IESG for consideration as a Proposed Standard
FEB 02  Handoff Discovery Protocol to IESG for consideration as a Proposed Standard
MAY 02  Dormant Mode Host Alerting Protocol MIB to IESG for consideration as a Proposed Standard
JUN 02  Submit Inter Access Point Context Transfer Protocol MIB to IESG for consideration as a Proposed Standard
JUN 02  Submit Handoff Discovery Protocol MIB to IESG for consideration as a Proposed Standard
  • - draft-ietf-seamoby-context-transfer-problem-stat-04.txt
  • - draft-ietf-seamoby-ct-reqs-03.txt
  • - draft-ietf-seamoby-cardiscovery-issues-03.txt
  • - draft-ietf-seamoby-paging-protocol-assessment-01.txt
  • - draft-ietf-seamoby-card-requirements-01.txt
  • Request For Comments:
    RFC3132 I Dormant Mode Host Alerting ('IP Paging') Problem Statement
    RFC3154 I Requirements and Functional Architecture for an IP Mobile Node Alerting Protocol

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