One document matched: draft-russert-netlmm-hmap-00.txt
Network Working Group S. Russert, Ed.
Internet-Draft F. Templin, Ed.
Intended status: Standards Track Boeing Phantom Works
Expires: August 24, 2007 February 20, 2007
Hierarchical Mobility Anchor Points (HMAPs) for Network Localized
Mobility Mangement (NETLMM)
draft-russert-netlmm-hmap-00.txt
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
The Mobility Anchor Point (MAP) for Network Localized Mobility
Management (NETLMM) is a single point of failure for the Localized
Mobility Management Domain (LMMD) and a focal point for all mobile
node (MN) traffic. These shortcomings can be addressed by
distributing the MAP function equally among the Access Routers (ARs)
in the LMMD and deploying hierarchically organized supporting nodes
in the backhaul network. This document specifies a Hierarchical MAP
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(HMAP) and its use in operational delployments that support traffic
distribution and fault tolerance. Solutions for both IPv4 and IPv6
are given.
1. Introduction
This document specifies a Hierarchical Mobility Anchor Point (HMAP)
that combines the DHCP [RFC2131][RFC3315] client, server, and relay
functions together with a router function for Network-based Localized
Mobility Management (NETLMM). HMAPs are deployed in a prefix
delegation hierarchy that is automatically configured and/or
operationally determined by the administrative authority for the
Localized Mobility Management Domain (LMMD). The lowest level HMAPs
in the prefix delegation hierarchy correspond to the Access Routers
(ARs) in the NETLMM model represented in
[I-D.templin-autoconf-netlmm-dhcp].
Each HMAP except the root for the LMMD has a delegating HMAP, and
each delegating HMAP serves requesting HMAPs that it provisions with
more-specific prefixes derived from its own prefixes. Each HMAP
advertises the prefix(es) it aggregates via the LMMD's Interior
Gateway Protocol (IGP).
HMAPs relay DHCP client messages to the authoritative HMAP for the
address(es)/prefix(es) represented in the messages. HMAPs include
the Classless Static Route (CSR) option in DHCP messages per
([I-D.templin-autoconf-netlmm-dhcp], Section 5.4) to update other
HMAPs based on MN arrivals and departures.
2. Terminology
The terminology in the normative references applies; the following
terms are defined within the scope of this document:
Hierarchical Mobility Anchor Point (HMAP)
A backhaul network router that also configures the server, relay,
and client functions of DHCP; as a server, the HMAP aggregates one
or more prefixes.
delegating HMAP
An HMAP that delegates prefixes per
[I-D.ietf-dhc-subnet-alloc][RFC3633].
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requesting HMAP
An HMAP that requests prefixes from a delegating HMAP per
[I-D.ietf-dhc-subnet-alloc][RFC3633].
home HMAP
The HMAP that is authoritative for a particular MN, i.e., the HMAP
that delegated the MN's addresses/prefixes.
visited HMAP
The HMAP that currently acts as Access Router (AR) for a roaming
MN.
3. Model of Operation
HMAPs are configured to form a hierarchy based on prefix delegation,
with each requesting HMAP in turn delegating progressively longer
prefixes to form a chain of delegating/requesting HMAPs. The lowest
level of the hierarchy delegates addresses/prefixes to MNs. (The
same HMAP may both delegate prefixes to requesting HMAPs and delegate
addresses/prefixes directly to MNs.)
Data packets destined for a MN are forwarded to the home HMAP (e.g.,
by standard IGP routing) which either delivers them to the MN on an
attached access network or tunnels them to the MN's current visited
HMAP. DHCP messages are relayed in the control plane to the
authoritative HMAP for the MN's delegated address(es)/prefix(es).
Each HMAP has DHCP server, client, and relay functions. The client
function allows the HMAP to request prefixes from a delegating HMAP,
act as a DHCP proxy on behalf of a MN, and respond to server commands
such as FORCERENEW (DHCPv4) and Reconfigure (DHCPv6). Server and
relay functions interact; when an HMAP receives a client's DHCP
message requesting renewal or confirmation of a MN's address(es)/
prefix(es) its server function begins processing the message to
determine whether it is authoritative for the MN. If it is
authoritative, it continues processing in server mode; otherwise, it
shifts to relay-mode and forwards the message to the nexthop toward
the authoritative HMAP.
4. HMAP Functional Specification
An HMAP serves as a home, visited, or relaying HMAP depending on its
relationship to the MN's address(es)/prefix(es); an HMAP may perform
all three functions concurrently on behalf of different MNs.
Each HMAP initializes, registers, and responds to the discovery of
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new MNs as specified in ([I-D.templin-autoconf-netlmm-dhcp], Section
5) and in the following sections:
4.1. Home HMAP
When an HMAP receives a DHCP DISCOVER, REQUEST, INFORM (DHCPv4),
Solicit, Request, or Information-request (DHCPv6) from a MN attached
to one of its access links (or, when the HMAP acts as a DHCP proxy on
behalf of a MN), it serves the request normally per
[RFC2131][RFC3315].
For messages other than DISCOVER or Solicit, the home HMAP checks for
route entries in its IP forwarding table to determine whether the MN
is returning home from a visited HMAP. If the MN is returning home,
the home HMAP creates a Classless Static Route Option (CSR) per
([I-D.templin-autoconf-netlmm-dhcp], Section 5), to inform the
previously-visited HMAP that routes for the MN's address(es)/
prefix(es) should be deleted. It then sends a FORCERENEW (v4) or
Reconfigure (v6) containing the CSR to the client function of the
previously-visited HMAP.
When an HMAP receives a DHCP REQUEST, INFORM (DHCPv4), Request, or
Information-request (DHCPv6) for which it is authoritative that has
been relayed, it:
1. Forms a tunnel to the visited HMAP.
2. Creates IP forwarding table entries for the MN via the tunnel.
3. For DHCPv4, sends the DHCP ACK, including in the message a CSR
option that adds a route for the MN with the visited HMAP as
next-hop. This CSR is not intended for use at the MN, but is
used by the visited HMAP to create a route entry for the roaming
MN.
For DHCPv6, sends the reply within a Relay-reply message
including a CSR option that adds a route for the MN at the
visited HMAP, with the visited HMAP as nexthop.
4.2. Visited HMAP
When an HMAP receives a REQUEST, INFORM (v4), Request, Confirm, or
Information-Request (v6) concerning addresses/prefixes for which it
is not authoritative, it relays the message to the nexthop in the
path toward the authoritative server per standard DHCP relay
behavior.
When a visited HMAP receives a server's DHCP message concerning a MN
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that has roamed onto one of its access links, it updates its IP
forwarding table according to information in CSR options attached to
the message.
4.3. Relaying HMAP
HMAPs that are not authoritative for the address(es)/prefixe(es)
represented in a specific client-server message relay the message to
the nexthop in the path toward the authoritative server per standard
DHCP relay behavior.
If an HMAP cannot relay the message, it sends a NAK (DHCPv4) or a
Reply message with lifetimes for the IA set to 0 and a StatusCode
option containing status code NotOnLink (DHCPv6) to the client. In
response to these messages, a DHCPv4 client will restart the
configuration process, and a DHCPv6 client will perform DHCP server
solicitation and client-initiated reconfiguration.
4.4. HMAP Failover
When a delegating HMAP discovers that one of its requesting HMAPs has
become unreachable (e.g., fails to renew its leases), it ceases to
relay messages to it. The delegating HMAP also begins to respond to
DHCP messages on behalf of the departed requesting HMAP.
5. IANA Considerations
This document has no actions for IANA.
6. Security Considerations
The security considerations in [I-D.templin-autoconf-netlmm-dhcp]
apply also to this specification.
7. Acknowledgements
The following individuals have provided valuable input:
8. References
8.1. Normative References
[I-D.templin-autoconf-netlmm-dhcp]
Templin, F., "Network Localized Mobility Management using
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DHCP", draft-templin-autoconf-netlmm-dhcp-04 (work in
progress), October 2006.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003.
8.2. Informative References
[I-D.ietf-dhc-subnet-alloc]
Johnson, R., "Subnet Allocation Option",
draft-ietf-dhc-subnet-alloc-04 (work in progress),
October 2006.
[RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
Host Configuration Protocol (DHCP) version 6", RFC 3633,
December 2003.
Authors' Addresses
Steven W. Russet (editor)
Boeing Phantom Works
P.O. Box 3707 MC 7L-49
Seattle, WA 98124
USA
Email: steven.w.russert@boeing.com
Fred L. Templin (editor)
Boeing Phantom Works
P.O. Box 3707 MC 7L-49
Seattle, WA 98124
USA
Email: fred.l.templin@boeing.com
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