Subject: [nemo] Submitted NEMOv4 draft-ietf-nemo-v4-base-01.txt, with changelog

From: Alexandru Petrescu <[email-masked]>
Date: Mon, 26 Jun 2006 18:30:41 +0200

Dear NEMO WG members,

I've just submitted draft-ietf-nemo-v4-base-01.txt.  Following
discussions since last meeting the modifications are minor, here's the
changelog:

       -removed error code HA_MOBNET_UNSUPPORTED.
       -changed all values to be assigned by IANA, from specific
        numbers to "TBA" (To Be Assigned).
       -substituted "egress interface" for "roaming interface".
       -changed HA behaviour upon reception of MNPs.  In 00 the HA
        replied positively only if all MNPs in RegReq were valid, in 01
        a reply is constructed specifying which MNP was valid and which
        not.
       -clarified a 3-line paragraph saying that RegRep may contain
        both implicit and explicit acknowledgements.

A confirmation from the people who raised these issues would be great
(namely GT and  HL).

Alex
Network Working Group                                           K. Leung
Internet-Draft                                                G. Dommety
Expires: December 26, 2006                                 Cisco Systems
                                                            V. Narayanan
                                                          QUALCOMM, Inc.
                                                             A. Petrescu
                                                                Motorola
                                                           June 26, 2006

	  IPv4 Network Mobility (NEMO) Basic Support Protocol
		     draft-ietf-nemo-v4-base-01.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
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   This Internet-Draft will expire on December 26, 2006.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This document describes the support of Mobile Networks, as defined in
   Mobile IPv4, by the Mobile Router and Home Agent.  A Mobile Router is
   responsible for the mobility of one or more network segments or
   subnets moving together.  The Mobile Router hides its mobility from
   the nodes on the mobile network.  The nodes on the Mobile Network may
   be fixed in relationship to the Mobile Router and may not have any
   mobility function.

   Extensions to Mobile IPv4 are introduced to support Mobile Networks.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Mobile Network Extensions  . . . . . . . . . . . . . . . . . . 4
     4.1.  Mobile Network Request Extension . . . . . . . . . . . . . 4
     4.2.  Mobile Network Acknowledgement Extension . . . . . . . . . 5
   5.  Mobile Router Operation  . . . . . . . . . . . . . . . . . . . 6
     5.1.  Error Processing . . . . . . . . . . . . . . . . . . . . . 7
   6.  Home Agent Operation . . . . . . . . . . . . . . . . . . . . . 7
     6.1.  Summary  . . . . . . . . . . . . . . . . . . . . . . . . . 7
     6.2.  Data Structures  . . . . . . . . . . . . . . . . . . . . . 8
       6.2.1.  Registration Table . . . . . . . . . . . . . . . . . . 8
       6.2.2.  Prefix Table . . . . . . . . . . . . . . . . . . . . . 8
     6.3.  Mobile Network Prefix Registration . . . . . . . . . . . . 9
     6.4.  Advertising Mobile Network Reachability  . . . . . . . . .10 
     6.5.  Establishment of Bi-directional Tunnel . . . . . . . . . .10 
     6.6.  Sending Registration Replies . . . . . . . . . . . . . . .10 
     6.7.  Mobile Network Prefix De-registration  . . . . . . . . . .11
   7.  Data Forwarding Operation  . . . . . . . . . . . . . . . . . .11
   8.  Nested Mobile Networks . . . . . . . . . . . . . . . . . . . .11
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . .12
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . .13
   11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .14
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . .14
     12.1. Normative References . . . . . . . . . . . . . . . . . . .14
     12.2. Informative References . . . . . . . . . . . . . . . . . .14
   13. Changelog  . . . . . . . . . . . . . . . . . . . . . . . . . .14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .15
   Intellectual Property and Copyright Statements . . . . . . . . . .16

1.  Introduction

   This document describes protocol extensions to Mobile IPv4
   ([RFC3344]) to enable support for Mobile Networks.  A Mobile Network
   is defined as a network segment or subnet that can change its point
   of attachment to the routing infrastructure.  Such movement is
   performed by a Mobile Router, which is the mobility entity that
   provides connectivity and reachability as well as session continuity
   for all the nodes in the Mobile Network.  The Mobile Router typically
   serves as the default gateway for the devices on the Mobile Network.

   Mobility for the Mobile Network is supported by the Mobile Router
   registering the point of attachment to its Home Agent.  This
   signaling sets up the tunnel between the two entities.  The Mobile
   Networks (either implicitly configured on the Home Agent or
   explicitly identified by the Mobile Router) are advertised by the
   Home Agent for route propagation.  Traffic to and from nodes in the
   Mobile Network are tunneled by the Home Agent to the Mobile Router,
   and vice versa.  Though packets from the Mobile Network can be
   forwarded directly without tunneling when reverse tunneling is not
   enabled, reachability is still subject to ingress filtering
   conditions for the path in this case.

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   This document specifies an additional tunnel between Mobile Router's
   Home Address and the Home Agent.  This tunnel is encapsulated within
   the normal tunnel between the Care-of Address (CoA) and Home Agent.
   In Foreign Agent CoA mode, the tunnel between the Mobile Router and
   Home Agent is needed to allow the Foreign Agent to direct the
   decapsulated packet to the proper visiting Mobile Router.  However,
   in Collocated CoA mode, the additional tunnel is not essential and
   can be eliminated because the Mobile Router is the recipient of the
   encapsulated packets for the Mobile Network.

   All traffic between the nodes in the Mobile Network and Correspondent
   Nodes passes through the Home Agent.  This document does not cover
   route optimization of this traffic.

   A similar protocol has been documented in [RFC3963] for supporting
   IPv6 moving networks with Mobile IPv6 extensions.

   Multihoming for Mobile Routers is outside of scope of this document.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   Terminology for network mobility support is defined in [RFC3344].  In
   addition, this document defines the following terms.

      Mobile Network Prefix

         The network prefix of the subnet delegated to a Mobile Router
         as the Mobile Network.

      Prefix Table

         A list of Mobile Network Prefixes indexed by the Home Address
         of a Mobile Router.  The Home Agent manages and uses Prefix
         Table to determine which Mobile Network Prefixes belong to a
         particular Mobile Router.

3.  Requirements

   Although Mobile IPv4 stated that Mobile Network can be supported by
   the Mobile Router and Home Agent using static configuration or
   running a routing protocol, there is no solution for explicit
   registration of the Mobile Networks served by the Mobile Router.  The
   following requirements for Mobile Network support are enumerated:

   o  A Mobile Router should be able to operate in explicit or implicit
      mode.  A Mobile Router may explicitly inform the Home Agent which
      Mobile Network(s) need to be propagated via routing protocol.  A
      Mobile Router may also function in implicit mode, where the Home
      Agent may learn the mobile networks through other means, such as
      from the AAA server or via pre-configuration.

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   o  The Mobile Network should be supported using Foreign Agents that
      are compliant to RFC 3344 without any changes.

   o  The mobile network should allow Fixed nodes, Mobile Nodes, or
      Mobile Routers to be on it.

4.  Mobile Network Extensions

4.1.  Mobile Network Request Extension

   For Explicit Mode, the Mobile Router informs the Home Agent about the
   Mobile Network Prefixes during registration.  The Registration
   Request contains zero, one or several Mobile Network Request
   extensions in addition to any other extensions defined by or in the
   context of ([RFC3344]).  When several Mobile Networks are needed to
   be registered, each is included in a separate Mobile Network Request
   extension, with its own Type, Length, Sub-Type, Prefix Length and
   Prefix fields.  A Mobile Network Request extension is encoded in
   Type-Length-Value (TLV) format and respects the following format:

       0               1               2               3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |    Length     |   Sub-Type    | Prefix Length |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Prefix                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type:

         Mobile Network Extension (skippable type range to be assigned
         by IANA)

      Length:

         6

      Sub-Type:

         1 (Mobile Network Request)

      Prefix Length:

         8-bit unsigned integer indicating the number of bits covering
         the network part of the address contained in the Prefix field.

      Prefix:

         32-bit unsigned integer in network byte-order containing an
         IPv4 address whose first Prefix Length bits make up the Mobile
         Network Prefix.

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4.2.  Mobile Network Acknowledgement Extension

   The Registration Reply contains zero, one or several Mobile Network
   Acknowledgement extensions in addition to any other extensions
   defined by or in the context of ([RFC3344]).  For Implicit Mode,
   the Mobile Network Acknowledgement informs the Mobile Router the
   prefixes served by the Home Agent.  Policies such as permitting
   only traffic from these Mobile Networks to be tunneled to the Home
   Agent may be applied by the Mobile Router.  For Explicit Mode, when
   several Mobile Networks are needed to be acknowledged explicitly,
   each is included in a separate Mobile Network Acknowledgement
   extension, with its own Type, Sub-Type, Length and Prefix Length
   fields.  Optionally, all requested Mobile Networks could be
   acknowledged using only one Mobile Network Acknowledgement
   extension with "Prefix Length" and "Prefix" fields set to zero.  At
   least one Mobile Network Acknowledgement extension MUST be in a
   successful Registration Reply to indicate to the Mobile Router that
   the Mobile Network Request extension was processed, thereby not
   skipped by the Home Agent.  A Registration Reply may contain any
   non-zero number of Explicit Mode and Implicit Mode Acknowledgements
   sub-types. Both sub-types can be present in a single Registration
   Reply.  A Mobile Network Acknowledgement extension is encoded in
   Type-Length-Value (TLV) format and respects the following format:

   When the registration is denied with code HA_MOBNET_ERROR, the Code
   field in the extension provides the reason for the failure.

      0               1               2               3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |    Length     |   Sub-Type    |      Code     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Prefix Length |    Reserved   |            Prefix
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type:

         Mobile Network Extension (skippable type range to be assigned
         by IANA)

      Length:

         8

      Sub-Type:

         TBA (Explicit Mode Acknowledgement)

         TBA (Implicit Mode Acknowledgement)

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      Code:

         Value indicating success or failure.

            0 Success

            TBA Invalid prefix (MOBNET_INVALID_PREFIX_LEN)

            TBA MR is not authorized for prefix (MOBNET_UNAUTHORIZED)

            TBA Forwarding setup failed (MOBNET_FWDING_SETUP_FAILED)

      Prefix Length:

         8-bit unsigned integer indicating the number of bits covering
         the network part of the address contained in the Prefix field.

      Reserved:

         Sent as zero; ignored on reception.

      Prefix:

         32-bit unsigned integer in network byte-order containing an
         IPv4 address whose first Prefix Length bits make up the Mobile
         Network Prefix.

5.  Mobile Router Operation

   A Mobile Router's operation is generally derived from the behavior of
   a Mobile Node, as set in ([RFC3344]).  In addition to maintaining
   mobility bindings for its Home Address, the Mobile Router, together
   with the Home Agent, maintains forwarding information for the Mobile
   Network Prefix(es) assigned to the Mobile Router.

   A Mobile Router SHOULD set the 'T' bit to 1 in all Registration
   Request messages it sends to indicate the need for reverse tunnels
   for all traffic.  Without reverse tunnels, all the traffic from the
   mobile network will be subject to ingress filtering in the visited
   networks.  Upon reception of successful registration reply, the
   Mobile Router processes the registration in accordance to RFC 3344.
   In addition, the following steps are taken:

   o  Check for Mobile Network Acknowledgement extension(s) in
      Registration Reply

   o  Create tunnel to the Home Agent if registered in reverse tunneling
      mode

   o  Set up default route via this tunnel or egress interface when
      registered with or without reverse tunneling, respectively

   In accordance with this specification, a Mobile Router may operate in
   one of the following two modes: explicit and implicit.  In explicit
   mode, the Mobile Router includes Mobile Network Prefix information in

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   all Registration Requests (as Mobile Network Request extensions),
   while in implicit mode it does not include this information in any
   Registration Request.  In this latter case, the Home Agent obtains
   the Mobile Network Prefixes by other means than Mobile IP.

   A Mobile Router can obtain a Collocated or Foreign Agent Care-of-
   Address while operating in explicit or implicit modes.

   For de-registration, the Mobile Router sends a registration request
   with lifetime set to zero without any Mobile Network Request
   extensions.

5.1.  Error Processing

   A Mobile Router interprets the values of the Code field in Mobile
   Network Acknowledgement Extension of the Registration Reply in order
   to identify any error related to managing the Mobile Network Prefixes
   by the Home Agent.

   If the value of the Code field in the Registration Reply is set to
   HA_MOBNET_DISALLOWED, then the Mobile Router MUST stop sending
   Registration Requests with any Mobile Network Prefix extensions to
   that Home Agent.

   If the value of the Code field in the Registration Reply is set to
   HA_MOBNET_ERROR then the Mobile Router MUST stop sending Registration
   Requests that contain any of the Mobile Network Prefixes that are
   defined by the values of the fields Prefix and Prefix Length in the
   Mobile Network Acknowledgement extension.  Note that the registration
   is denied in this case and no forwarding for any Mobile Network
   Prefixes would be set up by the Home Agent for the Mobile Router.

   It is possible that the Mobile Router receives a registration reply
   with no mobile network extensions if the registration was processed
   by a Mobile IPv4 home agent that does not support this specification
   at all.  In that case, the absence of mobile network extensions must
   be interpreted by the Mobile Router as the case where the Home Agent
   does not support mobile networks.

   All the error code values are TBA (To Be Assigned) subject to IANA
   allocation.

6.  Home Agent Operation

6.1.  Summary

   A Home Agent MUST support all the operations specified in ([RFC3344])
   for mobile node support.  The Home Agent MUST support both implicit
   and explicit modes of operation for a Mobile Router.

   The Home Agent processes the registration in accordance to RFC 3344,
   which includes route set up to the Mobile Router's home address via
   the tunnel to the Care-of Address.  In addition, for a Mobile Router
   registering in explicit mode, the following steps are taken:

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   1.  Check that the subnet information is valid

   2.  Ensure such subnet is authorized to be on the Mobile Router

   3.  Create tunnel to the Mobile Router if it does not already exist

   4.  Set up route for the subnets via this tunnel

   5.  Propagate subnet routes via routing protocol

   6.  Send the Registration Reply with the Mobile Network
       Acknowledgement extension(s)

   If there are any subnet routes via the tunnel to the Mobile Router
   that are not specified in the Mobile Network extensions, these routes
   are removed.

   In the case where the Mobile Node is not permitted to act as a Mobile
   Router, the Home Agent sends a registration denied message with error
   code HA_MOBNET_DISALLOWED.

   For a Mobile Router registering in implicit mode, the Home Agent
   performs steps 3-6 above, once the registration request is processed
   successfully.

   For deregistration, the Home Agent removes the tunnel to the Mobile
   Router and all routes using this tunnel.  The Mobile Network
   extensions are ignored.

6.2.  Data Structures

6.2.1.  Registration Table

   The registration table in the Home Agent, in accordance with
   ([RFC3344]), contains binding information for every mobile node
   registered with it.  In addition to all the parameters specified by
   ([RFC3344]), the home agent MUST store the mobile network prefixes
   associated with the Mobile Router in the corresponding registration
   entry, when the corresponding registration was performed in explicit
   mode.  When the Home Agent is advertising reachability to mobile
   network prefixes served by a Mobile Router, this information stored
   in the registration table can be used.

6.2.2.  Prefix Table

   The Home Agent must be able to authorize a Mobile Router for use of
   mobile network prefixes when the Mobile Router is operating in
   explicit mode.  Also, when the Mobile Router operates in implicit
   mode, the Home Agent must be able to locate the mobile network
   prefixes associated with that Mobile Router.  The Home Agent may
   store the home address of the Mobile Router along with the mobile
   network prefixes associated with that Mobile Router.  If the Mobile
   Router does not have a home address assigned, this table may store
   the NAI ([RFC2794]) of the Mobile Router that will be used in dynamic
   home address assignment.

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6.3.  Mobile Network Prefix Registration

   The Home Agent must process registration requests coming from Mobile
   Routers in accordance with this section.  ([RFC3344]) specifies that
   the home address of a mobile node registering with a Home Agent must
   belong to a prefix advertised on the home network.  In accordance
   with this specification, however, the home address must be configured
   from a prefix that is served by the Home Agent, not necessarily the
   one on the home network.

   If the registration request is valid, the Home Agent checks to see
   if there are any Mobile Network Prefix extensions included in the
   Registration Request.  If so, the Mobile Network Prefix information
   is obtained from the included extensions, and the Home Address from
   the Home Address field of the UDP header Registration Request.  For
   every Mobile Network Prefix extension included in the registration
   request, the Home Agent MUST perform a check against the Prefix
   Table.  If the Prefix Table does not contain at least one entry
   pairing that Home Address to that Mobile Network Prefix then the
   check fails, otherwise it succeeds.

   Following this check against the Prefix Table, the Home Agent MUST
   construct a Registration Reply containing Mobile Network
   Acknowledgement extensions.  For a Mobile Network Prefix for which
   the check was unsuccessfull the Code field in the corresponding
   Mobile Network Acknowledgement extension should be set to
   MOBNET_UNAUTHORIZED.  For a Mobile Network Prefix for which the
   check was successfull the Code field in the respective Mobile
   Network Acknowledgement extensions should be set to 0.

   The Home Agent MUST attempt to set up forwarding for each Mobile
   Network Prefix extension for which the Prefix Table check was
   successfull.  If the forwarding setup fails for a particular Mobile
   Network Prefix (for reasons like not enough memory available, or
   not enough devices available, or other similar) the Code field in
   the respective Mobile Network Acknowledgement extension should be
   set to MOBNET_FWDING_SETUP_FAILED.

   If forwarding and setup was successful for at least one Mobile
   Network Prefix then the Code field of the Registration Reply
   message should be set to 0.  Otherwise that Code should be
   HA_MOBNET_ERROR.

   If the registration request is sent in implicit mode, i.e., without
   any Mobile Network Request extension, the Home Agent may use pre-
   configured mobile network prefix information for the Mobile Router to
   set up forwarding.

   If the Home Agent is updating an existing binding entry for the
   Mobile Router, it MUST check all the prefixes in the registration
   table against the prefixes included in the registration request.
   If one or more mobile network prefix is missing from the included
   information in the registration request, it MUST delete those
   prefixes from the registration table.  Also, the Home Agent MUST
   disable forwarding for those prefixes.

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   If all checks are successful, the Home Agent either creates a new
   entry(ies) for the Mobile Router or updates an existing binding
   entry(ies) for it and returns a successful registration reply back
   to the Mobile Router or the Foreign Agent (if the registration
   request was received from a Foreign Agent).

   In accordance with ([RFC3344]), the Home Agent does proxy ARP for
   the Mobile Router home address, when the Mobile Router home address
   is derived from the home network.  If the 'T' bit is set, the Home
   Agent creates a bi-directional tunnel for the corresponding mobile
   network prefixes or updates the existing bi-directional tunnel.
   This tunnel is maintained independent of the reverse tunnel for the
   Mobile Router home address itself.

6.4.  Advertising Mobile Network Reachability

   If the mobile network prefixes served by the Home Agent are
   aggregated with the home network prefix and if the Home Agent is the
   default router on the home network, the Home Agent does not have to
   do anything different than normal.  The routes for the mobile network
   prefix are automatically aggregated into the home network prefix.  If
   the Mobile Router updates the mobile network prefix routes via a
   dynamic routing protocol, the Home Agent SHOULD propagate the routes
   on the appropriate networks.

6.5.  Establishment of Bi-directional Tunnel

   The Home Agent creates and maintains a bi-directional tunnel for the
   mobile network prefixes of a Mobile Router registered with it.  A
   home agent supporting IPv4 Mobile Router operation MUST be able to
   forward packets destined to the mobile network prefixes served by the
   mobile router to its care-of-address.  Also, the Home Agent MUST be
   able to accept packets tunneled by the Mobile Router with the source
   address of the outer header is set to the care-of-address of the
   mobile router and that of the inner header is set to the Mobile
   Router's home address or an address from one of the registered mobile
   network prefixes.

6.6.  Sending Registration Replies

   The Home Agents MUST set the status code in the registration reply to
   0 to indicate successful processing of the registration request and
   successful set up of forwarding for all the mobile network prefixes
   served by the Mobile Router.  The registration reply MUST contain at
   least one Mobile Network Acknowledgement extension.

   If the Home Agent is unable to set up forwarding for one of more
   mobile network prefixes served by the Mobile Router, it MUST set the
   Mobile Network Acknowledgement Extension status code in the
   registration reply to MOBNET_FWDING_SETUP_FAILED.  When the prefix
   length is zero or greater than 32, the status code MUST be set to
   MOBNET_INVALID_PREFIX_LEN.

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   If the Mobile Router is not authorized to forward packets to one or
   mobile network prefixes included in the request, the Home Agent MUST
   set the code to MOBNET_UNAUTHORIZED_MR.

6.7.  Mobile Network Prefix De-registration

   If the received registration request is for de-registration of the
   care-of-address, the Home Agent, upon successful processing of it,
   MUST delete the entry(ies) from its registration table.  The home
   agent tears down the bi-directional tunnel and stops forwarding any
   packets to/from the Mobile Router.  The Home Agent MUST ignore any
   included Mobile Network Request extension in a de-registration
   request.

7.  Data Forwarding Operation

   For traffic to the nodes in the Mobile Network, the Home Agent MUST
   perform double tunneling of the packet, if the Mobile Router had
   registered with a Foreign Agent care-of-address.  In this case, the
   Home Agent MUST encapsulate the packet with tunnel header (source IP
   address set to Home Agent and destination IP address set to Mobile
   Router's home address) and then encapsulate one more time with tunnel
   header (source IP address set to Home Agent and destination IP
   address set to CoA).

   For optimization, the Home Agent SHOULD only encapsulate the packet
   with the tunnel header (source IP address set to Home Agent and
   destination IP address set to CoA) for Collocated CoA mode.

   When a Home Agent receives a packet from the mobile network prefix in
   the bi-directional tunnel, it MUST de-encapsulate the packet and
   route it as a normal IP packet.  It MUST verify that the incoming
   packet has the source IP address set to the care-of-address of the
   Mobile Router.  The packet MUST be dropped if the source address is
   not set to the care-of-address of the Mobile Router.

   For traffic from the nodes in the Mobile Network, the Mobile Router
   encapsulates the packet with tunnel header (source IP address set to
   Mobile Router's home address and destination IP address set to Home
   Agent) if reverse tunnel is enabled.  Otherwise, the packet is routed
   directly to the Foreign Agent or access router.

   In Collocated CoA mode, the Mobile Router MAY encapsulate one more
   time with tunnel header (source IP address set to the CoA and
   destination IP address set to Home Agent).  For optimization, the
   Mobile Router SHOULD encapsulate the packet only with the tunnel
   header (source IP address set to CoA and destination IP address set
   to the Home Agent).

8.  Nested Mobile Networks

   Nested Network Mobility is a scenario where a Mobile Router allows
   another Mobile Router to attach to its Mobile Network.  There could
   be arbitrary levels of nested mobility.  The operation of each Mobile

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   Router remains the same whether the Mobile Router attaches to another
   Mobile Router or to a fixed Access Router on the Internet.  The
   solution described here does not place any restriction on the number
   of levels for nested mobility.  But note that this might introduce
   significant overhead on the data packets as each level of nesting
   introduces another tunnel header encapsulation.

9.  Security Considerations

   The Mobile Network extension is protected by the same rules for
   Mobile IP extensions in registration messages.  See the Security
   Considerations section in RFC 3344.

   The Home Agent MUST be able to verify that the Mobile Router is
   authorized to provide mobility service for the Mobile Networks in the
   registration request, before anchoring these subnets on behalf of the
   Mobile Router.  Forwarding for prefixes MUST NOT be set up without
   successful authorization of the Mobile Router for those prefixes.  A
   registration failure MUST be notified to the mobile router when it
   cannot be successfully authorized for prefixes requested by it.

   All registration requests and replies MUST be authenticated by the
   MN-HA Authentication Extension as specified in ([RFC3344]).  When the
   registration request is sent in explicit mode, i.e., with one or more
   Mobile Network Prefix extensions, all the Mobile Network Prefix
   extensions MUST be included before the MN-HA Authentication
   extension.  Also, these extensions MUST be included in the
   calculation of the MN-HA authenticator value.

   The Mobile Router should perform ingress filtering on all the packets
   received on the mobile network prior to reverse tunneling them to the
   Home Agent.  The Mobile Router MUST drop any packets that do not have
   a source address belonging to the mobile network.  The Mobile Router
   MUST also ensure that the source address of packets arriving on the
   mobile network is not the same as the Mobile Router's IP address on
   any interface.  These checks will protect against nodes attempting to
   launch IP spoofing attacks through the bi-directional tunnel.

   The Home Agent, upon receiving packets through the bi-directional
   tunnel, MUST verify that the source addresses of the outer IP header
   of the packets are set to the Mobile Router's care-of-address.  Also,
   it MUST ensure that the source address of the inner IP header is a
   topologically correct address on the mobile network.  This will
   prevent nodes from using the Home Agent to launch attacks inside the
   protected network.

   If a dynamic routing protocol is used between the Mobile Router and
   the Home Agent to propagate the mobile network information into the
   home network, the routing updates SHOULD be protected with IPsec ESP
   confidentiality between the Mobile Router and Home Agent, to prevent
   information about home network topology from being visible to
   eavesdroppers.

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10.  IANA Considerations

   IANA to modify rules for the existing registry "Mobile IPv4 numbers -
   per RFC 3344".  The numbering space for Extensions that may appear in
   Mobile IP control messages (those sent to and from UDP port number
   434) should be modified.

   The new Values and Names for the Type for Extensions appearing in
   Mobile IP control messages are the following:

               Value  Name
                -----  ------------------------------------------
                  TBA  Mobile Network Extension (To Be Assigned by IANA)

   The new Values and Names for the Sub-Type for Mobile Network
   Extension are the following:

               Value  Name
                -----  ------------------------------------------
                  TBA  Mobile Network Request Extension
                  TBA  Explicit Mode Acknowledgement Extension
                  TBA  Implicit Mode Acknowledgement Extension

   The new Code values for Mobile IP Registration Reply messages are the
   following:

      Code Values for Mobile IP Registration Reply messages
      -----------------------------------------------------

      Registration denied by the Home Agent: (To Be Assigned by IANA)

         TBA     Mobile Network Prefix operation error (HA_MOBNET_ERROR)
         TBA     MR operation is not permitted (HA_MOBNET_DISALLOWED)

   The new Code Values for Mobile IP Registration Reply messages are the
   following:

      Code Values for Mobile Network Acknowledgement Extension
      --------------------------------------------------------

      Registration denied by the Home Agent:

         TBA     Invalid prefix length (MOBNET_INVALID_PREFIX_LEN)
         TBA     MR is not authorized for prefix (MOBNET_UNAUTHORIZED)
         TBA     Forwarding setup failed (MOBNET_FWDING_SETUP_FAILED)

   The current (non-modified) numbering spaces could be consulted at the
   following URL: http://www.iana.org/assignments/mobileip-numbers

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11.  Acknowledgements

   The authors would like to thank Christophe Janneteau, George
   Popovich, Ty Bekiares, Ganesh Srinivasan, Alpesh Patel, Ryuji
   Wakikawa, George Tsirtsis and Henrik Levkowetz for their helpful
   discussions, reviews and comments.

12.  References

12.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2794]  Calhoun, P. and C. Perkins, "Mobile IP Network Access
              Identifier Extension for IPv4", RFC 2794, March 2000.

   [RFC3344]  Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
              August 2002.

12.2.  Informative References

   [RFC3963]  Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
              Thubert, "Network Mobility (NEMO) Basic Support Protocol",
              RFC 3963, January 2005.

13.  Changelog

   From version 00 to 01:
      -removed error code HA_MOBNET_UNSUPPORTED.
      -changed all values to be assigned by IANA, from specific
       numbers to "TBA" (To Be Assigned).
      -substituted "egress interface" for "roaming interface".
      -changed HA behaviour upon reception of MNPs.  In 00 the HA
       replied positively only if all MNPs in RegReq were valid, in 01
       a reply is constructed specifying which MNP was valid and which
       not.
      -clarified a 3-line paragraph saying that RegRep may contain
       both implicit and explicit acknowledgements.

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Authors' Addresses

   Kent Leung
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   US

   Phone: +1 408-526-5030
   Email: [email-masked]

   Gopal Dommety
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   US

   Phone: +1 408-525-1404
   Email: [email-masked]

   Vidya Narayanan
   QUALCOMM, Inc.
   5775 Morehouse Dr
   San Diego, CA
   USA

   Phone: +1 858-845-2483
   Email: [email-masked]

   Alexandru Petrescu
   Motorola
   Parc les Algorithmes Saint Aubin
   Gif-sur-Yvette  91193
   France

   Email: [email-masked]

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