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Versions: 00 01 02 03 04 05 06 07 RFC 4584

MIP6 WG                                                   S. Chakrabarti
Internet-Draft                                               E. Nordmark
Expires: June 10, 2006                                  Sun Microsystems
                                                        December 7, 2005


                Extension to Sockets API for Mobile IPv6
                  draft-ietf-mip6-mipext-advapi-06.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
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   This Internet-Draft will expire on June 10, 2006.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document describes data structures and API support for Mobile
   IPv6 as an extension to the Advanced Socket API for IPv6.

   Just as the Advanced Sockets API for IPv6 gives access to various
   extension headers and the ICMPv6 protocol, this document specifies
   the same level of access for Mobile IPv6 components.  It specifies a
   mechanism for applications to retrieve and set information for
   Mobility Header messages, Home Address destination options and



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   Routing Header Type 2 extension headers.  It also specifies the
   common data structures and definitions that might be used by certain
   advanced Mobile IPv6 socket applications.

Table of Contents

   1.   Introduction . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.   Applicability  . . . . . . . . . . . . . . . . . . . . . . .   5
   3.   Overview . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.   Common Structures and Definitions  . . . . . . . . . . . . .   7
     4.1  The Mobility Header Data Structures  . . . . . . . . . . .   7
       4.1.1  The ip6_mh Structure . . . . . . . . . . . . . . . . .   7
       4.1.2  Binding Refresh Request Mobility Message . . . . . . .   8
       4.1.3  Home Address Test Init (HoTI) Message  . . . . . . . .   8
       4.1.4  Care-of Address Test Init (CoTI) Message . . . . . . .   8
       4.1.5  Home Address Test (HOT) Message  . . . . . . . . . . .   9
       4.1.6  Care Of Address Test (COT) Message . . . . . . . . . .   9
       4.1.7  Binding Update Mobility Message  . . . . . . . . . . .   9
       4.1.8  Binding Acknowledgment Mobility Message  . . . . . . .  10
       4.1.9  Binding Error Mobility Message . . . . . . . . . . . .  10
       4.1.10   Mobility Option TLV data structure . . . . . . . . .  10
       4.1.11   Mobility Option Data Structures  . . . . . . . . . .  11
     4.2  Mobility Header Constants  . . . . . . . . . . . . . . . .  11
     4.3  IPv6 Home Address Destination Option . . . . . . . . . . .  13
     4.4  Type 2 Routing Header  . . . . . . . . . . . . . . . . . .  14
     4.5  New ICMP Messages for Mobile IPv6  . . . . . . . . . . . .  14
     4.6  IPv6 Neighbor Discovery Changes  . . . . . . . . . . . . .  16
   5.   Access to Home Address Destination Option and Routing
        Headers  . . . . . . . . . . . . . . . . . . . . . . . . . .  18
     5.1  Routing Header access functions  . . . . . . . . . . . . .  19
     5.2  Content of Type 2 Routing Header . . . . . . . . . . . . .  21
     5.3  Order of extension headers for Home Address Destination
          Options  . . . . . . . . . . . . . . . . . . . . . . . . .  21
     5.4  Home Address Destination Option access functions . . . . .  22
     5.5  Content of Home Address Destination option . . . . . . . .  23
   6.   Mobility Protocol Headers  . . . . . . . . . . . . . . . . .  24
     6.1  Receiving and Sending Mobility Header Messages . . . . . .  24
   7.   Protocols File . . . . . . . . . . . . . . . . . . . . . . .  26
   8.   IPv4-Mapped IPv6 Addresses . . . . . . . . . . . . . . . . .  27
   9.   Security Considerations  . . . . . . . . . . . . . . . . . .  28
   10.  IANA Considerations  . . . . . . . . . . . . . . . . . . . .  29
   11.  Changes from last revisions  . . . . . . . . . . . . . . . .  30
   12.  Acknowledgement  . . . . . . . . . . . . . . . . . . . . . .  31
   13.  References . . . . . . . . . . . . . . . . . . . . . . . . .  32
     13.1   Normative References . . . . . . . . . . . . . . . . . .  32
     13.2   Informative References . . . . . . . . . . . . . . . . .  32
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  32
        Intellectual Property and Copyright Statements . . . . . . .  34



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1.  Introduction

   Mobility Support in IPv6 [2] defines a new Mobility Protocol header,
   a Home Address destination option and a new Routing Header type.  It
   is expected that Mobile IPv6 user-level implementations and some
   special applications will need to access and process these IPv6
   extension headers.  This document is an extension to the existing
   Advanced Sockets API document [1]; it addresses the Advanced IPv6
   Sockets API for these new protocol elements defined by Mobile IPv6.

   The applicability of this API mainly targets user-level applications.
   However, it has also shown to be useful within some Mobile IPv6
   implementations; for instance, where part of the Mobile IPv6 protocol
   is implemented at user-level and part in the kernel.  It is up to any
   such implementations to architect which part of the Mobile IPv6 and
   IPSec packet processing should be done at the user-level in order to
   meet the design needs of the particular platform and operating
   system.

   The target user-level applications for this socket API are believed
   to be debugging and diagnostic applications as well as some policy
   applications which would like to receive a copy of protocol
   information at the application layer.

   The packet information along with access to the extension headers
   (Routing header and Destination options) are specified using the
   "ancillary data" fields that were added to the 4.3BSD Reno sockets
   API in 1990.  The reason is that these ancillary data fields are part
   of the Posix.1g standard and should therefore be adopted by most
   vendors.  This document is consistent with Advanced Sockets API for
   IPv6 [1] in structure definitions, header files and function
   definitions.  Thus, the implementors of this API document are assumed
   to be familiar with the data structures, data sending and receiving
   procedures and the IPv6 extension header access funtions described in
   the Advanced Sockets API for IPv6 [1].

   Non-goals

   This document does not address application access to either the
   authentication header or the encapsulating security payload header.
   This document also does not address any API that might be necessary
   for Mobile Network [4] specific needs.  Furthermore, it should be
   noted that this API document excludes discussion on application level
   API.  It assumes that address selection socket API [5] takes care of
   selection of Care-of-address or home-address as the source address by
   the application, when source address selection is required due to the
   nature of the application.




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   Providing mobility "awareness" to applications, such as applications
   being able to tell whether the host is at home or not, is out of
   scope for this API.
















































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2.  Applicability

   This API document can be applied in the following cases:

   1.  User-level debugging and monitoring tools: This socket API is
       useful for accessing Mobility Headers, Home-address options and
       Type 2 Routing Headers .  For example, mh-ping might be a
       monitoring tool which can process mobility headers on the
       receiving side to check binding status.

   2.  Partial user-level implementation of Mobile IPv6: We assume that
       some implementations may choose to do the Mobility header
       processing at user level.  In that case, this document recommends
       implementing at least the handling of Home-address options and
       Type 2 Routing Header in the main IP processing paths in the
       kernel.  The API can then be used to send and receive the
       Mobility Header packets used for Mobile IPv6 signalling.

   3.  Complete header processing at the kernel-level: Many
       implementations of Mobile IPv6 [2] perform processing of Home
       Address Options, Routing Headers and Mobility headers at the
       kernel level.  However, the kernel keeps a copy of the received
       extension headers and passes them up to the API which is used by
       the user-level applications purely for monitoring and debugging
       Mobile IPv6 packets.

   On an IPv6 host which does not implement Mobile IPv6, the IPv6
   specification [3] requires that packets with the Home Address option
   or Routing Header of type 2 (where segments left is non-zero) be
   dropped on receipt.  This means that it is not possible to implement
   Mobile IPv6 as an application on such a system.  Thus on such a
   system, the applicability of this API is limited to the first case
   above of debugging and monitoring applications (such as tcpdump)
   being able to parse and interpret Mobile IPv6 packets.

















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3.  Overview

   This document can be divided into the following parts:

   1.  Definitions of constants and structures for C programs that
       capture the Mobile IPv6 packet formats on the wire.  A common
       definition of these is useful at least for packet snooping
       applications.  This is captured in Section 4.  In addition,
       Section 4 also defines data structures for Home Address
       destination option, Type 2 Routing Header, and new ICMPv6
       messages related to Mobile IPv6.

   2.  Notes on how to use the IPv6 Advanced API to access Home Address
       options and type 2 Routing Headers.  This is captured in
       Section 5.

   3.  Notes on how user-level applications can observe MH (Mobility
       Header) packets using raw sockets (in Section 6).  The IPv6 RAW
       socket interface described in this document allows applications
       to receive  MH packets whether or not the system's MH processing
       takes place in the "kernel" or at the "user space".

   4.  Suggested  name for /etc/protocols (in Section 7).

   All examples in this document omit error checking in favor of
   brevity, as it is following the same style as the Advanced Socket API
   [1].

   We note that many of the functions and socket options defined in this
   document may have error returns that are not defined in this
   document.

   Data types in this document follow the Posix.1g format: intN_t means
   a signed integer of exactly N bits (e.g., int16_t) and uintN_t means
   an unsigned integer of exactly N bits (e.g., uint32_t).

   Once the API specification becomes mature and is deployed, it may be
   formally standardized by a more appropriate body, such as has been
   done with the Basic API [6].  However, since this specification
   largely builds upon the Advanced Socket API [1], such standardization
   would make sense only if the Advanced Socket API [1] were also
   standardized.

   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 RFC 2119.





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4.  Common Structures and Definitions

   ANSI-C provides few guarantees about the size and alignment of data
   structures.  Thus, depending on the implementation of a compiler, the
   structures below might, when compiled, not match the packet formats
   defined in RFC 3775 [2].  However, the structures are specified in a
   way to maximize the probability that compilers will lay out the
   structure in a way that is identical to the packet formats on the
   wire.

   Thus, the mobility header message data structures include the
   mobility header fields such that they are consistent across different
   compilers.

   The structure definitions below are merely examples; the requirement
   is that the structures contain the fields specified below.  Depending
   on the compiler used as well as the host byte order, the layout of
   the structures might need to be different.  But as long as they
   provide the same fields as below we can ensure application
   portability when using this API.

   The constants shown below are in network byte order, so an
   application needs to perform the appropriate byte order conversion
   (ntohs(), etc) when using the constants.

   The structures and constants below will be included when including
   the (new) header file : <netinet/ip6mh.h>

4.1  The Mobility Header Data Structures

4.1.1  The ip6_mh Structure

   The following structure is defined as a result of including <netinet/
   ip6mh.h>.  This is the fixed part of the Mobility Header.  Different
   Mobility message types are defined Mobile IPv6 [2].  For portability
   and alignment reasons, each mobility message type includes the
   mobility header fields as opposed to including the ip6_mh structure
   followed by the message-specific fields.

       struct  ip6_mh {
           uint8_t    ip6mh_proto;   /* NO_NXTHDR by default */
           uint8_t    ip6mh_hdrlen;  /* Header Len in unit of 8 Octets
                                        excluding the first 8 Octets */
           uint8_t    ip6mh_type;    /* Type of Mobility Header */
           uint8_t    ip6mh_reserved;   /* Reserved */
           uint16_t   ip6mh_cksum;   /* Mobility Header Checksum */
           /* Followed by type specific messages */
       };



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4.1.2  Binding Refresh Request Mobility Message

       struct  ip6_mh_binding_request {
           uint8_t    ip6mhbr_proto;
           uint8_t    ip6mhbr_hdrlen;
           uint8_t    ip6mhbr_type;
           uint8_t    ip6mhbr_reserved;
           uint16_t   ip6mhbr_cksum;
           uint16_t   ip6mhbr_reserved;
           /* Followed by optional Mobility Options */
       };


4.1.3  Home Address Test Init (HoTI) Message

        struct   ip6_mh_home_test_init {
           uint8_t    ip6mhhti_proto;
           uint8_t    ip6mhhti_hdrlen;
           uint8_t    ip6mhhti_type;
           uint8_t    ip6mhhti_reserved;
           uint16_t   ip6mhhti_cksum;
           uint16_t   ip6mhhti_reserved;
           uint32_t   ip6mhhti_cookie[2]; /* 64 bit Cookie by MN */
           /* Followed by optional Mobility Options */
        };


4.1.4  Care-of Address Test Init (CoTI) Message

        struct   ip6_mh_careof_test_init {
           uint8_t    ip6mhcti_proto;
           uint8_t    ip6mhcti_hdrlen;
           uint8_t    ip6mhcti_type;
           uint8_t    ip6mhcti_reserved;
           uint16_t   ip6mhcti_cksum;
           uint16_t   ip6mhcti_reserved;
           uint32_t   ip6mhcti_cookie[2]; /* 64 bit Cookie by MN */
           /* Followed by optional Mobility Options */
        };












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4.1.5  Home Address Test (HOT) Message

        struct  ip6_mh_home_test {
           uint8_t    ip6mhht_proto;
           uint8_t    ip6mhht_hdrlen;
           uint8_t    ip6mhht_type;
           uint8_t    ip6mhht_reserved;
           uint16_t   ip6mhht_cksum;
           uint16_t   ip6mhht_nonce_index;
           uint32_t   ip6mhht_cookie[2];    /* Cookie from HOTI msg */
           uint32_t   ip6mhht_keygen[2];  /* 64 Bit Key by CN */
           /* Followed by optional Mobility Options */
       };


4.1.6  Care Of Address Test (COT) Message

        struct  ip6_mh_careof_test {
           uint8_t    ip6mhct_proto;
           uint8_t    ip6mhct_hdrlen;
           uint8_t    ip6mhct_type;
           uint8_t    ip6mhct_reserved;
           uint16_t   ip6mhct_cksum;
           uint16_t   ip6mhct_nonce_index;
           uint32_t   ip6mhct_cookie[2]; /* Cookie from COTI message */
           uint32_t   ip6mhct_keygen[2];  /* 64bit key by CN */
           /* Followed by optional Mobility Options */
        };


4.1.7  Binding Update Mobility Message

       struct ip6_mh_binding_update {
           uint8_t     ip6mhbu_proto;
           uint8_t     ip6mhbu_hdrlen;
           uint8_t     ip6mhbu_type;
           uint8_t     ip6mhbu_reserved;
           uint16_t    ip6mhbu_cksum;
           uint16_t    ip6mhbu_seqno;      /* Sequence Number */
           uint16_t    ip6mhbu_flags;
           uint16_t    ip6mhbu_lifetime; /* Time in unit of 4 sec */
           /* Followed by optional Mobility Options */
       };

       /* Binding Update Flags, in network byte-order */
       #define IP6_MH_BU_ACK    0x8000  /* Request a binding ack */
       #define IP6_MH_BU_HOME   0x4000  /* Home Registration */
       #define IP6_MH_BU_LLOCAL 0x2000  /* Link-local compatibility */



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       #define IP6_MH_BU_KEYM   0x1000  /* Key management mobility  */


4.1.8  Binding Acknowledgment Mobility Message

        struct  ip6_mh_binding_ack {
           uint8_t   ip6mhba_proto;
           uint8_t   ip6mhba_hdrlen;
           uint8_t   ip6mhba_type;
           uint8_t   ip6mhba_reserved;
           uint16_t  ip6mhba_cksum;
           uint8_t   ip6mhba_status;    /* Status code */
           uint8_t   ip6mhba_flags;
           uint16_t  ip6mhba_seqno;
           uint16_t  ip6mhba_lifetime;
           /* Followed by optional Mobility Options */
        };

       /* Binding Acknowledgement Flags */
       #define IP6_MH_BA_KEYM       0x80  /* Key management mobility */


4.1.9  Binding Error Mobility Message

        struct   ip6_mh_binding_error {
           uint8_t   ip6mhbe_proto;
           uint8_t   ip6mhbe_hdrlen;
           uint8_t   ip6mhbe_type;
           uint8_t   ip6mhbe_reserved;
           uint16_t  ip6mhbe_cksum;
           uint8_t   ip6mhbe_status;  /* Error Status */
           uint8_t   ip6mhbe_reserved;
           struct in6_addr ip6mhbe_homeaddr;
           /* Followed by optional Mobility Options */
         };


4.1.10  Mobility Option TLV data structure

          struct   ip6_mh_opt {
             uint8_t    ip6mhopt_type;   /* Option Type */
             uint8_t    ip6mhopt_len;    /* Option Length */
             /* Followed by variable length Option Data in bytes */
          };







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4.1.11  Mobility Option Data Structures

4.1.11.1  Binding Refresh Advice

          struct ip6_mh_opt_refresh_advice {
              uint8_t  ip6mora_type;
              uint8_t  ip6mora_len;
              uint16_t ip6mora_interval; /* Refresh interval in 4 sec */
          };


4.1.11.2  Alternate Care-of Address

          struct ip6_mh_opt_altcoa {
              uint8_t ip6moa_type;
              uint8_t ip6moa_len;
              struct in6_addr ip6moa_addr; /* Alternate CoA */
          };


4.1.11.3  Nonce Indices

           struct ip6_mh_opt_nonce_index {
               uint8_t ip6moni_type;
               uint8_t ip6moni_len;
               uint16_t ip6moni_home_nonce;
               uint16_t ip6moni_coa_nonce;
           };


4.1.11.4  Binding Authorization Data

           struct ip6_mh_opt_auth_data {
               uint8_t ip6moad_type;
               uint8_t ip6moad_len;
               uint8_t ip6moad_data[12];
           };


4.2  Mobility Header Constants

   IPv6 Next Header Value for Mobility:

   <netinet/in.h>


        #define IPPROTO_MH       135 /* IPv6 Mobility Header: IANA */




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   Mobility Header Message Types:

   <netinet/ip6mh.h>


       #define IP6_MH_TYPE_BRR       0   /* Binding Refresh Request */
       #define IP6_MH_TYPE_HOTI      1   /* HOTI Message   */
       #define IP6_MH_TYPE_COTI      2   /* COTI Message  */
       #define IP6_MH_TYPE_HOT       3   /* HOT Message   */
       #define IP6_MH_TYPE_COT       4   /* COT Message  */
       #define IP6_MH_TYPE_BU        5   /* Binding Update */
       #define IP6_MH_TYPE_BACK      6   /* Binding ACK */
       #define IP6_MH_TYPE_BERROR    7   /* Binding Error */

   Mobility Header Message Option Types:

   <netinet/ip6mh.h>


       #define  IP6_MHOPT_PAD1       0x00  /* PAD1 */
       #define  IP6_MHOPT_PADN       0x01  /* PADN */
       #define  IP6_MHOPT_BREFRESH   0x02  /* Binding Refresh */
       #define  IP6_MHOPT_ALTCOA     0x03  /* Alternate COA */
       #define  IP6_MHOPT_NONCEID    0x04  /* Nonce Index */
       #define  IP6_MHOPT_BAUTH      0x05  /* Binding Auth Data */

   Status values accompanied with Mobility Binding Acknowledgement:

   <netinet/ip6mh.h>






















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       #define IP6_MH_BAS_ACCEPTED          0   /* BU accepted */
       #define IP6_MH_BAS_PRFX_DISCOV       1   /* Accepted, but prefix
                                                   discovery Required */
       #define IP6_MH_BAS_UNSPECIFIED       128 /* Reason unspecified */
       #define IP6_MH_BAS_PROHIBIT          129 /* Administratively
                                                   prohibited */
       #define IP6_MH_BAS_INSUFFICIENT      130 /* Insufficient
                                                   resources */
       #define IP6_MH_BAS_HA_NOT_SUPPORTED  131 /* HA registration not
                                                   supported */
       #define IP6_MH_BAS_NOT_HOME_SUBNET   132  /* Not Home subnet */
       #define IP6_MH_BAS_NOT_HA            133  /* Not HA for this
                                                    mobile node */
       #define IP6_MH_BAS_DAD_FAILED        134  /* DAD failed */
       #define IP6_MH_BAS_SEQNO_BAD         135  /* Sequence number out
                                                    of range */

       #define IP6_MH_BAS_HOME_NI_EXPIRED   136  /* Expired Home nonce
                                                    index */
       #define IP6_MH_BAS_COA_NI_EXPIRED    137  /* Expired Care-of
                                                    nonce index */
       #define IP6_MH_BAS_NI_EXPIRED        138  /* Expired Nonce
                                                    Indices */
       #define IP6_MH_BAS_REG_NOT_ALLOWED   139  /* Registration type
                                                    change disallowed */

   Status values for the Binding Error mobility messages:

   <netinet/ip6mh.h>



       #define IP6_MH_BES_UNKNOWN_HAO    1 /* Unknown binding for HOA */
       #define IP6_MH_BES_UNKNOWN_MH     2 /* Unknown MH Type */


4.3  IPv6 Home Address Destination Option

   Due to alignment issues in the compiler, and the alignment
   requirements for this option, the included IPv6 address must be
   specified as an array of 16 octets.

   <netinet/ip6.h>








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       /* Home Address Destination Option */
       struct ip6_opt_home_address {
            uint8_t           ip6oha_type;
            uint8_t           ip6oha_len;
            uint8_t           ip6oha_addr[16];   /* Home Address */
       };

       Option Type Definition:

       #define IP6OPT_HOME_ADDRESS        0xc9    /* 11 0 01001 */


4.4  Type 2 Routing Header

   <netinet/ip6.h>


       /* Type 2 Routing header for Mobile IPv6 */
       struct ip6_rthdr2 {
            uint8_t  ip6r2_nxt;       /* next header */
            uint8_t  ip6r2_len;       /* length : always 2 */
            uint8_t  ip6r2_type;      /* always 2 */
            uint8_t  ip6r2_segleft;   /* segments left: always 1 */
            uint32_t ip6r2_reserved;  /* reserved field */
            struct in6_addr ip6r2_homeaddr;  /* Home Address */
       };


4.5  New ICMP Messages for Mobile IPv6

   ICMP message types and definitions for Mobile IPv6 are defined in

   <netinet/icmp6.h>

        #define MIP6_HA_DISCOVERY_REQUEST    144
        #define MIP6_HA_DISCOVERY_REPLY      145
        #define MIP6_PREFIX_SOLICIT          146
        #define MIP6_PREFIX_ADVERT           147

   The following data structures can be used for the ICMP message types
   discussed in Section 6.5 through 6.8 in the base Mobile IPv6 [2]
   specification.









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        struct mip6_dhaad_req {    /* Dynamic HA Address Discovery */
               struct  icmp6_hdr   mip6_dhreq_hdr;
        };

        #define  mip6_dhreq_type      mip6_dhreq_hdr.icmp6_type
        #define  mip6_dhreq_code      mip6_dhreq_hdr.icmp6_code
        #define  mip6_dhreq_cksum     mip6_dhreq_hdr.icmp6_cksum
        #define  mip6_dhreq_id        mip6_dhreq_hdr.icmp6_data16[0]
        #define  mip6_dhreq_reserved  mip6_dhreq_hdr.icmp6_data16[1]


        struct mip6_dhaad_rep {    /* HA Address Discovery Reply */
               struct icmp6_hdr   mip6_dhrep_hdr;
               /* Followed by Home Agent IPv6 addresses */
        };

        #define  mip6_dhrep_type      mip6_dhrep_hdr.icmp6_type
        #define  mip6_dhrep_code      mip6_dhrep_hdr.icmp6_code
        #define  mip6_dhrep_cksum     mip6_dhrep_hdr.icmp6_cksum
        #define  mip6_dhrep_id        mip6_dhrep_hdr.icmp6_data16[0]
        #define  mip6_dhrep_reserved  mip6_dhrep_hdr.icmp6_data16[1]


        struct mip6_prefix_solicit {   /* Mobile Prefix Solicitation */
               struct icmp6_hdr     mip6_ps_hdr;
        };

        #define  mip6_ps_type          mip6_ps_hdr.icmp6_type
        #define  mip6_ps_code          mip6_ps_hdr.icmp6_code
        #define  mip6_ps_cksum         mip6_ps_hdr.icmp6_cksum
        #define  mip6_ps_id            mip6_ps_hdr.icmp6_data16[0]
        #define  mip6_ps_reserved      mip6_ps_hdr.icmp6_data16[1]


        struct mip6_prefix_advert {  /* Mobile Prefix Advertisements */
               struct  icmp6_hdr   mip6_pa_hdr;
                /* Followed by one or more PI options */
        };

        #define  mip6_pa_type            mip6_pa_hdr.icmp6_type
        #define  mip6_pa_code            mip6_pa_hdr.icmp6_code
        #define  mip6_pa_cksum           mip6_pa_hdr.icmp6_cksum
        #define  mip6_pa_id              mip6_pa_hdr.icmp6_data16[0]
        #define  mip6_pa_flags_reserved  mip6_pa_hdr.icmp6_data16[1]

       /* Mobile Prefix Advertisement Flags in network-byte order */
        #define  MIP6_PA_FLAG_MANAGED    0x8000
        #define  MIP6_PA_FLAG_OTHER      0x4000



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   Prefix options are defined in IPv6 Advanced Socket API [1].  Mobile
   IPv6 Base specification [2] describes the modified behavior in
   'Modifications to IPv6 Neighbor Discovery' Section.  Prefix Options
   for Mobile IP are defined in the following Section.

4.6  IPv6 Neighbor Discovery Changes

   IPv6 Neighbor Discovery changes are also defined in <netinet/icmp6.h>

      New 'Home Agent' flag in router advertisement:
      #define  ND_RA_FLAG_HOMEAGENT   0x20  /* Home Agent flag in RA */

      New Router flag with prefix information of the home agent:
      #define  ND_OPT_PI_FLAG_ROUTER  0x20  /* Router flag in PI */

   As per Mobile IPv6 specification [2] Section 7.2,  a Home Agent MUST
   include at least one prefix option with the Router Address (R) bit
   set.  Advanced Socket API [1] defines data structure for prefix
   option as follows:

      struct nd_opt_prefix_info {    /* prefix information */
           uint8_t   nd_opt_pi_type;
           uint8_t   nd_opt_pi_len;
           uint8_t   nd_opt_pi_prefix_len;
           uint8_t   nd_opt_pi_flags_reserved;
           uint32_t  nd_opt_pi_valid_time;
           uint32_t  nd_opt_pi_preferred_time;
           uint32_t  nd_opt_pi_reserved2;
           struct in6_addr  nd_opt_pi_prefix;
      };

   New advertisement interval option and home agent information options
   are defined in Mobile IPv6 [2] base specification.

      struct nd_opt_adv_interval { /* Advertisement interval option */
           uint8_t        nd_opt_ai_type;
           uint8_t        nd_opt_ai_len;
           uint16_t       nd_opt_ai_reserved;
           uint32_t       nd_opt_ai_interval;
      };

   The option types  for the new Mobile IPv6 specific options:









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      #define  ND_OPT_ADV_INTERVAL    7     /* Adv Interval Option  */
      #define  ND_OPT_HA_INFORMATION  8     /* HA Information option */

      struct nd_opt_homeagent_info {  /* Home Agent information */
         uint8_t        nd_opt_hai_type;
         uint8_t        nd_opt_hai_len;
         uint16_t       nd_opt_hai_reserved;
         uint16_t       nd_opt_hai_preference;
         uint16_t       nd_opt_hai_lifetime;
      };









































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5.  Access to Home Address Destination Option and Routing Headers

   Applications that need to be able to access home address destination
   option and routing header type 2 information can do so by setting the
   appropriate setsockopt option and using ancillary data objects.  The
   order of extension headers is defined in Mobile IPv6 [2] when sending
   an IPv6 packet with a Home Address Destination Option with other
   possible extension headers.  Section 5.3 elaborates the extension
   header order when all the possible cases are present.  This document
   does not recommend the user-level program to set Home Address
   destination option or Routing Header Type 2 option; however, for
   clarity it defines the order of extension headers.  See  Section 2 of
   this document for appropriate usage of sending and receiving of Home
   Address destination options and Routing Header Type 2 extension
   headers.

   This document defines a new socket option, IPV6_MIPDSTOPTS for
   sending Home Address destination options.  In order to receive a Home
   Address destination option or Route Header Type 2 extension header,
   applications must call setsockopt() to turn on the corresponding flag
   ( for brevity, error checking is not performed in the examples):

      int  on = 1;

      setsockopt(fd, IPPROTO_IPV6, IPV6_RECVRTHDR,    &on, sizeof(on));
      setsockopt(fd, IPPROTO_IPV6, IPV6_RECVDSTOPTS,
                   &on, sizeof(on));

   When any of these options are enabled, the corresponding data is
   returned as control information by recvmsg(), as one or more
   ancillary data objects.  Receiving the above information for TCP
   applications is not defined in this document (see Section 4.1 of
   Advanced Sockets API for IPv6 [1]).

   Note that if the IP implementation on the host does not implement the
   handling of type 2 routing headers or Home Address options, then per
   RFC 2460 [3], the IP  stack is required to drop the packet.  Hence
   the applications using this mechanism only work on hosts where at
   least those pieces of RFC 3775 [2] are implemented in the IP layer.

   For receiving the Home Address destination option header, the Mobile
   IPv6 implementation follows the initial processing of the Home
   Address destination option (Section 9.3.1 of Mobile IPv6 [2]) before
   passing the information to the API level.  This includes initial
   processing of IPSec authentication data in a packet when it exists.
   Each Destination options header is returned as one ancillary data
   object described by a cmsghdr structure with cmsg_level set to
   IPPROTO_IPV6 and cmsg_type set to IPV6_DSTOPTS.



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   For sending Home Address destination option, ancillary data can be
   used to specify the option content for a single datagram.  This only
   applies to datagram and raw sockets; not to TCP sockets.  The
   Advanced API [1] document restricts one IPV6_xxx ancillary data
   object for a particular extension header in the control buffer.
   Thus, there would be a single ancillary data object for the Home
   address destination option in a ancillary data buffer.  If multiple
   destination options are present then the header order should be in
   compliance with Section 6.3 and 9.3.2 of the Mobile IPv6 [2] base
   specification.

   For TCP data packets with Home Address destination option, the
   "sticky" option may be used for all transmitted packets.  The
   application can remove the sticky Home Destination option header by
   calling setsockopt() for IPV6_MIPSTOPTS with a zero option length.

   Note that Section 2 of this document does not encourage setting the
   Home Address destination option at the user-level.  A Mobile IPv6
   implementation should set and process the Home Address destination
   option and Routing Header Type 2, at the kernel level.  The setting
   of Routing Header Type 2 and Home Address destination option are
   described in this document for completeness and flexibility to use
   them in future if there is a need.

   The following socket option parameters and cmsghdr fields may be used
   for sending:

       opt level/    optname/          optval/
       cmsg_level    cmsg_type         cmsg_data[]
       ------------  ------------      ------------------------
       IPPROTO_IPV6  IPV6_MIPDSTOPTS      ip6_dest structure
       IPPROTO_IPV6  IPV6_RTHDR           ip6_rthdr structure

   Some IPv6 implementations may support "sticky" options [1] for IPv6
   destination option for datagram and RAW sockets.

   Behavior of legacy IPv6 socket applications:

   Legacy IPv6 applications/implementations using the Advanced Socket
   API [1] mechanisms, upon receiving Home Address destination options
   or Routing headers(Type 2), will discard the packet as per Section
   4.2 and 4.4 of IPV6 Protocol [3] specification respectively;
   otherwise, they should properly handle the Home Address destination
   option and the Routing Header Type 2 specified in this document.

5.1  Routing Header access functions

   IPV6 Protocol [3] defines a Routing header extension header for Type



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   0.  Thus, in order to access the IPv6 Routing header Type 2 extension
   header, one MUST use type = 2 and segment = 1.  The following
   existing functions defined in Advanced API for IPv6 Sockets [1] are
   supported for Mobile IPv6 applications for sending and receiving
   Routing Header Type 2 headers:

   For sending:

     size_t inet6_rth_space(int type, int segments);
     void *inet6_rth_init(void *bp, int bp_len, int type, int segments);
     int inet6_rth_add(void *bp, const struct in6_addr *addr);

   For receiving:

     int inet6_rth_segments(const void *bp);
     struct in6_addr *inet6_rth_getaddr(const void *bp, int index);


   NOTE: Reversing operation is not possible using the Route Header Type
   2 extension header.  Thus inet6_rth_reverse() is not used.

   Detailed descriptions and examples of accessing an IPv6 Routing
   Header are discussed in the Advanced Sockets API for IPv6 [1].
   However, Section 7 of Advanced API for IPv6 Sockets [1] indicates
   that multiple types of routing headers can be received as multiple
   ancillary data objects to the application (with cmsg_type set to
   IPV6_RTHDR).  Currently there are no API functions defined to return
   the routing header type.  However, this document does not define a
   helper function, since it is easy to access the Routing Header Type
   field just as easily as the ip6r_segleft field.  An excerpt of a code
   sample is provided for extracting the type of the received routing
   header:



















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         if (msg.msg_controllen != 0 &&
             cmsgptr->cmsg_level == IPPROTO_IPV6 &&
             cmsgptr->cmsg_type == IPV6_RTHDR) {
                 struct in6_addr *in6;
                 char asciiname[INET6_ADDRSTRLEN];
                 struct ip6_rthdr *rthdr;
                 int    segments, route_type;

                 rthdr = (struct ip6_rthdr *)extptr;
                 segments = inet6_rth_segments(extptr);
                 printf("route (%d segments, %d left): ",
                     segments, rthdr->ip6r_segleft);
                 route_type = rthdr->ip6r_type;
                 if (route_type == 2) {
                         printf ("Routing header Type 2 present\n");
                 }
         }

   The function inet6_rth_gettype() returns the routing header type on
   success.  It returns -1 on error.

5.2  Content of Type 2 Routing Header

   It is recommended that no portable applications will send Routing
   Header Type 2 ancillary data from the application layer, since many
   implementations take care of that at the kernel layer and may not
   support the API for sending routing header type 2.

   For user-level applications that receive Routing Header Type 2,
   inet6_rth_getaddr() returns the Care-Of Address or the original
   destination address of the received packet.  This complies with the
   existing Routing header Type=0 processing for IPv6 [1].

   Thus on the receive side, the socket application will always receive
   data packets at its original home-address.  The implementations are
   responsible for processing the routing header type 2 packet as per
   Mobile IPv6 RFC [2], before passing the routing header type 2
   information to the Socket API.

   If a pure IPv6 [3] system receives the Routing Header Type 2 packets,
   it will follow the process described in Section 4.4 of the IPv6 [3]
   base specification.

5.3  Order of extension headers for Home Address Destination Options

   Section 6.3 of Mobile IPV6 [2] defines the extension header order for
   Home address destination option.




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    Routing Header
    Home Address Destination Option
    Fragment Header
    AH/ESP Header


   IPv6 [3] specifies that the destination header can be either before
   the Routing header or after the AH/ESP header if they are all
   present.

   Thus, when the Home Address destination option is present along with
   other extension headers, the order will be:


          Hop-by-Hop Options header
          Destination Options header (note 1)
          Routing header
          Destination Options [Home Address Option]
          Fragment header
          Authentication header (note 2)
          Encapsulating Security Payload header (note 2)
          Destination Options header (note 3)
          upper-layer header


   Any user-level implementation or application that sends Home address
   destination option through ancillary data objects should follow the
   order extension header defined in this document when using
   IPV6_MIPDSTOPTS socket options.

5.4  Home Address Destination Option access functions

   The application must enable the IPV6_RECVDSTOPTS socket option in
   order to receive the Home Address destination option (error checking
   is not performed in the example for brevity):

     int  on = 1;

     setsockopt(fd, IPPROTO_IPV6, IPV6_RECVDSTOPTS, &on, sizeof(on));

   Each Destination option header is returned as one ancillary data
   object described by a cmsghdr structure with cmsg_level set to
   IPPROTO_IPV6 and cmsg_type set to IPV6_DSTOPTS.

   The received side Home Address destination option is further
   processed by calling the inet6_opt_next(), inet6_opt_find(), and
   inet6_opt_get_value() functions as defined in Advanced API for IPv6
   sockets [1].



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   This document assumes that portable Mobile IPv6 applications will not
   send a Home Address Destination Option from the application level, as
   the Mobile IPv6 implementation underneath takes care of sending the
   Home Address option and the routing header type 2 at the kernel.
   However, some embedded software implementations may implement the
   IPv6 packet processing/sending at the user-level; those
   implementations may choose to provide the API support for sending a
   home-address option at the application layer.  In this case, the Home
   Address destination options are normally constructed by using the
   inet6_opt_init(), inet6_opt_append(), inet6_opt_finish(), and
   inet6_opt_set_val() functions, described in Section 10 of the
   Advanced sockets API for IPv6 [1].

5.5  Content of Home Address Destination option

   The received ancillary data object for the Home Address destination
   option SHOULD contain the Care-Of-Address of the mobile node.  It is
   assumed that the initial processing of the Home Address destination
   option will verify the validity of home-address as described in 6.3
   and 9.5 of the Mobile IPv6 Specification [2] and swap the source
   address of the packet (COA) with the contents of Home Address
   destination option.

   Note that whether or not these new APIs are used, the sender's home
   address is contained in the source address (which is passed to the
   application using the socket-level functions recvfrom(), recvmsg(),
   accept() and getpeername()).  This is  necessary for:

      maintaining consistency between simple user-level applications
      running between mobile nodes and the diagnostic applications on
      home-agent or on correspondent node, which use this API.

      obtaining the COA address of the mobile node when the Home Address
      destination option is used.

      maintaining consistency of existing IPv6 Socket APIs and
      processing of the Home Address destination option.

   If an implementation supports send-side Home Address destination API,
   then it must follow the same rule for data content as specified in
   Mobile IPv6 RFC [2] for sending a home-address option.  Thus the
   home-address option will contain the home-address and the
   implementation will use the care-of-address as the source address of
   the outgoing packet.  If the implementation uses IPSec, then it
   should use the content of Home Address destination option as source
   address of the packet for security association.  Note that regular
   user applications must not set the Home-address destination option.




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6.  Mobility Protocol Headers

   Mobile IPv6 [2] defines a new IPv6 protocol header to carry mobility
   messages between  Mobile Nodes, Home Agents and Correspondent Nodes.
   These protocol headers carry Mobile IPv6 Binding messages as well as
   Return Routability [2] messages.  Currently the specification [2]
   does not allow transport packets (piggybacking) along with the
   mobility messages.  Thus the mobility protocol header can be accessed
   through an IPv6 RAW socket.  An IPv6 RAW socket that is opened for
   protocol IPPROTO_MH should always be able to see all the MH (Mobility
   Header) packets.  It is possible that future applications may
   implement part of Mobile IPv6 signal processing at the application
   level.  Having a RAW socket interface may also enable an application
   to execute the Return Routability protocol or other future
   authentication protocol involving the mobility header at the user-
   level.

6.1  Receiving and Sending Mobility Header Messages

   This specification recommends the IPv6 RAW sockets mechanism to send
   and receive Mobility Header (MH) packets.  The behavior is similar to
   ICMPV6 processing, where the kernel passes a copy of the mobility
   header packet to the receiving socket.  Depending on the
   implementation, the kernel may process the mobility header in
   addition to passing the mobility header to the application.  In order
   to comply with the restriction in the Advanced Sockets API for IPv6
   [1], applications should set the IPV6_CHECKSUM socket option with
   IPPROTO_MH protocol RAW Sockets.  A Mobile IPv6 implementation that
   supports the Mobile IPv6 API, must implement Mobility Header API
   checksum calculations by default at the kernel for both incoming and
   outbound path.  A Mobile IPv6 implementation must not return error on
   the IPV6_CHECKSUM socket option setting, even if the socket option is
   a NO-OP function for that implementation because it verifies the
   checksum at the kernel level.  Mobility Header checksum procedure is
   described in the Mobile IPv6 Protocol [2] specification.  Again, for
   application portability it is recommended that the applications set
   the IPV6_CHECKSUM socket option along with the RAW sockets for
   IPPROTO_MH protocol.

   As an example, a program that wants to send or receive a mobility
   header protocol(MH), could open a socket as following (for brevity,
   the error checking is not performed in the example below):

        fd = socket(AF_INET6, SOCK_RAW, IPPROTO_MH);

        int offset = 4;
        setsockopt(fd, IPPROTO_IPV6, IPV6_CHECKSUM, &offset,
             sizeof(offset));



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   For example, if an implementation likes to handle HOTI/HOT and COTI/
   COT message processing, it can do so by using IPv6 RAW Sockets for
   IPPROTO_MH at the application layer.  The same application may also
   set the IPV6_RECVDSTOPTS socket option for receiving home-address
   option in a binding update [2] from the mobile node.

   IPv6 RAW sockets are described in Section 3 of the IPv6 Advanced
   Socket API [1] specification.  All data sent and received via raw
   sockets must be in network byte order.  The data structures that are
   defined in this document are in network byte order and they are
   believed to be supported by most compilers to directly hold packet-
   formats for transmission on the wire.

   The usual send/recv functions for datagram should be used for the
   Mobile IPv6 RAW sockets in order to send and receive data,
   respectively.



































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7.  Protocols File

   Many hosts provide the file /etc/protocols that contains the names of
   the various IP protocols and their protocol numbers.  The protocol
   numbers are obtained through function getprotoXXX() functions.

   The following addition should be made to the /etc/protocols file, in
   addition to what is defined in Section 2.4 of the Advanced Sockets
   API for IPv6 [1].

   The protocol number for Mobility Header:
   (http://www.iana.org/assignments/protocol-numbers)

      ipv6-mh           135      # Mobility Protocol Header





































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8.  IPv4-Mapped IPv6 Addresses

   The various socket options and ancillary data specifications defined
   in this document apply only to true IPv6 sockets.  It is possible to
   create an IPv6 socket that actually sends and receives IPv4 packets,
   using IPv4-mapped IPv6 addresses, but the mapping of the options
   defined in this document to an IPv4 datagram is beyond the scope of
   this document.  The above statement is in compliance with Section 13
   of the IPv6 Socket API [1].










































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9.  Security Considerations

   The setting of the Home Address Destination option and Route Header
   Type 2 IPV6_RTHDR socket option may not be allowed at the application
   level in order to prevent denial-of-service attacks or man-in-the-
   middle attacks by hackers.  Sending and receiving of mobility header
   messages are possible by IPv6 RAW sockets.  Thus it is assumed that
   this operation is only possible by privileged users.  However, this
   API does not prevent the existing security threat from a hacker
   sending a bogus mobility header or other IPv6 packets using the Home
   Address option and Type 2 Routing Header extensions.








































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10.  IANA Considerations

   This document does not define a new protocol.  However, it uses the
   Mobility Header Protocol for IPv6 to define an API for /etc/protocols
   file. (ref: http://www.iana.org/assignments/protocol-numbers)














































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11.  Changes from last revisions


     [ TO BE DELETED BY THE RFC EDITOR BEFORE PUBLISHING AS A RFC]

     Version 05 changes:
     * Addressed IESG review comments.

     Version 04 changes:
     * Addressed Last call comment remaining issues and Area Director
       review comments

     Version 03 changes:
     * Modified new ICMPv6 type definition values to match RFC3775.

     Version 02 changes:
     * Added section 3.1.1 and 3.2.1 to clarify content of routing
       header type 2 and destination options.

     * Clarified existing socket application behavior in section 3.

     * Updated introduction to clarify scope of the applications wrt
       this API

     * Added IANA section and Full Copyright statement and internet
       draft boiler plate

     * Updated acknowledgement section and fixed typo etc.

     The following changes were made in 01 version per feedback from
     the implementors at Connectathon 2004.

     * Section 2.1.11.2 now  defines alternate COA address data
       structure as struct in6_addr for consistency. It was defined as
       16 unit of bytes.

     * Added Binding Update Authdata of 12 bytes in the
       struct ip6_mh_opt_auth_data

     * Added a new function inet6_rth_gettype() in section 3.1 in order
       to distinguish routing header type 2 ancillary data items from
       type 0 routing header ancillary data items on the receive side.

     * Updated the Acknowledgement and Authors' address section







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12.  Acknowledgement

   Thanks to Brian Haley for the thorough review of this draft and many
   helpful comments.  Keiichi Shima, Alexandru Petrescu, Ryuji Wakikawa,
   Vijay Devarapalli, Jim Bound, Suvidh Mathur, Karen Nielsen, Mark
   Borst, Vladislav Yasevich and other mobile-ip working group members
   provided valuable input.  Antti Tuominen suggested the routing header
   type function for this API document.  During IESG review, Bill Fenner
   suggested accessing routing header type directly for being consistent
   with RFC3542.  A new socket option for Home Address Destination
   Option is added as per Bill Fenner's suggestion for clarity of
   extension header orders.  Thanks to Thomas Narten and Jari Arkko for
   the review of this document.






































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13.  References

13.1  Normative References

   [1]  Stevens, W., Thomas, M., Nordmark, E., and T. Jinmei, "Advanced
        Sockets Application Program Interface (API) for IPv6", RFC 3542,
        May 2003.

   [2]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
        IPv6", RFC 3775, June 2004.

13.2  Informative References

   [3]  Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
        Specification", RFC 2460, December 1998.

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

   [5]  Nordmark, E., "IPv6 Socket API for source address selection",
        draft-chakrabarti-ipv6-addrselect-api-03 (work in progress),
        July 2005.

   [6]  Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.
        Stevens, "Basic Socket Interface Extensions for IPv6", RFC 3493,
        February 2003.


Authors' Addresses

   Samita Chakrabarti
   Sun Microsystems
   16 Network Circle
   Menlo Park, CA 94025
   USA

   Phone: +1 650 786 5068
   Email: samita.chakrabarti@sun.com












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   Erik Nordmark
   Sun Microsystems
   17 Network Circle
   Menlo Park, CA 94025
   USA

   Phone: +1 650 786 2921
   Email: erik.nordmark@sun.com











































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Internet-Draft         Sockets API for Mobile IPv6         December 2005


Intellectual Property Statement

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Chakrabarti & Nordmark    Expires June 10, 2006                [Page 34]


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