Skip to main content

Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Options for IEEE 802.21 Mobility Services (MoS) Discovery
draft-ietf-mipshop-mos-dhcp-options-14

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 5678.
Authors Gabor Bajko , Subir Das
Last updated 2015-10-14 (Latest revision 2009-05-04)
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Proposed Standard
Formats
Reviews
Additional resources Mailing list discussion
Stream WG state (None)
Document shepherd (None)
IESG IESG state Became RFC 5678 (Proposed Standard)
Action Holders
(None)
Consensus boilerplate Unknown
Telechat date (None)
Responsible AD Jari Arkko
Send notices to (None)
draft-ietf-mipshop-mos-dhcp-options-14
Internet Engineering Task force                           Gabor Bajko 
Internet Draft                                                  Nokia 
Intended Status: Proposed Standard                          Subir Das 
Expires: October 31, 2009                      Telcordia Technologies
                                                         May 01, 2009  
 

Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Options for 
                    IEEE 802.21 Mobility Services (MoS) Discovery 
                    draft-ietf-mipshop-mos-dhcp-options-14 

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with 
   the provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on October 31, 2009.

Copyright and License Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors. All rights reserved.
   
   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

   
Abstract 
    
   This document defines new Dynamic Host Configuration Protocol  
   (DHCPv4 and DHCPv6) options that contain a list of IP addresses and 
   a list of domain names that can be mapped to servers providing IEEE
  
G. Bajko & S Das           Expires 10/31/09                  [Page 1] 
 
Mobility Services DHCP Options                             May 2009 

   802.21 type of Mobility Service (MoS)[MSFD]. These Mobility 
   Services are used to assist a mobile node (MN) in handover 
   preparation (network discovery) and handover decision (network 
   selection). The services addressed in this document are the Media 
   Independent Handover Services defined in [IEEE802.21].  
        
    
Table of Contents 
    
   1. Introduction ................................................2 
   2. MoS IPv4 address option for DHCPv4............................3 
   3. MoS Domain Name List option for DHCPv4........................5      
   4. MoS IPv6 address option for DHCPv6............................7     
   5. MoS Domain Name List option for DHCPv6........................9    
   6. Option Usage.................................................10 
        6.1 Usage of MoS Options for DHCPv4........................10 
        6.2 Usage of MoS Options for DHCPv6........................11 
   7. Security Considerations .....................................12 
   8. IANA Considerations .........................................12 
   9. Acknowledgements ............................................13 
   10. References .................................................13 
       10.1 Normative References ..................................13
       10.2 Informative References ................................14 
   Author's Addresses .............................................14 
   

(1) Conventions used in this document 
    
   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. 
    
 (2) Terminology and abbreviations used in this document 
    
   Mobility Services: a set of services provided by the network to 
   mobile nodes to facilitate handover preparation and handover 
   decision. In this document, Mobility Services refer to
   the services defined in IEEE 802.21 specifications [IEEE802.21]
    
   Mobility Server: a network node providing Mobility Services. 
    
   MIH: Media Independent Handover, as defined in [IEEE802.21]. 
    
   MIH Service: IS, ES or CS type of service, as defined in 
   [IEEE802.21]  
 

G. Bajko & S. Das          Expires 10/31/09                [Page 2]  

Mobility Services DHCP Options                            May 2009 
  

1. Introduction 
    
   IEEE 802.21 [IEEE802.21] defines three distinct service types to 
   facilitate link layer handovers across heterogeneous technologies: 
    
   a) Information Services (IS) 
        IS provides a unified framework to the higher layer entities 
   across the heterogeneous network environment to facilitate 
   discovery and selection of multiple types of networks existing 
   within a geographical area, with the objective to help the higher 
   layer mobility protocols to acquire a global view of heterogeneous 
   networks and perform seamless handover across these networks. 

     b) Event Services (ES) 
        Events may indicate changes in state and transmission behavior
   of the physical, data link and logical link layers, or predict state 
   changes of these layers. The Event Service may also be used to 
   indicate management actions or command status on the part of the 
   network or some management entity. 
    
   c) Command Services (CS) 
        The command service enables higher layers to control the 
   physical, data link, and logical link layers. The higher layers may 
   control the reconfiguration or selection of an appropriate link 
   through a set of handover commands. 
    
   In IEEE terminology these services are called Media Independent 
   Handover (MIH) services. While these services may be co-located, 
   the different pattern and type of information they provide does not 
   necessitate the co-location. 
    
   An mobile node (MN) may make use of any of these MIH service types 
   separately or any combination of them [MSFD]. In practice a Mobility 
   Server may not necessarily host all three of these MIH services 
   together, thus there is a need to discover the MIH services types 
   separately. 
    
   This document defines new DHCPv4 and DHCPv6 options and sub-options
   called the MoS IP Address and Domain Name List Options, which allow
   the MN to locate a Mobility Server which hosts the 
   desired service type (i.e. IS, ES or CS) as defined in [IEEE802.21]. 
   Apart from manual configuration, this is one of the possible 
   solutions for locating a server providing Mobility Services.  
    
2. MoS IPv4 Address Option for DHCPv4
    
   This section describes the MoS IPv4 Address Option for DHCPv4. 
   Whether the MN receives an MoS address from local or home network 
   will depend on the actual network deployment [MSFD]. The MoS IPv4
  
G. Bajko & S. Das           Expires 10/31/09                 [Page 3]

 Mobility Services DHCP Options                             May 2009 

   Address Option begins with a option code followed by a length and 
   sub-options. The value of the length octet does not include itself 
   or the option code. The option layout is depicted below:

     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 
                                     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
                                     | Option Code   |    Length     | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                     Sub-Option 1                              |
     .                                                               . 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       ...                                     |
     .                                                               . 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                     Sub-Option n                              | 
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 
         Option Code 
    
                OPTION-IPv4_Address-MoS (To Be Assigned) - 1 byte  
    
         Length 
        
                An 8-bit field indicating the length of the option  
                excluding the 'Option Code' and the 'Length' fields 

         Sub-options 
    
                A series of DHCPv4 sub-options 

   When the total length of a MoS IPv4 Address Option exceeds 254 
   octets, the procedure outlined in [RFC3396] MUST be employed to 
   split the option into multiple, smaller options.

   A sub-option begins with a sub-option code followed by a length 
   and one or more IPv4 addresses.  The sub-option layout is 
   depicted below:

       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 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      | Sub-opt Code  |    Length     |    IP Address . . . . . 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .                                                               . 
      .                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  
 

 G. Bajko & S. Das           Expires 10/31/09                  [Page 4] 
 Mobility Services DHCP Options                                May 2009 
 
 
 The sub-option Codes are summarized below.
      +--------------+---------------+
      |  Sub-opt     | Service       |                               
      |   Code*      | Name          |                                            
      +==============+===============+
      |    1         |   IS          |     
      +--------------+---------------+
      |    2         |   CS          | 
      +--------------+---------------+
      |    3         |   ES          | 
      +--------------+---------------+      

*Note: The values `0` and '4' to '255' are reserved.
 
If the length is followed by a list of IPv4 addresses indicating 
appropriate MIH servers available to the MN for a requested option, 
servers MUST be listed in order of preference and the client should 
process them in decreasing order of preference. In case there is no 
MIH server available, the length is set to 0, otherwise it is a 
multiple of 4. 

The sub-option has the following format: 
   
           Code Len   IPv4 Address 1    IPv4 Address 2 
         +-----+---+---+----+----+----+----+----+--- 
         |1..3 | n |a1 | a2 |a3  | a4 | a1 |  ... 
         +-----+---+---+----+----+----+-----+----+-- 
 
     
 
3. MoS Domain Name List Option for DHCPv4 
    
   This section describes the MoS Domain Name List Option for DHCPv4. 
   The general format of this option is depicted below:
  
     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 
                                     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
                                     | Option Code   |    Length     | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                     Sub-Option 1                              |
     .                                                               . 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       ...                                     |
     .                                                               . 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     
  

   
   G. Bajko & S. Das          Expires 10/31/09               [Page 5]  

   Mobility Services DHCP Options                          May 2009 

     
     
     |                     Sub-Option n                              | 
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   
    Option Code 
    
                OPTION-IPv4_FQDN-MoS (To Be Assigned) - 1 byte  
    
  
     Length     
                An 8-bit field indicating the length of the option  
                excluding the 'Option Code' and the 'Length' fields 

         Sub-options 
    
                A series of DHCPv4 sub-options. 

   When the total length of a MoS Domain Name List Option exceeds 254 
   octets, the procedure outlined in [RFC3396] MUST be employed to 
   split the option into multiple, smaller options.

   A sub-option begins with a sub-option Code followed by a length 
   and one or more FQDNs.  The sub-option layout is depicted below:

       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 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      | Sub-opt Code  |    Length     |  FQDN(s) . . . . . .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .                                                               . 
      .                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The sub-option Codes are summarized below.
      +--------------+---------------+
      |  Sub-opt     | Service       |                               
      |   Code*      | Name          |                                            
      +==============+===============+
      |    1         |   IS          |     
      +--------------+---------------+
      |    2         |   CS          | 
      +--------------+---------------+
      |    3         |   ES          | 
      +--------------+---------------+      

*Note: The values `0` and '4' to '255' are reserved.

G. Bajko & S. Das           Expires 10/31/09                [Page 6]  

  Mobility Services DHCP Options                           May 2009  

  Thus the sub-option for this encoding has the following format: 

           Code  Len   DNS name of MoS server 
         +-----+----+----+-----+-----+-----+-----+-- 
         |1..3 | n  | s1 |  s2 |  s3 |  s4 | s5  |  ... 
         +-----+----+----+-----+-----+-----+-----+-- 

   The Sub-option begins with a sub-option code followed by a length 
   and a sequence of labels that are encoded according to Section 8 of 
   [RFC3315]. 

   The Sub-option MAY contain multiple domain names, but these should 
   Refer to the NAPTR records of different providers, rather than 
   different A records within the same provider. That is, the use of 
   multiple domain names is not meant to replace NAPTR and SRV records,
   but rather to allow a single DHCP server to indicate MIH servers 
   operated by multiple providers.

   The client MUST try the records in the order listed, applying the
   mechanism described in [MoS-DNS] for each. The client only resolves 
   the subsequent domain names if attempts to contact the first one 
   failed or yielded no common transport protocols between the MN and 
   the server. 
 
   As an example, consider the case where the server wants to offer 
   two MIH IS servers, "example.com" and "example.net".  These would 
   be encoded as follows:  
   +-----+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ 
   |1..3 |26 | 7 |'e'|'x'|'a'|'m'|'p'|'l'|'e'| 3 |'c'|'o'|'m'| 0 | 
   +-----+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ 
   +---+---+---+---+---+---+---+---+---+---+---+---+---+ 
   | 7 |'e'|'x'|'a'|'m'|'p'|'l'|'e'| 3 |'n'|'e'|'t'| 0 | 
   +---+---+---+---+---+---+---+---+---+---+---+---+---+ 

4. MoS IPv6 Address Option for DHCPv6 
    
   This section describes the MoS IPv6 Address Option for DHCPv6. 
   Whether the MN receives an MoS address from local or home network 
   will depend on the actual network deployment [MSFD]. The MoS 
   Discovery Option begins with a option code followed by a length 
   and sub-options. The value of the length octet does not include 
   itself or the option code. The option layout is depicted below:

     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 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |       Option Code             |           Length              | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                     Sub-Option 1                              | 
     .                                                               .
     
   G. Bajko & S. Das           Expires 10/31/09               [Page 7]  

   Mobility Services DHCP Options                           May 2009 

 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       ...                                     |
     .                                                               . 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                     Sub-Option n                              | 
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       Option Code 
    
             OPTION-IPv6_Address-MoS (To Be Assigned) - 2 bytes  
  
       Length 
   
             A 16-bit field indicating the length of the option  
             excluding the 'Option Code' and the 'Length' fields.    

       Sub-options 
    
             A series of DHCPv6 sub-options 
                
   The sub-options follow the same format (except the Sub-opt Code and  
   Length value) as described in Section 2. The value of the Sub-opt 
   Code and Length are 2-octets and the Length does not include itself 
   or the Sub-opt Code field. The sub-option layout is depicted below: 

      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 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     | sub-opt Code                  |     Length                    | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                   IP Address                                  |
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      
  The sub-option Codes are summarized below.
      +----------------+---------------+
      |  Sub-opt Code* | Service Name  |                               
      +================+===============+
      |    1           |   IS          |
      +----------------+---------------+
      |    2           |   CS          | 
      +----------------+---------------+
      |    3           |   ES          | 
      +----------------+---------------+
*Note: The values `0` and '4' to '65535' are reserved.

If the length is followed by a list of IPv6 addresses indicating 
appropriate MIH servers available to the MN for a requested option,
servers MUST be listed in order of preference and the client should 

G. Bajko & S. Das           Expires 10/31/09                 [Page 8]  

Mobility Services DHCP Options                             May 2009 

process them in decreasing order of preference. In case there is no MIH 
server available, the length is set to 0, otherwise it is a multiple of 
16.

5. MoS Domain Name List option for DHCPv6    

   This section describes the MoS Domain List Option for DHCPv6. The 
   general format of this option for is depicted below: 

      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 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |       Option Code             |           Length              | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                     Sub-Option 1                               | 
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                       ...                                     |
     .                                                               .                                                                                                                        
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                     Sub-Option n                              | 
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  
       Option Code 
    
             OPTION-IPv6_FQDN-MoS (To Be Assigned) - 2 bytes  
  
       Length 
   
             A 16-bit field indicating the length of the option  
             excluding the 'Option Code' and the 'Length' fields.    

       Sub-options 
    
             A series of DHCPv6 sub-options 
                
   The Sub-options follow the same format (except the Sub-opt Code and  
   Length value) as described in Section 3. The value of the Sub-opt 
   Code and Length are 2-octets and the Length does not include itself 
   or the Sub-opt Code field. The sub-option layout is depicted below: 

      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 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     | sub-opt Code                  |     Length                    | 
     
   
  G. Bajko & S. Das           Expires 10/31/09               [Page 9]  
 

   Mobility Services DHCP Options                            May 2009 

     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                   FQDN(s)                                     |
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 

 The sub-option Codes are summarized below.
      +----------------+---------------+
      |  Sub-opt Code* | Service Name  |                               
      +================+===============+
      |    1           |   IS          |
      +----------------+---------------+
      |    2           |   CS          | 
      +----------------+---------------+
      |    3           |   ES          | 
      +----------------+---------------+
   
   *Note: The values `0` and '4' to '65535' are reserved.

   The semantics and content of the DHCPv6 encoding of this option are
   exactly the same as the encoding described in Section 3, except the  
   Option Code and Length value.
      

                 
6. Option Usage 
    
6.1 Usage of MoS Options for DHCPv4 
     
   The requesting and sending of the proposed DHCPv4 options follow 
   the rules for DHCP options in [RFC2131]. 
     
6.1.1 Mobile Node behavior 
    
   The mobile node may perform a MoS discovery either during initial 
   association with a network or when the mobility service is required. 
   It may also try to perform the MoS discovery when it lacks the 
   network information for MoS or needs to change the MoS for some 
   reasons, for instance, to recover from the single point of failure 
   of the existing MoS. 

   In order to discover the IP address or FQDN of a MoS, the mobile 
   node (DHCP client) MUST include either a MoS IPv4 Address Option 
   or a MoS Domain Name List Option in the Parameter Request List 
  (PRL) in the respective DHCP messages as defined in [RFC2131].

   The client MAY include a MoS IPv4 Address Option or a MoS Domain
   Name List Option that includes one or more sub-option(s) with the
 
 
 G. Bajko & S. Das           Expires 10/31/09                [Page 10]  

  Mobility Services DHCP Options                             May 2009 
   
  Sub-opt Code(s) that represents the service(s) the mobile node is
  interested in. However, a client SHOULD be prepared to accept a
  response from a server that includes other sub-option(s) or does
  not include the requested sub-option(s).

6.1.2 DHCP Server behavior 
    
   When the DHCP Server receives either a MoS IPv4 Address Option or 
   a MoS Domain Name List Option in the PRL, the DHCP server MUST
   include the option in its response message as defined in [RFC2131]. 

   A server MAY use the sub-options in the received MoS IPv4 Address
   Option or MoS Domain Name List Option from the client's message
   to restrict its response to the client requested sub-options. In
   the case when the server cannot find any Mobility Server satisfying 
   a requested sub-option, the server SHOULD return the MoS Option 
   with that sub-option and the length of the sub-option set to 0. 
  
  
6.2 Usage of MoS Options for DHCPv6  
    
   The requesting and sending of the proposed DHCPv6 options follow 
   the rules for DHCP options in [RFC3315]. 
    
6.2.1 Mobile node behavior 
    
   The mobile node may perform the MoS discovery either during initial 
   association with a network or when the mobility service is required.
   It may also try to perform the MoS discovery when it lacks the 
   network information for MoS or needs to change the  MoS for some 
   reasons, for instance, to recover from the single point of failure 
   of the existing MoS. 
   
   In order to discover the IP address or FQDN of a MoS, the mobile 
   node (DHCP client) MUST include either a MoS IPv6 Address Option 
   or a MoS Domain Name List Option in the Option Request Option (ORO)
   in the respective DHCP messages as defined in [RFC3315].

   The client MAY include a MoS IPv6 Address Option or a MoS Domain
   Name List Option that includes one or more sub-option(s) with the
   Sub-opt Code(s) that represents the service(s) the mobile node is
   interested in. However, a client SHOULD be prepared to accept a
   response from a server that includes other sub-option(s) or does
   not include the requested sub-option(s).

6.2.2 DHCP Server behavior 
   
   When the DHCP Server receives either a MoS IPv6 Address Option or 
  
 G. Bajko & S. Das           Expires 10/31/09               [Page 11]  
 Mobility Services DHCP Options                             May 2009

  
   a MoS Domain Name List Option in the ORO, the DHCP server MUST
   include the option in its response message as defined in [RFC3315].

   A server MAY use the sub-options in the received MoS IPv6 Address
   Option or MoS Domain Name List Option from the client's message
   to restrict its response to the client requested sub-options. In
   the case when the server cannot find any Mobility Server satisfying 
   a requested sub-option, the server SHOULD return the MoS Option 
   with that sub-option and the length of the sub-option set to 0. 
  

7. Security Considerations 
    
   The security considerations in [RFC2131] apply. If an adversary 
   manages to modify the response from a DHCP server or insert its own 
   response, an MN could be led to contact a rogue Mobility Server, 
   possibly one that then would provide wrong information, event or 
   command for handover.  

   It is recommended to use either DHCP authentication option described 
   in [RFC3118] where available. This will also protect the denial of 
   service attacks to DHCP servers. [RFC3118] provides mechanisms for 
   both entity authentication and message authentication. 

   In deployments where DHCP authentication is not available, lower 
   layer security services may be sufficient to protect DHCP messages. 

   Regarding domain name resolution, it is recommended to consider the 
   usage of DNSSEC [RFC4033] and the aspects of DNSSEC Operational
   Practices [RFC4641]. Security considerations described in [MoS-DNS] 
   also apply. 
    

8. IANA Considerations 

   This document defines two new DHCPv4 options as described in Sections 
   2 and 3. 

   MoS IPv4 Address Option for DHCPv4 (OPTION-IPv4_Address-MoS)    TBA

   MoS Domain Name List option for DHCPv4 (OPTION-IPv4_FQDN-MoS)   TBA   
  
   This document creates a new registry for the Sub-Option fields in 
   the MoS DHCPv4 Address and FQDN options called the "IEEE 802.21
   Service Type" (Section 2 and 3).
      IS                       1
      CS                       2
      ES                       3  

G. Bajko & S. Das           Expires 10/31/09                [Page 12]  

 Mobility Services DHCP Options                             May 2009

  The values '0', and '4' to '255' are reserved. New Values can be
  allocated via Standards Action as defined in [RFC5226].

  This document also defines two DHCPv6 options as described in 
  sections 4 and 5.

   MoS IPv6 Address Option for DHCPv6 (OPTION-IPv6_Address-MoS)   TBA  

   MoS Domain Name List option for DHCPv6 (OPTION-IPv6_FQDN-MoS)  TBA   
   
   This document creates a new registry for the sub-option field in 
   the MoS DHCPv6 Address and FQDN options called the "IEEE 802.21 
   Service Type" (Section 4 and 5).
        IS                       1
        CS                       2
        ES                       3
        
  The values '0', and '4' to '65535' are reserved. New Values can be
  allocated via Standards Action as defined in [RFC5226].
  

    
9. Acknowledgements 
    
   Authors would like to acknowledge the following individuals for 
   their valuable comments. 
   Alfred Hoenes, Bernie Volz,  David W. Hankins, Jari Arkko, 
   Telemaco Melia, Ralph Droms Ted Lemon, Vijay Devarapalli,  and 
   Yoshihiro Ohba 

10. References

    10.1 Normative References 
                
   [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 
      2131, March 1997. 

   [RFC3315] Dynamic Host Configuration Protocol for IPv6 (DHCPv6), 
      Droms et al, July 2003 

   [RFC3118] Authentication for DHCP Messages, Droms et al, June 2001 

   [RFC3396] Lemon, T. and S. Cheshire, "Encoding Long DHCP Options", 
      RFC3396, November 2002. 
    
   
 

 G. Bajko & S. Das           Expires 10/31/09              [Page 13]  

  Mobility Services DHCP Options                            May 2009
 
  [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 
       Rose, "DNS Security Introduction and Requirements", RFC 4033, 
       March 2005.

  [RFC5226] T. Narten and H. Alvestrand, "Guidelines for Writing an 
    IANA  Considerations Section in RFCs" , May 2008. 
  
  
  [MSFD] T Melia, Ed., "Mobility Services Framework Design (MSFD)",
      draft-ietf-mipshop-mstp-solution-12.txt (Work in Progress).

   [MoS-DNS] Bajko, G., "Locating Mobility Servers",
      draft-ietf-mipshop-mos-dns-discovery-04.txt (Work in Progress), 

   10.2 Informative References 
    
   
   [RFC4641] Kolkman, O. and R. Gieben, "DNSSEC Operational Practices", 
       RFC 4641, September 2006. 

   [IEEE802.21] IEEE 802.21 Standard for Local and Metropolitan Area 
      Networks: Media Independent Handover Services. 

   
    

Authors' Addresses 
    
   Gabor Bajko 
   Nokia 
   e-mail: gabor.bajko@nokia.com 
   
   Subir Das 
   Telcordia Technologies Inc.
   e-mail: subir@research.telcordia.com   
 

G. Bajko & S. Das           Expires 10/31/09                [Page 14]