path: root/doc/rfc/rfc4280.txt

Network Working Group                                       K. Chowdhury
Request for Comments: 4280                              Starent Networks
Category: Standards Track                                      P. Yegani
                                                           Cisco Systems
                                                               L. Madour
                                                                Ericsson
                                                           November 2005


         Dynamic Host Configuration Protocol (DHCP) Options for
                Broadcast and Multicast Control Servers

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document defines new options to discover the Broadcast and
   Multicast Service (BCMCS) controller in an IP network.  BCMCS is
   being developed for Third generation (3G) cellular telephone
   networks.  Users of the service interact with a controller in the
   network via the Mobile Node (MN) to derive information required to
   receive Broadcast and Multicast Service.  Dynamic Host Configuration
   Protocol can be used to configure the MN to access a particular
   controller.  This document defines the related options and option
   codes.
















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Table of Contents

   1. Motivation ......................................................2
   2. Overview of the 3GPP2 BCMCS Network .............................3
   3. Terminology .....................................................4
   4. Broadcast and Multicast Service Controller Options ..............4
      4.1. Broadcast and Multicast Service Controller Domain
           Name List for DHCPv4 .......................................4
      4.2. Broadcast and Multicast Service Controller Domain
           Name List Option for DHCPv6 ................................5
      4.3. Broadcast and Multicast Service Controller IPv4
           Address Option for DHCPv4 ..................................6
      4.4. Broadcast and Multicast Service Controller IPv6
           Address Option for DHCPv6 ..................................6
      4.5. Consideration for Client Operation .........................7
      4.6. Consideration for Server Operation .........................7
   5. Security Considerations .........................................8
   6. IANA Considerations .............................................8
   7. Acknowledgements ................................................8
   8. Normative References ............................................9

1.  Motivation

   Dynamic Host Configuration Protocol [RFC2131] and [RFC3315] can be
   used to configure various non-IP address type of parameters.  These
   parameters are required for normal operation of various services that
   are offered over an IP network.

   Broadcast and Multicast Service (BCMCS) is one such service that is
   being standardized in various mobile wireless standard bodies such as
   Third Generation Partnership Project 2 (3GPP2), Open Mobile Alliance
   (OMA), and 3GPP.  A description of the BCMCS as defined in 3GPP2 can
   be found in [BCMCS].

   While DHCP already defines many options for device configuration, no
   option exists for configuring a mobile device to use BCMCS.  This
   memo defines extensions for both DHCPv4 and DHCPv6 so that DHCP can
   be used to provide necessary configuration information to a mobile
   device about the BCMCS controllers.

   DHCP is being used in 3GPP2, to assist Mobile Nodes (MNs) with the
   discovery of the BCMCS Controller in a mobile operator's IP network.
   The BCMCS includes a controller component that is responsible for
   managing the service via interaction with the MN and other network
   entities.  In this document, we will call this a BCMCS controller.






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   An overview of the 3GPP2 BCMCS architecture is given in the next
   section.  It provides enough information to understand the basics of
   the 3GPP2 BCMCS operation.  Readers are encouraged to find a more
   detailed description in [BCMCS].

   As described in [BCMCS], the MNs are required to know the IPv4 or the
   IPv6 address of the BCMCS controller entity so that they can download
   all the necessary information about a desired broadcast and/or a
   multicast program.  In a roaming environment, static configuration of
   the BCMCS controller's IP address becomes unrealistic.  Therefore,
   DHCP is considered to be a method to dynamically configure the MNs
   with the IP address or the fully qualified domain name (FQDN) of the
   BCMCS controller in the 3G cellular telephone networks.

   In order to allow the MNs to discover the BCMCS controllers, the MNs
   request the appropriate option codes from the DHCP server.  The DHCP
   servers need to return the corresponding configuration options that
   carry either BCMCS controller's IP address or FQDN based on
   configuration.  This document defines the necessary options and
   option codes.

2.  Overview of the 3GPP2 BCMCS Network

   The Broadcast and Multicast Service architecture in a 3G cellular
   telephone network such as 3GPP2 has the following model:

                              +------------+   +--------+
                              |   BCMCS    |   |        |
                              | Controller |   |  DHCP  |
                              |            |   | Server |
                              +------------+   +--------+
                                     ^
                              Control|
                                 Info|
                                     |
                                     |
                                     V
   +----+        +------------+    +------------+
   |    |        |            |    |            |
   | MN/| bearer |   Radio    |    | BCMCS      |
   |User|<-------|   Access   |<---| Content    |
   |    |        |   Network  |    | Server     |
   +----+        +------------+    +------------+

   Note that this figure is shown here for a basic understanding of how
   Broadcast and Multicast Service works in a 3G cellular telephone
   network.  The network elements except MN/user and the DHCP server are
   not relevant to the text in this document.



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   The MN interacts with the BCMCS Controller to request broadcast/
   multicast program information from the network (e.g., scheduled time,
   multicast IP address, port numbers).  The MN may also be
   authenticated by the BCMCS Controller while downloading the relevant
   program-security-related information (such as encryption key).  These
   interactions may happen via HTTP and XML as defined in [BCMCS].
   There may be more than one BCMCS controller in the network.  The MN
   should discover the appropriate BCMCS controller to request the
   relevant program information.  For details of Broadcast and Multicast
   Service operation in 3GPP2, see [BCMCS].

3.  Terminology

   The keywords "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 [RFC2119].

4.  Broadcast and Multicast Service Controller Options

   This section defines the configuration option for the BCMCS
   controller of the Broadcast and Multicast Service.

4.1.  Broadcast and Multicast Service Controller Domain Name List for
      DHCPv4

   The general format of the BCMCS Controller Domain list option for
   DHCPv4 is as follows:

           Code  Len  FQDN(s) of BCMCS Controller
         +-----+-----+-----+-----+-----+-----+-----+--
         | 88  |  n  |  s1 |  s2 |  s3 |  s4 | s5  |  ...
         +-----+-----+-----+-----+-----+-----+-----+--

   The option MAY contain multiple domain names, but these domain names
   SHOULD be used to construct Service Record (SRV) lookups as specified
   in [BCMCS], rather than querying for different A records.  The client
   can try any or ALL of the domain names to construct the SRV lookups.
   The list of domain names MAY contain the domain name of the access
   provider and its partner networks that also offer Broadcast and
   Multicast Service.

   As an example, the access provider may have one or more partners or
   resellers often termed as MVNOs (Mobile Virtual Network Operators)
   for Broadcast and Multicast Service.  In this case, the access
   provider should be able to use the same DHCP option to send multiple
   of those domain names (MVNOs).  To illustrate this further, let's
   assume that the access provider (operator) has a reseller agreement
   with two MVNOs: mvno1 and mvno2.  Therefore, the Broadcast and



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   Multicast Service Controller Domain Name list for the DHCPv4 option
   will contain three domain names: operator.com, mvno1.com, and
   mvno2.com.  Upon receiving this option, the BCMCS client may choose
   to use one of the domain names to fetch the appropriate BCMCS
   controller address (based on user's preference or configuration).  If
   no preferred domain name is found in the received list, the client
   should use a default setting, e.g., use the first one in the list.

   If the length of the domain list exceeds the maximum permissible
   length within a single option (254 octets), then the domain list MUST
   be represented in the DHCPv4 message as specified in [RFC3396].  An
   example case when two controller domain names, example.com and
   example.net, are returned will be:

   +----+----+----+----+----+----+----+----+----+----+----+
   | 88 | 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 |
   +----+----+----+----+----+----+

4.2.  Broadcast and Multicast Service Controller Domain Name List Option
      for DHCPv6

   The semantics and content of the DHCPv6 encoding of this option are
   exactly the same as the encoding described in the previous section,
   other than necessary differences between the way options are encoded
   in DHCPv4 and DHCPv6.

   Specifically, the DHCPv6 option for the BCMCS Control Server Domain
   Names has 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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      OPTION_BCMCS_SERVER_D    |         option-length         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          BCMCS Control Server Domain Name List                |
     |                              ...                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   option-code: OPTION_BCMCS_SERVER_D (33).

   option-length: Length of the 'BCMCS Control Server Domain Name List'
   field in octets; variable.



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   BCMCS Control Server Domain Name List: Identical format as in Section
   4.1 (except the Code and Len fields).

4.3.  Broadcast and Multicast Service Controller IPv4 Address Option for
      DHCPv4

   The Length byte (Len) is followed by a list of IPv4 addresses
   indicating BCMCS controller IPv4 addresses.  The BCMCS controllers
   MUST be listed in order of preference.  Its minimum length is 4, and
   the length MUST be a multiple of 4.  The DHCPv4 option for this
   encoding has the following format:

          Code   Len  Address 1               Address 2
         +-----+-----+-----+-----+-----+-----+-----+--
         | 89  |  n  | a1  | a2  | a3  | a4  | a1  |  ...
         +-----+-----+-----+-----+-----+-----+-----+--

4.4.  Broadcast and Multicast Service Controller IPv6 Address Option for
      DHCPv6

   This DHCPv6 option MUST carry one or more 128-bit IPv6 address(es) of
   the BCMCS Controller in an operator's network.

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      OPTION_BCMCS_SERVER_A    |         option-length         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     |    BCMCS Control server-1 address (IPv6 address)              |
     |                                                               |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     |    BCMCS Control server-2 address (IPv6 address)              |
     |                                                               |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                              ...                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   option-code: OPTION_BCMCS_SERVER_A (34).

   option-length: Length of the 'BCMCS Control Server IPv6 address'
   field in octets; variable.






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4.5.  Consideration for Client Operation

   For DHCPv4, the client MAY request either or both of the BCMCS
   Controller Domain Name List and the IPv4 Address options in the
   Parameter Request List option (code 55) as defined in [RFC2132].

   For DHCPv6, the client MAY request either or both of the BCMCS
   Controller Domain Name List and the IPv6 Address options in the
   Options Request Option (ORO) as described in [RFC3315].

   If the client receives both the BCMCS Controller Domain Name List and
   IPv6 or IPv4 Address options, it SHOULD use the Domain Name List
   option.  In this case, the client SHOULD NOT use the BCMCS Controller
   IPv6 or IPv4 Address option unless the server(s) in the BCMCS
   Controller Domain Name List cannot be resolved or reached.

4.6.  Consideration for Server Operation

   A server MAY send a client either the BCMCS Controller Domain Name
   List Option or the BCMCS Controller IPv6 Address/IPv4 Address options
   if the server is configured to do so.

   If a client requests both the options and the server is configured
   with both types of information, the server MAY send the client only
   one of the options if it is configured to do so.  In this case, the
   server SHOULD send the BCMCS Controller Domain Name List option.

   A server configured with the BCMCS Controller IPv6 or IPv4 Address
   information MUST send a client the BCMCS Controller IPv6 or IPv4
   Address option if that client requested only the BCMCS Controller
   IPv6 or IPv4 Address option and not the BCMCS Controller Domain Name
   List option in the ORO or Parameter Request List option.

   If a client requests for the BCMCS Controller IPv6 or IPv4 Address
   option and the server is configured only with the domain name(s), the
   server MUST return the Domain Name List and vice versa.

   The domain names MUST be concatenated and encoded using the technique
   described in Section 3.3 of "Domain Names - Implementation and
   Specification" [RFC1035].  DNS name compression MUST NOT be used.











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   The following table summarizes the server's response:

      Client sends in ORO/
      Parameter Request List   Domain Name List        IPv6/IPv4 Address
      __________________________________________________________________

      Neither option               SHOULD                  MAY
      Domain Name List             MUST                    MAY
      IPv6/IPv4 Address            MAY                     MUST
      Both options                 SHOULD                  MAY

5.  Security Considerations

   This document does not introduce any new security concerns beyond
   those specified in the basic DHCP [RFC2131] and DHCPv6 [RFC3315]
   specifications.  In the absence of message integrity protection for
   these options, an attacker could modify the option values to divert
   requests for broadcast service.

6.  IANA Considerations

   The following option codes for Broadcast and Multicast Service
   Controller option have been assigned by IANA:

   1.  The BCMCS Controller Domain Name list (Section 4.1) has been
   assigned a value of 88 from the DHCPv4 option space.

   2.  The BCMCS Controller Domain Name list (Section 4.2) has been
   assigned a value of 33 from the DHCPv6 option space, and a name of
   OPTION_BCMCS_SERVER_D.

   3.  The BCMCS Controller IPv4 Address option (Section 4.3) has been
   assigned a value of 89 from the DHCPv4 option space.

   4.  The BCMCS Controller IPv6 Address option (Section 4.4) has been
   assigned a value of 34 from the DHCPv6 option space, and a name of
   OPTION_BCMCS_SERVER_A.

7.  Acknowledgements

   Thanks to the following individuals for their review and constructive
   comments during the development of this document:

   AC Mahendran, Jun Wang, Raymond Hsu, Jayshree Bharatia, Ralph Droms,
   Ted Lemon, Margaret Wasserman, Thomas Narten, Elwyn Davies, Pekka
   Savola, Bert Wijnen, David Kessens, Brian E. Carpenter, and Stig
   Venaas.




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8.  Normative References

   [BCMCS]    3GPP2, www.3gpp2.org,
              http://www.3gpp2.org/Public_html/specs/tsgx.cfm, "X.S0022,
              Broadcast and Multicast Service in cdma2000 Wireless IP
              Network.", December 2005.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

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

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

   [RFC2132]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
              Extensions", RFC 2132, March 1997.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC3396]  Lemon, T. and S. Cheshire, "Encoding Long Options in the
              Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396,
              November 2002.

























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Authors' Addresses

   Kuntal Chowdhury
   Starent Networks
   30 International Place
   Tewksbury, MA  01876
   US

   Phone: +1 214-550-1416
   EMail: kchowdhury@starentnetworks.com


   Parviz Yegani
   Cisco Systems
   3625 Cisco Way
   San Jose, CA  95134
   US

   Phone: +1 408-832-5729
   EMail: pyegani@cisco.com


   Lila Madour
   Ericsson
   8400, Decarie Blvd
   Town of Mount Royal, Quebec  H4P 2N2
   CANADA

   Phone: +1 514-345-7900
   EMail: Lila.Madour@ericsson.com





















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Full Copyright Statement

   Copyright (C) The Internet Society (2005).

   This document is subject to the rights, licenses and restrictions
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.







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