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rfc:rfc4280

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.

Chowdhury, et al. Standards Track [Page 1] RFC 4280 DHCP Options for BMCS November 2005

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.

Chowdhury, et al. Standards Track [Page 2] RFC 4280 DHCP Options for BMCS November 2005

 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.

Chowdhury, et al. Standards Track [Page 3] RFC 4280 DHCP Options for BMCS November 2005

 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

Chowdhury, et al. Standards Track [Page 4] RFC 4280 DHCP Options for BMCS November 2005

 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.

Chowdhury, et al. Standards Track [Page 5] RFC 4280 DHCP Options for BMCS November 2005

 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.

Chowdhury, et al. Standards Track [Page 6] RFC 4280 DHCP Options for BMCS November 2005

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.

Chowdhury, et al. Standards Track [Page 7] RFC 4280 DHCP Options for BMCS November 2005

 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.

Chowdhury, et al. Standards Track [Page 8] RFC 4280 DHCP Options for BMCS November 2005

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.

Chowdhury, et al. Standards Track [Page 9] RFC 4280 DHCP Options for BMCS November 2005

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

Chowdhury, et al. Standards Track [Page 10] RFC 4280 DHCP Options for BMCS November 2005

Full Copyright Statement

 Copyright (C) The Internet Society (2005).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

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Acknowledgement

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

Chowdhury, et al. Standards Track [Page 11]

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