Network Working Group K. Chowdhury

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: [email protected]

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

Phone: +1 408-832-5729
EMail: [email protected]

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

Phone: +1 514-345-7900
EMail: [email protected]

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.

Intellectual Property

The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.

Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.

The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf-
[email protected].

Acknowledgement

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

Chowdhury, et al. Standards Track [Page 11]