Network Working Group K. Chowdhury
Internet-Draft Starent Networks
Expires: June 27, 2005 P. Yegani
Cisco Systems
L. Madour
Ericsson
December 27, 2004
DHCPv4 Options for Broadcast and Multicast Control Servers
draft-ietf-dhc-bcmcv4-option-00.txt
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2004).
Abstract
This document defines new options for Broadcast and Multicast Service
controller discovery in an IP network. Broadcast service is being
developed for 3G wireless networks. Users of the service interact
with a controller in the network to derive informations that are
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required to receive broadcast service. Dynamic Host Configuration
Protocol can be used to configure the controller IPv4 addresses or
fully qualified domain names in the user's devices. This document
defines the related options and option codes.
Table of Contents
1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overview of the 3GPP2 BCMCS Network . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Broadcast Service Controller Options . . . . . . . . . . . . . 6
4.1 Broadcast Service Controller Domain Name list . . . . . . 6
4.2 Broadcast Service Controller IPv4 address option . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
8. Normative References . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 10
Intellectual Property and Copyright Statements . . . . . . . . 12
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1. Motivation
Dynamic Host Configuration Protocol [RFC2131] 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
currently being standardized in various mobile wireless standard
bodies such as 3GPP, 3GPP2 and OMA. A description of the BCMCS, for
example, in 3GPP2 can be found in [BCMCS].
While DHCP offers necessary mechanisms for device configuration, it
lacks the information elements required to configure a mobile device
to support BCMCS. This memo is an effort to define the extensions
needed for DHCP to provide necessary configuration information to a
mobile device in a BCMCS network.
DHCP is being used in 3GPP2, for example, to assist with the
discovery of the BCMCS Controller in a mobile operators IP network.
The BCMCS includes a controller component that is responsible for
managing the service via interaction with the users and other network
entities.
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 users of the service are required to
know the IPv4 address of the controller entity so that they can
download all the necessary information about a desired broadcast
program. In a roaming environment static configuration of the
controller IPv4 address becomes unrealistic. Therefore, DHCP is
considered to be a method to dynamically configure the controller
IPv4 address or the fully qualified domain name of the controller in
the 3G wireless networks.
In order to allow the users to discover the broadcast controllers,
the clients request for appropriate option codes from the DHCP
servers using Parameter Request List option. The DHCP servers need
to return the corresponding configuration options that carry either
broadcast and multicast service controller IPv4 address or fully
qualified domain name based on configuration. The motivation for
this document is to define the necessary option and option code.
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2. Overview of the 3GPP2 BCMCS Network
The Broadcast and Multicast Service architecture in a 3G wireless
network such as 3GPP2 has the following model:
+------------+ +--------+
| | | |
| Controller | | DHCP |
| | | Server |
+------------+ +--------+
^
Control|
Info|
|
|
V
+----+ +------------+ +------------+
| | | | | |
| MN/| bearer | Radio | | Broadcast |
|User|<-------| Access |<---| Content |
| | | Network | | Server |
+----+ +------------+ +------------+
Note that this figure is shown here for broad understanding of how
Broadcast and Multicast service works in a 3G mobile wireless IP
network. The network elements except MN/user and the DHCP server are
not relevant to the text in this document.
The user interacts with the Controller to request for
broadcast/multicast program information from the network (e.g.,
scheduled time, multicast IP address, port numbers). The User may
also be authenticated by the Controller while downloading the
relevant program security related information (such as encryption
key). These interactions happen via HTTP and XML. There may be more
than one controller in the network. The user should discover the
appropriate controller to request the relevant program information.
For details of Broadcast and Multicast Service operation in 3GPP2,
see [BCMCS]
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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.
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4. Broadcast Service Controller Options
This section defines the configuration option for the controller of
Broadcast Service. The Configuration Option contains the IPv4
address or the fully qualified domain names of the broadcast service
controller.
4.1 Broadcast Service Controller Domain Name list
If the 'enc' byte has a value of 0, the encoding byte is followed by
a sequence of labels, encoded according to Section 3.1 of RFC 1035
[RFC1035].
The option MAY contain multiple domain names, but these domain names
SHOULD be used to construct SRV lookups as specified in [BCMCS],
rather than querying for different A records. The client MUST try
the records in the order listed, applying the mechanism described in
[BCMCS] for each entry. The client only resolves the subsequent
domain names if attempts to contact the first one failed or yielded
no common transport protocols between the client and the controller
or denote a domain administratively prohibited by client's policy.
Use of multiple domain names is not meant to replace the SRV records,
but rather to allow a single DHCP server to indicate the broadcast
controllers in the access provider's network.
Clients MUST support compression according to the encoding in Section
4.1.4 of "Domain Names - Implementation And Specification [RFC1035].
Since the domain names are supposed to be different domains,
compression will likely have little effect, however. If the length
of the domain list exceeds the maximum permissible within a single
option (254 octets), then the domain list MUST be represented in the
DHCP message as specified in [RFC3396] .
The DHCP option for this encoding has the following format:
Code Len enc FQDN(s) of Broadcast Controller
+-----+-----+-----+-----+-----+-----+-----+-----+--
| TBD | n | 0 | s1 | s2 | s3 | s4 | s5 | ...
+-----+-----+-----+-----+-----+-----+-----+-----+--
An example case when two controller domain names e.g.
bcmc1.carrier1.com, bcmc2.carrier1.com are returned will be:
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+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|TBD|38 | 5 |'b'|'c'|'m'|'c'|'1'| 8 |'c'|'a'|'r'|'r'|'i'|'e'|'r'|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|'1'| 3 |'c'|'o'|'m'| 5 |'b'|'c'|'m'|'c'|'2'| 8 |'c'|'a'|'r'|'r'|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
+---+---+---+---+---+---+---+---+
|'i'|'e'|'r'|'1'| 3 |'c'|'o'|'m'|
+---+---+---+---+---+---+---+---+
4.2 Broadcast Service Controller IPv4 address option
If the 'enc' byte has a value of 1, the encoding byte is followed by
a list of IPv4 addresses indicating broadcast controller IPv4
addresses. The controllers MUST be listed in order of preference.
Its minimum length is 5, and the length MUST be a multiple of 4 plus
one. The DHCP option for this encoding has the following format:
Code Len enc Address 1 Address 2
+-----+-----+-----+-----+-----+-----+-----+-----+--
| TBD | n | 1 | a1 | a2 | a3 | a4 | a1 | ...
+-----+-----+-----+-----+-----+-----+-----+-----+--
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5. Security Considerations
The security considerations in the base DHCP spec [RFC2131] applies.
An attacker may change information of the Broadcast Service
Controller in packets that are in-tranist from DHCP server to the MN,
if integrity protection is not in place. In that event, the user of
the Broadcast service may be diverted to a rogue broadcast service
controller. In the absence of a mutual authentication procedure
between MN and the Broadcast controller, the MN may receive wrong or
fraudulent information about Broadcast Service.
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6. IANA Considerations
The option code for Broadcast Service Controller option must be
assigned by IANA.
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7. Acknowledgements
Thanks to the following indivduals for their review and constructive
comments during the development of this document:
AC Mahendran, Jun Wang, Raymond Hsu, Jayshree Bharatia, Ralph Droms,
Ted Lemon.
8 Normative References
[BCMCS] 3GPP2, www.3gpp2.org, "X.S0022, Broadcast and Multicast
Service in cdma2000 Wireless IP Network.", February 2005.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, March 1997.
[RFC3396] Lemon, T. and S. Cheshire, "Encoding Long Options in the
Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396,
November 2002.
Authors' Addresses
Kuntal Chowdhury
Starent Networks
2540 Coolwater Dr.
Plano, TX 75025
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
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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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