Network Working Group K. Chowdhury
Internet-Draft Starent Networks
Expires: November 17, 2005 P. Yegani
Cisco Systems
L. Madour
Ericsson
May 16, 2005
DHCP Options for Broadcast and Multicast Control Servers
draft-ietf-dhc-bcmc-options-01.txt
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document defines new options for Broadcast and Multicast Service
controller discovery in an IP network. Broadcast service is being
developed for 3rd 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
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service. Dynamic Host Configuration Protocol can be used to
configure the MN to acccess a particular controller. 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 Domain Name List Option
for DHCPv6 . . . . . . . . . . . . . . . . . . . . . . . . 7
4.3 Broadcast Service Controller IPv4 address option . . . . . 8
4.4 Broadcast Service Controller IPv6 Address Option . . . . . 8
4.5 Consideration for Client Operation . . . . . . . . . . . . 9
4.6 Consideration for Server Operation . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
8. Normative References . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . 14
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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
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 defines 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 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.
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 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'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 of the controller in the 3G cellular
telephone networks.
In order to allow the MNs to discover the broadcast controllers, the
DHCP clients request for appropriate option codes from the DHCP
server using Parameter Request List option. The DHCP servers need to
return the corresponding configuration options that carry either
broadcast and multicast service controller's IP address or fully
qualified domain name based on configuration. This document defines
the necessary options and option codes.
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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:
+------------+ +--------+
| | | |
| 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 cellular telehone
network. The network elements except MN/user and the DHCP server are
not relevant to the text in this document.
The MN interacts with the 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
Controller while downloading the relevant program security related
information (such as encryption key). These interactions may happen
via HTTP and XML. There may be more than one controller in the
network. The MN 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
the broadcast service.
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 that is administratively prohibited by client's
policy.
The 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 wireless access provider's network.
Clients MAY 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. 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
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.example.com, bcmc2.example.com are returned will be:
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+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|TBD|38 | 5 |'b'|'c'|'m'|'c'|'1'| 8 |'e'|'x'|'a'|'m'|'p'|'l'|'e'|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 3 |'c'|'o'|'m'| 5 |'b'|'c'|'m'|'c'|'2'| 8 |'e'|'x'|'a'|'m'|'p'|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
+---+---+---+---+---+---+---+---+
|'l'|'e'|'1'| 3 |'c'|'o'|'m'|
+---+---+---+---+---+---+---+
4.2 Broadcast Service Controller Domain Name List Option for DHCPv6
The option length is followed by a sequence of labels, encoded
according to Section 3.1 of RFC 1035.
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 DHCPv6 server to indicate the broadcast
controllers in the access provider's network.
The DHCPv6 option for Boradcast Service Controller Domain Names has
the format shown below.
option-code: OPTION_BCMCS_SERVER_D (TBD).
option-length: Length of the 'Broadcast Control Server Domain Name
List' field in octets; variable.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Broadcast Control Domain Name List |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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4.3 Broadcast Service Controller IPv4 address option
The encoding byte (enc) 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 | ...
+-----+-----+-----+-----+-----+-----+-----+-----+--
4.4 Broadcast Service Controller IPv6 Address Option
This DHCPv6 option MUST carry one or more 128-bit IPv6 address(es) of
the Broadcast Service Controller in a operators network.
option-code: OPTION_BCMCS_SERVER_A (TBD).
option-length: Length of the 'Broadcast Control Server IPv6 address'
field in octets; variable.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Broadcast Control server-1 address (IPv6 address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Broadcast Control server-2 address (IPv6 address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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4.5 Consideration for Client Operation
For DHCPv6, a client MAY request either or both of the Broadcast
Service Controller Domain Name List and the IPv6 Address options in
the Options Request Option (ORO) as described in [RFC3315].
If a client receives both the Broadcast Service Controller Domain
Name List and IPv6 Address options, it SHOULD use the Domain Name
List option. In this case, the client MAY use the Broadcast Service
Controller IPv6 Address option only if the servers in the Broadcast
Service Controller Domain Name List can not be resolved or reached.
4.6 Consideration for Server Operation
A server MAY send a client either the Broadcast Service Controller
Domain Name List Option or the Broadcast Service Controller IPv6
Address/IPv4 Address options if the server is configured to do so.
In case of DHCPv6, If a client requests both options and the server
is configured with both types of information, the server MAY send the
client only one of these options if it is configured to do so. In
this case the server SHOULD send the Broadcast Service Controller
Domain Name List option.
A server configured with the Broadcast Service Controller IPv6
Address information MUST send a client the Broadcast Service
Controller IPv6 Address option if that client requested only the
Broadcast Service Controller IPv6 address option and not the
Broadcast Service Controller Domain Name List option in the ORO
[RFC3315].
If a client requests for the Broadcast Service Controller IPv6 option
and the Server is configured only with the Domain Names, the Server
MUST return the Domain Names List and vice versa.
The following table summarizes the server's response for DHCPv6:
Client sends in ORO Domain Name List IPv6 Address List
__________________________________________________________________
Neither option SHOULD MAY
Domain Name List MUST MAY
IPv6 Address MAY MUST
Both options SHOULD MAY
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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 following option codes for Broadcast Service Controller option
must be assigned by IANA:
1. Broadcast Service Controller Domain Name list (section 4.1)
2. OPTION_BCMCS_SERVER_D (section 4.2)
3. Broadcast Service Controller IPv4 address option (section 4.3)
4. OPTION_BCMCS_SERVER_A (section 4.4)
The DHCP options should be registered in
http://www.iana.org/assignments/bootp-dhcp-extensions
The DHCPv6 options should be registered in
http://www.iana.org/assignments/dhcpv6-parameters
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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, and Margaret Wasserman.
8. Normative References
[BCMCS] 3GPP2, www.3gpp2.org,
ftp://ftp.3gpp2.org/TSGX/Projects/X.P0022 2ndV&V.zip,
"X.S0022, Broadcast and Multicast Service in cdma2000
Wireless IP Network. (work in progress)", December 2004.
[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.
[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.
Authors' Addresses
Kuntal Chowdhury
Starent Networks
30 International Place
Tewksbury, MA 01876
US
Phone: +1 214-550-1416
Email: kchowdhury@starentnetworks.com
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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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