DHC L. Yeh, Ed.
Internet-Draft L. Niu
Intended status: Standards Track S. Wang
Expires: April 16, 2011 T. Tsou
Huawei Technologies
October 13, 2010
Prefix Pool Option for DHCPv6 Relay Agent
draft-yeh-dhc-dhcpv6-prefix-pool-opt-00
Abstract
The Prefix Pool option provides an automatic mechanism for the
information exchange between DHCPv6 server and DHCPv6 Relay Agent.
The information about Prefix Pools maintained on DHCPv6 server can be
transferred from server to relay agent through this DHCPv6 option to
support the necessary route aggregation on the provide edge router,
which has a huge number of routes pointing to the customer networks
before the aggregation.
Status of this Memo
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This Internet-Draft will expire on April 16, 2011.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology and Language . . . . . . . . . . . . . . . . . . . 4
3. Scenario and Network architecture . . . . . . . . . . . . . . . 4
4. Prefix Pool option . . . . . . . . . . . . . . . . . . . . . . 5
5. Relay Agent Behavior . . . . . . . . . . . . . . . . . . . . . 6
6. Server Behavior . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
DHCPv6 Relay Agents [RFC3315] are deployed to relay messages between
clients and servers when they are not on the same link, and are often
implemented alongside a routing function in the provider edge (PE)
routers [BBF WT-177]. Meanwhile, DHCPv6 Prefix Delegation [RFC3633]
provides a mechanism for the automated delegation of IPv6 prefix to
the customer network.
In order to make the customer network to be reachable in the IPv6
network, the PE routers always need to add or remove the route entry
directing to each customer network in its routing table per the
relay-forward or relay-reply message between DHCPv6 Server
(Delegation Router) and Customer router (CPE, DHCPv6 Client, DHCPv6
Requesting Router) when the PE router acts as DHCPv6 Relay Agent [BBF
WT-177].
When the routing protocol is enabled on the network-facing interface
of the PE router, all the routes directing to the customer networks
are supposed to advertise in the ISP core network. This will make
the number of entries in the routing table on the ISP core router to
be an unacceptable huge one, so that it is necessary to aggregate the
routes directing to the customer networks on the PE router.
Because the prefixes of the customer networks can not guarantee
always to be valid and continuous, the routing protocol on the PE
router can not make one aggregation route automatically to cover all
the prefixes delegated to the customer networks, which are associated
to the same client-facing link of the PE. On the other hand, the
information of the prefix pools associated to each client-facing
interface of PEs is always maintained on the DHCPv6 server. When the
PE router acts as the DHCPv6 Server, the aggregation route can be
generated by this information directly, but when the PE router acts
as the DHCPv6 Relay Agent, a new mechanism to transfer the
information of the prefix pools from the server to the relay agent
for each client-facing interface of the PE is requested.
After the PE got the information of the prefix pools associated to
its client-facing interfaces, the black-hole route entry pointing to
each of these prefix pools can be added in the routing table of PE.
When the routing protocol is enabled on PE's network-facing
interface, the above black-hole route will be advertised to the whole
ISP network as the aggregation route pointing to all of the customer
networks attached on the same link of the PE's client-facing
interface.
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2. Terminology and Language
This document describes new DHCPv6 options of prefix pool and the
associated mechanism for the configuration on the Relay Agent. This
document should be read in conjunction with the DHCPv6 specification,
RFC 3315 and RFC 3633, for a complete mechanism. Definitions for
terms and acronyms not specifically defined in this document are
defined in RFC 3315, RFC 3633 and RFC 3769 [RFC3769].
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in BCP 14, RFC 2119
[RFC2119].
3. Scenario and Network architecture
The following figure illustrates a typical ISP-Customer network
architecture.
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+------+------+
| DHCPv6 | DHCPv6-PD Delegating Router
| Server |
+------+------+
_________|_________
/ \
| ISP Core Network |
\___________________/
|
| Network-facing interface
+------+------+
| PE | Provider Edge Router
| | DHCPv6 Relay Agent
+------+------+
| Client-facing interface (Interface ID)
_________|_________
/ \
| Access Network |
\___________________/
|
+------+------+ Customer Router
| CPE | DHCPv6 Client
| | DHCPv6-PD Requesting Router
+------+------+
_________|_________
/ \
| Customer Network |
\___________________/
Figure 1: An example of ISP-Customer network architecture
4. Prefix Pool option
The format of the Prefix Pool option is:
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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_PREFIX_POOL | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| pfx-pool-len | |
+-+-+-+-+-+-+-+-+ IPv6 prefix +
| (16 octets) |
| |
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code: OPTION_PREFIX_POOL (TBD)
option-length: 18
pfx-pool-len: Length for this prefix-pool in bits
IPv6 prefix: An IPv6 prefix of prefix pool
Status: Status of the prefix pool
The Status field in the Prefix Pool option indicates the availability
of the prefix pool maintained on the Server. The code of the Status
is defined in the following table.
Name Code
Valid 0
Released 1
Reserved 2~255
5. Relay Agent Behavior
The Relay Agent who needs the information from the
ServerGBP[not]shall includes Option Request Option (OPTION_ORO, 6) to
request Prefix Pool option from the Server, which contains the
information about the prefix pool that will be configured on the
associated client-facing interface of the Relay agent. The Relay
Agent may include this ORO in the relay-forward (12) message of
SOLICIT (1), REQUEST (3), RENEW (5) or REBIND (6).
The Relay Agent should includes Interface-ID Option
(OPTION_INTERFACE_ID, 18) for the server to identify the associated
interface on which the prefix pool is configured, if the Server would
not like to use link-address specified in the DHCPv6 message
encapsulation of relay-forward message to identify the interface of
the link on which the client is located.
The Relay Agent shall advertise the aggregation route based on the
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information of prefix pool when the routing protocol is enabled on
its network-facing interface.
6. Server Behavior
The Server must include Prefix Pool option in the relay-reply (13)
message of REPLY (7) after it receives the relay-forward message,
which is included an associated ORO.
The Server shall use the Interface-ID included by the Relay Agent to
identify the client-facing interface of the Relay Agent on which the
associated prefix pool is configured.
When multiple Prefix Pools are associated to the same client-facing
interface of the Relay Agent, the server must include multiple Prefix
Pool options in the same relay-reply message.
The Server shall include Prefix Pool option when it initiates the
relay-reply message of RECONFIGURE (10). The Status of 'Valid' for
the Prefix Pool option can be used to set up the Prefix Pool on the
Relay Agent; the Status of 'Released' for the Prefix Pool option can
be used to release the configuration of the Prefix Pool on the Relay
Agent.
7. Security Considerations
Security issues related DHCPv6 are described in section 23 of RFC
3315.
8. IANA Considerations
IANA is requested to assign an option code to Option_Prefix_Pool from
the "DHCPv6 and DHCPv6 options" registry (http://www.iana.org/
assignments/dhcpv6-parameters/dhcpv6-parameters.xml).
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for
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IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
Host Configuration Protocol (DHCP) version 6", RFC 3633,
December 2003.
[RFC3769] Miyakawa, S. and R. Droms, "Requirements for IPv6 Prefix
Delegation", RFC 3769, June 2004.
9.2. Informative References
[BBF WT-177]
Broadband Forum, "IPv6 in the context of TR-101, Rev.16,
Straw Ballot", September 2010.
Authors' Addresses
Leaf Y. Yeh (editor)
Huawei Technologies
Area F, Park Huawei, Bantian
Longgang District, Shenzhen 518129
P.R.China
Phone: +86-755-28971871
Email: leaf.y.yeh@huawei.com
Lehong Niu
Huawei Technologies
Email: niulehong@huawei.com
Shuxiang Wang
Huawei Technologies
Email: wangshuxiang@huawei.com
Tina Tsou
Huawei Technologies
Email: tena@huawei.com
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