DHC Working Group L. Yeh, Ed.
Internet-Draft T. Tsou
Intended status: Standards Track Huawei Technologies
Expires: December 29, 2011 M. Boucadair
France Telecom
J. Hu
China Telecom
June 27, 2011
Prefix Pool Option for DHCPv6 Relay Agent on Provider Edge Router
draft-yeh-dhc-dhcpv6-prefix-pool-opt-04
Abstract
The Prefix Pool option provides an automatic mechanism based on the
DHCPv6-PD, allowing the DHCPv6 server to notify the DHCPv6 relay
agent implemented only on the Provider Edge (PE) router about the
information of prefix pools. The information of prefix pools can be
used to enforce IPv6 route aggregation on the PE router by adding or
removing the aggregated routes per the status of the prefix pools.
The advertising of the aggregated routes in the routing protocol
enabled on the network-facing interface of PE router will
dramatically decreases the number of the routes entries in the ISP
network.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on December 29, 2011.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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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 . . . . . . . . . . . . . . . . . . . . . . 6
5. Relay Agent Behavior . . . . . . . . . . . . . . . . . . . . . 7
6. Server Behavior . . . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
10. Changes Log . . . . . . . . . . . . . . . . . . . . . . . . . 11
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
11.1. Normative References . . . . . . . . . . . . . . . . . . 11
11.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
DHCPv6 [RFC3315] protocol specifies a mechanism for the assignment of
IPv6 address and configuration information to IPv6 nodes. DHCPv6
Prefix Delegation (DHCPv6-PD) [RFC3633] specifies a mechanism for the
delegation of IPv6 prefixes from the Delegating Router (DR) acting as
the DHCPv6 server to the Requesting Router (RR) acting as the DHCPv6
Client. DHCPv6 servers always maintain authoritative information
related to their operations including, but not limited to, binding
data of the delegated IPv6 prefixes, lease data of the delegated IPv6
prefixes, and binding data of their prefix pools, etc.
In the scenario of the centralized DHCP server, the Provider Edge
(PE) routers act as a DHCPv6 relay agents when the DHCPv6 Server
acting as DR and the DHCPv6 clients acting as RRs are not on the same
link. For the reachability purpose, the PE routers always need to
add or withdraw the route entries directing to each customer network
in their routing table to reflect the status of IPv6 prefixes
delegated by the DHCPv6 Server to customer routers (a.k.a. Routed-RG
or Routed-CPE), which acts as RRs. (see Section 6.2, [BBF TR-177]).
When a routing protocol is enabled on the network-facing interface of
the PE router, all the routes directing to the customer networks are
advertised in the ISP network. This will make the number of route
entries in the routing table on the ISP router to be unacceptable
huge, 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 enabled on
the PE router can not make one aggregated route automatically to
cover all the prefixes delegated within the prefix pool. The PE
router needs other ways to make the aggregated routes. One way to
make the aggregated routes is to configure them manually and
permanently per the provision of the prefix pools, but PE router
doesn't know the information about the prefix pools when it acts as
the relay agent.
This document proposes a new Prefix Pool option for the DHCPv6 reply
agent implemented only on the PE routers, allowing the server to
notify the relay agent about the information of prefix pools. After
the PE router got the information of the prefix pools, the aggregated
route entries (e.g., black-hole routes) pointing to each of the
prefix pools can be added or withdrawn in the routing table of the PE
router. The aggregated routes will be advertised into the ISP
network through the routing protocol enabled on the PE's network-
facing interface.
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DHCPv6 Bulk Leasequery [RFC5460] specifies a mechanism for bulk
transfer of the binding data of each delegated prefix from the server
to the requestor (i.e. DHCPv6 relay agent), to support the
replacement or reboot event of relay agent. In this document, the
capability of DHCPv6 Bulk Leasequery will be extended to support the
bulk transfer of the binding data of prefix pool for the route
aggregation.
2. Terminology and Language
This document describes new DHCPv6 options of prefix pool and the
associated mechanism on the relay agent and server. This document
should be read in conjunction with the DHCPv6 specification, RFC3315,
RFC3633, RFC5007 and RFC5460 for a complete mechanism. Definitions
for terms and acronyms not specifically defined in this document are
defined in RFC3315, RFC3633, [RFC3769], [RFC5007] and RFC5460.
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, [RFC2119].
3. Scenario and Network Architecture
Figure 1 and Figure 2 illustrate two typical cases of the targeted
network architectures.
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+------+------+
| DHCPv6 | DHCPv6-PD Delegating Router
| Server | (e.g. binding entry:
+------+------+ pe#1 - 2001:db8:1230::/44
_________|_________ extract pe_id=pe#1
/ \ from the interface_id=pe#1_cfi#2)
| ISP Core Network |
\___________________/
|
| Network-facing interface
+------+------+
| | Provider Edge Router
| PE | DHCPv6 Relay Agent
| | (e.g. pe_id=pe#1;
+------+------+ prefix pool=2001:db8:1230::/44)
| Customer-facing interface (Interface ID)
| (e.g., interface_id=pe#1_cfi#2)
|
+------+------+ Customer Router
| CPE | DHCPv6 Client
| | DHCPv6-PD Requesting Router
+------+------+ (e.g. customer network
| =2001:db8:1234:5600:/56)
_________|_________
/ \
| Customer Network |
\___________________/
Figure 1: Use case of ISP-Customer network where CPE is directly
connected to PE
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+------+------+
| DHCPv6 | DHCPv6-PD Delegating Router
| Server | (e.g. binding entry:
+------+------+ pe#3_cfi#4 - 2001:db8:3400::/40)
_________|_________
/ \
| ISP Core Network |
\___________________/
|
| Network-facing interface
+------+------+
| PE | Provider Edge Router
| | DHCPv6 Relay Agent
+------+------+
| Customer-facing interface (Interface ID)
| (e.g. interface_id=pe#3_cfi#4;
| prefix pool=2001:db8:3400::/40)
_________|_________
/ \
| Access Network |
\___________________/
|
+------+------+ Customer Router
| CPE | DHCPv6 Client
| | DHCPv6-PD Requesting Router
+------+------+ (e.g. customer network
| =2001:db8:3456:7800::/56)
_________|_________
/ \
| Customer Network |
\___________________/
Figure 2: Use case of ISP-Customer network where CPE is connected to
PE through access network
4. Prefix Pool Option
The format of the Prefix Pool option is shown is Figure 3.
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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 the prefix pool in bits
ipv6-prefix: IPv6 prefix of the prefix pool
status: Status of the prefix pool, indicating the
availability of the prefix pool maintained
on the server.
The codes of the status are defined in the following table.
Name Code
Valid 0
Released 1
Reserved 2~255
The status of 'Valid' in the Prefix Pool option can be used to add
the prefix pool and the associated aggregated route on the relay
agent; while the status of 'Released' in the Prefix Pool option can
be used to withdraw the prefix pool and the associated aggregated
route on the relay agent.
If the administrative policy on the server permit and support the
route aggregation on the relay agent, the status of prefix pool can
be determined by the delegated prefixes within the associated prefix
pool. If there is one delegated prefix within the pool that has
valid lease, the status of prefix pool will be 'Valid'. Otherwise,
the status of prefix pool is 'Released'. If the administrative
policy on the server don't permit or support the route aggregation on
the relay agent, the status of prefix pool will always be 'Released'.
5. Relay Agent Behavior
The relay agent who needs the information of prefix pools, must
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includes Option Request option (OPTION_ORO, 6) to request Prefix Pool
option from the server, who maintains the status of the prefix pools
associated to the relay agent itself (Figure 1) or its particular
customer-facing interface (Figure 2) where receiving the DHCPv6-PD
message from clients. The relay agent can include this Option
Request option for Prefix Pool option in the relay-forward (12)
message of SOLICIT (1), REQUEST (3), RENEW(5), REBIND (6) and RELEASE
(8). The relay agent may also include Prefix Pool option with the
field values of pfx-pool-len and IPv6-prefix as its preference which
the relay agent would like the server to return.
The relay agent should include Interface ID option
(OPTION_INTERFACE_ID, 18) for the server to identify the relay agent
itself or its particular customer-facing interface where the prefix
pool is associated, 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 clients
are located.
After received the Prefix Pool option for the relay agent itself or
its particular customer-facing interface in the relay-reply message
(13) of REPLY (7) from the server, the relay agent shall add or
withdraw the aggregated route entry per the status of the prefix
pool. If the status of the prefix pool got from the server is
'Valid', the relay agent shall add an aggregated route entry in its
routing table, if the same entry has not been added in. If the
status of the prefix pool got from the server is 'Released', the
relay agent shall withdraw the associated aggregated route entry in
its routing table, if the same entry has not been withdrawn. If
there is no route entry directing to the customer network within the
associated aggregated route, the relay agent shall automatically
withdraw the aggregated route.
The relay agent advertises its routing table including the entries of
the aggregated routes based on the information of prefix pools when
the routing protocol is enabled on its network-facing interface.
The Relay Agent (i.e. Requestor) can use DHCPv6 Bulk Leasequery
[RFC5460] to query the binding data of prefix pools in the 'Valid'
status from the server. After established a TCP connection with the
DHCPv6 server, the relay agent must include Query option
(OPTION_LQ_QUERY, 44) and set the proper query-type
(QUERY_BY_RELAY_ID, QUERY_BY_LINK_ADDRESS, QUERY_BY_REMOTE_ID), link-
address and query-options in the LEASEQUERY (14) message. The query
options must include Option Request option (OPTION_ORO, 6) to request
Prefix Pool option from the server.
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6. Server Behavior
Per DHCPv6-PD [RFC3633], if the prefix of the customer network
requested in relay-forward message of SOLICIT , REQUEST, RENEW,
REBIND by the Client (i.e. RR) has valid lease, the Server (i.e.
DR) will delegate the prefix with the relevant parameters in the
relay-reply message of REPLY. In order to give a meaningful reply,
the server has to be able to maintains the binding data of the
delegated IPv6 prefixes with the identification of the client.
Interface ID option (OPTION_INTERFACE_ID, 18) nested in the relay-
forward message is usually used to identify the access line of the
client.
After receiving the Option Request option (OPTION_ORO, 6) to request
Prefix Pool option in the relay-forward message of PD, the server
must include Prefix Pool option with the status indicated for the
associated relay agent itself (Figure 1) or its customer-facing
interface (Figure 2) in the relay-reply message of PD if the relay-
forward message of PD received is valid.
The server may use the link-address specified in relay-forward
message to identify the relay agent itself or its particular
customer-facing interface where the prefix pool is associated, but
the server has to maintain the binding data of prefix pools in
association with these link-addresses. To be more readable, the
server can alternatively use the Interface ID option
(OPTION_INTERFACE_ID, 18) included in the relay-forward message by
the relay agent, to identify the relay agent itself (Figure 1) or its
particular customer-facing interface (Figure 2) where the prefix pool
is associated. In order to give a meaningful reply, the server has
to maintain the binding data of prefix pools in association with the
information derived from the Interface ID option.
Per DHCPv6 [RFC3315], the server shall copy the same Interface ID
option got from the relay-forward message into the relay-reply
message.
If the server is set to support the route aggregation on the relay
agent for the particular prefix pool, the status of this prefix pool
can be determined by the delegated prefixes within the associated
prefix pool. If at least one of delegated prefix in the associated
prefix pool has valid lease, the server shall set the status of the
prefix pool to be 'Valid'. If the lease of each delegated prefix
within the associated prefix pool got expired, or if the delegated
prefix in the relay-forward message of RELEASE is the last prefix
releasing in the associated prefix pool, the server shall set the
status of the associated prefix pool to be 'Released'. If the server
is set to not support the route aggregation on the relay agent for
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the particular prefix pool, the status of prefix pool will always be
'Released'.
When the administrator of the server changes the setting to support
the route aggregation on the relay agent for the particular prefix
pool or not, the server may initiates the relay-reply message of
RECONFIGURE (10) including Prefix Pool option to add or withdraw the
prefix pool and the associated aggregated route on the relay agent if
at least one delegated prefix within the prefix pool still has the
valid lease.
Note that multiple prefix pools may associate with the same PE router
implementing relay agent (Figure 1) or its customer-facing interface
(Figure 2) in the binding table on the server, and the delegated
prefix is only from one prefix pool.
After received the LEASEQUERY (14) message from the relay agent with
the Query option (OPTION_LQ_QUERY, 44) including Option Request
option (OPTION_ORO, 6) to request Prefix Pool option, the server must
include the Client Data options (OPTION_CLIENT_DATA, 45) in the
LEASEQUERY-REPLY (15) and LEASEQUERY-DATA (16) message to convey the
binding data of the associated prefix pools with the 'Valid' status
through the established TCP connection per RFC5460. Each Client Data
option shall contain Prefix Pool option, and might contain the
Interface ID option. In order to be able to give the meaningful
replies to different type of query, the server has to be able to
maintain the relevant association of prefix pools with the RELAY_ID,
link addresses or Remote_ID of the relay agent in its binding
database.
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. Acknowledgements
Thanks to the DHC working group members, Bernie Volz, Eliot Lear, Ole
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Troan, Roberta Maglione, Ted Lemon, for the discussion in the mailing
list. Thanks to Christian Jacquenet for pointing out the draft
should cover one more use case of ISP-Customer network where CPE is
directly connected to PE. Thanks to Sven Ooghe for some revison
after the email review. Thanks to Shrinivas Ashok Joshi for pointing
out the draft should cover the robust mechanism against the case of
reboot.
10. Changes Log
If this document is accepted for publication as an RFC, this change
log is to be removed before publication.
Rev. -04
a. Re-titled the draft to emphasize that the new mechanism with
DHCPv6-PD is only designed for the PE router.
b. Re-write the abstract and some words in the introduction.
Rev. -03
a. Revisions on the behavior of Relay Agent about the automatic
withdrawal of the aggregated route.
b. Re-correct the behavior of Server about the Interface ID option.
Rev. -02
a. Add one more use case of ISP network architecture where CPE is
directly connected to PE.
b. Revisions on the usage of the 'status' field in Prefix Pool
option.
c. Extend DHCPv6 Bulk Leasequery (RFC5460) for the new usage.
11. References
11.1. 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.
[RFC5007] Brzozowski, J., Kinnear, K., Volz, B., and S. Zeng,
"DHCPv6 Leasequery", RFC 5007, September 2007.
[RFC5460] Stapp, M., "DHCPv6 Bulk Leasequery", RFC 5460,
February 2009.
11.2. Informative References
[BBF TR-177]
Broadband Forum, "IPv6 in the context of TR-101, Issue 1",
November 2010.
Authors' Addresses
Leaf Y. Yeh (editor)
Huawei Technologies
Area F, Huawei Park, Bantian,
Longgang District, Shenzhen 518129
P.R.China
Phone: +86-755-28971871
Email: leaf.y.yeh@huawei.com
Tina Tsou
Huawei Technologies
USA
Email: tena@huawei.com
Mohamed Boucadair
France Telecom
Rennes, 35000
France
Email: mohamed.boucadair@orange-ftgroup.com
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Jie Hu
China Telecom
No.118, Xi Zhi Men-Nei Da Jie,
Xicheng District, Beijing 100035
P.R.China
Phone: +86-10-58552808
Email: huj@ctbri.com.cn
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