DHC L. Yeh, Ed.
Internet-Draft T. Tsou
Intended status: Standards Track Huawei Technologies
Expires: August 13, 2011 J. Hu
Q. Sun
China Telecom
February 9, 2011
Prefix Pool Option for DHCPv6 Relay Agent
draft-yeh-dhc-dhcpv6-prefix-pool-opt-02
Abstract
The Prefix Pool option provides an automatic mechanism for the
messages 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.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 13, 2011.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
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to this document. Code Components extracted from this document must
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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 . . . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
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
The DHCPv6 [RFC3315] protocol specifies a mechanism for the
assignment of IPv6 address and configuration information to IPv6
nodes. IPv6 Prefix Delegation (PD) of DHCPv6 [RFC3633] specifies a
mechanism for the delegation of IPv6 prefixes and configuration
information to the Requesting Router (DHCPv6 Client). The DHCPv6
servers (Delegating Router) 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.
The provider edge (PE) routers can act as a DHCPv6 relay agents when
the DHCPv6 Server (Delegating Router) and the DHCPv6 Client
(Requesting Router) are not on the same link. 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 messages between DHCPv6
Server (Delegation Router) and Customer router (CPE, DHCPv6 Client,
DHCPv6 Requesting Router) relayed by the PE (Section 6.2 of BBF TR-
177) [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 advertised in the ISP core network. This will make the number of
entries in the routing table on the ISP core 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 on the PE
router can not make one aggregation route automatically to cover all
the prefixes delegated. The PE router (Relay) here requires a new
mean to transfer the information of the prefix pools from the server
to the relay agent. This document will address a new Prefix Pool
option for this purpose. After the PE got the information of prefix
pools, the aggregation route entries (eg. black-hole routes) pointing
to each of the prefix pools can be added or withdrawed in the routing
table of PE. The aggregation routes will then be advertised to the
whole ISP network through the routing protocol enabled on the PE's
network-facing interface.
The DHCPv6 Bulk Leasequery [RFC5460] protocol specifies a mechanism
for bulk transfer of the binding data of each delegated prefix from
the server to the Requestor (DHCPv6 Relay), to support the
replacement or reboot event of Relay. In this document, the
capabilty of DHCPv6 Bulk Leasequery will be extended to support the
bulk transfer of the binding data of prefix pool for the route
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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 RFC 3315, RFC 3633, RFC 3769 [RFC3769], RFC5007 [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, RFC 2119
[RFC2119].
3. Scenario and Network architecture
The following figures illustrates some typical cases of ISP-Customer
network architectures.
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+------+------+
| DHCPv6 | DHCPv6-PD Delegating Router
| Server | (eg. binding entry:
+------+------+ pe#1 - 3ffe:ffff:1200::/40
_________|_________ 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
| | (eg. pe_id=pe#1;
+------+------+ prefix pool=3ffe:ffff:1200::/40)
| Client-facing interface (Interface ID)
| (eg. interface_id=pe#1_cfi#2)
|
+------+------+ Customer Router
| CPE | DHCPv6 Client
| | DHCPv6-PD Requesting Router
+------+------+ (eg. customer network
| =3ffe:ffff:1234:5600:/56)
_________|_________
/ \
| Customer Network |
\___________________/
Figure 1: Use case of ISP-Customer network where CE is directly
connected to PE
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+------+------+
| DHCPv6 | DHCPv6-PD Delegating Router
| Server | (eg. binding entry:
+------+------+ pe#1_cfi#2 - 3ffe:ffff:1200::/40)
_________|_________
/ \
| ISP Core Network |
\___________________/
|
| Network-facing interface
+------+------+
| PE | Provider Edge Router
| | DHCPv6 Relay Agent
+------+------+
| Client-facing interface (Interface ID)
| (eg. interface_id=pe#1_cfi#2;
| prefix pool=3ffe:ffff:1200::/40)
_________|_________
/ \
| Access Network |
\___________________/
|
+------+------+ Customer Router
| CPE | DHCPv6 Client
| | DHCPv6-PD Requesting Router
+------+------+ (eg. customer network
| =3ffe:ffff:1234:5600::/56)
_________|_________
/ \
| Customer Network |
\___________________/
Figure 2: Use case of ISP-Customer network where CE is connected to
PE through access network
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 the prefix pool in bits
ipv6-prefix: IPv6 prefix of the 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
The status of 'Valid' in the Prefix Pool option can be used to add
the prefix pool and the associated aggregation 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 aggregation
route on the relay agent.
If the adminstrative 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 adminstrative 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
client-facing interface (Figure 2) where receiving the DHCPv6-PD
message from clients. The relay agent can include this ORO 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 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 client-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 client-facing interface in the relay-reply message
(13) of REPLY (7) from the server, the relay agent shall add or
remove the aggregation 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 aggregation 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 aggregation route entry in its routing table.
The relay agent advertises its routing table including the entries of
the aggregation routes based on the information of prefix pools when
the routing protocol is enabled on its network-facing interface.
The Relay Agent (Requestor) can use DHCPv6 Bulk Leasequery [RFC5460]
protocol to query the binding data of prefix pools in the !(R)Valid'
status from the server. After estblished a TCP connetion 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.
6. Server Behavior
Per RFC3633, if the prefix of the customer network requested in
relay-forward message of SOLICIT , REQUEST, RENEW, REBIND by the
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Client (requesting router) has valid lease, the Server (delegating
router) 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. When
Interface ID (OPTION_INTERFACE_ID, 18) included or nested in the
relay-forward message is used to identify the client, it can support
both of the typical use cases (Figure 1 and Figure 2) dicussed in
section 3.
After received the ORO (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
(Figure 1) or its client-facing interface (Figure 2) in the relay-
reply message of PD if the relay-forward message of PD received is
valid per RFC3633.
The server may use the link-address specified in relay-forward
message to identify the relay agent itself or its particular client-
facing interface where the prefix pool is associated, but the server
has to maintain the binding data of prefix pools in asscociation with
these link-addresses. To be more readable, the server can
alternatively use the Interface ID (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 client-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 asscociation with the Interface ID. In the
case that the CE is directly connected to PE (Figure 1), the server
can extract explicitly the ID of relay agent (PE) from the interface
ID.
Per RFC3315, the server shall copy the same Interface ID option got
from the relay-forward message into the relay-reply message. If the
prefix pool is associated with the relay agent itself, the Interface
ID option replied in the relay-reply message only include the ID of
the relay agent; if the preix pool is associated with the particular
client-facing interface of the relay agent, the Interface ID option
replies the whole ID of this interface.
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 turn 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
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releasing in the associated prefix pool, the server shall turn 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
the particular prefix pool, the status of prefix pool will always be
'Released'.
Once received the ORO to request Prefix Pool option in the relay-
forward message, the server must include Prefix Pool option with its
status in the relay-reply message of REPLY.
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 aggregation 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 client-facing interface
(Figure 2) in the binding table on the server, and one 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
throught 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
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(http://www.iana.org/assignments/dhcpv6-parameters/dhcpv6-
parameters.xml).
9. Acknowledgements
Thanks to the DHC working group members, Bernie Volz, Eliot Lear, Ole
Troan, Roberta Maglione, Ted Lemon, for the disussion in the mailing
list. Thanks to Christian Jacquenet for pointing out the draft
should cover one more of ISP-Customer network where CE is connected
to PE through access network. Thanks to Sven OOghe and Shrinivas
Ashok Joshi for the discussion during IETF79, and pointing out the
mechanism introduced in this draft should cover 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. -02
a. Add one more use case of ISP network architecture where CE is
directly connected to PE.
b. A bit of 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
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.
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[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 WT-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
Email: tena@huawei.com
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
Qiong Sun
China Telecom
Email: sunqiong@ctbri.com.cn
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