Internet DRAFT - draft-yeh-dhc-dhcpv6-prefix-pool-opt
draft-yeh-dhc-dhcpv6-prefix-pool-opt
DHC Working Group L. Yeh, Ed.
Internet-Draft Huawei Technologies
Intended status: Standards Track M. Boucadair
Expires: January 29, 2013 France Telecom
T. Lemon
Nominum, Inc
J. Hu
China Telecom
July 28, 2012
Prefix Pool Option for DHCPv6 Relay Agents on Provider Edge Routers
draft-yeh-dhc-dhcpv6-prefix-pool-opt-08
Abstract
The DHCPv6 Prefix Pool option provides a mechanism for DHCPv6 Prefix
Delegation (DHCPv6-PD), allowing the DHCPv6 server to notify a DHCPv6
relay agent implemented on a Provider Edge (PE) router about active
prefix pools allocated by the DHCPv6 server to the PE router. The
information of active prefix pools can be used to enforce IPv6 route
aggregation on the PE router by adding or removing aggregated routes
according to the status of the prefix pools. The advertising of the
aggregated routes in the routing protocol enabled on the network-
facing interface of PE routers will dramatically decreases the number
of the routing table 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 January 29, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology and Conventions . . . . . . . . . . . . . . . . . 4
3. Scenario and Network Architecture . . . . . . . . . . . . . . 5
4. Prefix Pool Option . . . . . . . . . . . . . . . . . . . . . . 6
5. Relay Agent Behavior . . . . . . . . . . . . . . . . . . . . . 8
6. Server Behavior . . . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
9. Contributors List . . . . . . . . . . . . . . . . . . . . . . 11
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
11.1. Normative References . . . . . . . . . . . . . . . . . . 12
11.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
The DHCPv6 protocol [RFC3315] specifies a mechanism for the
assignment of IPv6 address and configuration information to IPv6
nodes. The 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 Routers
(RR) acting as the DHCPv6 Clients. DHCPv6 servers always maintain
authoritative information associated to their operations including,
but not limited to, the binding data of the delegated IPv6 prefixes,
the lease data of the delegated IPv6 prefixes, and the status of
their prefix pools. A prefix pool configured and maintained on the
server can usually be a short prefix (e.g., a /40 prefix) out of
which the longer prefixes (e.g., /56 prefixes) are delegated to
customer networks.
In the scenario of a centralized DHCPv6 server, the Provider Edge
(PE) routers act as DHCPv6 relay agents when the DHCPv6 server and
the Customer Edge (CE) router (a.k.a. Routed-RG or Routed-CPE)
acting as RRs and DHCPv6 clients are not on the same link. For
ensuring reachability, 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 CE routers (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 be unacceptable large.
Hence, it is desirable to aggregate the routes directing to the
customer networks on the PE router.
Because the prefixes of the customer networks can not be guaranteed
to be active and continuous, the routing protocol enabled on the PE
router in general can not create one aggregated route automatically
to cover all the prefixes delegated within the prefix pool. One way
to make the aggregated routes (e.g., black-hole routes) pointing to
each of the prefix pools is to configure them manually and
permanently, but the PE router is not really aware about the status
of the prefix pools, especially when it acts as the relay agent.
This document proposes a new Prefix Pool option for the DHCPv6 relay
agent implemented on PE routers, allowing the DHCPv6 server to notify
the DHCPv6 relay agent about the prefix of pools. After the PE
router received information about the prefix pools, the aggregated
route entries per the provision status of the prefix pools can be
added or withdrawn in the routing table of the PE router. The
aggregated routes will then be advertised into the ISP network
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through the routing protocol enabled on the PE's network-facing
interface.
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., a DHCPv6 relay agent), to support the
replacement or reboot event of a relay agent. In this document, the
capability of DHCPv6 Bulk Leasequery will be extended to support the
bulk transfer of the status of the prefix pools for route
aggregation.
The automatic mechanisms described in this document depends on the
existing DHCPv6 protocols and implementations without requiring a new
DHCPv6 message or a new interface for the configuration of the
aggregated route. The administrator of the ISP network can decide
whether to inject the aggregated route or not based on the policies
defined on the DHCPv6 server.
2. Terminology and Conventions
This document defines a new DHCPv6 option to communicate the prefix
of an IPv6 prefix pool. This document should be read in conjunction
with the DHCPv6 specifications, [RFC3315], [RFC3633], [RFC5007] and
[RFC5460], for understanding the complete mechanism. Definitions for
terms and acronyms not specified in this document are defined in
[RFC3315], [RFC3633], [RFC3769], [RFC5007] and [RFC5460].
The following terms can be found in this document:
o Requesting Router (RR): A router defined in [RFC3633] that acts as
a DHCPv6 client, and is requesting prefix(es) to be assigned.
o Delegating Router (DR): A router defined in [RFC3633] that acts as
a DHCPv6 server, and is responding to the prefix request.
o Prefix Pool: An IPv6 address space allocated with a common prefix
out of which the longer prefixes are delegated via prefix
delegation.
o Aggregated Route: A route entry created on an edge router, is
based on the knowledge of a delegated prefix pool.
o Requestor: A router defined in [RFC5007] that acts as a DHCPv6
relay agent, is leasequery client.
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
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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.
+------+------+ DHCPv6 Server
| DHCPv6 | (e.g. Binding entry
| Server | 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 | DHCPv6 Relay Agent, DHCPv6 Requestor
| Edge | (e.g. prefix pool=2001:db8:1230::/44)
| Router |
+------+------+
| Customer-facing interface
| (e.g. Interface_ID=pe#1_cfi#2)
|
+------+------+
| Customer | DHCPv6 Client
| Edge | DHCPv6-PD Requesting Router
| 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 Server
| Server | (e.g. Binding entry
| | pe#3_cfi#4 - 2001:db8:3400::/40)
+------+------+
|
_________|_________
/ \
| ISP Core Network |
\___________________/
|
| Network-facing interface
+------+------+
| Provider | DHCPv6 Relay Agent, DHCPv6 Requestor
| Edge | (e.g. prefix pool=2001:db8:3400::/40)
| Router |
+------+------+
| Customer-facing interface
| (e.g. Interface_ID=pe#3_cfi#4)
_________|_________
/ \
| Access Network |
\___________________/
|
|
+------+------+
| Customer | DHCPv6 Client
| Edge | DHCPv6-PD Requesting Router
| Router | (e.g. customer network
+------+------+ =2001:db8:1234:5600:/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 in 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
Active 0
Released 1
Reserved 2~255
The 'Active' status of the prefix pool indicated in this option can
be used to add the prefix pool and its associated aggregated route on
the relay agent; while the 'Released' status of prefix pool indicated
in this option can be used to withdraw the prefix pool and its
associated aggregated route on the relay agent.
If the administrative policy on the DHCPv6 server permits to support
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 a
valid lease, the status of the prefix pool will be 'Active'.
Otherwise, the status of the prefix pool is 'Released'. If the
administrative policy on the server does not permit to support route
aggregation on the DHCPv6 relay agent, the status of the prefix pool
will always be 'Released'.
Discussion:
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The alternative option might include the lease information in the
prefix pool, then populate it to relay agent, make the state
machine on the relay agent keep synchronizing the lease and status
of the associated prefix pool with the server. But the solution
proposed in this draft is to let relay agent confirm the received
status of the prefix pool by itself as per the leases of delegated
customer prefixes within it, and build its own lease for the
prefix pool.
5. Relay Agent Behavior
The relay agent who needs the information of prefix pools, must
include the associated requested-option-code in Option Request option
(OPTION_ORO, 6) to request the Prefix Pool option
(OPTION_PREFIX_POOL, [TBD]) from the DHCPv6 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),
when receiving the DHCPv6-PD message from clients. The DHCPv6 relay
agent can include this Option Request option for the 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 the Prefix Pool option with the values of pfx-pool-len and
IPv6-prefix to indicate its preference, which the prefix pool the
relay agent would like the server to return.
The relay agent should include the Interface ID option
(OPTION_INTERFACE_ID, 18) so that the DHCPv6 server can identify the
relay agent itself or its particular customer-facing interface to
which the prefix pool is associated, if the server would not like to
use the link-address field specified in the encapsulation of the
DHCPv6 relay-forward message to identify the interface of the link on
which the clients are located.
The relay agent may set up a table for the leases or status of the
prefix pools on it as per the delegated customer prefixes within it.
The lease of the prefix pools must dynamically set to be the maximum
lease of the delegated customer prefixes. If there is no route entry
directing to the customer network within the aggregated route
associated with the prefix pool, the relay agent shall automatically
withdraw the aggregated route.
After receiving 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 DHCPv6 server, the relay agent acting as
the PE router shall confirm the status of the prefix pool as per the
leases of delegated customer prefixes within it, then add or withdraw
the aggregated route entry per the status of the prefix pool. If the
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status of the prefix pool received and confirmed is 'Active', the
relay agent shall add an aggregated route entry in its routing table,
if the same entry has not been added in before. If the status of the
prefix pool received is 'Released', the relay agent shall withdraw
the associated aggregated route entry in its routing table, if the
same entry has not been withdrawn before.
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 the DHCPv6 Bulk Leasequery
[RFC5460] to query the binding data of prefix pools in the 'Active'
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
the Prefix Pool option (OPTION_PREFIX_POOL, [TBD]) from the server.
6. Server Behavior
Per DHCPv6-PD [RFC3633], if the prefix of the customer network
requested in relay-forward (12) message of SOLICIT, REQUEST, RENEW,
REBIND from the DHCPv6 client (i.e., the RR) has a valid lease, the
DHCPv6 server (i.e., the DR) will delegate the prefix with the
relevant parameters in the relay-reply (13) message of REPLY. In
order to give a meaningful reply, the server has to be able to
maintain the binding data of the delegated IPv6 prefixes with the
identification of the client. The 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) requesting
the Prefix Pool option (OPTION_PREFIX_POOL, [TBD]) in the relay-
forward messages of the PD, the server must include the 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 messages if the relay-forward messages received are
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
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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 received via the relay-forward message into the relay-reply
message.
If the administrative policy on the DHCPv6 server permits to support
route aggregation on the relay agent for some particular prefix, the
status of prefix pool can be determined by the delegated prefixes
within the associated prefix pool. If there is at least one
delegated prefix within the pool that has a valid lease, the server
shall set the status of the associated prefix pool to be 'Active'.
After 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 administrative policy on the server does not
permit to support route aggregation on the DHCPv6 relay agent, the
server shall set the status of the prefix pools always to be
'Released'.
When the administrator of the server changes the setting to support
route aggregation on the relay agent for the particular prefix pool,
the status of the prefix pool may change from 'Released' to be
'Active' if at least one delegated prefix within the prefix pool has
the valid lease. When the administrator of the server changes the
setting not to support route aggregation on the relay agent for the
particular prefix pool, the status of the prefix pool may change from
'Active' to be 'Released' if at least one delegated prefix within the
prefix pool has the valid lease. Then the server may send a relay-
reply message of RECONFIGURE (10) to initiate immediately a Renew (5)
/ Reply (7) PD message exchange with Prefix Pool option between one
active client and the server.
Multiple prefix pools may be associated with the same PE router
implementing a DHCPv6 relay agent (Figure 1) or its customer-facing
interface (Figure 2) in the binding table on the server. Note that
the delegated prefix is only from one prefix pool.
After receiving the LEASEQUERY (14) message from the relay agent with
the Query option (OPTION_LQ_QUERY, 44) including the Option Request
option (OPTION_ORO, 6) to request the Prefix Pool option
(OPTION_PREFIX_POOL, [TBD]), the server must include the Client Data
options (OPTION_CLIENT_DATA, 45) in the LEASEQUERY-REPLY (15) and
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LEASEQUERY-DATA (16) message to convey the binding data of the
associated prefix pools with the 'Active' status through the
established TCP connection per [RFC5460]. Each Client Data option
shall contain a Prefix Pool option, and may contain the Interface ID
option (OPTION_INTERFACE_ID, 18). In order to be able to provide
meaningful replies to different query types, 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
[RFC3315].
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. Contributors List
Juergen Schoenwaelder
Jacobs University Bremen
Bremen
Germany
Email: j.schoenwaelder@jacobs-university.de
Tina Tsou
Huawei Technologies
Santa Clara, CA
USA
Email: tina.tsou.zouting@huawei.com
10. Acknowledgements
Thanks to Ralph Droms for the inspiration from his expired draft
(RAAN option), to the DHC working group members, Bernie Volz, Ole
Troan and Roberta Maglione for the discussion in the mailing list, to
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Christian Jacquenet for pointing out the draft should cover one more
use case of ISP-Customer network where CPE is directly connected to
PE, to Sven Ooghe for some revisions in the email review, to
Shrinivas Ashok Joshi for pointing out the draft should cover the
robust mechanism against the case of reboot, to Adrian Farrel for the
orientation guide on this draft in IETF80 at Prague.
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.
[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.
[RFC3769] Miyakawa, S. and R. Droms, "Requirements for IPv6 Prefix
Delegation", RFC 3769, June 2004.
Authors' Addresses
Leaf Y. Yeh (editor)
Huawei Technologies
Shenzhen,
P. R. China
Email: leaf.y.yeh@huawei.com
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Mohamed Boucadair
France Telecom
Rennes,
France
Email: mohamed.boucadair@orange.com
Ted Lemon
Nominum, Inc
USA
Email: Ted.Lemon@nominum.com
Jie Hu
China Telecom
Beijing,
P. R. China
Email: huj@ctbri.com.cn
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