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Versions: (draft-yeh-dhc-dhcpv6-prefix-pool-opt) 00 01 02 03

DHC Working Group                                                 L. Yeh
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                                T. Lemon
Expires: April 22, 2013                                     Nominum, Inc
                                                            M. Boucadair
                                                          France Telecom
                                                        October 19, 2012


  Prefix Pool Option for DHCPv6 Relay Agents on Provider Edge Routers
                draft-ietf-dhc-dhcpv6-prefix-pool-opt-01

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 through adding or removing aggregation
   routes according to the status of the prefix pools.  The advertising
   of the aggregation 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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 22, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal



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   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


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 with 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.  It 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 aggregation route automatically
   to cover all the prefixes delegated within the prefix pool.  When the
   PE router acts as the relay agent, it in general can not be aware
   about the status of the prefix pools.  One way to make the
   aggregation routes (e.g., black-hole routes) pointing to each of the
   prefix pools is to configure them manually and permanently, but it is
   meant to a large amount of the handwork on each PE router for its
   operation and maintenance.

   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 aggregation
   route entries can be added or withdrawn in the routing table of the



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   PE router according to the provision status of the prefix pools.  The
   aggregation routes will then be advertised into the ISP network
   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, typically a 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 prefix and its status of the prefix pools for route
   aggregation.

   The automatic mechanisms described in this document depend on the
   existing DHCPv6 protocols and implementations without requiring a new
   DHCPv6 message or a new interface for the configuration of the
   aggregation route.  The administrator of the ISP network can decide
   whether to inject the aggregation 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
   and its status of an IPv6 prefix pool.  Definitions for terms and
   acronyms not specified in this document are defined in [RFC3315],
   [RFC3633], [RFC5007] and [RFC5460].

   The following terms have been employed in this document:

   o  Requesting Router (RR): A router defined in [RFC3633] that acts as
      a DHCPv6 client, and is requesting prefix to be delegated.

   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  aggregation route: A route entry created on an edge router, is
      based on the knowledge of a prefix pool of the delegated prefixes.

   o  Requestor: A node defined in [RFC5007] that acts as the 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         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    status     | pfx-pool-len  |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                                                               |
   |                 ipv6-prefix (variable length)                 |
   |                                                               |
   +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   option-code:    OPTION_PREFIX_POOL (TBA-IANA)
   option-length:  2 + length of ipv6-prefix (in Octets)
   pfx-pool-len:   Length for the prefix pool in bits
   status:         Status of the prefix pool, indicating the
                   availability of the prefix pool maintained
                   on the server.
   ipv6-prefix:    IPv6 prefix of the prefix pool, which is up to 16
                   octets in length. Bits outsides of the
                   pfx-pool-len, if included, MUST be zero.

   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 aggregation 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 aggregation route on the relay agent.

   If the administrative policy on the 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 relay agent, the status of the prefix pool will
   always be 'Released'.

   Prefix Pool Option MAY be included by the DHCPv6 server in RELAY-REPL



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   (13), LEASEQUERY-REPLY (15) and LEASEQUERY-DATA (17) message, and MAY
   be included by the DHCPv6 relay agent in the RELAY-FORW (12).


5.  Relay Agent Behavior

   The DHCPv6 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-IANA]) from the DHCPv6 server, who
   maintains the status of the prefix pools associated with the relay
   agent itself (Figure 1) or its particular customer-facing interface
   (Figure 2), when receiving the DHCPv6-PD message from clients.  The
   relay agent MAY include this Option Request option for the Prefix
   Pool option in the RELAY-FORW (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
   'ip6-prefix' to indicate its preference for which 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 server can identify the relay
   agent itself or its particular customer-facing interface with 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 lease or status of the
   prefix pool on it according to the leases of 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
   aggregation route associated with the prefix pool or the lease of
   prefix pool runs out, the relay agent Should automatically withdraw
   the aggregation route.

   After receiving the Prefix Pool option for the relay agent itself or
   its particular customer-facing interface in the RELAY-REPL (13)
   message of REPLY (7) from the server, the relay agent acting as the
   PE router Should confirm the status of the prefix pool according to
   the leases of delegated customer prefixes within it.  If the status
   of the prefix pool received and confirmed is 'Active', the relay
   agent Should add an aggregation route entry in its routing table, if
   the same entry has not been added before.  If the status of the
   prefix pool received is 'Released', the relay agent Should withdraw
   the associated aggregation route entry in its routing table, if the
   same entry has not been withdrawn before.



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   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 (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
   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 or 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

   According to DHCPv6-PD [RFC3633], if the prefix of the customer
   network requested in RELAY-FORW (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-REPL (13) message of REPLY.  In
   order to give a meaningful reply, the server has 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 DHCPv6-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
   server can alternatively use the Interface ID option included in the
   relay-forward message by the relay agent to identify the relay agent
   itself or its particular customer-facing interface 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.  According to
   DHCPv6 [RFC3315], the server MUST copy the Interface ID option from



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   the relay-forward message into the relay-reply message.

   If the administrative policy on the server permits to support route
   aggregation on the relay agent for some particular prefix pool, 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
   Should set the status of the associated prefix pool to be 'Active'.
   After the last prefix released in the associated prefix pool, the
   server Should 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 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) prefix delegation 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 the relay agent, or its customer-facing interface in the
   binding table on the server.  Note that these prefix pools Should not
   overlay, and the delegated customer prefix is only from one prefix
   pool.

   After receiving the LEASEQUERY (14) message from the relay agent with
   the OPTION_LQ_QUERY (44) including the OPTION_ORO (6) to request the
   OPTION_PREFIX_POOL (TBD), the server MUST include the Prefix Pool
   option in the LEASEQUERY-REPLY (15) and LEASEQUERY-DATA (17) messages
   to convey the binding data of the associated prefix pools through the
   established TCP connection according to mechanism defined in the
   DHCPv6 Bulk Leasequery [RFC5460].  Each LEASEQUERY-REPLY (15) and
   LEASEQUERY-DATA (17) message only contains one OPTION_PREFIX_POOL or
   and the associated OPTION_INTERFACE_ID (18) if the status of the
   prefix pool is 'active'.  In order to be able to provide meaningful
   replies to different query types, the server has 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.





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7.  Security Considerations

   Security issues related DHCPv6 are described in Section 23 of
   [RFC3315] and Section 15 of [RFC3633].


8.  IANA Considerations

   IANA is requested to assign an option code to Option_Prefix_Pool from
   the DHCPv6 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

   Jie Hu
   China Telecom
   Beijing,
   P. R. China

   Email: huj@ctbri.com.cn

   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
   [I-D.ietf-dhc-dhcpv6-agentopt-delegate-04], to the DHC working group
   members, Bernie Volz, Ole Troan and Roberta Maglione for the
   discussion in the mailing list, to Christian Jacquenet for pointing
   out the draft shall 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 shall cover the mechanism against the case of reboot,
   to Adrian Farrel for the orientation guide on this draft in IETF80 at



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   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.

   [I-D.ietf-dhc-dhcpv6-agentopt-delegate-04]
              Droms, R., Volz, B., and O. Troan, "DHCPv6 Relay Agent
              Assignment Notification (RAAN) Option", July 2009.


Authors' Addresses

   Leaf Y. Yeh
   Huawei Technologies
   Shenzhen,
   P. R. China

   Email: leaf.y.yeh@huawei.com








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   Ted Lemon
   Nominum, Inc
   USA

   Email: Ted.Lemon@nominum.com


   Mohamed Boucadair
   France Telecom
   Rennes,
   France

   Email: mohamed.boucadair@orange.com






































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