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

DHC Working Group                                                 L. Yeh
Internet-Draft                                   Freelancer Technologies
Intended status: Standards Track                                T. Lemon
Expires: October 28, 2013                                   Nominum, Inc
                                                            M. Boucadair
                                                          France Telecom
                                                          April 26, 2013


 Prefix Pool Option for DHCPv6 Relay Agent on the Provider Edge Routers
                draft-ietf-dhc-dhcpv6-prefix-pool-opt-03

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
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   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 October 28, 2013.

Copyright Notice

   Copyright (c) 2013 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
     5.1.  Leasequery Requestor Behavior  . . . . . . . . . . . . . .  9
   6.  Server Behavior  . . . . . . . . . . . . . . . . . . . . . . .  9
     6.1.  Leasequery Server Behavior . . . . . . . . . . . . . . . . 11
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 12
     10.2. 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.  The 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, the status
   of their prefix pools, etc.  A prefix pool configured and maintained
   on the server can usually be a short prefix (e.g., a /40 prefix), out
   of which a longer prefixes (e.g., /56 prefixes) are delegated to
   customer networks.

   In the scenarios 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 the 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 the 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 routers 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 can not be aware about the
   status of the prefix pools in general.  The way to make the
   aggregation routes (e.g., black-hole routes) pointing to each of the
   prefix pools could be 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 the information about the prefix pools.  After
   the PE router received the prefix pools, the aggregation route
   entries can be added or withdrawn in the routing table of the PE



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   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 the
   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 key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this



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   document are to be interpreted as described in [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   |        Relay=nfi-GUA#1,
             |             |        Prefix Pool=2001:db8:3450::/44)
             +------+------+
                    |
           _________|_________
          /                   \
         |   ISP Core Network  |
          \___________________/
                    |
                    |
                    |  Network-facing interface
                    |         (e.g. IPv6 address=nfi-GUA#1)
             +------+------+
             |   Provider  |
             |     Edge    |  DHCPv6 Relay Agent, DHCPv6 Requestor
             |    Router   |  (e.g. prefix pool=2001:db8:3450::/44)
             +------+------+
                    |  Customer-facing interface
                    |
                    |
             +------+------+
             |   Customer  |  DHCPv6 Client
             |     Edge    |  DHCPv6-PD Requesting Router
             |    Router   |  (e.g. customer network
             +------+------+        =2001:db8:3456:7800:/56)
                    |
           _________|_________
          /                   \
         |  Customer Network   |
          \___________________/

    Figure 1: ISP-to-Customer network where CE is directly connected to
                                    PE








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             +------+------+  DHCPv6 Server
             |    DHCPv6   |  (e.g. Binding entry:
             |    Server   |        Relay=nfi-GUA#2,
             |             |        Interface-ID=cfi#3,
             +------+------+        Prefix Pool=2001:db8:1200::/40)
                    |
           _________|_________
          /                   \
         |  ISP Core Network   |
          \___________________/
                    |
                    |
                    |  Network-facing interface
                    |         (e.g. IPv6 address=nfi-GUA#2)
             +------+------+
             |   Provider  |
             |     Edge    |  DHCPv6 Relay Agent, DHCPv6 Requestor
             |    Router   |
             +------+------+
                    |  Customer-facing interface
                    |         (e.g. Interface-ID=cfi#3)
                    |               Prefix Pool=2001:db8:1200::/40)
           _________|_________
          /                   \
         |   Access Network    |
          \___________________/
                    |
                    |
             +------+------+
             |   Customer  |  DHCPv6 Client
             |     Edge    |  DHCPv6-PD Requesting Router
             |    Router   |  (e.g. customer network
             +------+------+        =2001:db8:1234:5600:/56)
                    |
           _________|_________
          /                   \
         |  Customer Network   |
          \___________________/

   Figure 2: ISP-to-Customer network where CE 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
   status:         Status of the prefix pool, indicating the
                   availability of the prefix pool maintained
                   on the server.
   pfx-pool-len:   Length for the prefix pool in bits
   ipv6-prefix:    IPv6 prefix of the prefix pool, which is
                   floor((pfx-pool-len+7)/8) 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'.




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   Prefix Pool Option MAY be included by the DHCPv6 server in RELAY-REPL
   (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,
   SHOULD 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 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
   SHOULD 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 Interface-ID option
   (OPTION_INTERFACE_ID, 18) so that the server can identify the
   particular customer-facing interface of the relay agent (i.e., the PE
   router) with which the prefix pool is associated, if the server can
   not use the link-address field specified in the encapsulation of the
   DHCPv6 RELAY-FORW message to identify the interface of the link on
   which the client is located.

   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 PE router acting as the
   relay agent 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 PE router
   acting as 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 PE router
   acting as the relay agent SHOULD withdraw the associated aggregation
   route entry in its routing table, if the same entry has not been
   withdrawn before.

   The PE router acting as the relay agent MAY set up a table for the
   lease or status of the prefix pools on it according to the leases of
   the delegated customer prefixes within the prefix pools.  The lease
   of the prefix pool SHOULD dynamically set to be the maximum lease of
   the delegated customer prefix within it.  If there is no route entry
   directing to the customer network within the aggregation route



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   associated with the prefix pool or the lease of prefix pool runs out,
   the PE router acting as the relay agent SHOULD automatically withdraw
   the aggregation route.

   The PE router acting as 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.

5.1.  Leasequery Requestor Behavior

   The PE router acting as 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 SHOULD 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 SHOULD include Option Request option to request the
   Prefix Pool option 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 (1), REQUEST
   (3), RENEW(5), REBIND (6) 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 (7).  In order to give a meaningful reply, the server has
   always to maintain the binding data of the prefix pool in association
   with the identification of the relay itself (Figure 1) or its
   customer-facing interface (Figure 2).

   The source address in the IPv6 packet header of RELAY-FORW message
   can be used to identify the DHCPv6 relay agent (i.e., the PE router)
   in the case when there is only one relay between the server and the
   client; or the peer-address nested in the RELAY-FORW message can be
   used to identify the DHCPv6 relay agent (i.e., the PE router) in the
   case when there are multiple relays between the server and the
   client.  The source address or the peer-address mentioned here is
   always the globe unique address (GUA) of the network-facing interface
   of the PE router.  The Interface ID option (OPTION_INTERFACE_ID, 18)
   nested in the RELAY-FORW message can be used to identify the access
   line of the client.

   The server MAY use the link-address specified in RELAY-FORW message
   to identify the relay agent itself and its particular customer-facing



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   interface where the prefix pool is associated, if these link-address
   are possible GUA, but the server has to maintain the binding data of
   prefix pools in association with these GUA of link-addresses.

   After receiving the Option Request option (OPTION_ORO, 6) requesting
   the Prefix Pool option (OPTION_PREFIX_POOL, TBD) in the RELAY-FORW
   messages of the DHCPv6-PD, the server SHOULD include the Prefix Pool
   option with the prefix and its status indicated for the associated
   relay agent itself or its customer-facing interface in the RELAY-REPL
   messages, if the RELAY-FORW messages received are valid.  As per
   DHCPv6 [RFC3315], the server SHOULD copy the Interface-ID option from
   the RELAY-FORW message into the RELAY-REPL message.

   If the administrative policy on the server permits to support route
   aggregation on the relay agents for some particular prefix pools, 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 agents, the server
   shall set the status of the associated 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 SHOULD 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 SHOULD change
   from 'Active' to be 'Released' if at least one delegated prefix
   within the prefix pool has the valid lease.  The server MAY initiate
   a RELAY-REPL message of RECONFIGURE (10) to immediately trigger RENEW
   (5) and REPLY (7) prefix delegation message exchange with Prefix Pool
   option between one active client and the server.

   Multiple prefix pools can be associated with the same PE router
   acting as the relay agent, or its customer-facing interface in the
   binding table on the server.

   Note that the prefix pools SHOULD not overlap, and the delegated
   customer prefix is only from one prefix pool.






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6.1.  Leasequery Server Behavior

   After receiving the LEASEQUERY (14) message from the relay agent with
   the OPTION_LQ_QUERY (44) including the OPTION_ORO (6) to request the
   Prefix Pool option, the server SHOULD include the OPTION_PREFIX_POOL
   (TBD) 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 MAY only contain one OPTION_PREFIX_POOL,
   or and the associated OPTION_INTERFACE_ID, 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_IDs of the relay agent in its binding database.


7.  Security Considerations

   Security issues related DHCPv6 are described in Section 23 of
   [RFC3315] and Section 15 of [RFC3633].  The administrator of the
   DHCPv6 server should pay more attention to the configuration of the
   prefix pools, for examples, a. ::/0 may cause a routing problem in
   the whole ISP network; b. the configuration of prefix pool should
   avoid overlap in the address plan, and etc.


8.  IANA Considerations

   This document requests to assign a new option code for
   Option_Prefix_Pool in the registry of DHCPv6 Option Codes (http://
   www.iana.org/assignments/dhcpv6-parameters/dhcpv6-parameters.xml).


9.  Acknowledgements

   Thanks to Ralph Droms for the inspiration from his expired
   [I-D.ietf-dhc-dhcpv6-agentopt-delegate-04], to Tomek Mrugalski,
   Bernie Volz, Ole Troan and Alexandru Petrescu for their discussion in
   the mailing list of DHC, to Acee Lindem for his discussion in the
   mailing list of routing-discussion, to Christian Jacquenet for
   pointing out the draft shall cover one more use case of ISP-to-
   Customer network where CPE is directly connected to PE, to Sven
   Ooghe, Juergen Schoenwaelder and Jie Hu 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 Prague.




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10.  References

10.1.  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.

10.2.  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
   Freelancer Technologies
   P. R. China

   Email: leaf.yeh.sdo@gmail.com


   Ted Lemon
   Nominum, Inc
   USA

   Email: Ted.Lemon@nominum.com





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   Mohamed Boucadair
   France Telecom
   France

   Email: mohamed.boucadair@orange.com














































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