Internet Engineering Task Force                              R. Gagliano
Internet-Draft                                                    LACNIC
Intended status: Informational                          October 23, 2009
Expires: April 8, 2010

           IPv6 Deployment in Internet Exchange Points (IXPs)

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   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (
   Please review these documents carefully, as they describe your rights
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   This document provides guidance on IPv6 deployment in Internet
   Exchange Points (IXP).  It includes information regarding the switch
   fabric configuration, the addressing plan and general organizational
   tasks that need to be performed.  IXPs are mainly a layer 2
   infrastructure and in many cases the best recommendations suggest
   that the IPv6 data, control and management plane should not be
   handled differently than in IPv4.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Switch Fabric Configuration  . . . . . . . . . . . . . . . . .  3
   3.  Addressing Plan  . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Multicast IPv6 . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  Multicast Support and Monitoring for ND at an IXP  . . . .  6
     4.2.  IPv6 Multicast traffic exhange at an IXP . . . . . . . . .  7
   5.  Reverse DNS  . . . . . . . . . . . . . . . . . . . . . . . . .  7
   6.  Route Server . . . . . . . . . . . . . . . . . . . . . . . . .  7
   7.  External and Internal support  . . . . . . . . . . . . . . . .  8
   8.  IXP Policies and IPv6  . . . . . . . . . . . . . . . . . . . .  8
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   10. Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     12.1. Normative References . . . . . . . . . . . . . . . . . . .  9
     12.2. Informative References . . . . . . . . . . . . . . . . . . 10
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10

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1.  Introduction

   Most Internet Exchange Points (IXP) work at the Layer 2 level, making
   the adoption of IPv6 an easy task.  However, IXPs normally implement
   additional services such as statistics, route servers, looking
   glasses and broadcast control that may be impacted by the
   implementation of IPv6.  This document clarifies the impact of IPv6
   on a new or an existing IXP.  The document assumes an Ethernet switch
   fabric, although other layer 2 configurations can be deployed.

2.  Switch Fabric Configuration

   An Ethernet based IXP switch fabric implements IPv6 over Ethernet as
   described in [RFC2464].  Therefore, the switching of IPv6 traffic
   happens in the same way as in IPv4.  However, some management
   functions require explicit IPv6 support (such as switch management,
   SNMP [RFC1157] support and flow analysis exportation) and this should
   be assessed by the IXP operator.

   There are two common configurations of IXP switch ports to support

   1.  dual-stack LAN: both IPv4 and IPv6 traffic share a common LAN.
       No extra configuration is required in the switch.  In this
       scenario, participants will typically configure dual-stack
       interfaces, although independent interfaces are an option.

   2.  independent LAN: an exclusive IPv6 LAN is created for IPv6
       traffic.  If IXP participants are already using Virtual LAN
       (VLAN) tagging on the interfaces of their routers that are facing
       the IXP switch, this only requires passing one additional VLAN
       tag across the interconnection.  If participants are using
       untagged interconnections with the IXP switch and wish to
       continue doing so, they will need to facilitate a separate
       physical port to access the IPv6-specific LAN.

   The "independent LAN" configuration provides a physical separation
   for IPv4 and IPv6 traffic simplifying separate analysis for IPv4 and
   IPv6 traffic.  However, it can be more costly in both capital
   expenses (if new ports are needed) and operational expends.
   Conversely, the dual-stack implementation allows a quick and capital
   cost-free start-up for IPv6 support in the IXP, allowing the IXP to
   avoid transforming untagged ports into tagged ports.  In this
   implementation, traffic-split for statistical analysis may be done
   using flows techniques such as IPFIX [RFC5101] considering the
   different ether-types (0x0800 for IPv4, 0x0806 for ARP and 0x86DD for

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   The only technical requirement for IPv6 referring link MTUs is that
   they need to be greater than or equal to 1280 octets [RFC2460].
   Common MTU sizes in IXPs are 1500, 4470, or 9216 bytes.
   Consequently, no MTU changes are typically required.  The MTU size
   for every LAN in an IXP should be well known by all its participants.

3.  Addressing Plan

   Regional Internet Registries (RIRs) have specific address policies to
   assign Provider Independent (PI) IPv6 address to IXPs.  Those
   allocations are usually /48 or shorter prefixes [RIR_IXP_POLICIES].
   Depending on the country and region of operation, address assignments
   may be made by NIRs (National Internet Registries).  Unique Local
   IPv6 Unicast Addresses ([RFC4193]) are normally not used in an IXP
   LAN as global reverse DNS resolution and whois services are required.

   From the allocated prefix, following the recommendations of
   [RFC4291], a /64 prefix should be allocated for each of the exchange
   point IPv6 enabled LANs.  A /48 prefix allows the addressing of 65536
   LANs.  As IXP will normally use manual address configuration.  Longer
   prefixes (/65-/127), are technically feasible but are normally
   discouraged because of operational practices.  The manual
   configuration of IPv6 addresses allows IXP participants to replace
   network interfaces with no need to reconfigure Border Gateway
   Protocol (BGP) sessions information and it also facilitates
   management tasks.

   When selecting the use of static Interface Identifiers (IIDs), there
   are different options on how to "intelligently" fill its 64 bits (or
   16 hexadecimal characters).  A non-exhausted list of possible IID
   selection mechanisms is the following:

   1.  Some IXPs like to include the participants' ASN number decimal
       encoding inside each IPv6 address.  The ASN decimal number is
       used as the BCD (binary code decimal) encoding of the upper part
       of the IID such as shown in this example:

       *  IXP LAN prefix: 2001:DB8::/64

       *  ASN: 64496

       *  IPv6 Address: 2001:DB8::0000:0006:4496:0001/64 or its
          equivalent representation 2001:DB8::6:4496:1/64

       In this example we are right justifying the participant' ASN
       number from the 112nd bit.  Remember that 32 bits ASNs require a
       maximum of 10 characters.  With this example, up to 2^16 IPv6

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       addresses can be configured per ASN.

   2.  Although BCD encoding is more "human-readable", some IXPs prefer
       to use the hexadecimal encoding of the ASNs number as the upper
       part of the IID as follow:

       *  IXP LAN prefix: 2001:DB8::/64

       *  ASN: 64496 (DEC) or FBF0 (HEX)

       *  IPv6 Address: 2001:DB8::0000:0000:FBF0:0001/64 or its
          equivalent representation 2001:DB8::FBF0:1/64

   3.  A third scheme for statically assigning IPv6 addresses on an IXP
       LAN could be to relate some portions of a participant's IPv6
       address to its IPv4 address.  In the following example, the last
       three decimals of the IPv4 address are copied to the last
       hexadecimals of the IPv6 address, using the decimal number as the
       BCD encoding for the last three characters of the IID such as in
       the following example:

       *  IXP LAN prefix: 2001:DB8::/64

       *  IPv4 Address:

       *  IPv6 Address: 2001:DB8::132/64

   4.  A fourth approach might be based on the IXPs ID for that

   IPv6 prefixes for IXP LANs are typically publicly well known and
   taken from dedicated IPv6 blocks for IXP assignments reserved for
   this purpose by the different RIRs.The current practice that applies
   to IPv4 about publishing IXP allocations to the DFZ (Default Free
   Zone) should also apply to the IPv6 allocation.  When considering the
   routing of the IXP LANs two options are identified:

   o  IXPs may decide that LANs should not to be globally routed in
      order to limit the possible origins of a Distributed Denial of
      Service (DDoS) attack to its particpant' AS boundries.  In this
      configuration participants may route these prefixes inside their
      networks (e. g. using BGP no-export communities or routing the IXP
      LANs within the participants' IGP) to perform fault management.
      Using this configuration, the monitoring of the IXP LANs from
      outside of its participants' AS boundaries is not possible.

   o  IXP may decide that LANs should be globally routed.  In this case,
      IXP LANs monitoring from outside its participants' AS boundaries

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      is possible but the IXP LANs will be vulnerable to DDoS from
      outside of those broundries.

   IXP external services (such as dns, web pages, ftp servers) need to
   be globally routed.  Strict prefix length filtering could be the
   reason for requesting more than one /48 assignment from a RIR (i.e.
   requesting one /48 assignment for the IXPs LANs that may not be
   globally routed and a different /48 assignment for the IXP external
   services that will be globally routed).

4.  Multicast IPv6

   There are two elements that need to be evaluated when studying IPv6
   multicast in an IXP: multicast support for neighbor discovery and
   multicast peering.

4.1.  Multicast Support and Monitoring for ND at an IXP

   IXPs typically control broadcast traffic across the switching fabric
   in order to avoid broadcast storms by only allowing limited ARP
   [RFC0826] traffic for address resolution.  In IPv6 there is not
   broadcast support but IXP may intend to control multicast traffic in
   each LAN instead.  ICMPv6 Neighbor Discovery [RFC4861] implements the
   following necessary functions in an IXP switching fabric: Address
   Resolution, Neighbor Unreachability Detection and Duplicate Address
   Detection.  In order to perform these functions, Neighbor
   Solicitation and Neighbor Advertisement packets are exchanged using
   the link-local all-nodes multicast address (FF02::1) and/or
   solicited-node multicast addresses (FF02:0:0:0:0:1:FF00:0000 to FF02:
   0:0:0:0:1:FFFF:FFFF).  As described in [RFC4861] routers will
   initialize its interfaces by joining its solicited-node multicast
   addresses using either Multicast Listener Discovery (MLD) [RFC2710]
   or MLDv2 [RFC3810].  MLD messages may be sent to the corresponding
   group address FF02::2 (MLD) or FF02::16 (MLDv2).  Depending on the
   addressing plan selected by the IXP, each solicited-node multicast
   group may be shared by a sub-set of participants' conditioned by how
   the last three octets of the addresses are selected.  In Section 3
   example 1, only participants with ASNs with the same two last digits
   are going to share the same solicited-node multicast group.

   Similarly to the ARP policy an IXP may limit multicast traffic across
   the switching fabric in order to only allow ICMPv6 Neighbor
   Solicitation, Neighbor Advertisement and MLD messages.  Configuring
   default routes in an IXP LAN without an agreement between the parties
   is normally against IXP policies.  ICMPv6 Router Advertisement
   packets should neither be issued nor accepted by routers connected to
   the IXP.  Where possible, the IXP operator should block link-local RA

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   packets using IPv6 RA-GUARD [I-D.ietf-v6ops-ra-guard].  If this is
   not possible, the IXP operator should monitor the exchange for rogue
   Router Advertisement packets as decribed in

4.2.  IPv6 Multicast traffic exhange at an IXP

   For IPv6 Multicast traffic exchange, an IXP may decide to use either
   the same LAN being used for unicast IPv6 traffic exchange, the same
   LAN being used for IPv4 Multicast traffic exchange or a dedicated LAN
   for IPv6 Multicast traffic exchange.  The reason for having a
   dedicated LAN for multicast is to prevent unwanted multicast traffic
   to reach participants that do not have multicast support.  Protocol
   Independent Multicast [RFC4601] messages will be sent to the link-
   local IPv6 'ALL-PIM-ROUTERS' multicast group ff02::d in the selected
   LAN and should be allowed.  Implementing IPv6 PIM snooping will allow
   only the participants associated to a particular group to receive its
   multicast traffic.  BGP reachability information for IPv6 multicast
   address-family (SAFI=2) is normally exchanged using MP-BGP [RFC4760]
   and is used for Reverse Path Forwarding (RPF) lookups performed by
   the IPv6 PIM.  If a dedicated LAN is configured for Multicast IPv6
   traffic exchange, reachability information for IPv6 Multicast address
   family should be carried in new BGP sessions.  ICMPv6 Neighbor
   Discovery should be allowed in the Multicast IPv6 LAN as described in
   the previous paragraph.

5.  Reverse DNS

   The inclusion of PTR records for all addresses assigned to
   participants in the IXP reverse zone under "" facilitates
   troubleshooting, particularly when using tools such as traceroute.
   If reverse DNS is configured, DNS servers should be reachable over
   IPv6 transport for complete IPv6 support.

6.  Route Server

   IXPs may offer a Route Server service, either for Multi-Lateral
   Peering Agreements (MLPA) service, looking glass service or route-
   collection service.  IPv6 support needs to be added to the BGP
   speaking router.  The equipment should be able to transport IPv6
   traffic and to support Multi-protocol BGP (MP-BGP) extensions for
   IPv6 address family ([RFC2545] and [RFC4760]).

   A good practice is that all BGP sessions used to exchange IPv6
   network information are configured using IPv6 data transport.  This
   configuration style ensures that both network reachability

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   information and generic packet data transport use the same transport
   plane.  In the event of IPv6 reachability problems between IPv6
   peers, the IPv6 BGP session may be terminated independently of any
   IPv4 sessions.  The use of MD5 [RFC2385] or IPSEC [RFC4301] to
   authenticate the BGP sessions and the use of GTSM (The Generalized
   TTL Security Mechanism) [RFC3682] should be considered.

   The Router-Server or Looking Glass external service should be
   available for external IPv6 access, either by an IPv6 enabled web
   page or an IPv6 enabled console interface.

7.  External and Internal support

   Some external services that need to have IPv6 support are traffic
   graphics, DNS, FTP, Web, Route Server and Looking Glass.  Other
   external services such as NTP servers, or SIP Gateways need to be
   evaluated as well.  In general, each service that is currently
   accessed through IPv4 or that handle IPv4 addresses should be
   evaluated for IPv6 support.

   Internal services are also important when considering IPv6 adoption
   at an IXP.  Such services may not deal with IPv6 traffic but may
   handle IPv6 addresses; that is the case of provisioning systems,
   logging tools and statistics analysis tools.  Databases and tools
   should be evaluated for IPv6 support.

8.  IXP Policies and IPv6

   IXP Policies and contracts should be revised as any mention of IP
   should be clarified if it refers to IPv4, IPv6 or both.

9.  IANA Considerations

   This memo includes no request to IANA.

10.  Security Considerations

   This memo includes information on practices at IXPs for monitoring
   and/or avoiding broadcast storms in IXP LANs caused by IPv6 multicast
   traffic.  It also mentions avoiding IPv6 DDoS attacks to the IXP
   switching fabric by not globally announce the IXP LANs prefix and
   recommends to monitor ICMPv6 activity.

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11.  Acknowledgements

   The author would like to thank the contributions from Alain Aina,
   Bernard Tuy, Stig Venaas, Martin Levy, Nick Hilliard, Martin Pels,
   Bill Woodcock, Carlos Frias, Arien Vijn, Fernando Gont and Louis Lee,

12.  References

12.1.  Normative References

              Levy-Abegnoli, E., Velde, G., Popoviciu, C., and J.
              Mohacsi, "IPv6 RA-Guard", draft-ietf-v6ops-ra-guard-03
              (work in progress), May 2009.

              Chown, T. and S. Venaas, "Rogue IPv6 Router Advertisement
              Problem Statement", draft-ietf-v6ops-rogue-ra-00 (work in
              progress), May 2009.

   [RFC0826]  Plummer, D., "Ethernet Address Resolution Protocol: Or
              converting network protocol addresses to 48.bit Ethernet
              address for transmission on Ethernet hardware", STD 37,
              RFC 826, November 1982.

   [RFC1157]  Case, J., Fedor, M., Schoffstall, M., and J. Davin,
              "Simple Network Management Protocol (SNMP)", STD 15,
              RFC 1157, May 1990.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2385]  Heffernan, A., "Protection of BGP Sessions via the TCP MD5
              Signature Option", RFC 2385, August 1998.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [RFC2464]  Crawford, M., "Transmission of IPv6 Packets over Ethernet
              Networks", RFC 2464, December 1998.

   [RFC2545]  Marques, P. and F. Dupont, "Use of BGP-4 Multiprotocol
              Extensions for IPv6 Inter-Domain Routing", RFC 2545,
              March 1999.

   [RFC2710]  Deering, S., Fenner, W., and B. Haberman, "Multicast
              Listener Discovery (MLD) for IPv6", RFC 2710,

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              October 1999.

   [RFC3682]  Gill, V., Heasley, J., and D. Meyer, "The Generalized TTL
              Security Mechanism (GTSM)", RFC 3682, February 2004.

   [RFC3810]  Vida, R. and L. Costa, "Multicast Listener Discovery
              Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, October 2005.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.

   [RFC4601]  Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
              "Protocol Independent Multicast - Sparse Mode (PIM-SM):
              Protocol Specification (Revised)", RFC 4601, August 2006.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              January 2007.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007.

   [RFC5101]  Claise, B., "Specification of the IP Flow Information
              Export (IPFIX) Protocol for the Exchange of IP Traffic
              Flow Information", RFC 5101, January 2008.

12.2.  Informative References

              Numbers Resource Organization (NRO)., "RIRs Allocations
              Policies for IXP. NRO Comparison matrix", 2008,

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Author's Address

   Roque Gagliano
   Rambla Rep Mexico 6125
   Montevideo,   11400

   Phone: +598 2 4005633

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