Internet Engineering Task Force R. Gagliano
Internet-Draft LACNIC
Intended status: Informational November 24, 2009
Expires: May 28, 2010
IPv6 Deployment in Internet Exchange Points (IXPs)
draft-ietf-v6ops-v6inixp-04.txt
Abstract
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.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
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Copyright Notice
Copyright (c) 2009 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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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 exchange 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. Informative References . . . . . . . . . . . . . . . . . . . . 9
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 may 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
IPv6:
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 provision 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
IPv6).
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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.
IXPs will normally use manual address configuration. Address prefix
between /64 and /127 are technically feasible [RFC4291]. Because of
operational practices, IXP will normally chose a /64 prefix to be
allocated for each of the IXP's IPv6 enabled LANs. In this case, a
/48 prefix allows the addressing of 65536 LANs. 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 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:db8:0000:0000:0000:0006:4496:0001/64 or its
equivalent representation 2001:db8::6:4496:1/64
In this example we are right justifying the participant's 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
addresses can be configured per ASN.
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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:db8:0000:0000:0000:0000: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
four 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: 192.0.2.123/23
* IPv6 Address: 2001:db8:2:123/64
4. A fourth approach might be based on the IXPs ID for that
participant.
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 Denial of Service (DoS)
attack to its particpants' AS boundaries. 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
is possible but the IXP LANs will be vulnerable to DoS from
outside of those boundaries.
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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
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 described in
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[I-D.ietf-v6ops-rogue-ra].
4.2. IPv6 Multicast traffic exchange 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 (PIM) [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 "ip6.arpa" 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
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
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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. Because of
the size of the IPv6 space, limiting the maximum number of IPv6
prefixes in every session should be studied.
External services 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.
Policies for IPv6 traffic monitoring and filtering may be in place as
described in Section Section 4.
9. IANA Considerations
This memo includes no request to IANA.
10. Security Considerations
This memo includes procedures for monitoring and/or avoiding
particular ICMPv6 traffic at IXPs' LANs. It also mentions how to
limit IPv6 DoS attacks to the IXP switch fabric by not globally
announce the IXP LANs prefix.
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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. Informative References
[I-D.ietf-v6ops-ra-guard]
Levy-Abegnoli, E., Velde, G., Popoviciu, C., and J.
Mohacsi, "IPv6 RA-Guard", draft-ietf-v6ops-ra-guard-03
(work in progress), May 2009.
[I-D.ietf-v6ops-rogue-ra]
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,
October 1999.
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[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.
[RIR_IXP_POLICIES]
Numbers Resource Organization (NRO)., "RIRs Allocations
Policies for IXP. NRO Comparison matrix", 2008,
<http://www.nro.net/documents/comp-pol.html#3-4-2>.
Author's Address
Roque Gagliano
LACNIC
Rambla Rep Mexico 6125
Montevideo, 11400
Uruguay
Phone: +598 2 4005633
Email: roque@lacnic.net
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