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requirements-06



Revised draft, attached below, has been sent in and should appear in the usual places in due course. Apologies for the delay in making these changes.

RFC 2629 source diff follows.

[jabley@snowfall]% cvs diff -u -r 1.5 -r 1.6 draft-ietf-multi6-multihoming-requirements.xml
Index: draft-ietf-multi6-multihoming-requirements.xml
===================================================================
RCS file: /home/cvs/doc/ietf/draft-ietf-multi6-multihoming-requirements.xml,v
retrieving revision 1.5
retrieving revision 1.6
diff -u -r1.5 -r1.6
--- draft-ietf-multi6-multihoming-requirements.xml 16 Apr 2003 13:40:47 -0000 1.5
+++ draft-ietf-multi6-multihoming-requirements.xml 16 May 2003 17:19:43 -0000 1.6
@@ -5,7 +5,7 @@
<?rfc compact="yes"?>
<?rfc subcompact="no"?>

-<rfc ipr="full2026" docName="draft-ietf-multi6-multihoming-requirements-05">
+<rfc ipr="full2026" docName="draft-ietf-multi6-multihoming-requirements-06">
<front>
<title abbrev="IPv6 Site-Multihoming Goals">
Goals for IPv6 Site-Multihoming Architectures
@@ -15,13 +15,13 @@
<organization abbrev="ISC">Internet Software Consortium</organization>
<address>
<postal>
- <street>10805 Old River Road</street>
- <country>Canada</country>
- <code>N0L 1R0</code>
- <region>ON</region>
- <city>Komoka</city>
+ <street>950 Charter Street</street>
+ <country>USA</country>
+ <code>94063</code>
+ <region>CA</region>
+ <city>Redwood City</city>
</postal>
- <phone>+1 519 641 4368</phone>
+ <phone>+1 650 423 1317</phone>
<email>jabley@isc.org</email>
</address>
</author>
@@ -43,7 +43,7 @@
<date month="April" year="2003" />

<area>Operations and Management</area>
- <workgroup>multi6</workgroup>
+ <workgroup>Network Working Group</workgroup>

<abstract>
<t>Site-multihoming, i.e. connecting to more than one IP service
@@ -65,16 +65,15 @@

<t>However,
it appears that this hierarchy is being supplanted by a dense mesh
- of interconnections <xref target="refs.Huston" />. Additionally,
+ of interconnections <xref target="refs.RFC3221" />. Additionally,
there has been an enormous growth in the number of multihomed
sites. For purposes of redundancy and load-sharing, the
- multihomed address blocks, which are almost always a longer prefix
- than the provider aggregate, are announced along with the larger,
- covering
- aggregate originated by the provider. This contributes to the
- rapidly-increasing size
- of the global routing table. This explosion places significant
- stress on the inter-provider routing system.</t>
+ multihomed address blocks are introduced into the global table
+ even if they are covered by a provider aggregate.
+ This contributes to the
+ rapidly-increasing size of both
+ the global routing table and the turbulence exhibited within
+ it, and places stress on the inter-provider routing system.</t>

<t>Continued growth of both the Internet and the practice of
site-multihoming will seriously exacerbate this stress. The
@@ -123,7 +122,8 @@
circuits ordered from different suppliers and connecting
a site to independent transit providers may share a single
conduit from the street into a building; in this case
- backhoe-fade of both circuits may be experienced due to a
+ physical disruption (sometimes referred to as
+ "backhoe-fade") of both circuits may be experienced due to a
single incident in the street. The two circuits are said
to "share fate".</t>

@@ -146,7 +146,7 @@
<section anchor="loadshare" title="Load Sharing">
<t>By multihoming, a site should be able to
distribute both inbound and outbound traffic between multiple
- transit providers. This requirement is for concurrent
+ transit providers. This goal is for concurrent
use of the multiple transit providers, not just the usage
of one provider over one interval of time and another provider
over a different interval.</t>
@@ -184,9 +184,12 @@
<t>As any proposed multihoming solution must be deployed in real
networks with real customers, simplicity is paramount. The
current multihoming solution is quite
- straightforward to deploy and maintain. A new IPv6 multihoming
- proposal should not be substantially more complex to deploy and
- operate than current IPv4 multihoming practices.</t>
+ straightforward to deploy and maintain.</t>
+
+ <t>A new IPv6 multihoming
+ solution should not be substantially more complex to deploy and
+ operate (for multihomed sites or for the rest of the Internet)
+ than current IPv4 multihoming practices.</t>
</section>

<section anchor="transportSurvivability" title="Transport-Layer
@@ -213,13 +216,14 @@
<t>Multi-homing solutions either should be compatible with the
observed dynamics of the current DNS system, or the solutions
should demonstrate that the modified name resolution
- system required to support them are readily deployable.</t>
+ system required to support them is readily deployable.</t>
</section>

<section anchor="antiSpoofing" title="Packet Filtering">
<t>Multihoming solutions should not preclude filtering packets
with forged or otherwise inappropriate source IP addresses
- at the administrative boundary of the multihomed site.</t>
+ at the administrative boundary of the multihomed site, or
+ at the administrative boundaries of any site in the Internet.</t>
</section>
</section>

@@ -231,7 +235,7 @@
is a concern both because of the hardware requirements
it imposes and also because of the impact on the stability
of the routing system. This issue is discussed in great
- detail in <xref target="refs.Huston" />.</t>
+ detail in <xref target="refs.RFC3221" />.</t>

<t>A new IPv6 multihoming architecture should scale
to accommodate orders of magnitude more multihomed sites
@@ -240,7 +244,7 @@
</section>

<section anchor="routerImpact" title="Impact on Routers">
- <t>The solution may require changes to IPv6 router implementations,
+ <t>The solutions may require changes to IPv6 router implementations,
but these changes should be either minor, or in the form of logically
separate functions added to existing functions.</t>

@@ -253,7 +257,7 @@
<t>The solution should not destroy IPv6 connectivity for a legacy host
implementing RFC 3513 <xref target="refs.RFC3513" />,
RFC 2460 <xref target="refs.RFC2460" />,
- RFC 2553 <xref target="refs.RFC2553" /> and other basic IPv6
+ RFC 3493 <xref target="refs.RFC3493" /> and other basic IPv6
specifications current in April 2003. That is to say, if a host
can work
in a single-homed site, it should still be able to work in a
@@ -274,7 +278,7 @@
cannot benefit from multihoming.</t>

<t>The multihoming solution may allow host or application
- changes if that would enhance session survivability.</t>
+ changes if that would enhance transport-layer survivability.</t>
</section>

<section anchor="hostrouter" title="Interaction between Hosts and
@@ -285,7 +289,7 @@
</section>

<section anchor="operations" title="Operations and Management">
- <t>It should be posssible for staff responsible for the operation
+ <t>It should be possible for staff responsible for the operation
of a site to monitor and configure the site's
multihoming system.</t>
</section>
@@ -296,6 +300,11 @@
and its transit providers, but should not require cooperation
(relating specifically to the multihomed site)
directly between the transit providers.</t>
+
+ <t>The impact of any inter-site cooperation that might be
+ required to facilitate the multihoming solution should be
+ examined and assessed from the point of view of operational
+ practicality.</t>
</section>

<section anchor="multipleSolutions" title="Multiple Solutions">
@@ -381,23 +390,6 @@
<seriesInfo name="RFC" value="3513" />
</reference>

- <reference anchor="refs.RFC2374">
- <front>
- <title>An IPv6 Aggregatable Global Unicast Address Format</title>
- <author initials="R." surname="Hinden">
- <organization>Nokia</organization>
- </author>
- <author initials="M." surname="O'Dell">
- <organization>UUNET</organization>
- </author>
- <author initials="S." surname="Deering">
- <organization>Cisco</organization>
- </author>
- <date month="July" year="1998" />
- </front>
- <seriesInfo name="RFC" value="2374" />
- </reference>
-
<reference anchor="refs.RFC2460">
<front>
<title>Internet Protocol, Version 6 (IPv6) Specification</title>
@@ -412,34 +404,35 @@
<seriesInfo name="RFC" value="2460" />
</reference>

- <reference anchor="refs.RFC2553">
+ <reference anchor="refs.RFC3493">
<front>
<title>Basic Socket Interface Extensions for IPv6</title>
<author initials="R." surname="Gilligan">
- <organization>FreeGate</organization>
+ <organization>Intransa, Inc.</organization>
</author>
<author initials="S." surname="Thomson">
- <organization>Bellcore</organization>
+ <organization>Cisco Systems</organization>
</author>
<author initials="J." surname="Bound">
- <organization>Compaq</organization>
+ <organization>Hewlett-Packard Company</organization>
</author>
- <author initials="W." surname="Stevens">
- <organization>Consultant</organization>
+ <author initials="J." surname="McCann">
+ <organization>Hewlett-Packard Company</organization>
</author>
- <date month="March" year="1999" />
+ <date month="February" year="2003" />
</front>
- <seriesInfo name="RFC" value="2553" />
+ <seriesInfo name="RFC" value="3493" />
</reference>

- <reference anchor="refs.Huston">
+ <reference anchor="refs.RFC3221">
<front>
- <title>Analyzing the Internet's BGP Routing Table</title>
+ <title>Commentary on Inter-Domain Routing in the Internet</title>
<author initials="G." surname="Huston">
<organization>Telstra</organization>
</author>
- <date month="January" year="2001" />
+ <date month="December" year="2001" />
</front>
+ <seriesInfo name="RFC" value="3221" />
</reference>
</references>
</back>



Network Working Group                                           J. Abley
Internet-Draft                                                       ISC
Expires: September 30, 2003                                     B. Black
                                                         Layer8 Networks
                                                                 V. Gill
                                                         AOL Time Warner
                                                              April 2003


             Goals for IPv6 Site-Multihoming Architectures
             draft-ietf-multi6-multihoming-requirements-06

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
   groups may also distribute working documents as Internet-Drafts.

   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."

   The list of current Internet-Drafts can be accessed at http://
   www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on September 30, 2003.

Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.

Abstract

   Site-multihoming, i.e. connecting to more than one IP service
   provider, is an essential component of service for many sites which
   are part of the Internet.

   This document outlines a set of goals for proposed new IPv6
   site-multihoming architectures.

1. Introduction




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   Current IPv4 site-multihoming practices have been added on to the
   CIDR architecture [1], which assumes that routing table entries can
   be aggregated based upon a hierarchy of customers and service
   providers.

   However, it appears that this hierarchy is being supplanted by a
   dense mesh of interconnections [6].  Additionally, there has been an
   enormous growth in the number of multihomed sites. For purposes of
   redundancy and load-sharing, the multihomed address blocks are
   introduced into the global table even if they are covered by a
   provider aggregate. This contributes to the rapidly-increasing size
   of both the global routing table and the turbulence exhibited within
   it, and places stress on the inter-provider routing system.

   Continued growth of both the Internet and the practice of
   site-multihoming will seriously exacerbate this stress. The
   site-multihoming architecture for IPv6 should allow the routing
   system to scale more pleasantly.

2. Terminology

   A "site" is an entity autonomously operating a network using IP and,
   in particular, determining the addressing plan and routing policy for
   that network. This definition is intended to be equivalent to
   "enterprise" as defined in [2].

   A "transit provider" operates a site which directly provides
   connectivity to the Internet to one or more external sites. The
   connectivity provided extends beyond the transit provider's own site.
   A transit provider's site is directly connected to the sites for
   which it provides transit.

   A "multihomed" site is one with more than one transit provider.
   "Site-multihoming" is the practice of arranging a site to be
   multihomed.

   The term "re-homing" denotes a transition of a site between two
   states of connectedness, due to a change in the connectivity between
   the site and its transit providers' sites.

3. Multihoming Goals

3.1 Capabilities of IPv4 Multihoming

   The following capabilities of current IPv4 multihoming practices
   should be supported by an IPv6 multihoming architecture.





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3.1.1 Redundancy

   By multihoming, a site should be able to insulate itself from certain
   failure modes within one or more transit providers, as well as
   failures in the network providing interconnection among one or more
   transit providers.

   Infrastructural commonalities below the IP layer may result in
   connectivity which is apparently diverse sharing single points of
   failure. For example, two separate DS3 circuits ordered from
   different suppliers and connecting a site to independent transit
   providers may share a single conduit from the street into a building;
   in this case physical disruption (sometimes referred to as
   "backhoe-fade") of both circuits may be experienced due to a single
   incident in the street. The two circuits are said to "share fate".

   The multihoming architecture should accommodate (in the general case,
   issues of shared fate notwithstanding) continuity of connectivity
   during the following failures:

   o  Physical failure, such as a fiber cut, or router failure,

   o  Logical link failure, such as a misbehaving router interface,

   o  Routing protocol failure, such as a BGP peer reset,

   o  Transit provider failure, such as a backbone-wide IGP failure, and

   o  Exchange failure, such as a BGP reset on an inter-provider
      peering.


3.1.2 Load Sharing

   By multihoming, a site should be able to distribute both inbound and
   outbound traffic between multiple transit providers. This goal is for
   concurrent use of the multiple transit providers, not just the usage
   of one provider over one interval of time and another provider over a
   different interval.

3.1.3 Performance

   By multihoming, a site should be able to protect itself from
   performance difficulties directly between the site's transit
   providers.

   For example, suppose site E obtains transit from transit providers T1
   and T2, and there is long-term congestion between T1 and T2. The



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   multihoming architecture should allow E to ensure that in normal
   operation none of its traffic is carried over the congested
   interconnection T1-T2. The process by which this is achieved should
   be a manual one.

   A multihomed site should be able to distribute inbound traffic from
   particular multiple transit providers according to the particular
   address range within their site which is sourcing or sinking the
   traffic.

3.1.4 Policy

   A customer may choose to multihome for a variety of policy reasons
   beyond technical scope (e.g. cost, acceptable use conditions, etc.)
   For example, customer C homed to ISP A may wish to shift traffic of a
   certain class or application, NNTP, for example, to ISP B as matter
   of policy.  A new IPv6 multihoming proposal should provide support
   for site-multihoming for external policy reasons.

3.1.5 Simplicity

   As any proposed multihoming solution must be deployed in real
   networks with real customers, simplicity is paramount. The current
   multihoming solution is quite straightforward to deploy and maintain.

   A new IPv6 multihoming solution should not be substantially more
   complex to deploy and operate (for multihomed sites or for the rest
   of the Internet) than current IPv4 multihoming practices.

3.1.6 Transport-Layer Survivability

   Multihoming solutions should provide re-homing transparency for
   transport-layer sessions; i.e. exchange of data between devices on
   the multihomed site and devices elsewhere on the Internet may proceed
   with no greater interruption than that associated with the transient
   packet loss during the re-homing event.

   New transport-layer sessions should be able to be created following a
   re-homing event.

   Transport-layer sessions include those involving transport-layer
   protocols such as TCP, UDP and SCTP over IP. Applications which
   communicate over raw IP and other network-layer protocols may also
   enjoy re-homing transparency.

3.1.7 Impact on DNS

   Multi-homing solutions either should be compatible with the observed



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   dynamics of the current DNS system, or the solutions should
   demonstrate that the modified name resolution system required to
   support them is readily deployable.

3.1.8 Packet Filtering

   Multihoming solutions should not preclude filtering packets with
   forged or otherwise inappropriate source IP addresses at the
   administrative boundary of the multihomed site, or at the
   administrative boundaries of any site in the Internet.

3.2 Additional Requirements

3.2.1 Scalability

   Current IPV4 multihoming practices contribute to the significant
   growth currently observed in the state held in the global
   inter-provider routing system; this is a concern both because of the
   hardware requirements it imposes and also because of the impact on
   the stability of the routing system. This issue is discussed in great
   detail in [6].

   A new IPv6 multihoming architecture should scale to accommodate
   orders of magnitude more multihomed sites without imposing
   unreasonable requirements on the routing system.

3.2.2 Impact on Routers

   The solutions may require changes to IPv6 router implementations, but
   these changes should be either minor, or in the form of logically
   separate functions added to existing functions.

   Such changes should not prevent normal single-homed operation, and
   routers implementing these changes should be able to interoperate
   fully with hosts and routers not implementing them.

3.2.3 Impact on Hosts

   The solution should not destroy IPv6 connectivity for a legacy host
   implementing RFC 3513 [3], RFC 2460 [4], RFC 3493 [5] and other basic
   IPv6 specifications current in April 2003. That is to say, if a host
   can work in a single-homed site, it should still be able to work in a
   multihomed site, even if it cannot benefit from site-multihoming.

   It would be compatible with this goal for such a host to lose
   connectivity if a site lost connectivity to one transit provider,
   despite the fact that other transit provider connections were still
   operational.



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   If the solution requires changes to the host stack, these changes
   should be either minor, or in the form of logically separate
   functions added to existing functions.

   If the solution requires changes to the socket API and/or the
   transport layer, it should be possible to retain the original socket
   API and transport protocols in parallel, even if they cannot benefit
   from multihoming.

   The multihoming solution may allow host or application changes if
   that would enhance transport-layer survivability.

3.2.4 Interaction between Hosts and the Routing System

   The solution may involve interaction between a site's hosts and its
   routing system; such an interaction should be simple, scaleable and
   securable.

3.2.5 Operations and Management

   It should be possible for staff responsible for the operation of a
   site to monitor and configure the site's multihoming system.

3.2.6 Cooperation between Transit Providers

   A multihoming strategy may require cooperation between a site and its
   transit providers, but should not require cooperation (relating
   specifically to the multihomed site) directly between the transit
   providers.

   The impact of any inter-site cooperation that might be required to
   facilitate the multihoming solution should be examined and assessed
   from the point of view of operational practicality.

3.2.7 Multiple Solutions

   There may be more than one approach to multihoming, provided all
   approaches are orthogonal (i.e. each approach addresses a distinct
   segment or category within the site multihoming problem). Multiple
   solutions will incur a greater management overhead, however, and the
   adopted solutions should attempt to cover as many multihoming
   scenarios and goals as possible.

4. Security Considerations

   A multihomed site should not be more vulnerable to security breaches
   than a traditionally IPv4-multihomed site.




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   Any changes to routing practices made to accommodate multihomed sites
   should not cause non-multihomed sites to become more vulnerable to
   security breaches.

Normative References

   [1]  Fuller, V., Li, T., Yu, J. and K. Varadhan, "Classless
        Inter-Domain Routing (CIDR): an Address Assignment and
        Aggregation Strategy", RFC 1519, September 1993.

   [2]  Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G. and E.
        Lear, "Address Allocation for Private Internets", RFC 1918,
        February 1996.

   [3]  Hinden, R. and S. Deering, "Internet Protocol Version 6 (IPv6)
        Addressing Architecture", RFC 3513, April 2003.

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

   [5]  Gilligan, R., Thomson, S., Bound, J. and J. McCann, "Basic
        Socket Interface Extensions for IPv6", RFC 3493, February 2003.

   [6]  Huston, G., "Commentary on Inter-Domain Routing in the
        Internet", RFC 3221, December 2001.


Authors' Addresses

   Joe Abley
   Internet Software Consortium
   950 Charter Street
   Redwood City, CA  94063
   USA

   Phone: +1 650 423 1317
   EMail: jabley@isc.org


   Benjamin Black
   Layer8 Networks

   EMail: ben@layer8.net








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   Vijay Gill
   AOL Time Warner

   EMail: vijaygill9@aol.com















































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Intellectual Property Statement

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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.











































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