Subject: [RADIR] PI /48s impact on the problem

From: Jason Schiller <[email-masked]>
Date: Tue, 01 May 2007 17:44:11 -0400 (EDT)

I put together some text sourround the RIR PI /48 discussion we had
today.  It is a bit drawn out, with a few long quotes from RFC-1887 and
the ARIN NRPM.  

I suspect, if we all agree in concept, we can try to distill it down a bit
to somehting that is cloaser to Marla's "RIR IPv6 POLICY IS NOT BALANCED
[as it] ENCOURAGES PI DEAGGREGATION [but] DOES NOT [support] PA
DEAGGREGATE[s] FOR MULTIHOMING OR TE." but still acceptable to Thomas.

Maybe we can start the distilling by removing the quotes?

Sorry the text is so long...

Please note this is a factor contributing to the problem... in other words
section 4.  disagreement on this text should not prevent us from agreeing
on the problem (section 3) and movig forward with that piece.

___Jason

The carrying of more specific routes to support multi-homing contributes
to a growth of routes in the DFZ.  This pressure is increased as end sites
advertise multiple prefixes to gain a more fine grained, granular control
of their in-bound routing.

Specifically in IPv6, many transit providers have tried to avoid
de-aggregation believing that such growth in the routing table is
unsustainable.  The problem may become more severe due to a dual stack
environment where routes are replicated in both IPv4 and IPv6.  IPv6 with
its larger address space seems to leave more rope for one to hang oneself.  

Many transit providers have referenced old RFCs such as RFC-1887 pointing
out that the "ability of routing to scale is dependent upon the use of
data abstraction based on hierarchical IPv6 addresses" and that there is a
"recommended mapping between Internet topological entities (i.e., service
providers, and service subscribers) and IPv6 addressing and routing
components." 

Some of this language has carried over to RIR policy such as the
importance of aggregation to IPv6 policy.  Section 6.3.8 of the ARIN NRPM
states "In IPv6 address policy, the goal of aggregation is considered to
be the most important."  Section 6.3.4 on aggregation states "Wherever
possible, address space should be distributed in a hierarchical manner,
according to the topology of network infrastructure. This is necessary to
permit the aggregation of routing information by ISPs, and to limit the
expansion of Internet routing tables.

This goal is particularly important in IPv6 addressing, where the size of
the total address pool creates significant implications for both internal
and external routing.

IPv6 address policies should seek to avoid fragmentation of address
ranges.

Further, RIRs should apply practices that maximize the potential for
subsequent allocations to be made contiguous with past allocations
currently held. However, there can be no guarantee of contiguous
allocation."

The lack of IPv6 de-aggregation has led many end-site operators to the
conclusion that there is no acceptable solution to multi-homing or
provider independence.  This lead to a push to pass ARIN policy 2005-1
which allows for IPv6 Provider Independent (PI) address assignments of a
/48.  Policy 2005-1 has opened the door to allow for support of more
specific routes in the routing table to support multi-homing (and
indirectly provider independence).  

Transit providers are currently struggling with weather more specifics in
the routing table should be allowed to support multi-homing.  To not allow
them will render the PI address space useless.  To allow a limited set of
more specifics may be workable in the short term, but likely lacks long
term sustainability, and risks creating a "swamp" that will never be
drained.  To allow only PI /48 puts end sites utilizing Provider Aggregate
(PA) /48s at a disadvantage as they will be unable to multi-home
successfully.  This may drive an artificial migration to PI address space,
for end-sites that do not require provider independence.  

An important note is that when routing tables become full, transit
providers could filter more specifics of PA multi-homers, and still be
able to reach them (although sub-optimally).  If a transit provider
filters routes to PI destinations, then these destinations become
unreachable.

Furthermore there seems to be not equatable way to determine which routes
to keep which routes to ignore.  

==========================================================================
Jason Schiller                                               (703)886.6648
Senior Internet Network Engineer                         fax:(703)886.0512
Public IP Global Network Engineering                       [email-masked]
UUNET / Verizon                         [email-masked]

The good news about having an email address that is twice as long is that
it increases traffic on the Internet.

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