[arin-ppml] Feedback on ARIN 53 question on micro-allocations for IXPs

[Ryan Woolley]

At ARIN 53, John Sweeting asked for clarification from the community on
whether an internet exchange needs IP space beyond that used for the
switching fabric, and whether IP allocations made to an IXP operator may
need to be routable.  Additionally, John shared a suggestion that the
historical basis for maintaining a pool specific to IXPs was to enable the
building of filters to prevent those addresses from being globally routable.

Community IX operates two IXPs, FL-IX in south Florida and CIX-ATL in
Atlanta.  FL-IX was founded in 2015 and now connects 158 member networks.
CIX-ATL began operations in 2019 and currently connects 66 member networks.

Both IXPs have been assigned IP address space from ARIN.  Each IXP uses one
prefix for the member LAN, which is not announced outside of our members’
networks, and a second, routed, prefix for the IXP infrastructure.

The routed prefix supports operations critical to the operation of the
exchange.  Our member portal, network management systems, and equipment
loopback addresses are, by need and design, addressed in routable IP
space.  For example, route servers build filters based on ROAs and IRR
databases, and configurations are replicated off-site.

Unlike an IXP affiliated with an ISP or data center operator, we have no
line of business which would enable us to borrow IP space from, for
example, a pool maintained for allocation to IP transit customers.  Our
transit is provided as a donation by members, who may come or go as their
connectivity needs require, so we cannot reasonably use
non-provider-independent IP space.

On the second question of whether space reserved for IXP allocations should
be unroutable as a feature, we have not, in our years of operation,
encountered any issues with reachability for these allocations.  If
networks are building filters for this purpose, our experience suggests
that is not a common practice.

IXPs do commonly have a desire to prevent their member LAN prefix from
being routable.  The current best practice is that this prefix is signed in
RPKI with an origin ASN of zero (as described in RFC 6483), and Community
IX does this for both our IXPs’ member LANs.  To the extent that filtering
based on IP addressing may have been contemplated in the past, is it now
obsoleted by RPKI.

Regards,

Ryan Woolley
Community IX
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