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RE: Query: What policies do backbone providers use to determine IP ownership?
From: "Daniel Golding" <dan () netrail net>
Date: Wed, 23 May 2001 09:14:09 -0700


Customers want to be able to multihome. This is not an unreasonable desire,
and it is what they are, ostensibly, paying us  for.

Your main complaint seems to be advertisement of individual netblocks from
larger aggregates. While this does contribute to the growth of the internet
routing table, this is an artifact of the way routing processes and BGP
work, rather than any fault from your customers. What are your customer's
options for multihoming?

1) Advertise smaller blocks out of larger aggregates to other providers
2) Get their own, PI space, and advertise it - if they are large enough to
obtain it. Of course, this causes one or more additional route announcements
as well.
3) The customer sucks it up, and sticks with a single provider

Clearly, most customers are going with #1 or #2, which will increase the
size of the routing table. They can minimize this by renumbering into
consecutive address space, but that assumes that this greatly disrupt their
business, and that they can indeed get a quantity of consecutive space from
an upstream.

"It seems that other providers are allowing our customers to hijack our
routing space piece by piece."

Is your complaint that other providers aren't calling you to get permission
to route your space? Although there may be some disagreement on the
etiquette of routing other provider's blocks, if someone has a block swip'ed
to them, that's pretty much license to route that block through a secondary
provider, unless the policy of the original provider specifically forbids
it. And in that case, the duty is on the customer to know his provider's
policies, rather than on the second provider to somehow research the
policies of the first provider. Of course, in the absence of affirmative
WHOIS information stating that a customer has the right to advertise a
block, it's wise to get written permission from the "owner of the block".

The routing table will increase in size, as the number of issued AS numbers
go up, as multihoming increases, as new address space is advertised.
However, current core router hardware is more than capable of dealing with
this growth. I certainly encourage customers to aggregate wherever possible.
However, requiring renumbering is a heavy, and unnecessary burden.

Multihoming has become part of basic transit service functionality.

- Daniel Golding

Tony Mumm Said....

All,

I'm curious to what extent everyone is checking to determine
ownership of IP addresses when taking on new customers.

Lately, multi-homing has become a very hot topic for even the
smallest of providers.  With that, customers are bringing along
their IP addresses from their previous providers.   Are we
required, as providers, to determine if that block is actually
owned by that customer, and facilitates good Internet routing?

I've seen a trend lately where I'm finding out, after the fact,
where pieces of larger CIDR blocks are being taken apart by a
myriad of unaggregated routes.   The other backbone providers
freely allowed an announcement of that non-portable space to the
Internet without regard to either the owning provider, or to
general Internet routing.

My concern is two fold:

      1)      This contributes to terrible Internet routing.  By not
addressing this with the customer                     right away,
we'll continue
to deal with a proliferation of /24s and Internet bloat.   I
realize the customer needs its address space to announce
separately, but should we allow                       them to
freely announce random
/24's?   This is only due to that the customer received IPs           by
growing over the years, rather than getting a single block up
front.

      2)      It seems that other providers are allowing our customers to
hijack our routing space piece                by piece.   I will happily
participate in multihoming a customer, but I would hope it
involves us.  We can make a contiguous allocation from our CIDR
blocks, and then work with            the customer in a more consistent
manner.  Much of this is customer education about
multihoming,
but unfortunately we often find out too late.

So the question becomes, what do providers do to determine where
a block is coming from, and what is its implications on the
global routing system?   Just cutting and pasting an email from
the customer into an access-list seems to be what we have now...

I'd be interested to hear what others thoughts and experience are
with this.  Perhaps I'm just overly concerned with a normal
happening on the Internet.

Comments?

Tony

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