HE.net and BGP Communities

Forrest Christian (List Account) lists at packetflux.com
Tue Jul 26 01:34:01 UTC 2022

I think the key difference here is that I really just wanted HE to treat my
routes no differently no matter how they learned them.   I wanted them to
apply normal BGP routing rules to them..  that is, pick the path with the
shortest AS path.

>From a strictly technical basis, its silly to prefer a path of
AS6939-ASxxxx-A4043 to a path of AS6969‐AS4043.    I understand the
business reasons of wanting to send traffic down circuits where you get
paid, but how many intermediate ASNs do there need to be in the middle
before it makes sense to ignore the business reasons for doing so?    I
guess once you get paid for pushing the traffic one doesn't really care,
but at some point one has to look at the network efficiencies here.

In this case, we were purchasing a DSL aggregation service from another
regional provider after our DSL customer base reached the point where it no
longer made sense for us to maintain our own infrastructure.  What we
really needed was a peering connection with them but they were technically
unable to make this happen, so it ended up being transit which we found out
after the agreement was signed.

I vaguely remember them giving some reason why they couldn't do a no export
on our routes inside their network (maybe running multiple networks under
different ASNs due to acquisitions or some technical shortcomings of their
network, don't remember for sure).  But one way or another they ended up
announcing our routes to HE and couldn't or wouldn't stop doing so.

This basically bit us in the rear with HE which is why I was griping.   HE
has such a big footprint that that connection attracted a large percentage
of our overall traffic. I would have been happy with any of several common
community strings that people use.    Set localpref. Don't export.  And so
on.  Just send us traffic literally any other way other than this one.   Or
less traffic.  Ideally, setting the localpref to the same value as a
peering customer would have been ideal, because then the path length would
have been taken as the selection criteria.  I would have been fine if
no-export came along for the ride as a side effect.

What ended up happening instead is that the only way we could fix this is
that we did the evil things that you discussed and split all of our
prefixes in half and announced them everywhere else both ways.    The
regional ISP for whatever reason didn't learn the smaller prefixes so the
peering worked fine (I suspect they may not have been taking a full table)
  And, since we now appeared as a customer of HE we ended up getting
transit from them for free across our IX link, although in realty the
amount of extra traffic was minimal (except during a couple of network
events) .

I really would have rather been able to tell Hurricane to just ignore this
route or treat it as a peer or something like that.

This whole service has been disconnected for some time now, so it doesn't
really matter much to me other than it still frustrates me that we had to
go down the other path to fix this when a commonly implemented community
string may have eliminated the need to do so.

On Mon, Jul 25, 2022, 4:51 PM Tony Wicks <tony at wicks.co.nz> wrote:

> >
> > I do understand the reasoning behind preferring customer routes.
> > However in the case where a customer of a customer also connects to
> > you directly via peering doesn't it make sense to prefer the direct
> > connection?  or at least not prefer the customer learned routes.
> So from my experience of working at transit providers over more years than
> I care to contemplate I can assure you what may seem to make sense as a
> customer does not necessarily translate to how IP routing works. IP has no
> concept of Customer or Peer it is simply designed to hand the packet to a
> valid next hop as determined by policies. As such routes are normally
> divided into customer, peer or further upstream transit if you are not one
> of the tier 1 providers. A peer provides you no income, a customer (a
> customer of a customer is largely the same thing as being a direct
> customer). Take the example of the customer buying a transit service on a
> 95th percentile basis. So as a transit provider I get paid based on how
> much traffic I hand to that port(s) and in turn I provide connectivity to
> all my peers, customers and upstream transits all over the world. I can't
> do this for free as then I can't pay for my network and I am a company not
> a charity. Customer X advertises his lets say a /22 to me, all good. But
> then customer X advertises his /22 and some disaggregated /24's to a local
> peering exchange that I am also connected to. If I do not both prioritise
> customer X's customer port routes AND drop any more specific routes learnt
> from customer X then I will end up handing all customer X's outgoing
> traffic to them over the peering instead of the revenue generating port. I
> have seen customers do this both through innocent and malicious intent.
> Sure, there are a lot of complex policies that I might apply to accept
> local traffic in one area and hand other traffic via the transit port but
> why on earth would I do that and likely cause all sorts of other potential
> routing issues while reducing the revenue I am entitled to?
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