The MPLS WG Archive

[Olivier Bonaventure <Olivier.Bonaventure@info.fundp.ac.be>]

Ping,

> > i do not mean to be pedantic, but i am not aware of how, from a policy
> > routing perspective, traffic would go through multiple naps.  i push the
> > point because the suckyness (sp?) of some of the naps is one of the worst
> > sources of interprovider problems.
> >
> > i am not sure what 'domains' are.  if you mean autonomous systems, then
> > this devolves to naps, inter-provider private circuits, and intra-provider
> > pops.
> >
> 
> I meant AS's. I first saw the data in http://moat.nlanr.net/ASPL/. I
> chatted with one of my colleagues in Bell Labs (he had gone already) a
> couple of months ago. He was working on inter-domain network topology
> stuff, and collected bunch of more up to date traces. He told me that
> the average AS length in his data was 5-6.

Some time ago, we looked at the BGP routing table of the Belgian research ISP and
found a similar result. We looked at the number of reachable IP addresses
(i.e. IP addresses announced through BGP) and found that most
addresses were between two and 5 AS away from our small ISP. 

LEVEL = 1  ADDRESSES =  43131944   
LEVEL = 2  ADDRESSES = 177739421   
LEVEL = 3  ADDRESSES = 410798057   
LEVEL = 4  ADDRESSES = 347784802   
LEVEL = 5  ADDRESSES = 114262352   
LEVEL = 6  ADDRESSES =  14626560   
LEVEL = 7  ADDRESSES =    943360   
LEVEL = 8  ADDRESSES =    235264   
LEVEL = 9  ADDRESSES =      4352   

This concentration of the addresses is probably due to the fact that BGP
prefers shortest path (measured in AS path length) and thus ISPs tend
to establish as much peerings as possible to obtain short paths.
I'm not convinced that the shortest path in terms of BGP path length
is the best path, but that's how the market it working today.

Concerning QoS, an interesting point was mentionned this week at the COST263 QoS
workshop in Berlin, Germany by the IETF chairman (Fred Baker). Today, the main factor
againts the development of interdomain QoS are the ISPs themselves. They don't believe
that having interdomain QoS is the best solution from their selfish marketing/economical
point of view and they are relunctant to work on this topic. Since ISPs (at least big ones)
are not interested in interdomain QoS, network providers do not work on enhancing protocols
to support interdomain QoS since they don't see a business case for such features today.
The presentation is available from http://www.fokus.gmd.de/events/qofis2000/slides/25ix00/session-00/fred-baker-new.pdf

My personnal feeling is that interdomain QoS is key to the deployment of QoS within
the Internet. We won't really have QoS until we manage to find a suitable interdomain
method to provide it. I guess that small ISPs could have a strong interest in
such interdomain QoS, but they usually don't have people able to influence the work
within IETF or network equipment vendors. 


Olivier Bonaventure

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