In einer eMail vom 28.11.2007 03:39:10 Westeuropäische Normalzeit schreibt
[EMAIL PROTECTED]:
Advertising all of ISP A's prefix isn't the issue at all. The real question
is: what happens at the geo-patch abstraction (action) boundary? Where is
that boundary?
Which 1x1 square degree geo-patches are supposed to form a cluster for the
next upper nxm-square degree patch, and which n1xm1-square-degree geopatches
are supposed to form the next upper n2xm2 quare-degree geopatch - this is up
to IANA directives.
I think I have explained this: At the event that an IP packet shall be
forwarded, the first (like the following) inside some geopatch realizes that
its
own as well as the packet's destination have the same longitude/latitude and
therefore the next hop is determined based on the recognized destination node
which has a best suitable reachability info.
And I think I have explained the routing protocol. Maybe I should write more
about the recursion.
I'm interested in the abstractions in the routing protocol, not the
forwarding plane.
Who is responsible for traffic arriving into the geo-patch?
the receiving node, who else ? but maybe I do not understand the question.
Who administers that receiving node? Can it receive traffic for a different
AS? If so, what does it do with it? How do they get compensated for
forwarding it?
Can a border node of some geo-patch receive packets for different ISPs? Of
course it can.
And of course policies can be implemented which mark certain loose links to
be non-transit.
How do adjacent ISPs get paid ? I guess they make a mutual contract.
I am convinced that a viewed topology provides more for implementing
policies which overrule the absolute shortest path principle, than a multitude
of
AS-path strings. BGP-Question: Can/would/does some AS advertise its access to
some destinations and combine it with a withdrawal threat in case that some
other, disliked AS wants to append itself to the AS-PATH ? I don't think so.
What happens if the topology within the geo-patch is internally
disconnected?
Permanent partition ( I placed just a few line to show that I am aware of
this problem which is certainly for further study). Maybe it should be
requested that at least one representative node must also show up in the next
higher
level map. Then any node of one particular partition will learn via the next
upper level map that there are more such representative nodes than
disposed/contributed by this partition. Hence the partition is detected. I am
sure that
there are several ways to treat this problem (partition id?, partition
bridging area,...
I am optimistic. When we started PNNI we had much less available.
I think that this needs to be made explicit. Partition repair is a
non-trivial subject, especially when it might have to be repaired at some
arbitrarily
higher level in the hierarchy.
Right, partition repair is not trivial, but it starts out with recognizing
that there is a partition.
There should be more than sufficient routing expertise all around to a)
define what is best, what is acceptable, what is not acceptable for any
solution
and b) implement the respective solution.
If you look at the newest graph picture on my website you will see that
there are many routes to the destination besides the blue shortest route.
The traditional explanation is that there must be regulations requiring an
interconnect for the geo-patch and all providers must connect to that
interconnect. The alternative is that providers with links outside of the
geo-patch
end up receiving traffic destined for other providers and end up providing
free transit.
COMMENT: At first it takes knowledge about shortest path routing. Then we
can come up with provider constraints and assign QOS/policy attributes to the
loose links.
Sorry, but the constraints frequently make the topologically shortest path
irrelevant. Again, this is why today's inter-domain routing is so much more co
mplicated than OSPF.
I would rather say, because the tools are less capable. With the current
interdomain-routing protocol you can neither afford nor do the implementation
of OSPF-MT like solutions.
More generally, if the entry point at an abstraction action boundary is not
directly connected to all of the sub-abstractions, then you have a situation
where traffic must traverse a sub-abstraction, which will violate commercial
constraints. Thus, the abstraction action boundary must be located where
there is common (or free) connectivity to all of the sub-abstractions. You can
conceivably shift the abstraction action boundary away from the abstraction
naming boundary to help with this (i.e., do proxy aggregation), but how is
this maintained in the face of changing topology and across hierarchical
levels?
I am not sure I understand your questions. Maybe I should write more about
the adjacency of two different nxm-square-degree geo-patches.
Maybe this helps to avoid wrong understanding: In the past Germany conquered
parts of France, and vice versa France conquered parts of Germany. But that
did not change the shortest path between Paris and Berlin at all.
No, that doesn't help at all, sorry.
Let's see if I can explain the problem differently: suppose that we have a
geo-patch that is "France". This abstraction is circulated outside of France
and is advertised outwards at each border. However, the administration of
Alsace-Lorraine has a grudge with the national government of France. All
traffic that arrives in Alsace-Lorraine that is not destined within
Alsace-Lorraine and is forwarded on to other areas has an associated charge of
1 Euro per
packet. If this is not paid, then the packet is dropped. How do you prevent
this situation?
Advertise policy attributes for respective loose links.
The OSPF assumption that all routers are willing to carry all traffic simply
doesn't hold in the inter-domain routing arena.
See COMMENT above. I assume, EBGP hops only won't deliver the packet either,
will they? Honestly, if you have a viewed topology (nicely sparsed to become
scalable), you can do better policies and TE than by just having AS-path
strings, right?
Yes, EBGP hops would compute paths around the non-transit domains and
deliver the traffic, albeit with the cost of only being able to aggregate to
the
prefix/AS level.
Yes, we could do better TE if we had a full map everywhere, but we can't
because propagating policy (and I include destination, transit, and source
policies) requires disclosure of policy information that is today considered
proprietary.
Tony
=
Some additional remark:
The drafted core algorithm was already published in 1988. This is more than
17 years ago. Hence no one can have IPRs on it. You may google for Voronoi,
Delaunay, Mehlhorn.
Heiner
