Re: [altoext] i2aex BOF

Hi Young, 

Very nice deck of slides with some very interesting use cases!

A quick comment/question on using approximate graphs to address the interesting issues of shared bottlenecks that may not be exposed by e2e links. In a dynamic, interactive constraint solving/joint optimization setting, such internal coupling will show up as "cost" increase on one source-dest pair, when using another independent pair.

But your use case does show another way to expose infrastructure info. We consider the use case that the path for a source, destination pair is computed by the infrastructure, not by the app (otherwise, it is a different story). Then one issue of exposing only a graph is ambiguity for an app to determine the path for a source, destination pair, unless the underlying graph has no loop, since then the computed path then will depend on the policy of the infrastructure. For example, consider a graph, where each s1, s2, rs, r1, r2, rd, d1, d2 is a pid, si is source ER, and di is destination ER in your example:

s1 -> rs
s2 -> rs
rs -> r1
rs -> r2
r1 -> rd
r2 -> rd
rd -> d1
rd -> d2

Then the app may not be able to figure out the path for s1 to d1, or s2 to d2.

One possibility is to expose the node path in a "cost" map, where the value of each entry is a (bgp style) path vector, in addition to a graph topology map. I get a feeling that others may have better, more compact representation, but the preceding seems simple.  What do you think?

Thanks!

Richard

On Mar 23, 2012, at 1:40 PM, Leeyoung <leeyoung@huawei.com> wrote:

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Re: [altoext] i2aex BOF - Large Bandwidth Use Case