Re: [alto] ALTO Extension: A document defining multi-metrics filtering?

[Qin Wu <[e-mail]>]

>In particular, suppose the filtering is based on metrics M1 and M2, and the output is M3, for a set src to a set dsts. The Client can use the following three queries:

>- Q1: Use single metric <M1, filter on M1, srcs, dsts> and obtains <srcs1, dsts1> in return;
>- Q2: Use single metric <M2, filter on M2, srcs1, dsts1> and obtains <srcs2, dsts2> in return;
>- Q3: Use single metric <M3, no filter, srcs2, dsts2> to get the final result.

>Although this is not too bad, it is inconvenient. Note that preceding is first discussed by Sabine, Wendy, Nico in:
>http://tools.ietf.org/html/draft-randriamasy-alto-multi-cost-07

>I saw that this is also the issue discussed in
>- http://tools.ietf.org/html/draft-wu-alto-json-te-01
>- http://tools.ietf.org/html/draft-lee-alto-app-net-info-exchange-02

>Hence, I propose that the WG extends the base protocol with this capability, as I see that it is quite useful. One issue is that I see three designs, and I am wondering if the authors are
>preparing on discussing their designs at the coming IETF, and if there is a possibility for a single, unified document, focusing on this issue.

By comparing the designs in three drafts, here is my rough analysis.
the difference between these drafts are:

a.       draft-randriamasy-alto-multi-cost-07 seems to assume filtering condition and output are based on the same Cost metrics or a set of same metrics.
               Both draft-lee-alto-app-net-info-exchange-02 and draft-wu-alto-json-te-01 allows filtering condition and output based on different cost metrics
              and therefore it require filtering constraint   relaxing In the ALTO base protocol.


b.      draft-randriamasy-alto-multi-cost-07 specifies one new cost metrics (i.e.,pathoccupationcost) while draft-lee-alto-app-net-info-exchange-02

defines a new object called DstCostsConstraints which contains a list of cost metrics that are not stable over a constant period(i.e., they are

 dynamic parameters). draft-wu-alto-json-te-01 gives a complete list of those cost metrics based on IETF standardization work

(see draft-ietf-idr-ls-distribution-03,RFC5305, draft-wu-idr-te-pm-bgp<http://tools.ietf.org/id/draft-wu-idr-te-pm-bgp-02.txt>,draft-ietf-ospf-te-metric-extensions-04, draft-ietf-isis-te-metric-extensions-00)

and define them as a list of independent cost metrics.


c.       draft-randriamasy-alto-multi-cost-07 requires cost value encoded as JSON Array rather than JSON while  draft-lee-alto-app-net-info-exchange-02

also encode cost value as JSON Array. In addition, draft-lee-alto-app-net-info-exchange-02 defines linkentry object and support representing a

end to end path with a list of links traversed in the path. draft-wu-alto-json-te-01 also defines link related metrics and uses linkname to identify each link.



Thanks a lot!

Richard