[e2e] traffic engineering considered harmful

Jonathan M. Smith jms at central.cis.upenn.edu
Wed Jun 13 06:24:02 PDT 2001

What are the timescales on which this information goes stale? That is,
does it matter?
At 10:48 AM 6/13/2001 +0200, Erik Nordmark wrote:

> >  >>In addition to Randy's point about navigation there is also
> >  >>the issue that exploring the available paths to find a good or better
> >  >>path isn't free - it requires sending some number of packets.
> >  >>And each host will do this exploration independently.
> >
> > funny, isn that what TCP does on a single path right now
>But those TCP packets are also used to carry data.
>If you want to measure N differents paths in parallel a per-host solution
>would need to send extra packets to measure the other paths. And to
>keep the information current this needs to be done every RTT.
>Of course, if you're thinking about having different hosts use different paths
>and share information then you don't have this issue. Merely a small
>issue of scalable information sharing of information that will be stale
>in about one RTT.
> >  >>I guess one could envision agents (e.g. in each site) that would do
> >  >>this type of exploration and be willing to share their information
> >  >>with hosts in the site. But that raises issues about stale information.
> >
> > there are a lot more hosts than routers and a lot more flows than
> > routing neighbour state entries - ergo, we already haev a lot of this
> > data and we jjust need to think a bit better about coordinating it
>And aggregating it.
>If the hosts have data about www.example.com (really about the IP address
>and not the name) how can the hosts tell whether this also applies
>to www2.example.com?
>    Erik

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