Re: [p2pi] Thoughts on how IETF standards can help P2P/ISPs

[Joe Touch <touch at ISI.EDU>]

Laird Popkin wrote:
> As we discussed last week at the IETF P2Pi Workshop, here are a list of some of the ways that IETF standards can potentially help P2P applications make better network decisions, and thus help ISPs. This isn't a complete list, but I hope that it's at least a useful starting point for a discussion.
>
> - Expose more information about TCP streams. For example, expose
> whether the stream is congested. Currently some p2p applications use a
> variety of techniques to attempt to guess whether a user's internet
> connection is congested (e.g. monitoring ping times), and measures
> stream throughput which could be viewed as a very rough measure of
> congestion, but it would be more accurate and efficient if TCP told the
> application when a stream was congested. 

As others have posted, this information should be accessible.

> Even better would be to get
> some indication of where the congestion occurred. For example, if the
> congestion is in the 'last mile', or the other peer's 'last mile', or
> somewhere in between, different responses would be appropriate. For
> example, if my internet connection is fine, but the peer's connection is
> congested, I should slow down transfers from that peer, and pull more
> from other peers. This is, of course, easier said than done.

This is not feasible for a number of reasons, including the use of 
tunnels and VPNs. It's possible to know whether the end systems are 
loaded (applications can tell each other), but path limits are hard to 
pin down. It's more useful to just try a few peers and see what works 
than to assume this kind of information is (or ever will be) available.

Joe

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