Subject: [Tsvwg] XCP slides from tsvwg, project page

From: Aaron Falk <[email-masked]>
Date: Wed, 10 Nov 2004 17:31:06 -0500

Project website: 
http://www.isi.edu/isi-xcp

Slides from TSVWG meeting:
http://www.isi.edu/isi-xcp/ietf/falk-xcp-tsvwg-ietf61.pdf 

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tsvwg mailing list
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https://www1.ietf.org/mailman/listinfo/tsvwg

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From: "Armando L. Caro, Jr." <[email-masked]>
Date: Wed, 10 Nov 2004 19:49:01 -0500 (EST)

I haven't gone through the draft in detail yet (but I did read the
Sigcomm paper previously), and I have a couple of comments:

I have another addition to the Security Considerations section: Malicious
Receivers. A receiver can lie about the delta_throughput received
downstream, and put whatever it wants in the feedback field sent back to
the sender. I suppose that this could be addressed by a policer at the
receiving edge similar to the one proposed to combat malicious senders,
but wouldn't that be too much state for it to scale well? Also, is there
enough incentive for these policing functions to be used?

Minor fix...
The wording under Malicious Sources in Section 5 should be:

	The XCP algorithms rely on senders to advertise information
                                                          ^

Thanks...

~armando

0--                                              --0
| Armando L. Caro, Jr. |  Protocol Engineering Lab |
| www.armandocaro.net  |    University of Delaware |
0--                                              --0

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From: Aaron Falk <[email-masked]>
Date: Wed, 17 Nov 2004 15:38:29 -0800

> enough incentive for these policing functions to be used?

Armando-

Thanks for your comments.  Dina discusses liars and cheaters in her
thesis.  Specifically, section 7.4 discusses receivers' misconduct.

To summarize, receivers can be policed at the edge of the network
through boxes which are in the path and can see packets flowing both
ways.  If a policing box sees negative feedback in packets going to a
receiver but that feedback is not being copied into packets destined
for a sender, it may take punitive action.  Since these boxes are at
the edge of the network they are subject to fewer scaling concerns.

Note, however, that there is no way for upstream senders or networks
to know that policers exist downstream.  So, a concerned upstream
sender or network may test the 'honesty' of a receiver by occasionally
setting some negative feedback and watching for it to be reflected by
the receiver.

If you have further thoughts on this subject, I invite you to join the
XCP mailing list.  Details at http://www.isi.edu/isi-xcp.

> 	The XCP algorithms rely on senders to advertise information

Got it.  Thanks,

--aaron 

--aaron