North American Network Operators Group

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Re: Can P2P applications learn to play fair on networks?

  • From: Mikael Abrahamsson
  • Date: Fri Oct 26 14:14:03 2007

On Fri, 26 Oct 2007, Sean Donelan wrote:

If Comcast had used Sandvine's other capabilities to inspect and drop particular packets, would that have been more acceptable?

Yes, definately.

Dropping random packets (i.e. FIFO queue, RED, not good on multiple-flows)
Dropping particular packets (i.e. AQM, WRED, etc, difficult for multiple flows)
Dropping DSCP marked packets first (i.e. scavenger class requires voluntary marking)
Dropping particular protocols (i.e. ACLs, difficult for dynamic protocols)

Dropping a limited ratio of the packets is acceptable at least to me.

Sending a TCP RST (i.e. most application protocols respond, easy for out-of-band devices)

... but terminating the connection is not. Spoofing packets is not something an ISP should do. Ever. Dropping and/or delaying packets, yes, spoofing, no.

Changing IP headers (i.e. ECN bits, not implemented widely, requires inline device)
Changing TCP headers (i.e. decrease windowsize, requires inline device)
Changing access speed (i.e. dropping user down to 64Kbps, crushes every application)
Charging for overuse (i.e. more than X Gbps data transferred per time period, complaints about extra charges)
Terminate customers using too much capacity (i.e. move the problem to a different provider)

These are all acceptable, where I think the adjust MSS is bordering on intrusion in customer traffic. An ISP should be in the market of forwarding packets, not changing them.

Mikael Abrahamsson    email: [email protected]