On Thu, 2005-03-17 at 19:25 -0500, Joe Abley wrote:
http://www.pbs.org/cringely/pulpit/pulpit20050317.html
"And there are other dirty tricks available to broadband ISPs. Telecom New Zealand, for example, is reportedly planning to alter TCP packet interleaving to discourage VoIP. By bunching all voice packets in the first half of each second, half a second of dead air would be added to every conversation, changing latency in a way that would drive grandmothers everywhere back to their old phone companies. This is because phone conversations happen effectively in real time and so are very sensitive to problems of latency. Where one-way video and audio can use buffering to overcome almost any interleaving issue, it is a deal-breaker for voice."
Maybe I misunderstand what Telecom is allegedly doing, but mucking about
with TCP won't do much. In order to specific target SIP (for example),
they'd have to intecept UDP/5060, parse off the SDP negotiations for
RTP, then muck about with the traffic on the ports mentioned in the SDP.
There's no specific port the audio will be on, tho some endpoints will
tend to use the same port.
Unless they're mucking with latency on _all_ packets, but that'd kill a
ton of other stuff off as well.
--
David Zanetti