In regards to Craig Spiers' comments, I doubt Telecom would see any amount
of processing power as justification not to render VoIP useless on their
networks. 20,000 Skype users must be hurting them.
I think you can be 99.9% confident that IDGs statements about UBS are
correct. Try using a VoIP application on a UBS line, especially during peak
times, and you'll see what I mean. In order to cap the speed to 256kbps
Telecom does just drop packets. I understand this is a limitation of the
current hardware at the exchanges, and that it will be replaced at some
point in the future by equipment which can queue packets instead (probably
when they roll out ADSL2+). While queuing packets isn't fantastic for VoIP
either, it's a step forward from dropping them altogether. Queuing is
certainly more efficient for ordinary TCP and even streamed UDP traffic,
because data doesn't need to be resent from the source.
NZ needs some competition in the Telco market.
Regards,
Erin Salmon
Managing Director
Unleash Computers Ltd
Mobile: 021 877 913
Landline: 03 365 1273
www.unleash.co.nz
-----Original Message-----
From: Ian McDonald [mailto:imcdnzl(a)gmail.com]
Sent: 18 March 2005 2:27 p.m.
To: Joe Abley
Cc: nznog
Subject: Re: [nznog] telecom planning to break VoIP over its network?
Telecom have denied multiple times in the press that they intend to do
this - particularly in reference to the use of Skype.
It should be noted that the Unbundled Bit Stream (UBS) offerings
specifically state that voice (or it might be all multimedia) is
excluded from working. In theory under the agreement they could do
this although they deny they will.
A bigger impact on VoIP is a couple of factors:
- lack of bandwidth. Most plans are 256 kb/s and upstream 128 kb/s.
Telecom had 192 kb/s on 1 mbit and 2 mbit plans but they are chopping
this back to 128 kb/s now. Don't get started on full speed plans as
they are far too expensive for most people. Basically if you are doing
anything else (e.g. P2P) it will kill your phone call unless you do
your own agressive traffic shaping. There is also lack of bandwidth at
peak times at present but one would hope that this is temporary
- packet dropping. Allegedly (it has been published in IDG but don't
want to guarantee it is correct) to get to a lower speed then ADSL
capable on UBS Telecom just throws the packets away semi-randomly.
This obviously has huge effect on TCP sessions and UDP streams as you
are going to get far less than what you have paid for as they will
retransmit the packet loss etc
Please note that these are my personal opinions and not those of any
organisation that I am associated with.
Regards,
Ian
On Thu, 17 Mar 2005 19:25:56 -0500, Joe Abley
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."
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