NNSquad - Network Neutrality Squad
[ NNSquad ] Re: [IP] BitTorrent uTorrent 2.0 uTP will self-throttle to protect networks
I've yet to see a hardware device that doesn't manage transmit queues do a
very good job. They might "work" in the strictest sense but they don't work
very well since they can't really control the downstream queue. What they
do is severely throttle the P2P application to about half speed and that
reduces the jitter a little but doesn't actually make it go away.
The end result is that they slow the file transfer application by several
Mbps when the VoIP or gaming application only wants 0.1 Mbps or less, and
they don't even do a good job removing jitter. The jitter might not be as
bad as before but 200 milliseconds jitter isn't a whole lot more desireable
than 600 milliseconds in the context of VoIP or gaming.
The other problem is that most consumers don't know how and don't care to
set one of these rigs up. Most of them want less complexity and not more.
Most of the "modems" these days come with routers. If the outbound queue on
the WAN interface had some default settings in it e.g., prioritize common
VoIP/Skype/Game ports, that would work very well for upstream jitter. The
user can still go into the modem (like they do today) and change those
settings.
On the downstream side, it makes sense for the ISP to have some default
settings on the transmit queue in the DSLAM or CMTS. In theory, the ISP
could have a web interface for the user to control their own transmit queue
on the DSLAM or CMTS. Such a technology doesn't exist as far as I know
today, and the utility of such a system is questionable to begin with if
we're going to let application/content providers set their own priority
preferences.
George Ou
-----Original Message-----
From: Andrew C Burnette [mailto:acb@acb.net]
Sent: Tuesday, November 03, 2009 9:06 AM
To: 'NNSquad'
Cc: George Ou
Subject: Re: [ NNSquad ] Re: [IP] BitTorrent uTorrent 2.0 uTP will
self-throttle to protect networks
George, et al,
One unmentioned but important aspect is perhaps a better understanding
of what equipment serves as your gateway to your ISP. Inherently
"inexpensive" SOHO NAT boxes are often well overrun by any p2p programs
simply due to limitations in NAT state tables and so on. Most of the $49
boxes fall apart long before you run out of capacity.
I find a "night and day" difference when using a real firewall (ultra
low power PC running a bsd variant) with user definable priorities based
upon traffic type or source/sink. Games, VoIP, all work just fine even
with the overall capacity saturated. These additional CPU cycles and
memory work reasonably in default mode, but measurably better when the
firewall has been configured "by the user" (me) to know what traffic
needs priority.
There's simply no magic that can predict what's the best setup for you
or your network. To the credit of many SOHO NAT box vendors, numerous
application layer gateway helpers do exist, but the pie of processing
resources hasn't increased, only that the most popular (as chosen by
that SOHO nat box vendor) on their default ports have a better chance.
best regards,
andy
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