On Mon, 23 Apr 2007 14:05:55 +0100, Chris Bagnall wrote:
>Greetings list,
>Hoping someone might have experience with poorly-performing net connections
>and which devices work best over them.
>One of our clients has a number of employees that work from home, and are
>given a SIP phone to take with them and hook up to their broadband. For the
>most part, this works fine, but
there are an increasing number where sound quality is poor ("chops" in and out,
generally only noticeable to the listener at the other end, not the employee).
Logic suggests it's an upstream
bandwidth issue, so we asked them to try when all other devices were turned off
(to cut out the "kids using bitTorrent" issues), but even with the phone the
only device, call quality was still
poor.
>Since the connections aren't paid for by the client, we aren't in a position
>to mandate particular providers or speeds, but in each case, the minimum was a
>1mb/256k up ADSL. We asked
the employees to run some speed tests to determine real-world speeds, and in
each case upstream was around 220-235k (a little off the "official speed" but
not bad). Certainly way more
than the ~35kbps necessary for a g729 call, even with packet overheads.
>We've also tested the connections with a constant ping, and latency for nearly
>all of them is sub-35ms.
>So, that leads me towards packet loss as the only thing left. Generally
>speaking, these connections are giving between 1 and 4% packet loss.
>Therefore, 3 questions:
>1) is this level of packet loss likely to have the effect we're seeing?
>2) If so, are there any phones people have tried with particularly good jitter
>buffering? If not, any ideas what else might be causing the issue.
>3) are some codecs naturally more "tolerant" of jitter than others? i.e. would
>there be an advantage to using something apart from g729, and if so, what
>would you recommend?
Chris,
The others responding on-list are certainly giving you good advice. I expect
that what you are suffering is unmanaged QoS at the roaming users end. This
almost certainly will be an issue
with 256k outbound on a network connection that is not dedicated to the voip
application alone.
Consider that companies like Packet8 or Vonage will sell their voip service to
these users, and generally make it work pretty well. They do it by providing
the a client side access device that
get inserted into the between the rest of the LAN and the DSL/cable modem. It
provides the bandwidth management to ensure workable voip.
Using a compressed codec like G729 or ILBC helps as well, but having a router
capable of QoS at each location is an absolute necessity. I prefer m0n0wall on
a Soekris Net4501. Others like
third party firmware on Linksys WRT devices....a little bit cheaper but less
professional IMHO.
Michael
_______________________________________________
--Bandwidth and Colocation provided by Easynews.com --
asterisk-users mailing list
To UNSUBSCRIBE or update options visit:
http://lists.digium.com/mailman/listinfo/asterisk-users
