[rescue] 802.11 + VoIP
kloch at gurunet.net
Fri Oct 17 00:28:48 CDT 2003
----- Original Message -----
From: "Geoffrey S. Mendelson" <gsm at mendelson.com>
Date: Thursday, October 16, 2003 9:37 pm
Subject: Re: [rescue] 802.11 + VoIP
> Eric Webb wrote:
> > I see a lot of opinions that 802.11 and VoIP are a bad
> combination, but I need
> > more proof and stats if anyone has anything. (I'm kind of anti-
> > anyway when it comes to wanting performance, which voice seems to
> Performance is not an issue with VoIP, latency is. To get a decent
> connection you need to sustain 64k BITS per second of DATA, which
> meansabout 96k-128k of IP throughput. Just about any WiFi network
> can do that,
> but if the delay is too long in getting a packet out there, then there
> will be echo and other problems.
> > Also, do they even make 802.11-based VoIP handsets? Can someone
> point me in
> > the direction of a few models?
> I was just searching and haven't seen any. The closest you can come is
> either a USB phone for your WiFI equiped laptop, or an ethernet phone
> and a WiFi router.
> Or for the real gearheads, a Cisco or Packet8 ATA (analog telephone
> adaptor),a WiFi router, and a "real" (POTS aka analog) phone.
> This is not as far fetched as you might think. Sambo will be here
> in a week,
> bringing WiFi access points and a Packet 8 ATA. I've got a Cisco
> 186 comming
> around the same time with service on a competing network. We can do
> some"real" testing in our spare time. :-)
> I've spent several hours this week getting QOS (quality of service)
> routingto work on my Linux based router/firewall machine. Tonight's
> installmentwas to put traffic limiting on the LAN side, so my son
> does not swamp
> the connection to the outside world with his downloads.
FreeBSD dummynet does traffic limiting very well. Just plumb a pipe,
assign it a bandwidth limit, then assign ipfw rules to match traffic
you want put through that pipe.
Here's an example:
Add these to your kernel config:
And something like this to your firewall script:
(assuming your local lan is 192.168.1.0/24 and
you are blocking 192.168.0.24 from coming in from
ipfw pipe 1 config bw xxKbit/s # xxx is outbound bandwidth for your son
ipfw pipe 2 config bw yyyKbit/s # yyy is inbound bandwidth for your son
ipfw add pass all from xx.xx.xx.xx to 192.168.1.0/24
ipfw add pass all from 192.168.1.0/24 to xx.xx.xx.xx
ipfw add pipe 1 all from xx.xx.xx.xx to any
ipfw add pipe 2 all from any to xx.xx.xx.xx
Or, you could put a rule to pass the traffic for the voip device and
then send all other traffic through the limiting pipes.
More information about the rescue