[asterisk-biz] Is ISP Blocking VoIP

[Rusty Shackleford]

> -----Original Message-----
> From: asterisk-biz-bounces at lists.digium.com 
> [mailto:asterisk-biz-bounces at lists.digium.com] On Behalf Of 
> trixter aka Bret McDanel
> Sent: Tuesday, January 31, 2006 3:59 PM
> To: Commercial and Business-Oriented Asterisk Discussion; 
> gcirino at cirelle.com
> Subject: Re: [asterisk-biz] Is ISP Blocking VoIP
> 
> outright block VoIP service.  There are devices being 
> marketed and p[resumably sold to ISPs that cause a high 
> amount of jitter virtually making it impossible to connect.  
> I could be wrong about all this, I dont have anything to cite 
> offhand, but if one were interested I would recommend google, 
> the inssue wasnt that long ago when I heard about it, 
> although admittedly I never read anything proper at the time.

I have every reason to believe that this is exactly what is happening.
Our company has some VOIP "extensions" from our IP PBX that live at the
end of Comcast cable modems. Within 3 minutes of commencing a call, the
audio quality (on the upstream leg) goes to hell (it actually sounds
more like packet loss). This will continue for a variable period of
time, then stop, then often reappear, but it ALWAYS starts shortly after
the call commences. Yes, it could be that everyone else in the
neighborhood is using up all the bandwidth with Torrent traffic, but the
consistent timing of the disruptions is suspicious indeed. Also, every
measurement we've taken at these times indicates that they are not
messing with other protocols, just SIP, though to be fair, I must state
that our tests are not sophisticated enough to analyze just exactly what
is happening to the SIP packets. Still, it is more than a little
suspicious.