[Asterisk-Users] VoIP Provider problems

[Johnathan Corgan]

Bob Goddard wrote:

> The apparent packet loss you are seeing may be just fine tuning
> of the routers in question.

This is the conclusion I came to as well; however, with the way 
PingPlotter works the router is not sending ICMP unreachables but rather 
ICMP TTL expired responses.  In any case, the routers in question may 
either be:

1) ...intentionally discarding the received UDP "ping" packets (these 
are not ICMP pings, but rather UDP packets with TTL down to zero when 
they get to the router), because the router has better things to do.

2) ...throttling the ICMP TTL expired responses to a certain rate per 
period of time, as you suggest.  This would appear as packet loss.

3) ...actually congested, with the received UDP "pings" (and other types 
of packets) getting discarded on the input side at the rate shown in the 
data.

I wish there was a way to measure 3) without being affected by 1) and 2).

I agree then, that PingPlotter is not a highly accurate way to measure 
path quality.  Still, though, looking over the data for a couple days 
now it is easy to see cyclical patterns that go from 1% to 30% 
(PingPlotter measured) loss, and an easily seen correlation with the 
voice quality of my outbound Broadvoice calls.

Interestingly enough, switching from a Firefly soft phone on my 
workstation, using IAX2/ulaw, to an analog phone->TDM400 FXS port right 
at the Asterisk server has made a big difference.  So some of the 
perceived crappiness was in the soft phone->Asterisk path and was 
probably being exacerbated by the network loss on the net or at 
Broadvoice's router.

-Johnathan