OT? - Broadband Troubleshooting

[Greg]

Comcast Cable

I use uTorrent (also subject to QoS filters to reduce it's priority) but 
this problem seems unrelated since I can power off the uTorrent machine 
and get the same results.

I appreciate the "Packet Delay Variation" and "Jitter" comments.  Fodder 
for the search engines.

I'll check out SmokePing.

Thank you.  GGK

On 03/08/10 02:12 PM, Benjamin Scott wrote:
> On Mon, Mar 8, 2010 at 10:48 AM, Greg<greg at kettmann.com>  wrote:
>    
>> The network setup is pretty standard.  Broadband connection ...
>>      
>    What type of Internet connection and who is the provider?  For
> example, "Comcast cable", "FairPoint DSL", "Verizon FiOS", etc.
>
>    
>>   It seems to be an outbound problem (I can hear fine always)
>> since the other end can't hear me for just a few seconds.
>>      
>    Any other traffic happening on the network?  In particular, any kind
> of server (HTTP, SMTP, FTP, etc.) or peer-to-peer file sharing
> (BitTorrent, eDonkey, etc.)?  Sometimes, the problem will be due to
> outbound traffic, with the asymmetric nature of most consumer Internet
> feeds able to saturate the outgoing channel long before the incoming
> channel fills.  This can confuse some traffic shaping/prioritization
> mechanisms, which often assume a symmetric feed.
>
>    
>> What's the best approach to isolating or identifying the details of this
>> problem?  One obvious solution is to log some pings for a day or two.
>>      
>    This is tricky because what you're looking for is not throughput,
> and not even latency (Round Trip Time), but rather, Packet Delay
> Variation, AKA jitter.  That is, you don't care how long it takes a
> packet to transit, but you need to characterize *variation* in how
> long it takes a packet to transit.
>
>    I've seen SmokePing recommended in this sort of scenario before,
> although I've never gotten around to trying it out myself.
>
>    You might also traceroute to whatever gateway ViaTalk is using.
> Maybe there's an obvious jump in latency, which, while not conclusive,
> might be a clue.
>
>    
>> Bandwidth is good (based on the web based measurement
>> tools) ...
>>      
>    Those tools, while not entirely useless, can be very misleading or
> inaccurate.  I am generally very hesitant to draw conclusions from
> them.  That said, throughput is rarely the problem with a single VoIP
> feed, and I don't suspect it here.  You only need about 50 Kbps for
> that.
>
> -- Ben
>
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