[NANOG] Comcast latency
John Osmon
josmon at rigozsaurus.com
Wed Apr 30 23:31:48 UTC 2008
On Wed, Apr 30, 2008 at 09:46:38AM -0400, Jim Popovitch wrote:
> Looks can sometimes be deceiving. ;-) I've seen Comcast drop packets
> left and right, but show 8Mbs/2Mbs on speed test sites. Other times
> I've seen the opposite, zero PL but extremely high latency (seconds,
> double digits!)... all the while non-dynamic web pages (probably
> cached upstream) loaded just fine.
I had mrt running across a Comcast connection that indicated a
14000 ms RTT for one packet out of several hundred. I wasn't sure
that was a trustworthy measurement, but it sure suprised me.
Another time, I had a VOIP conversation fall apart once with somone on a
Comcast link. When the jitter finally fell into a reasonable
range, the call sounded *great* again -- but there was a
4 second latency that had been introduced. It was wild. I kept
wondering -- "where was this buffered? Are we on a satellite
backup route?" We kept the conversation going for a while just for the
sheer novelty.
Overall, my data points on Comcast point to a pretty solid
service -- but the outliers are pretty impressive in their
own right.
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