Anyone from Verizon/TATA on here? Possible Packet Loss

Derek Ivey derek at derekivey.com
Thu Sep 27 01:21:57 UTC 2012


Thanks guys. Sorry for the noise...

Derek

On 9/26/2012 9:11 PM, Jay Ashworth wrote:
> ----- Original Message -----
>> From: "Derek Ivey" <derek at derekivey.com>
>> I'm at home now. I also have Verizon FiOS and believe I am seeing the
>> same thing our client saw. So you guys are saying that the response
>> times in traceroutes might not always be accurate because routers
>> prioritize ICMP messages. Does that mean values from MTR aren't
>> accurate? I fired up MTR and took 2 screenshots
>> (http://imgur.com/a/RDyXO). What do you guys think? Most of the time
>> the ping times seem fairly low, however I occasionally see these spikes.
>> It seems sporadic...
> To recap, traceroute, mtr, and similar utilities work by talking to each
> succesive router along a path.  Because this is so, and because Any Given
> Router may be too busy to deal with such packets in favor of "real" traffic
> (most routers handle data packets on the line cards, while they may have
> to expend actual CPU on things like ICMP), it's possible for a path with
> perfect connectivity to show some intermediate hops completely missing --
> No Reply At All, you might say -- to diagnostic tools.
>
> The traces you show look pretty decent; I've seen much worse on links
> with fine interactive shell session response.  The time you have to
> worry is when one router *and everything past it* shows packet loss of
> roughly the same amount, or when ping times jump markedly at a given
> spot (by which I mean, say, from 32 to 800ms, rather than from 32 to 125).
>
> The short version, though, which most people are are being uncharacteristically
> too nice to say (:-) is that this is still a tier 1 problem, and NANOG is
> generally tier 3 or 4.  :-)
>
> You're welcome to take the issue up over on outages at outages.org, if you
> like...
>
> Cheers,
> -- jra




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