Possible explanations for a large hop in latency

Frank Bulk - iNAME frnkblk at iname.com
Fri Jun 27 00:54:42 UTC 2008

Did that satisfy you?  I guess with MPLS they could tag the traffic and send
it around the country twice and I wouldn't see it at L3.


-----Original Message-----
From: John T. Yocum [mailto:john at fluidhosting.com] 
Sent: Thursday, June 26, 2008 7:04 PM
To: frnkblk at iname.com
Cc: nanog list
Subject: Re: Possible explanations for a large hop in latency

When I asked ATT about the sudden latency jump I see in traceroutes,
they told me it was due to how their MPLS network is setup.


Frank Bulk wrote:
> Our upstream provider has a connection to AT&T ( where I
> relatively consistently measure with a RTT of 15 msec, but the next hop
> ( comes in with a RTT of 85 msec.  Unless AT&T is sending
> traffic over a cable modem or to Europe and back, I can't see a reason why
> there is a consistent ~70 msec jump in RTT.  Hops farther along the route
> are just a few msec more each hop, so it doesn't appear that
> has some kind of ICMP rate-limiting.
> Is this a real performance issue, or is there some logical explanation?
> Frank

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