nanog mailing list archives
Re: Possible explanations for a large hop in latency
From: "John T. Yocum" <john () fluidhosting com>
Date: Thu, 26 Jun 2008 18:09:25 -0700
The explanation I got, was that the latency seen at the first hop was actually a reply from the last hop in the path across their MPLS network. Hence, all the following hops had very similar latency.
Personally, I thought it was rather strange for them to do that. And, I've never seen that occur on any other network.
Perhaps someone from ATT would like to chime in. --John Frank Bulk - iNAME wrote:
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. Frank -----Original Message-----From: John T. Yocum [mailto:john () fluidhosting com] Sent: Thursday, June 26, 2008 7:04 PMTo: frnkblk () 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. --John Frank Bulk wrote:Our upstream provider has a connection to AT&T (12.88.71.13) where I relatively consistently measure with a RTT of 15 msec, but the next hop (12.122.112.22) comes in with a RTT of 85 msec. Unless AT&T is sendingthattraffic 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 12.122.112.22 has some kind of ICMP rate-limiting. Is this a real performance issue, or is there some logical explanation? Frank
Current thread:
- Possible explanations for a large hop in latency Frank Bulk (Jun 26)
- Re: Possible explanations for a large hop in latency James R. Cutler (Jun 26)
- Re: Possible explanations for a large hop in latency John T. Yocum (Jun 26)
- RE: Possible explanations for a large hop in latency Frank Bulk - iNAME (Jun 26)
- Re: Possible explanations for a large hop in latency John T. Yocum (Jun 26)
- Re: Possible explanations for a large hop in latency Mikael Abrahamsson (Jun 26)
- Re: Possible explanations for a large hop in latency Robert Richardson (Jun 26)
- RE: Possible explanations for a large hop in latency Frank Bulk - iNAME (Jun 26)
- RE: Possible explanations for a large hop in latency Frank Bulk - iNAME (Jun 26)
- Re: Possible explanations for a large hop in latency Randy Bush (Jun 26)
- Re: Possible explanations for a large hop in latency Warren Kumari (Jun 27)
- RE: Possible explanations for a large hop in latency Frank Bulk - iNAME (Jun 26)
- RE: Possible explanations for a large hop in latency Mikael Abrahamsson (Jun 26)
- RE: Possible explanations for a large hop in latency Frank Bulk - iNAME (Jun 26)
- Re: Possible explanations for a large hop in latency Tim Peiffer (Jun 26)
- Re: Possible explanations for a large hop in latency bensons (Jun 26)