North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: T3 Latency
Charles, One thing I have a hard time explaining to some customers is that latency is one thing.... what does it tell me... it tells me that from one hop to another things are a bit slow.... the real important thing is how are you're throughput speeds... I started a thread a while back asking a similar question... is ping/traceroute a good measurement of throughput on the link? the unanimous response was use pathchar or mtr or ttcp which all give you a better guestimate of how your link is doing performance wise.. Thanks, Paul /////////////////////////////////////////////////////////////////////////////////////////////////////////// A little nonsense now and then is relished by the wisest men. -- Willie Wonka \ Paul A. Bradford CCNA Adelphia High Speed Data Voice: (814)274-6663 Network Engineer II Fax: (814)274-0780 [email protected] ICQ #6054021 [email protected] On Sat, 17 Feb 2001, Charles Scott wrote: > > > In response to all the questions below... > > The distance is from Northern Michigan to Chicago, apparently via > Detroit, which is about 500 Miles without knowing which way the fiber > really goes. There are I believe more than one SONET ring involved in the > transport. Also something like 13 cross connects, but no other routers in > that path. > When asked, the provider suggested that the latency was due to the > router I'm hitting being fairly busy. However, the latency is that same > when I ping it as when I go through it and it's always 20 ms, nothing > less. I'd think that if it's a matter of a low priority response issue, > that the latency would be variable and not be a fixed addition to the path > times going past the router. > OK, here's the funny thing, I have an account on anohter system here in > town that's also connected via a T3, but is 7 hops to the router that is > my first hop. When I ping the router that's my first hop from that system > I get about 22ms for all 7 hops while I get 20ms for just the first hop. > I've been looking for any system that would have low latency response on > the other side of that router, but so far nothing on the other side of it > is anything less than 20ms. > I guess the other question is how much of a marketing liability is this > going to be for my service. We're spending the money on this line to get > us the best connectivity we can from up here. Something tells me that some > dedicated or co-location customer is going to ask me about this latency > issue. > > Still wondering... > > Chuck Scott > > > > > > --From Chris > > > What distance is it running ? > > --From Jeff > > You may want to check with the carrier of the circuit and make sure > that it's taking the path you expect. If it's on someting like a SONET > ring, it may be riding a much longer path that you would expect. > > --From Brian > > keep in mind you are pinging/tracerouteing that is aimed at the router. > ICMP is very low on the routers priority > list. The major providor's aggrigate router is prob pushing a few loaded > links. Better test is ping to a idle host nearby off their router. > > > --From Jonathan > > With certain routers if they have enough stress, the RTT to the router > will be larger then though the router. This has to do with caching > algorithms the router uses. Also, some large providers do not have you > connect directly into a rotuer, but into a switch that acts as a MUX, and > then they have an OC48 link up to the router. If that OC48 has been > oversubscribed you might see latency, though I would hope not that > consistent. > > What does your ISP's install engineer say? For a T3 that is going less > then 100 miles, the latency really should be 10percent of what you are > seeing. > > > > > >
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