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Re: T3 Latency

  • From: Jeff Mcadams
  • Date: Sat Feb 17 14:45:53 2001

Also sprach Charles Scott
>  Have been testing from our 7204 router and from various linux boxes.
>No matter how small the packet size, we always see the 20 ms.  Yes, the
>total ping time to that other system is a minumum of 42 ms. Not running
>ATM and have not seen any times when the latency drops below 20ms.
 
>  This may be the key. More of an effect of the way they're bringing me
>in. I guess I need to ask them some specific questions.

I've been watching this thread with some interest...from reading it all,
my gut instinct is that some circuit provider has your circuit routed
all over creation, or there's some other sub-optimal aspect of your
circuit (well...I guess that's pretty obvious).

The question then really becomes...how important is the latency *to
you*.  Clearly, 20ms latency on a 300-400 mile (as the crow flies) T3 is
sub-optimal somehow.  You might very well have customers and potential
customers question that, because it *does* affect performance, however
slightly, and it might be an indicator of other, more in depth problems.
Also, if you're looking at several thousand fiber miles on a 300 mile
line of sight run...that gives more opportunity for backhoe fade and
other problems.

Honestly, if I were in your situation, I would give some very serious
thought to refusing the circuit.  I would be very likely to demand that
they get the circuit down to 10ms, and might even consider a demand of
around 7ms before I would accept it.  That, of course, is my thinking,
and I don't know all the details of your situation.

I believe you posted looking for input and what others thought on it
though, so, FWIW, there's my $.02.

Another possibility is to look into what the provider gives as far as
SLA's are concerned.  (I know some on the list have heard about this
before...forgive me for sharing an old, though still ongoing, story
again)  I have a T3 between Louisville, KY and Indianapolis, IN (around
3ms latency, unloaded) that is carried by 6 different telco's.  It took
7 months from time of order to get that circuit turned up.  When it has
gone down, it has taken no less than 18 hours to get it fixed, and the
conference calls involved have typically been to the point of outright
hilarity (depending on your perspective I guess).  The circuit was
ordered by UU.Net, and when we found out how the circuit was routed, we
were sure to sign up for their SLA agreements.  We have had very good
luck getting SLA credits when the circuit goes down...and with the
circuit typically being down for 24-30 hours...we typically gets a
free month of service when it dies.  I'm dumbfounded that UU.Net hasn't
kicked WCOM's butt into getting this circuit groomed onto WCOM
facilities in order to cut down the number of carriers to 2, but they
haven't done it yet, and we keep collecting the SLA credits when it goes
down, so I can deal with that...I'd rather it stay up and get fixed
quicker, but a day of credit per hour of outage does tend to take the
sting out of having the circuit down.

Anyway...my point in that story...if the provider has SLA's that
include latency provisions, it might be worthwhile to try to get it
fixed by pounding on the SLA issue until they realize that its in
*their* best interest to get the circuit fixed.  :)
-- 
Jeff McAdams                            Email: jeffm@iglou.com
Head Network Administrator              Voice: (502) 966-3848
IgLou Internet Services                        (800) 436-4456





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