[c-nsp] point to point dedicated t1 rtt ping times

[Church, Chuck]

Keep in mind that light doesn't travel at the speed of light when not in
a vacuum.  Check out:
http://www.fiber-optics.info/articles/fiber-types.htm  It's 50% slower
in glass than in a vacuum.  So that 20ms is now 30ms.  Figure in a few
ms here and there for interface delay, etc, and that 60 is looking
reasonable.  It's certainly possible that the circuit is making a few
stops at other cities though.

Chuck Church
Lead Design Engineer
CCIE #8776, MCNE, MCSE
Netco Government Services - Design & Implementation Team
1210 N. Parker Rd.
Greenville, SC 29609
Home office: 864-335-9473
Cell: 703-819-3495
cchurch at netcogov.com
PGP key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x4371A48D 


-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Curtis Doty
Sent: Tuesday, April 26, 2005 8:58 PM
To: Eric Kagan
Cc: Cisco-Nsp
Subject: Re: [c-nsp] point to point dedicated t1 rtt ping times

Eric Kagan wrote:

>Sorry if Off-topic, but we have a customer with a dedicated PTP from
Arizona
>to Illinois getting 60ms RTT ping times with Cisco 2800 at both ends.
Does
>anyone have any reference or baseline for me to check against ?  The
are
>reporing latency and that 60ms is too high.
>  
>

I'll probably get flamed for further leading the topic astray...and am 
clearly suffering from Googlephilia...

A quick gander at http://maps.google.com/?q=Phoenix,AZ+to+Chicago,IL 
shows an optimal one-way road travel distance of 1913 miles. And 
http://www.google.com/search?q=1913mi/m/c*1000*2 says that light would 
travel that round trip in 20.5ms. So that's the *absolute* minimum 
rtt--very presumptive, though.

Add in a few milliseconds for hdlc framing or ppp overhead on the full 
ds1, and the rest is your carrier; either encapsulating or stalling the 
frames in situ or backhauling them via Albuquerque, Calabasas, 
Kalamazoo, Tipperary...

../C

-- 
I knew I shoulda taken that left turn at Albuquerque.
  - Bugs Bunny

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