From: Yasmin&Alonso Martinez (Al-Min@worldnet.att.net)
Date: Tue Jul 08 2003 - 00:07:34 GMT-3
As I understand TS you can have an average of 64Kbps in many different ways:
traffic-shape rate 64000 1600... => Tc=25ms
traffic-shape rate 64000 3200... => Tc=50ms
traffic-shape rate 64000 4800... => Tc=75ms
traffic-shape rate 64000 6400... => Tc=100ms
traffic-shape rate 64000 8000... => Tc=125ms
but in any case you are limiting the amount of bits that you can
continuously transmit at T1 speed to less than 154800 (1548 Mbpsx100msec)
unless you set the excess-burst-size to something greater than 6400.
I would configure it like this:
traffic-shape rate 64000 6400 148400*
* I am not sure if I should make this 148400 or 154800 (I believe it is
148400 because the router would be given 6400 tokens on any particular
interval, so it would only need 148400 additional tokens to be able to
transmit during an entire 100 msec period)
which would allow the transmission of 6400 bits on every 100 msec interval
(though it would only take the router 4 ms to reach this limit) and would
also allow the router to transmit (burst) at full speed during an entire 100
msec period (assuming enough tokens have accumulated which would take 24
TCs).
Does this make sense?
P.S.: please note corrections to my previous email in upper cases.
-----Original Message-----
From: Glenn Johnson [mailto:gjcomcast@comcast.net]
Sent: Monday, July 07, 2003 10:05 PM
To: 'Yasmin&Alonso Martinez'
Subject: RE: Constrained Access Rate
If you didn't limit the bursts to 6400 per 100 ms interval, wouldn't you
exceed the 64000 bps average they desire?
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Yasmin&Alonso Martinez
Sent: Monday, July 07, 2003 9:56 PM
To: ccielab@groupstudy.com
Subject: Constrained Access Rate
Hi All,
Cisco documentation has an example on how to configure Constrained Access
Rate that doesn't make sense to me and I was wondering if any of you could
help me understand it. Here it is
"In this example, a T1 line may be used for 100 milliseconds (ms) in a
burst, but the long-term average is limited to 64 kbps. This configuration
example restricts the amount of load the system can induce on the outbound
network interface.
interface serial 4/1:0
traffic-shape rate 64000 6400 6400
If you need to restrict the amount of load the system can induce outbound,
and therefore the total load the system can impose on the Internet service
provider (ISP), configure traffic shaping on the outbound interfaces"
(http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_configurati
on_guide_chapter09186a00800c60cc.html#35156):
Why are the burst-size and the excess burst-size configured as 6400? My
understanding is this:
If the router transmitted at T1 speed for 100 msec it would be sending
1548000 bits (I MEANT 154800 bits); but setting the EXCESS-burst-size to
6400 does not allow this. This
configuration only allows the transmission of 6400 bits on each 100-msec
interval and bursts of 128000 bits. Am I wrong?
THANKS!
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