From: OhioHondo (ohiohondo@columbus.rr.com)
Date: Thu Feb 20 2003 - 22:51:11 GMT-3
The URL below is the best simple explanation I have found. Watch the wrap.
http://www.cisco.com/en/US/tech/tk713/tk237/technologies_configuration_examp
le09186a00800942f8.shtml
I'll attempt to summarize with the assumption that there is no Real Time
traffic:
The setting of the FRTS parameters totally depends on the situation. One
situation is where you have 2 sites with a pvc between them --- lets say
with a contracted 32K CIR. The sites need FRTS if the signalling rate at the
sites is different. So let's assume the HUB site has a signalling rate of
192K and the SPOKE site has a signalling rate of 64K.
CIR for the pvc at both sites is set to the maximum possible sustainable
rate between the sites --- that would be 64K which is the lowest signalling
rate between the sites.
minCIR is set to the actual CIR of the PVC.
Bc is set to 1/8 of the CIR. This means Tc is 125 milliseconds. Tc=Bc/CIR.
What this means is that transmission is divvied up into 8 time slots each
with 125 milliseconds. The 64Kbps CIR that we desire is divvied up into
eight 8Kbps blocks. (64K/8=8K)
Be will be set differently at each site. What you want is the highest
possible burst rate. The burst only occurs in the first of the 8 time
intervals. The calculation for highest possible burst rate is:
SR/8-Bc=Highest possible Be. (Where SR= Signalling Rate)
For the SPOKE router this is 64K/8-8K=0=Be
For the HUB router this is 192K/8-8K=16K=Be
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
balaji.balakrishnan
Sent: Thursday, February 20, 2003 5:39 PM
To: ccielab@groupstudy.com
Subject: Framerelay /ATM traffic shaping
Hi group,
I t is always confusing ( atleast for me ) to define and relate frame relay
traffic shaping parameters minCIR, CIR,Bc,Be and EIR
with reference to an practical example. For example, if I say a customer
frame-relay connection is configured for minCIR =64k,
CIR=128k and Bc=32k , Can someone explain what does it mean and how you
derive the remaining parameters Be,Be and EIR.
Also , in case of Framerelay to ATM internetworking, how these values maps
to ATM PCR,SCR and MBS.
Rdgs,
Bala.
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