From: perkinsr@xxxxxxxxxxxxxx
Date: Wed Aug 14 2002 - 13:04:10 GMT-3
This is a good question. My understanding before opening soiles book was
that the CIR is the max rate you want to transmit at. He says at the
begining of the chapter it is the average rate you want to transmit at, not
sure which is right, but if you are trying to average or max your
transmission rate to your line speed (say 1.544 mbs) and expect it to get to
the remote side (say 64k) then you are going to have some major problems. I
think you want to set the CIR to the minimum line speed on either end of the
PVC, then set the minCIR to the CIR you are paying for. With this setup you
will tranmit at or near the CIR you set (not the CIR you get from telco) and
when you get a BECN you will follow the throttling back algorithm down to
the minCIR and not go any lower.
CIR=theoretical max rate of transmission looking at the line speeds of the
routers.
minCIR=the CIR you are paying for, the garunteed rate through the frame
cloud.
Given all this, I am left to wonder what role Bc and Be play. From all my
reading, Bc seems to be used simply to define Tc in a round about way. This
is important because that defines the timeslices you are averaging over. Be
is something you have to buy if you want to use it. It alows you to exceed
your CIR when you have a burst of traffic.
Ray
-----Original Message-----
From: Volkov, Dmitry (Toronto - BCE) [mailto:dmitry_volkov@ca.ml.com]
Sent: Wednesday, August 14, 2002 6:01 AM
To: 'ccielab@groupstudy.com'
Subject: traffic shaping numbers - still unclear !!!
Hello group,
Can somebody clarify on it finally ?????
1st Question:==========
FRTS: 1)frame-relay CIR ; 2)frame relay MinCIR
GTS: 3)traffic-shape rate CIR
Is CIR from command 3) the same as CIR from command 1) ??? - A guess it's
true.
Or it has to be interpreted as MiCir from command 2) (i.e. rate guaranteed
rate obtained from provider) ???
2nd Question:==========
What CIR You have to configure on Central site if You have Central site
1544000 and remote 64000 ????
CCO says: http://www.cisco.com/warp/customer/125/21.shtml
"If the central side has a upper limit of 256 kbps, you should use the
LOWEST upper limit value"
the same conception showed in the example at
http://www.cisco.com/warp/customer/125/traffic_shaping_6151.html
However, Solie and some other guys (i.e. MADMAN) tell "set CIR to be the
phisycal port speed of the circuit at Central site"
I did look at archives this year and didn't find any good explanation .....
3rd Question: ==========
According to
http://www.cisco.com/warp/customer/125/traffic_shaping_6151.html and Solie :
Be (excess burst) is the number of excess bits to transmit during the FIRST
(???) interval (Tc) over and above Bc, once credit is built up.
How Be has to be calculated, when we place Be under "frame-relay be" command
:
How many bits can be send over bc per Tc ?? or
How many bits can we send over CIR during 1 second (i.e. spread in time)
??????
The difference is 8 times if Tc=125 ms !
Solie example: He did put Be 64000 on page 368 and 398 (so it doesn't look
like typo) - I absolutely don't understand this.
Can somebody explain that, please !!!
CCO http://www.cisco.com/warp/customer/125/21.shtml said: PEAK = DLCI
maximum speed = (Bc+Be)/Tc = CIR + Be/Tc = AR
if be=64000 sec and bc =8000 sec that is mean that AR = 576000bits/sec but
he mentioned that circuit on the far end only 64K.
http://www.cisco.com/warp/customer/125/traffic_shaping_6151.html gives the
following example:
Circuit speed 192 K, Bc =8000 ; Tc=125, CIR=64000 ====> Be =192000/8 - 8000
i.e. We can send 16000 bits over Bc 8000 bits during Tc only, which is equal
to rate 192K=(16000+8000)/Tc !
So, Be (as parameter in "frame-relay be" command) = bits during interval Tc
tabove Bc limited by access rate ???
Networkers 2002
http://www.cisco.com/networkers/nw02/presos/pws/docs/PS-570.pdf at page 66
gave wrong number for Be=32000 BPS ??? instead of Be=4000 BITS
4th Question: ==========
CCO http://www.cisco.com/warp/customer/125/traffic_shaping_6151.html said
Frame-relay traffic shaping is enabled on the main interface, and it applies
to all DLCIs under that interface. We cannot enable traffic shaping only for
a particular DLCI or subinterface under the main interface. If a certain
DLCI has no map class attached to it, and traffic shaping is enabled on the
main interface, the DLCI is assigned a DEFAULT MAP-CLASS with CIR = 56000.
So, If I enabled FRTS under physical interface I got default map class with
CIR=56000 on all DLCI / subinterfaces
What if I have 100 DLCs/subinterfaces and I want to implement shaping only
on some of them ??
How to do it ???
I see only one way to do it: put DLCIs where I want to implemet shaping
under separate subinterfaces and enable GTS on this subint.
Any comments ???
Thanks,
Dmitry
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