From: Volkov, Dmitry (Toronto - BCE) (dmitry_volkov@xxxxxxxxx)
Date: Wed Aug 14 2002 - 17:58:47 GMT-3
Jim,
As far as I understand Be is not rate it is measured in BITS.
1)
"Excess burst size (Be) is amount of excess burst of data allowed to be sent
during first interval when the token bucket is full" Srinivas Vegesna "IP
Quality of Service" ciscopress
2)
frame relay be
The amount of excess data allowed to be sent during first Tc interval in
bits once credit is built up. Configure Be only if the Frame Relay CIR value
is less than the AR. For PVCs carrying voice packets, the Be must be set to
zero to ensure best possible voice quality. The router only bursts (Be) when
there are tokens in the token bucket. The token bucket does not accrue
tokens unless the amount of traffic being sent out is less than the CIR. The
router can only burst for the first Tc, after which the token bucket is
empty. The value of Be by default is zero bits.
http://www.cisco.com/warp/customer/125/traffic_shaping_6151.html
3)
Excess Burst Size (Be)
The number of non-committed bits (outside of CIR) that are still accepted by
the Frame Relay switch but are marked as eligible to be discarded (DE).
The token bucket is a 'virtual' buffer. It contains a number of tokens,
enabling you to send a limited amount of data per time interval. The token
bucket is filled with Bc bits per Tc. The maximum size of the bucket is Bc +
Be. If the Be is very big and, if at T0 the bucket is filled with Bc + Be
tokens, you can send Bc + Be bits at the access rate. This is not limited by
Tc but by the time it takes to send the Be. This is a function of the access
rate.
http://www.cisco.com/warp/customer/125/21.shtml
So, EIR + CIR = Access Rate, EIR=Be/Tc, CIR=Bc/Tc
My confusion is about : what is parameter in "frame-relay be" ?
Maybe it is not realy Be but EIR ;) (bps)
Dmitry
-----Original Message-----
From: Jim Brown [mailto:Jim.Brown@caselogic.com]
Sent: Wednesday, August 14, 2002 3:30 PM
To: 'Volkov, Dmitry (Toronto - BCE)'; 'MADMAN'
Cc: 'ccielab@groupstudy.com'
Subject: RE: traffic shaping numbers - still unclear !!!
Dmitry,
Isn't BE equal to the bits allowed during a single TC interval?
Shouldn't this be set to 32000 when the Cisco CIR is set to 32000 for a
total of 64000 bits per second, equaling the access rate of the port.
In other words, should BE + CIR = Access Rate?
-----Original Message-----
From: Volkov, Dmitry (Toronto - BCE) [mailto:dmitry_volkov@ca.ml.com]
Sent: Wednesday, August 14, 2002 11:39 AM
To: 'MADMAN'
Cc: 'ccielab@groupstudy.com'
Subject: RE: traffic shaping numbers - still unclear !!!
Dave,
About Question Nr 3:
SOLIE:
central site (marlin):
port speed = 1544000 kbps
Remote site 1 (glock):
port speed = 64000 kbps
Remote site 2 (sig):
port speed = 1544000
PVC center -- remote 1 has CIR set by the carrier = 32 kbps
PVC center -- remote 2 has CIR set by the carrier = 512000 kbps
marlin:
map-class frame-relay toGLOCK64Kb
frame-relay adaptive-shaping becn
frame-relay cir 1544000 ?????
frame-relay bc 8000
frame-relay be 64000 ????????
frame-relay mincir 32000
map-class frame-relay toSIG1544Kb
frame-relay adaptive-shaping becn
frame-relay cir 1544000 ?????
frame-relay bc 8000
frame-relay be 64000 ????????
frame-relay mincir 512000
Now look at networkers 2002
Frame Relay Traffic Shaping Terms :
Tc-Committed rate Measurement Interval (Bc/CIR)
Bc-Committed Burst Size
Be-Excess Burst Size
CIR-Committed Information Rate
MinCIR-Minimum Committed Information Rate
Port Speed: 64000 Bps
CIR : 32000 Bps (Average Rate of Traffic Without Congestion)
Mincir: 16000 Bps (Average Rate of Traffic With Congestion)
Bc: 4000 Bps (Amount of Data Sent Per Interval)
Be: 32000 Bps (Amount of Excess Allowed Once Credit Has Built Up) - bps !!!!
????
Be Careful With Bits to Bytes and Bytes to Bits Conversions
Frame Relay Traffic Shaping Example
interface Serial0
ip address 10.10.10.1 255.255.255.0
encapsulation frame-relay
frame-relay traffic-shaping
frame-relay class ccie
Enable FRTS Enable FRTS
map-class frame-relay ccie
frame-relay adaptive-shaping becn
frame-relay cir 32000
frame-relay mincir 16000
frame-relay bc 4000
frame-relay be 32000 ?????????? should be 4000 Because
Be=(AR-CIR)*Tc=(64000-32000)*0.125
Be number of bits during interval Tc
Dmitry
-----Original Message-----
From: MADMAN [mailto:dave@interprise.com]
Sent: Wednesday, August 14, 2002 12:30 PM
To: Volkov, Dmitry (Toronto - BCE)
Cc: 'ccielab@groupstudy.com'
Subject: Re: traffic shaping numbers - still unclear !!!
> 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
Don't have the Solie book, can you phrase the question more concisely?
Dave
>
> Dmitry
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