From: OhioHondo (ohiohondo@columbus.rr.com)
Date: Sat Feb 22 2003 - 18:19:34 GMT-3
Sage
The URL I sent to you explains the use of Be. The Be parameter only seems to
be useful if there is a mismatch between the signalling rates of the two
sides of the pvc.
Some confusion comes in because of the use of the term CIR to mean two
different things. The contracted CIR from the vendor is the contracted
minimum bandwidth that they are committed to give your pvc.
Cisco uses the term CIR to mean the rate at which you want to transmit
data -- meaning the signalling rate. Cisco uses the term minCIR to mean the
contracted CIR for the pvc. Cisco uses these two values (Cisco CIR and
minCIR) in this manner --- if there are no BECN's received the pvc will
attempt to transmit at the Cisco CIR. If a router is receiving BECN's and
traffic shaping is configured, the pvc lowers its' transmit rate to
something less than the Cisco CIR. If it keeps receiving BECN's it continues
to lower the transmit rate. It will not lower the transmit rate any lower
than the minCIR which is the providers guaranteed CIR!! The use of CIR and
minCIR handle normal bursting up to the signalling rate.
If there is not a mismatch between signalling rates, or there is no real
time traffic, or you don't have several spokes with T1's feeding into a Hub
site with only a T1 -- the Be and Bc parameters probably don't have to be
set. The defaults, Be=0 and Bc=CIR/8, are fine.
-----Original Message-----
From: Sage Vadi [mailto:sagevadi@yahoo.co.uk]
Sent: Saturday, February 22, 2003 12:00 PM
To: OhioHondo; ccielab@groupstudy.com
Subject: RE: FRTS: Bc & minCIR
Ohio,
I disagree with your Be. I believe you got that
thought from this paragraph:
"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."
/end
Be should be able to OCCUR ANYTIME - the Tc interval
keeps recyling. I believe the above interpretation of
the paragraph, should be understood to be within each
Tc cyle.
Q) Otherwise why bother with a Be - if you can only
have it once?!?!?!
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