From: Yadav, Arvind K (CAP, GECIS) (Arvind.Yadav@xxxxxxxxxxxx)
Date: Thu Nov 01 2001 - 08:08:16 GMT-3
Please find the relation b/w Bc, Be, Tc
Committed Information Rate (CIR) Rate (bits per second) the frame relay
provider guarantees for data transfer. CIR values are set by the Frame Relay se
rvice provider and
configured by the user on the router.
Note: The port / interface access rate can be higher than CIR. The rate is aver
aged over a Tc period of time.
Committed Burst (Bc) Maximum number of bits the frame relay network commits
to transfer over a Committed Rate Measurement Interval (Tc).
Tc = Bc / CIR.
Excess Burst (Be) Maximum number of uncommitted bits the frame relay swit
ch attempts to transfer beyond the CIR over the Committed Rate Measurement Inte
rval (Tc).
Committed Rate Measurement Interval (Tc) Time interval over which Bc or
(Bc+ Be) bits are transmitted. Tc is calculated as Tc = Bc / CIR. The Tc value
is not directly
configured on Cisco routers. It is calculated after the Bc and CIR values are c
onfigured. Tc cannot exceed 125 ms.
Backwards Explicit Congestion Notification (BECN) A bit in the Frame Rela
y frame header that indicates congestion in the network. When a Frame Relay swi
tch recognizes
congestion, it sets the BECN bit on frames destined for the source router, inst
ructing the router to reduce the transmission rate.
Regds
Arvind
-----Original Message-----
From: Eddie [mailto:guitardudez@yahoo.com]
Sent: Thursday, November 01, 2001 12:14 PM
To: ccielab@groupstudy.com
Subject: Frame-Relay Traffic Shaping (FRTS)
Here is the lab question:
1. Your service provider has a policy to mark all
traffic exceed 48 K with DE bit. BECN will be sent.
2. Your service provider will discard all traffic
exceed 64 K.
3. You have decided perform traffic control as
follows. When receive a BECN, lower the speed to 16K.
You must use Map Class with CIR, Be, Bc, MINCIR to do
this. Measuring interval is 125ms.
Here is my guess at a config from Caslow-p812:
Int s0
Frame-relay traffic shaping
frame-relay interface-dlci102
class test
map-class frame-relay test
Frame-relay cir 64000
Frame-relay bc 8000
Frame-relay be 16000
frame-relay mincir 48000
My questions are:
1) How do I change the measuring interval from the
default of 142 to 125ms
2) Is this enough to trigger when I receive a BECN or
do I need to apply the map-class to the interface?
3) I am confused as to how the cir, the bc, and the be
relate to each other.
Thanks in Advance.
Regards,
-Eddie
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