From: BRZYSKI, ADAM E (SWBT) (ab1723@xxxxxxx)
Date: Wed Aug 29 2001 - 13:23:21 GMT-3
Committed Information Rate (CIR) Rate (bits per second) the frame relay
provider guarantees for data transfer. CIR values are set by the Frame Relay
service provider and configured by the user on the router.
Note: The port / interface access rate can be higher than CIR. The rate is
averaged 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 switch
attempts to transfer beyond the CIR over the Committed Rate Measurement
Interval (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 configured. Tc cannot exceed 125 ms.
Backwards Explicit Congestion Notification (BECN) A bit in the Frame Relay
frame header that indicates congestion in the network. When a Frame Relay
switch recognizes congestion, it sets the BECN bit on frames destined for
the source router, instructing the router to reduce the transmission rate.
I got this infor from the following:
http://www.cisco.com/warp/public/788/voice-qos/voip-ov-fr-qos.html
Hope this helps!
Adam Brzyski
Design Engineer II
CCIE #8082, NNCDE
-----Original Message-----
From: Martyniak, James [mailto:martynij@uphs.upenn.edu]
Sent: Wednesday, August 29, 2001 11:15 AM
To: CCIELAB (E-mail)
Subject: Traffic Shaping sanity check
Is the following correct?
CIR=Bc bits per second (bps)
CIR+EIR=(Bc+Be) bps
Tc is confusing to me, any plain english explanation. When it comes to
defining Bc or Be I assume 1 (for traffic rate)?
Jimmy Martyniak
Network Engineer
University of Pennsylvania Health System
(215)662-6243
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