07-17-2008 10:24 PM - edited 03-03-2019 10:47 PM
Hi Guys,
Could you please advise how to configure the shaping on the cisco router. I know about the first field but I am not sure how to calculate the second and third field in the command. For example
Shape 1000000 ? ?
The 1mb is the cir and the second field is the bc (the interface speed) and the third field is excess burst (be) in bytes. Am I right ?
If yes could you please let me know how to calculate them. I have seen on cisco as well as other sites but it is so confusing.
Tks & Regards
07-18-2008 02:35 AM
Kuldeep,
A simple explanation on simple shaping:-
Tc - Time interval, measured in milliseconds, over which the commited burst (bc) can be sent. With many shapiing tools, Tc = Bc/CIR.
Bc - Commited burst size, measured in bits. This is the amount of traffic that can be sent during the Tc interval. Typicall defined in the traffic contract.
CIR - Committed information rate, in bits per second, which defines the rate of a VC according to the buisness contract with the provider.
Shaped rate - the rate, in bits per second, to which a particular configuration wants to shape the traffic. It may or may not be set to the CIR.
Be - Excess burst size, in bits. This is the number of bits beyond the Bc that can be sent after a period of inactivity.
Shaping:- Tc=Bc/shaping rate
You can of course have other falvours of shaping:-
Class-Based Shaping
Shaping for voice using LLQ and a Small Tc
Shaping by banwidth percent
Class-based shaping to a Peak Rate
Frame-relay Traffic Shaping
HTH.
07-18-2008 03:10 AM
Shaping buffers pkts in a queue & sends Bc pkts every Tc interval. So even if you specify a CIR value, Bc & Be values will be calculated automatically by the IOS.
You have to be more specific about Bc & Be in policing, where if a couple of Tc interval passes without data then they will be accumulated & sent the next time pkt of bigger size comes to the queue.
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