Routing

Hi, everyone

i confuse the transmit-rate exact and shape-rate

i think transmit-rate exact can put the overrun data flow into the buffer directly, and not into the negative credit, is it right?

and shape-rate is also doing this way.

so, could you tell me what's the difference between them ?

thank you very much

Please search the forum for this question. There are numerous explanations and most recently I also did  an almost comprehensive research and answere to this question.

You would use shape-rate if you will allow "burst" activity above the normal rating for the traffic.  The shape-rate then puts the hard cut at the higher burst value for the cut off.

With transmit-rate exact you have the hard cut at the limit without any ability to burst higher if the resources are available.

http://www.juniper.net/techpubs/en_US/junos11.4/topics/reference/configuration-statement/shaping-rate-edit-cos-schedulers.html

The transmit-rate statement at the [edit class-of-service schedulers scheduler-name] hierarchy level configures the minimum bandwidth allocated to a queue. The transmission bandwidth can be configured as an exact value or allowed to exceed the configured rate if additional bandwidth is available from other queues. For J Series routers only, you limit the excess bandwidth usage with this statement.

You should configure the shaping rate as an absolute maximum usage and not the additional usage beyond the configured transmit rate.

Thank you very much!

and also, i have another question:

i knew that if i set the transmit-rate percentage, such as transmit-rate  percent 40, the junos can utilize the leftover bandwidth, but i don't know when i use the transmit-rate remainder, could it put the overrun data into the negative credit? or it only in the positive credit ?

hope your reply 🙂