Comments on Cisco IOS hints and tricks: Challenge: CB-WFQ Bandwidth+Police behavior

FYI :) ttcp is also available on Cisco IOS routers...

2009-11-11T10:11:45.186+01:00

FYI :) ttcp is also available on Cisco IOS routers as a hidden command and can be setup as either the sender or receiver.

A single TTCP session is running on port 5001 will...

2009-11-10T10:34:02.658+01:00

A single TTCP session is running on port 5001 will be allowed upto 100% from 256kbps bw as there is no congestion.

A single TTCP session is running on port 5002, this will get up to 50% of 256kps bw standard.

One thing I think is missing from the previous comments is that there is no command regarding maximum BW available.. And by default 25% will be left available for the default class!!

Three parallel TTCP sessions are running on ports 5001, 5002 and 5003.
5001 ~ guaranteed 50% of 75% of 256kps
5002 ~ no more than 50% of 256kbps.
5003 ~ guaranteed 25%

Sure. You can run one TTCP session on each line (c...

2009-11-09T15:19:57.322+01:00

Sure. You can run one TTCP session on each line (console/VTY) and you can create as many VTY lines as needed on a router.

Is it possible to run multiple parallel TTCP sessi...

2009-11-09T12:59:23.030+01:00

Is it possible to run multiple parallel TTCP sessions from one cisco router to another cisco router? :'(

1) ~100%. The router reserves some bw for routing,...

2009-11-07T20:00:23.590+01:00

1) ~100%. The router reserves some bw for routing, etc.
2) ~20%. The drops will cause the TCP session to under utilize it's offered bw.
3) The port 5001 session gets 50% and then the 5001 and 5002 share the remaning. So, 5001 gets ~75%, 5002 ges ~25% but 5003 won't get any bw since it has lower priority than any configured class.

Hehe i remember i've been running the same tests a...

2009-11-07T12:05:19.756+01:00

Hehe i remember i've been running the same tests and got pretty much surprised by case (3) :) That result of classic WFQ scheduling is not something one would expect. What I learned from that day is that you should always assign some bandwidth value in case if you want any guarantees - fair queue command in class-default makes sense only when used standalone.

The link i provided in my previous post demostrates how that stuff works in pre-HQF implementations.

Petr

1) 100% 2) 50% 3) 5001 - 75% (50% + 50% of rema...

2009-11-06T17:45:26.978+01:00

1) 100%
2) 50%
3) 5001 - 75% (50% + 50% of remaining unallocated)
5002 - 12.5%
5003 - 12.5%

Rephrasing what had already been stated: 1) Gaura...

2009-11-06T15:00:16.742+01:00

Rephrasing what had already been stated:

1) Gauranteed 50% during congestion, can use up to 100%.

2) Limited to 50% period.

3) 5003 AND 5002 split the available remaining bandwidth after 5001 has been provided it's gauranteed 50%.

That's what I would expect anyways.

I aggree with the posters above. I think the bigge...

2009-11-06T14:05:23.365+01:00

I aggree with the posters above.
I think the biggest problem is the misconception of what each of these lines do. To be clear:
class P5001
bandwidth percent 50
Guarantees 50 percent of the band width but does not restrict it to only 50 percent.

class P5002
police rate percent 50
violate-action drop
Restricts to no more than 50 percent of the bandwidth but does not guarantee any.

So, basically, CB-WFQ does exactly what it is supposed to do with the configurations you've posted.

* A single TTCP session is running on port 5001. ...

2009-11-06T09:47:59.706+01:00

* A single TTCP session is running on port 5001.
100% from availabe bw.

* A single TTCP session is running on port 5002. How much bandwidth does it get?
50% from 256 kbps

* Three parallel TTCP sessions are running on ports 5001, 5002 and 5003.
5001 ~ 50% to 100% from available bw.
5002 ~ no more then 128kbps. most probably near by 0%
5003 ~ most probably near by 0%

* A single TTCP session is running on port 5001. H...

2009-11-06T09:21:31.030+01:00

* A single TTCP session is running on port 5001. How much bandwidth does it get? ~100%
* A single TTCP session is running on port 5002. How much bandwidth does it get? 50%
* Three parallel TTCP sessions are running on ports 5001, 5002 and 5003. How much bandwidth does each session get?

5001 - 4x%
5002 - 4x%
5003 - ~5%