WRED query

[saif_farooq]

Hi,

I am testing tcp,voice & video over my network.What I found from WRED documentation is that WRED works fine with TCP traffic(bcauz of it's retransmission mechanism)but im a bit confused bcauz i have a mix of traffic,so my questions are:

1)Should WRED be configured on an interface which has TCP as well as UDP i.e. voip & video traffic passing through it?

2)Is WRED not suitable for an interface where we have voip & video traffic, or it doesn't support it at all?

I think that if we configure WRED is only suitable for interface that receices TCP traffic only & if there are UDP sources passing throough, it will only create problems!!

pls guide

[network.king]

Hi Saif,

You are correct , WRED works fine with TCP bcos dropping the TCP packets would cause the end systems Window size to decrease so that total utilisation is under control.

As there is no mechanism in case of UDP , WRED is not suitable for UDP applications

regards

vanesh k

[network.king]

Hi Saif,

Pls go through this document

http://www.cisco.com/en/US/tech/tk543/tk757/technologies_white_paper09186a008017f93b.shtml

regards

vanesh k

[saif_farooq]

hi vanesh,

Thanks a lot, it is a very helpful link that u sent me. Just one thing im asking to be sure, that if we have UDP & TCP both passing through the interface, u think should WRED be implemented.

regards

saif

[network.king]

Hi Saif,

You can do one thing , if you are sure abt the traffic utilisation of your UDP and TCP traffic , then create two class maps and police UPD traffic and Use WRED on the class-map for TCP traffic .

If without using any class-maps and generally if you go for WRED in the interface , then surely your TCP applications would get a hit and UDP would make through and would keep on using a higher part of the bandwidh.

regards

vanesh k

[saif_farooq]

thanx for previous replies, that were of gr8 help indeed. in the light of above I beleive I should test on an interface with UDP & TCP both passing through & also WRED enabled on it,this testing i will do step by step with first tcp only traffic & then only udp & finally both of them. this will help me come to some conclusion whether WRED has any impact on UDP traffic.one thing i read in the link u fwd me was, it says its better to rely on PQ or LLQ for real-time traffic & it even doesn't recommend policing for that purpose.

anyway, my whole point is that using WRED, its may not be harmful for real-time traffic

but IP precedence may have to be defined for UDP connections so that new connections may not be denied.

regards

saif

[network.king]

Hi Saif,

You are right , WRED would not impact any Real time applications as all are UDP based .The reason for relying on the PQ or LLQ is that real time traffic need to be sent first rather than waiting in the queue for other traffic , so that the delay sensitive traffic is not affected by other traffic .

Pls clarify me on the last point of setting ip precedence for UDP connections to have a better understanding.

regards

vanesh k

[saif_farooq]

hi,

about ip precedence:i meant that with WRED working, just to ensure more priority to real-time applications, we can possibly alter IP Precedence accordingly,but now i would rather stick to default precedence parameters cauz all this is getting mixed up u know.

I will definately tell u some of my findings as i will be working on it whole day today.

one last thing can u send me some link regarding PQ & LLQ cauz i was actually not thinking of it before for voip & video, & was only sticking to CBWFQ.

thanx & regards

saif.

[network.king]

Hi Saif,

You can use the two link for reference

http://www.cisco.com/en/US/products/sw/iosswrel/ps1830/products_feature_guide09186a0080087b13.html#wp5331

http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a0080087af0.html

Pls do your testing and let us know the results.

regards

vanesh k