Where to implement QoS ???

Answered Question
Mar 27th, 2008

Hi All,

I have the following scenario that i attached a jpg for !!

My router (RouterB) is connected to my ISPs router (RouterA) All my incoming traffic is through routerA.

After my RouterB i have a PIX515 with inside network and DMZ on the DMZ i have aproxy for internet access.

My connection between routers is only 256kbps, and the internet usage is hogging the line most of the time.

im not interested in other methods of controlling traffic on the proxy etc but rather perform QoS to allocate PRIORITY traffic to the PC1 and to a specific port for an aplication its using, as it becomes dead slow because the FR (256kbps) is hogged by internet traffic.

I do not have access to routerA. i have access to RouterB and PIX515.

My question is:

Router B is not aware of my QoS problems. if i configure QoS to prioritize traffic for PC1 where should i configure it..on routerB or on PIX515 !!! and which interface is the most effective.

I cannot help of thinking that routerA will send traffic to routerB as it is requested by the internet users and the appicaton of PC1. the internet users being more demanging than the PC1 application wont they stil hog up the bandwidth...or when i configure QoS on either of my machines will 'somehow tell' router A to limit its traffic to the proxy ???

with the above i mean that...if i have internet traffic of 200kbps and my application traffic is needing 200 kbps as well..Router A will send the internet traffic and application traffic as it comes on its interfaces (without QoS) and spitting it out the FR link with the same rates...so if it is already sending streams of 200kbps internet traffic. i will still only get 56 kbps for my application, untill the internet traffic dies down ??? (im confused)

please let me know if i am not clear with my request !!!

Thank you,

George

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Correct Answer by Jon Marshall about 8 years 11 months ago

George

If you could setup QOS on your router B outbound and the SP would setup QOS for the return traffic then yes that may well help.

I am not syaing for sure it will make no difference if you just do it on your router B just that it is very unlikely to make that much difference.

Jon

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Jon Marshall Thu, 03/27/2008 - 02:05

Hi George

Unfortunately because you do not control Router A anything you do will have little impact. Yes you could give priority to requests from the PC but the trouble is that the return traffic will not be prioritised.

Worse general internet surfing traffic is characterised by small requests and large responses and it these reponses which will not be prioritised.

If you suspect the blockage is at your end as the traffic goes out then it may be worth trying some QOS - i would do it on the router B rather than the Pix because IOS has a richer QOS toolset but i don't really think it will make much difference.

Jon

g-serghiou Thu, 03/27/2008 - 03:11

Hi jon,

so...in a few words theres nothing that can be done !!!! :( (on the QoS side) ...

so..in order for the QoS to work efficiently it should be configured at the source, where a HIGH BANDWIDTH Input is present (like 100Mbps ) and a smaller bandwidth output interface (2Mbps lets say ) in order for a QUEUE to be created !!! RIGHT !!! ???? so if in the node i want to apply QoS, a QUEUE is not created for traffic towards my machines i can only pray !!! So i would have to talk to the guys on RouterA ??? to apply QoS and prioritize traffic on their router (where a queue is being created !!!)

Did i get this right then ???

Thanks for the help,

George

Correct Answer
Jon Marshall Thu, 03/27/2008 - 03:14

George

If you could setup QOS on your router B outbound and the SP would setup QOS for the return traffic then yes that may well help.

I am not syaing for sure it will make no difference if you just do it on your router B just that it is very unlikely to make that much difference.

Jon

g-serghiou Thu, 03/27/2008 - 03:24

Hi Jon,

i understand completely what you are telling me.

I just want to run things from experienced people first and not assume myself that this is how things work...u covered my qustion !!!

I will nevetheless try QoS outbound (at least my pplication will be happy when sending documents !!! ) and observe the difference !!

Thanks for the help...

George

Goutam Sanyal Thu, 03/27/2008 - 02:12

Hi George, As per your requirement you can configure the QoS at RouterB, assuming the PIX is already performing with it's own tusk. Thanks Goutam

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