QoS to promote one protocol

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May 10th, 2010
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Is it possible to configure a router to use QoS to just have one protocol be a priority over everything else? I want to have RDP take precedence over everything without having to limit all non-RDP traffic along with making RDP the priority.


Here is what I have so far:


ip access-list extended RDP
permit tcp 172.16.23.0 0.0.0.255 any eq 3389


class-map match-any RDP
match access-group name RDP


Is there a way to make a policy use the RDP class-map to give it precedence over all other traffic without specifying all the other traffic?

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Overall Rating: 2.8 (6 ratings)
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spremkumar Mon, 05/10/2010 - 08:42
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Hi Jason


When you apply the class map under a policy map do configure the preference to RDP using Priority command followed by the bandwidth you wish to allocate for RDP during congestion.


If you are having voice traffic in your network i wont suggest to go ahead with priority instead you can make use of bandwidth command followed by the bandwidth you want to reserve/allocated to the RDP traffic.


regds

jasonww04 Mon, 05/10/2010 - 09:44
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There is no voice traffic.


If I use the priority percent 90, do I have to specify the total available bandwidth somewhere?


policy-map Inbound
class RDP
  priority percent 90


Is that enough? This is on a T1 so do I need to put bandwidth 1544 on the serial interface?

Jon Marshall Mon, 05/10/2010 - 10:09
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jasonww04 wrote:


There is no voice traffic.


If I use the priority percent 90, do I have to specify the total available bandwidth somewhere?


policy-map Inbound
class RDP
  priority percent 90


Is that enough? This is on a T1 so do I need to put bandwidth 1544 on the serial interface?


Jason


You should set the bandwidth on the T1 to be an accurate reflection of it's actual bandwidth.


Also you cannot usually allocate more than 75% of the bandwidth because the remaining 25% is used by the router for it's own traffic, best effort etc.


Finally you don't need to specific the overall bandwidth because it is 100% but your priority percent 90 is telling the router to use 90% for RDP. Even if you used priority percent 75 this could severly impact on non-RDP traffic. Are you sure this is what you want to do ?


Jon

spremkumar Mon, 05/10/2010 - 10:28
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Hi Jason


As clearly suggested by Jon its not a good idea to reserve/prioritize the whole bandwidth for a single class,do remember this will have a severe effect on your other application performance.


Better to strategize the requirement and build the QoS class maps / policies accordingly. Dont just plan with prioritizing the RDP traffic alone.



regds

jasonww04 Mon, 05/10/2010 - 13:35
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RDP is their most important protocol. Everything else is secondary. If they need to browse the internet, they do it through their RDP sessions so I don't care about making web traffic crawl. Would you suggest maybe setting the priority percent to 65?

spremkumar Mon, 05/10/2010 - 14:02
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Hi Jason


If you are sure about the applications and the environment there i would suggest to go ahead with the same and monitor the whole setup for sometime.


Monitoring the application performance / utilisation can give you a clarity on whether to increase or decrease the priority from the existing level.


regds

Jon Marshall Mon, 05/10/2010 - 14:35
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Jason


Just be aware that it might not just slow to a crawl, it might just stop working altogether. The percentage you reserve with the priority command should be based on how much RDP traffic needs to be prioritised in periods of congestion. It's not just a random figure.


Jon

jasonww04 Mon, 05/10/2010 - 15:15
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Thanks for all of the help everyone but it appears to be a moot point. According to the router I can't apply the policy to the inbound traffic because Class-based weighted fair queueing can only be used on outbound traffic. Guess I will be stuck using policing to make the policy work.

bgandhi Mon, 05/10/2010 - 21:55
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You can apply this policy on the other end router provided it is under your control.

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