QoS for Exchange

[Ricky S]

Hello everyone, I have a hub router at my data center serving approx. 90 spokes. While my infrastucture is implementing spoke-to-spoke tunnels for inter-branch communication, all my application servers are still behind the hub router at the data center. All exchange clients at the company are setup with the offline mode turned on which means, each and every single email is downloaded by the client. On a normal day this doesn't cause too much grief as we do have a 100 meg pipe out of the data centre however when someone returns after 2 weeks vacation and then start downloading their emails, it bogs down our bandwidth at the DC. We are an engineering firm therefore most my clients emails' contain large attachments. Just today I got an alert that the 100meg pipe had reached 70% of it's capacity.

So my question is this, is there a way I can implement some kind of qos policy on the router that will restrict bandwidth usage for exchange?

[smehrnia]

Hi rick,

generally its a Yes.

you can limit the bandwidth for certain applications with regards to server's ip address or service's tcp port, etc. but it depends on the equipment u r using, whats the router you have there?

how much bandwidth you have in mind for the exchange?

Soroush.

[Ricky S]

Hello Soroush, thanks for the reply.

I am using a Cisco 2951 ISR currently. I would say 20meg should be sufficient for exchange as I don't want it to affect my other mission critical apps.

[smehrnia · Accepted solution]

its better that u limit the bandwidth close to the server then. i say at the ingress port of the exchange server. i dont know if 2900 supports it this way though.

access-list 130 permit tcp host [exchange ip] eq 25 any

access-list 130 permit tcp host [exchange ip] eq 110 any

class-map MAIL

match ip address 130

policy-map MAIL_LIMIT

class MAIL

  police 20000000 exceed drop

exit

int Fx

service-policy input MAIL_LIMIT

this will limit all the EMAIL traffic (ONLY) from the server to 20mb.

Hope it Helps,

Soroush.

[Ricky S]

Exchange is actually plugged into a 3750. I'll apply the policy there. Thanks for your assitance. Much appreciated.

[Joseph W. Doherty]

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Posting

Although policing your exchange at its source will keep it from taking using too much bandwidth, a more optimal solution would be QoS prioritization at your bottleneck.  This so email can use bandwidth in such a way it isn't adverse to other traffic, but transfers as quickly as it can.  Activation of FQ at the WAN egress might be the most simple and yet beneficial (even beyond just email).  If your spokes have less than 100 Mbps, shaping for each might also be considered.