Implement LAN QoS

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Mar 17th, 2009

We have about 40 braches and they are connected to AT&T cloud by BGP routing protocol via T1 or ATM. All the servers are located in our headquarter. Sometimes, if one user in remote location downloads big files, the whole remote site is down. Each site has router connected to the AT&T and the switches are connected to the router. We'd like to implement QoS in LAN for all the switches so we can manage/control the bandwidth by port levels. We don't have voice network, it is only for data network. Please be advised that how we implement QoS in the switch in our network.

I have this problem too.
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Joseph W. Doherty Tue, 03/17/2009 - 18:47

You probably don't need to configure QoS throughout your LANs, initially the WAN connected routers, should do.

I'm guessing from the provider's name and the provider's AS number, you're working with AT&T MPLS VPN. If correct, what you want to do is, de-prioritze the bandwidth hungry traffic as it leaves the WAN edge router and take advantage of MPLS QoS offered by QoS to also de-prioritze the traffic as it leaves the provider's cloud.

With AT&T, you might find they offer a 4 class QoS model, real-time, BH (bursty high), BL (bursty low) and BE (best effort). Mark/treat "normal" traffic as BL, critical/important traffic BH, bandwidth hungry traffic as BE. (Real-time you can use for something like VoIP, if you ever use it.)

To make this all work, you'll need to identify different types of traffic.


If there's practically no remote site-to-site traffic, i.e. it's all mainly HQ to/from each remote site, it may also be possible to bypass the need to utilize the MPLS vendor's QoS features. This is done by shaping your egress to correspond to the remote site's bandwidth. In such a configuration, FQ within shaping may eliminate the need to identify the type of traffic.


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