QoS - Traffic Shaping

I need some guru help on this one.

I am dealing with several Wide Area Networks which have or are implementing VoIP. Here is an example of a network:

Host Site = 1.5MB Remote Site A = 512K Remote Site B = 768K Remote Site C = 512K Remote Site D = 768K Remote Site E = 960K

These are private circuits all brought back to a VLAN on the carrier?s network (Layer 2).

The ones that have implemented QoS, are either incomplete or not setup properly. They are having Voice Quality issues, such as, when someone downloads a large file from the internet, from a remote site to the host site, any calls going across those circuits get crushed and the quality stinks. This, to me, is a sign that the QoS is not working properly.

I have recommended some traffic shaping policies, basically determining how much bandwidth is needed for voice at each location, then putting a policy in place that allows data (all but voice), to have X amount of bandwidth on the circuits, and leaving the rest for Voice.

The big question that I have is:

How, with the Cisco IOS, would you handle the fact that a remote site could be flooded with data? Meaning the aggregate of the bandwidth of sites C,D, and E could flood site A. Is there a concept/technique that addresses this possibility? I made some suggestions about redesigning the network, and keeping all servers central, and minimizing data traffic between remote sites. I have to think there is something in Cisco?s QoS options that would address this, so Voice always has priority and NEVER takes a hit.

I hope I explained this well enough. I appreciate any help. Please yell at me if I am missing something important!



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Hello Mike,

traffic-shaping, for voice, is not a good solution. You have to implement LLC (Low Latency Queueing), so voice will be priority queued. Additionally you have to make sure that your voice traffic is marked with the right TOS/DSCP Parameters. For more information look at the IOS configuration guides at CCO

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They are listed under the IOS Menue.


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