Re: 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).

this shows that there is some contention in the carrier network - if each remote sends data to the centre, some packets are going to be dropped.

so - unless the carrier understands drop precedence so that your Voip traffic gets through preferentially under congestion, you are going to have voice quality issues.

> 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.

you need to check if this happens between sites as well. time for some testing.....

> 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?

there are 2 basic approaches.

1 limit the flow so that drops dont happen (i.e. limit the data rates from the remote sites). 2 mark the traffic so that high priority stuff gets better treatment inside the telco network.

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.

cisoc QoS on your routers cant influence what happens elsewhere in the network.

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