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Is VLAN really that important for voice traffic on switches?

Posted on 2013-01-16
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Last Modified: 2013-02-01
We currently use four-digit extension dial between two facilities which is connected with MPLS. Users have got break-up voice intermittently. Since ISP's connection between router to router is set up with QoS already. Therefore we have been thinking if the break-up/latency is caused by our own switches (HP V1810) since they the switches are not low-end products and cannot be properly set with QoS. My questions to you are:

1. Currently we don't have a separate VLAN for voice traffic. Do you think it is essential to set up a separate VLAN just for voice traffic in order to improve the voice quality?
2. Can you recommend a couple of models of switches good for QoS and VLAN please? Of course should not be too expensive; just better than what we have is okay.

Thanks.
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Question by:Castlewood
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tpitch-ssemc earned 1200 total points
ID: 38784226
I've never ran voice and data on the same VLAN. I've always, ALWAYS, had it separate. That way you can easily prioritize voice over data.

Now as for equipment, I'm going to recommend Cisco. I have to. I don't know what your budget looks like for this, but Cisco is easy to configure and of course bullet proof. The cheapest place I've found to buy Cisco gear is from Cables and Kits. Some of their stuff is used, if you don't mind, but generally they are much lower than most everyone else you can find. Customer service is great, I once ordered the wrong switch. They worked with me to return it and get the right one. Shipping is always fast; I'm in the same metro area as them and I usually get everything next day.

http://www.cablesandkits.com/
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Author Comment

by:Castlewood
ID: 38784279
Thanks for the prompt reply.  You said "That way you can easily prioritize voice over data.
" do we still need to "prioritize" voice traffic IF the voice is already running in a separate VLAN??

Regarding Cisco switch, can you recommend a model ?

Thanks.
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Expert Comment

by:tpitch-ssemc
ID: 38784312
I recommend 3560, 2960 is a layer 2 that could be used in remote closets but I'd make the 3560 or even the 3750 your core. Both 3560 and 3750 are layer 3 switches that can handle routing for you. I've personally used 3750 as a core, with some extra 3560 swtiches before the 2960s was released. 2960 works perfectly as an access layer switch, not your core. You could use the 2960 model assuming you have a router that can route traffic for you.

Yes, you still want to prioritize voice.
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Assisted Solution

by:t-work
t-work earned 400 total points
ID: 38784464
do we still need to "prioritize" voice traffic IF the voice is already running in a separate VLAN

Of course you should - otherwise your switch still handled "all traffic the same" - regardless in which VLAN the traffic flows. So your uplink could be blocked by data in vlan1 instead of voice flowing in vlan2. (if your uplink is sometimes  your issue or, if the switches' CPU is a bottleneck sometimes).
The only thing you would get rid of with vlans and without prioritizing would be the fact that data and voice could affect each other in one LAN (eg. in former times by broadcasts), but you won't help the traffic flowing fluently through uplinks or routers through your WAN.

So it could  help by silencing other (data) talkers in this (vlan) segment, but that has nothing to do with qos / priorities of data streams and wohn't help anything if your hardware shows any bottleneck.

So if your routers are the weak point you should at least prioritize "everything" that comes from the voice vlan.
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Assisted Solution

by:convergint
convergint earned 400 total points
ID: 38806056
I've run quite a few VOIP systems with and without VLANs, it can work fine without VLANs if the data traffic is low and your network infrastructure is excellent.

However, it is much better to design them with VLANs as you can QoS the VLANs.  I've always used HP Procurve switches for networking, fraction of the price of Cisco gear, true lifetime warranty and updates, as well as super easy to configure.  The ROI for Procurve is much better than Cisco.

Since you already have some HP gear, I assume you might have some experience with configuring them already.  Your 1810s are not that low-end.  They can be configured with 64 VLANS and QoS, just make sure that the firmware is updated.
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Author Closing Comment

by:Castlewood
ID: 38845421
Thank you guys.<br />It ends up with a dramatic result -- we didn't route the site-to-site 4 digit call via MPLS, instead via Internet. That's why the voice had been so terrible.
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