Why do we have to use Voice VLAN ?

[FabianoCh]

Dear folks, after reading about Voice VLAN in the 5500 manual , I can not figure out Why to use it with IP phones. I know that it sets QoS but the phones themselves already set their Packers with QoS priorities. So, has anyone had any expirience with IP phones to help me ? Is it necessary to configure Voice VLAN or is it some legacy option ? Thanks.

[Vince-Whirlwind]

Data tends to be high-volume, not particularly sensitive to latency, and using TCP has a mechanism to cope with lost packets.

Voice on the other hand is low volume and made up of lots of very small packets and *is* sensitive to latency and has no correction mechanism for lost packets.

It's therefore considered sensible to use VLANs to keep these two quite different traffic profiles separate from each other.

On a very small network it might be OK to put everything on a single VLAN, but as a rule of thumb, it's probably a good idea to consider a /24 to be the ideal subnet size. As you are breaking up Data subnets from each other, you may as well do the same with Voice subnets.

[FabianoCh]

Vince-Whirlwind thanks for your reply.  I understand that it is not good to mix data and voice traffic in the same vlan.

What I really wanna know is about the VOICE VLAN resources on the hp 5500.  Is it necessary to use it ? Why I should used it ?  Or just putting the voice traffic in another vlan and using qos trust is enought ?

I really do not understand the purpose of using the VOICE VLAN resources.  Thanks.

[Peter_Debruyne]

Hi, see http://h30499.www3.hp.com/t5/Comware-Based/PORT-HYBRID-ISSUE-WITH-AN-IMAGE-APPLICATION/td-p/6730322

[FabianoCh]

Thanks. So, it is not to use voice vlan anymore ? It's an old way to use voip phones ?