Introducing VoIP into our network

[BeckyBoo123]

Hi All,

We are a little behind the times and up until now we've been using analogue phone lines that connect up to a traditional PBX system.

We are now rolling out VoIP handsets to a test location which have been provided to us by Masergy. There is no Call Manager, its all just connects out to the web.

I had no clue how to approach this, all I knew is that my data needed to be kept separate. Separate VLAN for data, separate VLAN for voice.

So my router connects back to the corporate network on VLAN10 (10.11.18.0/24) and my voice data uses VLAN20 (192.168.1.0/24) and DHCP is provided by the router. All VLAN10 traffic goes down an IPSec tunnel, and VLAN20 goes straight out to the web.

I have a switch that also reflect this, it too has switchports assigned to VLAN10 and voice VLAN20.

So, I just wanted to check, is this the best approach? How do other people set their voice data network up? Should my VoIP handsets look to my corporate network for DHCP? How do I monitor this? I am completely in the dark, any suggestions/recommendations would be much appreciated! 

[Joseph W. Doherty]

Even when you have separate VLANs for data and VoIP, they generally, at some points in the network, share a medium.  When they do, it's often a good idea, sometime a true need, to use QoS to "protect" VoIP's bandwidth needs from data's bandwidth consumption.

Understand, it's often "easy" to control/manage egress bandwidth with QoS, it's often "very difficult" to control/manage ingress bandwidth.  So, for example, if you have a link that "shares" your IPSec tunnel and VoIP traffic, the former might cause issues with the latter.

BTW, a Call Manager is wonderful for limiting the number of concurrent calls, and their bandwidth needs, are bounded; very useful to know for QoS purposes, but still leaves open the issue of VoIP vs. data at a bandwidth bottleneck.

[BeckyBoo123]

Hi @Joseph W. Doherty 

Thank you for your reply. 

As we have corporate data going down the tunnel and voice data doesn't, should I still be concerned with ingress bandwidth? Do you mean ingress through the Cellular interface?

Do you have any recommendations what QoS to put in place on this interface so I don't run into any issues?

We are using a mixture of Cisco and Polycom IP phones which are cloud ready. Is there a standard tool that people tend to use to integrate into their systems to help on the call management side of things as this hasn't been offered to us as part of the package.

I have looked at a few third party tools for monitoring such systems (Solarwinds VNQM and a few others) but they all seem to expect a controller on site. I think I'm misunderstanding something somewhere.

[Joseph W. Doherty]

"As we have corporate data going down the tunnel and voice data doesn't, should I still be concerned with ingress bandwidth?"

If your VoIP and, again, share a medium (its bandwidth) then you should be concern about how they share the bandwidth, for both ingress and egress.  However, if we control both "sides" of a medium (and it's not multipoint) one side's egress is the other side's ingress.  I.e. controlling both sides egress we (implicitly) control the other side's ingress (again, if not multipoint).  If the shared medium is cellular, generally same applies (again if shared by VoIP and data, although "phone" cellular uses, I believe, a different "channel" for actual voice vs. data (i.e. bandwidth is not shared).

"Do you have any recommendations what QoS to put in place on this interface so I don't run into any issues?"

Yes both prioritize VoIP bearer traffic over all other traffic and insure it has the bandwidth for all its concurrent calls.  Also insure VoIP control has sufficient bandwidth packets are not dropped and sufficient bandwidth packets aren't "unduly" delayed.  Specific QoS commands very much depend on actual platform.

Your other questions are likely best posted in the relevant subject forums, like "Network Management" and "Collaboration, Voice and Video".