Calculating Bandwidth Needs for VOIP

LoopBack

Junior Member
Mar 21, 2016
14
0
36
The short of it:

How can I calculate/determine that approximately 450 VOIP phones connecting to an online hosted cloud provider won't experience quality issues within our network infrastructure.

Our setup, how I understand it:

Currently my employer has an on-site phone server connected to 3 T-1 lines, I believe. These lines are dedicated to only phone traffic. I don't manage this aspect of our infrastructure, so beyond the T-1 lines I'm not exactly sure what is happening, but it's no longer within our sphere of influence. Phones at each employees desk connect to a layer 2 48 port Gigabit switch, which has an uplink to Layer 3 Gigabit switches, where the phone servers reside, and the vendor provided switches needed to get access to the T-1 lines. The Layer 2 switches are nearly dedicated to only VOIP traffic. Non-VOIP traffic traverses a different stack of switches. Phone ---> Layer 2 Switch ---> Layer 3 Switch ---> Phone Server---> T-1

We are looking at moving our phone system to a hosted cloud solution. So our phone traffic would migrate from these dedicated switches to the stack of switches all other traffic flows, and utilizing our Internet connection all other Internet connected devices use. My question is what concerns should I have with this, and how can I confirm our infrastructure, more importantly the VOIP traffic quality, won't be affected by this change? I'm not a VOIP expert but what I do know is that all 450 of our phones in use are handled well by the 3 T-1 lines we are using. VOIP traffic would be moved to our primary (and secondary as a fail-over) Internet connections which are both 1 Gbps. We don't have any QoS configurations on our network, because we've never experienced any congestion issues. But I know that UDP traffic can be picky if there is congestion, and higher latency that came up for whatever issues.

Oh and one more thing, our Layer 3 switches connect to a firewall that sits at about 40% data plane capacity during normal business hours. All traffic is filtered through these firewalls. All traffic is inspected as it traverses the firewall to the Internet. The uplink between the Layer 3 switches and the firewall is a 1 Gbps uplink. Input port utilization is about 10% and Output utilization is about 5% capacity.
 

mxnerd

Diamond Member
Jul 6, 2007
6,799
1,101
126
T1 (1.544Mbps) can have 24 x 64k VOIP channels, you only have 3 T1, so it's 72 channels for 450 phones on 3 x1.544Mbps <= 5Mbps.

Usually VOIP companies recommends at least 80K or more for each call, however.

If 450 phones are all active, it will only take >= 36Mbps.
 
Last edited:

LoopBack

Junior Member
Mar 21, 2016
14
0
36
T1 (1.544Mbps) can have 24 x 64k VOIP channels, you only have 3 T1, so it's 72 channels for 450 phones on 3 x1.544Mbps <= 5Mbps.

Usually VOIP companies recommends at least 80K or more for each call, however.

If 450 phones are all active, it will only take >= 36Mbops.

Perfect! Thanks for the reply!
 

Genx87

Lifer
Apr 8, 2002
41,091
513
126
The short of it:

How can I calculate/determine that approximately 450 VOIP phones connecting to an online hosted cloud provider won't experience quality issues within our network infrastructure.

Our setup, how I understand it:

Currently my employer has an on-site phone server connected to 3 T-1 lines, I believe. These lines are dedicated to only phone traffic. I don't manage this aspect of our infrastructure, so beyond the T-1 lines I'm not exactly sure what is happening, but it's no longer within our sphere of influence. Phones at each employees desk connect to a layer 2 48 port Gigabit switch, which has an uplink to Layer 3 Gigabit switches, where the phone servers reside, and the vendor provided switches needed to get access to the T-1 lines. The Layer 2 switches are nearly dedicated to only VOIP traffic. Non-VOIP traffic traverses a different stack of switches. Phone ---> Layer 2 Switch ---> Layer 3 Switch ---> Phone Server---> T-1

We are looking at moving our phone system to a hosted cloud solution. So our phone traffic would migrate from these dedicated switches to the stack of switches all other traffic flows, and utilizing our Internet connection all other Internet connected devices use. My question is what concerns should I have with this, and how can I confirm our infrastructure, more importantly the VOIP traffic quality, won't be affected by this change? I'm not a VOIP expert but what I do know is that all 450 of our phones in use are handled well by the 3 T-1 lines we are using. VOIP traffic would be moved to our primary (and secondary as a fail-over) Internet connections which are both 1 Gbps. We don't have any QoS configurations on our network, because we've never experienced any congestion issues. But I know that UDP traffic can be picky if there is congestion, and higher latency that came up for whatever issues.

Oh and one more thing, our Layer 3 switches connect to a firewall that sits at about 40% data plane capacity during normal business hours. All traffic is filtered through these firewalls. All traffic is inspected as it traverses the firewall to the Internet. The uplink between the Layer 3 switches and the firewall is a 1 Gbps uplink. Input port utilization is about 10% and Output utilization is about 5% capacity.

We just went through an on prem to cloud conversion. We are now in the process of moving back to on-prem. Our biggest issue is loss of update control. The cloud provider performs updates on their schedule which then breaks our phones. This has happened about 6 times in ~3.5 months of operation. Impossible to run a business with that kind of down time.

Consult whatever phone provider you are going with for build out requirements. A lot of cloud providers will quote 95kbps per phone. Also, if possible to alleviate issues with quality and support. There should be an option for a dedicated circuit using a private VPN or MPLS to the cloud provider.

On the failover. In my experience you can put VOIP into their own VLAN and spit them out the same port as data traffic. My experience is this doesnt work as well as dedicating an internal port on the firewall for this duty. If you go with a dedicated circuit then the phone provider will handle this traffic with their dedicated router.
 

LoopBack

Junior Member
Mar 21, 2016
14
0
36
We just went through an on prem to cloud conversion. We are now in the process of moving back to on-prem. Our biggest issue is loss of update control. The cloud provider performs updates on their schedule which then breaks our phones. This has happened about 6 times in ~3.5 months of operation. Impossible to run a business with that kind of down time.

Consult whatever phone provider you are going with for build out requirements. A lot of cloud providers will quote 95kbps per phone. Also, if possible to alleviate issues with quality and support. There should be an option for a dedicated circuit using a private VPN or MPLS to the cloud provider.

On the failover. In my experience you can put VOIP into their own VLAN and spit them out the same port as data traffic. My experience is this doesnt work as well as dedicating an internal port on the firewall for this duty. If you go with a dedicated circuit then the phone provider will handle this traffic with their dedicated router.


Thank you for that insight. I like the idea of looking into the dedicated circuit. We'll take a look at that option.
 
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