atcomsystems.ca/forum Forums TDM Business Telephone Systems Inter-Tel Telephones & Systems bandwidth untilization and monitoring

Hello -

I have 7 Axxess systems networked on an MPLS network. We have been running into some low bandwidth issues recently and I though maybe this group could help answer a few questions.

How much bandwidth is comsumed by a typical network call? And is there any good way to determine how many networking ports are in use at any given time?

Any help you offer is greatly appreciated.

Thanks,
Dan

The B/W depends on the call configuration in your switches. For WAN traffic you should be using the G.729 vocoder. If that is the case you are looking at around 31.3kbps per call with default settings.

(Eth Head Size+IP-UDP Head Size+RTP Head Size)x8
_________________________________________________
Audio Frames Per IP Packety x Voice Frame Size

+
(Codec B/W + Burst Data) x Number of Calls

=kbps B/W Consumption

Where:
RTP Head Size = 4 (Intertel)/12 RTP Standard
IP-UDP Head Size = 28 bytes
Eth Head Size = 18 bytes
Frame Head Size = 6 bytes
Audio Frames per Packet = 3 (default)
Voice Frame Size = size in ms per frame
Codec B/W = 8kbps
Burst Data = Data Burst in Call Control Socket
Number of Calls = # of Calls

Example G.729 x1 Call
(18+28+4)x8 Divided by 3x10ms
+
(8kbps + 10 kbps) x 1 Call = 31.3kbps

I use PRTG Traffic Grapher to monitor all my bandwidth. It uses SNMP to connect to your switch, and i just have it monitor the bandwidth of the uplink ports on each switch. I also have it monitor the two WAN ports on my sonicwall so i can monitor my Internet bandwidth usage too.

I just migrated off an MPLS network as we went from 3 Branch Offices down to 2, and the 2nd was only a 1 person office so I have that connected via a Site to Site VPN and the other branch office i migrated to a Point to Point Fiber connection. The MPLS worked great when the T1 stayed up, i had horrible luck with reliability which is what prompted my migration off of it - i wish you good luck.

What worked well for me however was a good QoS setup on each switch in each branch office, making sure any call destined for the IPRC in my HQ office was "first inline". The 3Com switches i had while on the MPLS (recently upgraded to HP and i blieve they can do this as well) was set to prioritize anything going to the IP address of my IPRC. With my new setup i created a 2nd vlan just for the VOIP traffic and have QoS rules in place to priortize anything on that Vlan first.
Eitherway make sure you have these setup and as long as you don't have more possible VOIP traffic then you have bandwidth you should be ok.

Good tip beholder, MRTG or PRTG are great tools but require some time to set up. I suppose if you were and end user/IT/Telecom manager it is a great fit. I found a cool little tool that I use in conjuction with Wireshark to do quick on the fly B/W monitoring at customer sites.
Google: CommTraffic