Re: Need help to calculate bandwidth utilization for VOIP calls

gshrivastava · ‎10-17-2011

Hi All,

The environment I am working has Multisite WAN with centralized call processing structure. We have call managers at Delaware and have around 10 remote sites. I need to figure out the bandwidth utilization of calls in remote site. We are also using tools like MRTG, MAZU, RTMT.

Please tell me how to calculate b/w utilization for remote site in such scenario. Also guide me if these tools can be of any use in calculating b/w.

Muhammad Jawwad Habib · ‎10-17-2011

https://learningnetwork.cisco.com/servlet/JiveServlet/downloadBody/7873-102-2-37487/VoIP_Cisco_BTSC_2.xls

Please have a look at it.

gshrivastava · ‎10-18-2011

I appriciate your quick response Muhammad, but its gonna give me only per call consumption. I need to find the b/w consumtpion of remote site router for voice calls.

Muhammad Jawwad Habib · ‎10-18-2011

It depends on the usage and number of users on each site. There might be some statistics formula depending on the input but mainly we decide bandwidth on best practices.

ahochau_2 · ‎10-18-2011

You should be able to use NBAR to look at the RTP and RTCP to see what the throughput is. Depending on what protocols and Codecs you are using you could then take the bandwidth consumed and divide it by the bandwidth required per call for the codec. That would tell you how many calls are required for each time sampling. You could also look at your BCHA in CDR. Figure once you know how many calls are going take that times the bandwidth. Decide how much variance you will need and make your adjustments from there.

You could also use your QoS policy to see in a periond how many packets are matched. I've never confiugred this to be automated, but I'm guessing someone could figure it out in a day or two.

There are products from third party vendors that will help you accomplish this as well, I know Solar Winds has a VoIP plugin.

gshrivastava · ‎10-18-2011

Hi Ahochau,

I tried NBAR and captured the data. There is a huge count in unknown protocol. I need to figure out b/w utilization for VOIP calls only. I have totaled byte count of VOIP protocols Skinny and MGCP mentioned there. Is that sufficient or do I need to add some other protocols data as well to get the actual b/w utilization by VOIP calls?

Below is the data that I have collected:

Input Output

----- ------

Protocol Packet Count Packet Count

Byte Count Byte Count

30sec Bit Rate (bps) 30sec Bit Rate (bps)

30sec Max Bit Rate (bps) 30sec Max Bit Rate (bps)

------------------------ ------------------------ ------------------------

skinny 176 306

9148 14976

1000 2000

secure-http 0 55

0 10711

0 1000

rtp 1 177

44 7632

0 1000

http 0 12

0 3854

0 0

0 1000

ssh 26 10

1872 936

0 0

icmp 11 15

968 1434

0 0

mgcp 24 12

1080 700

0 0

winmx 5 2

663 194

0 0

snmp 2 1

540 284

0 0

bgp 4 4

214 206

0 0

syslog 0 2

0 266

0 0

ntp 1 1

100 78

0 0

netbios 0 1

0 95

0 0

unknown 4180 3204

513124 362370

35000 28000

42000 31000

Total 4430 3802

527753 403736

36000 32000

43000 36000

ahochau_2 · ‎10-18-2011

RTP is the actual media stream, MGCP, SCCP, H323 and SIP would be control protocols. That doesn't look like enough traffic for an actual phone call. How may packets is your voice priority queue matching?

gshrivastava · ‎10-18-2011

HI Ahochau,

It might be because I ran NBAR during non-business hours. Now I have cleared the counters on multilink interface and applied NBAR on the same during peak-business hours. After 15 mins I collected the data, which is attached. Please let me know your finding about voice data utilization in those 15 mins and how to do that.

ahochau_2 · ‎10-18-2011

You were using 8MB worth of bandwidth for rtp between when you cleared the counters and took your snap shot. Another 700 KB ish was being used for control traffic. Take your bytes/time and you have your average. The RTP is really what your are interested as the control will be a fraction of that. Since NBAR is polling the right data, you should now be able to graph the traffic over time if one of your applications can read NBAR. I've never configured any of those and don't have time to learn a new application today. I think CACTI can read NBAR as well. A graphing tool will serve you well here.Also use CDR to figure out your BHCA. Take the number of calls in the busiest hour times the bandwidth consumed by the codec with overhead and then add 10% and that should tell you how much bandwidth is required. Compare that to what is being consumed and away you go. But you really want to find a tool to graph the traffic.

gshrivastava · ‎10-19-2011

Hi Ahochau,

I got how you calculated the RTP data usage, but didnt get for control traffic.What specific details I need to add to get for control traffic? Can you tell me that?

ahochau_2 · ‎10-20-2011

RTP is the media stream. RTCP is the control stream for the RTP. H323, SCCP, MGCP and SIP are all for signaling so I lumped them all in the "control" group with RTCP as any of those would be part of your voice bandwidth.