Signaling Control Banwidth

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Oct 14th, 2008
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Hi,

consider the scenario:

I have centralized deployment.I have branch site which will make a call in ratio of 2:1 (if there is 2 phones one will be active ONcall).

I want to know

1.what will be the Bandwidth required for SCCP registration on CCM for single IP Phone

2.What will the bandwidth requirement for Keepalive messages between branch and data centre for single IP Phone with MGCP as wellas H323

3.Will there be any other thing utilizes the bandwidth if so what are they?


Thanks,

Hari

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esa786_2 Tue, 10/14/2008 - 22:42
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hi. This is information for bandwidth for ip phone per call



if it is G.729, 8 kbps plus 16 for header so total 24kbps.

If G.711 is used, then reserve 80 Kbps of bandwidth( 64+16 (header)

Note: RTP assumes 40-octets RTP/UDP/IP overhead per packet

Compressed RTP (cRTP) assumes 4-octets RTP/UDP/IP overhead per packet

Ethernet overhead adds 18-octets per packet

PPP/Frame Relay overhead adds 6-octets per packet


I have attached the the calculation aswell.

The link will be useful for you aswell

http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a0080094ae2.shtml

Rate is if it useful

regards

Esa





allan.thomas Tue, 10/14/2008 - 22:57
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The question is specifically regarding the amount on signalling bandwidth required not the amount of bandwidth required for either G.711 or G.729 Calls.


The recommended bandwidth needed for call control traffic can be obtained from the following formula:


Equation 1A: Recommended Bandwidth Needed for SCCP Control Traffic without Signaling Encryption.


Bandwidth (bps) = 265 * (Number of IP phones and gateways in the branch)


Equation 1B: Recommended Bandwidth Needed for SIP Control Traffic without Signaling Encryption.


Bandwidth (bps) = 538 * (Number of IP phones and gateways in the branch)


If a site features a mix of SCCP and SIP endpoints, the two equations above should be employed separately for the quantity of each type of phone used, and the results added.


Equation 1 and all other formulas within this section include a 25% over-provisioning factor. Control traffic has a bursty nature, with peaks of high activity followed by periods of low activity. For this reason, assigning just the minimum bandwidth required to a control traffic queue can result in undesired effects such as buffering delays and, potentially, packet drops during periods of high activity. The default queue depth for a Class-Based Weighted Fair Queuing (CBWFQ) queue in Cisco IOS equals 64 packets. The bandwidth assigned to this queue determines its servicing rate. Assuming that the bandwidth configured is the average bandwidth consumed by this type of traffic, it is clear that, during the periods of high activity, the servicing rate will not be sufficient to "drain" all the incoming packets out of the queue, thus causing them to be buffered. Note that, if the 64-packet limit is reached, any subsequent packets are either assigned to the best-effort queue or are dropped. It is therefore advisable to introduce this 25% over-provisioning factor to absorb and smooth the variations in the traffic pattern and to minimize the risk of a temporary buffer overrun. This is equivalent to increasing the servicing rate of the queue.


If encryption is configured, the recommended bandwidth is affected because encryption increases the size of signaling packets exchanged between Unified CM and the endpoints. The following formula takes into account the impact of signaling encryption:


Equation 2A: Recommended Bandwidth Needed for SCCP Control Traffic with Signaling Encryption.


Bandwidth with signaling encryption (bps) = 415 * (Number of IP phones and gateways in the branch)


Equation 2B: Recommended Bandwidth Needed for SIP Control Traffic with Signaling Encryption.


Bandwidth with signaling encryption (bps) = 619 * (Number of IP phones and gateways in the branch)


This information was taken from the SRND 6.x as refered to in an earlier post which may require CCO login.

Branch Office Size (Number of IP Phones and Gateways) Recommended Bandwidth for SCCP Control Traffic (no encryption) Recommended Bandwidth for SCCP Control Traffic (with encryption) Recommended Bandwidth for SIP Control Traffic (no encryption) Recommended Bandwidth for SIP Control Traffic (with encryption)


One word advice you need to cautious when you are configuring shared-lines and broadcast hunt-group in remote office with centralised CUCM.


The reason is that this will considerably increase your voice signalling requirements. For example you have a broadcast hunt-group of 10 phones, these 10 phones will be signalled simulateously, the same applies to shared lines.


Rgds

Allan.

Sharif Alkatib Mon, 03/20/2017 - 12:13
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Here is a screenshot from the latest 11.x SRND document showing how much bandwidth SCCP and SIP uses for call control.

Here are two equations to calculate bandwidth:

Equation 1A: Recommended Bandwidth Needed for SCCP Control Traffic without Signaling Encryption. Bandwidth (bps) = 265 ∗ (Number of IP phones and gateways in the branch)

Equation 1B: Recommended Bandwidth Needed for SIP Control Traffic without Signaling Encryption. Bandwidth (bps) = 538 ∗ (Number of IP phones and gateways in the branch)


150 phones on SCCP is 40 kbps and 150 phones on SIP is 81 kbps. Super tiny amounts that are practically negligible in bandwidth calculations today as these are kilo - BITS not BYTES.

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