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Hi all

I was asked the following question recently and thought you might find the answer interesting if you're working with SIGTRAN..

**Help me to
understand the TPS calculation for SMS traffic using SIGTRAN.**

-- How many association/SIGTRAN bandwidth I need for an SMSC of 1000 SMS per
second?

[Steve Madden] You will find the Dialogic SIGTRAN licenses are sold in terms "link equivalents" which means the equivalent amount of throughput of an SS7 TDM link at 60% utilization (e.g. high TDM link utilization).

Throughput of 1 SIGTRAN "link equivalent"
= **(total throughput of 1 x 64kbps SS7 TDM signaling link)** x **(60%
utilization)**

Where (**60%
utilization)
**= **0.6** Erlang where the
Erlang "is used to describe the total traffic volume of one hour"

see http://www.erlang.com/whatis.html#erlang

Where **(total throughput of
1 x 64kbps SS7 TDM signaling link)** = (throughput of incoming
direction + throughput of outgoing direction)

= (8000 + 8000) Bps

= **16000** Bps

Hence throughput of 1 SIGTRAN "link
equivalent"
= **16000** x **0.6**

**= 9600 Bps**

** **

For 1000 SMS/s I'll use the assumptions from the earlier Forum post "How to do the Dimensioning of SMS" located here..

http://www.dialogic.com/den/forums/t/3323.aspx

"A short SMS such as 'hello' will generate approx 100bytes of data on a signaling link (with an acknowledgement message of approx 75 bytes.)"

[Steve] Note the throughput of 1 SIGTRAN "link equivalent" is the complete throughput available in either direction.

So 1 SMS needs approx 175 Bytes of data - perhaps we could round this up to 200 Bytes of data to take into account slightly larger average text message size..

Number of SMS per SIGTRAN "link equivalent" = **9600
Bps / 200
= 48 SMS /s**

** **How many SIGTRAN "link equivalent" for 1000 SMS/ s?
= 1000 / 48

=
**approx 21 SIGTRAN "link equivalent"**

In terms of our licensing this could be handled by the 32 SIGTRAN "link equivalent" M3UA license. This license would give spare bandwidth to handle increases in SMS traffic flow.

Note, the Dialogic SIGTRAN licensing mechanism also supports the ability to handle spikes in traffic throughput - up to double the licensed amount of throughput for up to 30 secs, before any traffic throttling kicks in.

Kind regards

Steve Madden