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

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Dialogic SS7 and SIGTRAN Signalling

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

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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

     

  • Hi Steve!

    Trust  u are doing good.

    I have been working on SMSC and USSD gateways for quite a while and as per my experience, your throughput calulations are a bit on higher side as you probably have not considered SRI Query requried for delivering a SMS.

    I have tried to summarize the complete calculation for SMS per second over LSL and SIGTRAN, would request you to validate the same.

    Also, i have 2 queries regarding SIGTRAN; would appreciate if you could answer those:

    1. I have read somewhere that MSU size over network in SIGTRAN is 1.5 times that of normal SS7 over TDM considering SCTP / M3UA headers to be larger in size. Do you have any information on this? If yes, then would it impact SIGTRAN throughput calculation
    2. How much bandwidth in terms of Kbps should i ask for a SIGTRAN association equivalent to 1 LSL? Would it be 64kbps or something else?

    Looking for your resposne.

    AP Singh

     

      SS7 - LSL
     (at 40% utilization)
    SS7 - SIGTRAN
    (at 60% utilization)
    Capacity per link (bits per second each side) 64000 64000
    Capacity per link (bytes per second each side) 8000 8000
    Idealy usable Capacity  3200 4800
         
    MT SMSC  
         
    TX    
    SRI Request(bytes) 75 75
    Fwd MT Req(bytes - considering 140 bytes of SMS text) 250 250
    Total Tx Bytes (per MDA)  325 325
    Throughput TX (MDA per second) 10 15
    RX    
    SRI Response(bytes) 80 80
    Fwd MT Response(bytes) 75 75
    Total Rx Bytes (per MDA)  155 155
    Throughput RX ( MDA per second) 21 31
         
    As, Throuhgput TX < Throughput RX ;
    so Througput for (MDA per second / SMS per second)
    10 15

     

     

  • Hi Steve, Waiting for your response on this. Incase Steve is not available, request anybody from Dialogic team to comment. Regards
  • Hi

    1.     I have read somewhere that MSU size over network in SIGTRAN is 1.5 times that of normal SS7 over TDM considering SCTP / M3UA headers to be larger in size. Do you have any information on this? If yes, then would it impact SIGTRAN throughput calculation

    Throughput calculation of Dialogic Sigtran license model is based on the payload content of the protocol binaries and not the headers.

    2.    How much bandwidth in terms of Kbps should i ask for a SIGTRAN association equivalent to 1 LSL? Would it be 64kbps or something else?

    If comparing to a TDM, the Sigtran association assumes 60% of bandwidth occupancy ( compared to 40% TDM ), so 64kbps seems logical as shown in Steve's calculation above.

    Ukernie

  • Hi Amrit

    Many thanks for the figures you've quoted to give a more accurate view of SMS throughput over TDM And SIGTRAN networks   - It's excellent to have expert feedback!

    To your questions..

    Also, i have 2 queries regarding SIGTRAN; would appreciate if you could answer those:

    1. I have read somewhere that MSU size over network in SIGTRAN is 1.5 times that of normal SS7 over TDM considering SCTP / M3UA headers to be larger in size. Do you have any information on this? If yes, then would it impact SIGTRAN throughput calculation

    [Steve Madden]       The Dialogic SIGTRAN stack looks at the signaling payload only of each SIGTRAN message and so IP and SCTP data is not counted in the licensing mechanism.  Here is some information from earlier release notes to give some more detail on this..

    Throughput is calculated using the payload content of the API_MSG_TX_REQ message (sent towards the network) and the payload content (ie. PROTOCOL_Data – 4 octets) of the SCTP_MSG_RX_IND message (received from the network).

    For licensing purposes the sum of the TX and RX direction will be used. Other parameters or messages not listed above will not count towards the totals. For management and monitoring purposes individual sums of TX and RX will be maintained.

     

    1. How much bandwidth in terms of Kbps should i ask for a SIGTRAN association equivalent to 1 LSL? Would it be 64kbps or something else?

    [Steve Madden]      I checked some PCAP traces of SIGTRAN systems to understand the size of the IP and SCTP elements of each SIGTRAN message.  From those traces approximately 60 Bytes should be added to each message to account for IP, SCTP and partial M3UA elements not included in the throughtput calculation detailed above.

    My apologies for the delayed response!

    Kind regards

    Steve

     

  • Hi Steve!

    Thanks for clarification.

    I shall re-calculate SIGTRAN Bandwidth requirement considering your inputs and publish for wider audience's usage.

    Regards,

    Amritpal Singh

  • Hi,

     

    How many sms can sent in 1 LSL & sigtran

    LSL BW = 64kb/s

    1 msg means = 160 charactor

    Kindly help how many can sent per second

     

  • Hi Merinekc,

    I'm not sure I understand your question. 

    I can confirm that a LSL is 64KB/s in each direction. I can also confirm that for our SIGTRAN protocol license the 'Link Equivalent' Bandwidth provided is 76.8KB/s but this can be used for either TX or RX traffic (the response to an SMS is much shorter than the request so this is important).

    When sending an SMS it is important to know whether you are sending a Send Routing Info For Short Message request as well as the Forward Short Message as this will require additional bandwidth.

    Regards