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Can any one explain me how sms flow will work using ss7 network ?( from physical layer to application layer)
mullaguriswetha 15-October-2007 06:38:12 PM


Using these IP-based standards, devices such as personal computers can inter-operate ... 13 and 14 depict two flow charts of the various operations involved in an ..... An SS7 application 614 is also shown as part of the protocol stack of the node 502A. ... An IP-capable physical layer 606B is also included.
Posted by waqasahmad

Posted by crouse

In wireless infrastructure that supports SMS is based on the signalling system no. 7 (SS7) transactional capabilities application part (TCAP).

At application level MAP (mobile application part) layer is used, using the services of SS7 TCAP for SMS.
Posted by shalinig

Dear meetvetri and milo,
Thanks for your response


Posted by mullaguriswetha

Answer for Physical layer to Application Layer

It is OSI standard model.
MTP1 is physical, as in the wire or fiber between the network entities or nodes.
MTP2 is communication integrity, checksums and the like (FIB, BIB, etc.)
MTP3 is where the Telephone junk starts. Point codes (OPC, DPC), redundancy routes (route costing), congestion controls (priority bits), that sort of thing.
SCCP is the application layer that identifies the message flow (RI, NPI, NAI, GT Addresses ). This is the upper level, where the SMS magic happens.
Simply put, no.
SMS traffic is GT based, and must be signaled as such, in order to ensure delivery. It IS possible to signal without GT, but failure is the likely outcome.
The SCCP portion contains a field called the Routing Indicator (RI), and if this field is set wrong, or it is sent to an entity that does not support the RI setting, it will fail, for sure. The RI can be set to GT, for routing between networks, and DPC/SSN for routing to nodes.
Posted by milo

SMS Call Flow

1) SMS Flow (can apply for both prepaid/post paid)

MSC=switch (of the specific carrier)
SMSC=short message service centre of the given carrier
HLR=Home Location Register (used to manage MSC location of subscriber)

When the MS sends a message.. this is called a mobile originated message or MO for short. Delivery of a message is called Mobile Terminated..MT

Submission of message: (MO message.. "store")
MS --> MSC --> SMSC (MO message)
<-- MSC <-- SMSC (Response to indicate success/failure)

Delivery of message: (MT message "forward")
SMSC --> HLR (lookup of destination MSISDN/MDN)
<-- HLR (response contains IMSI or MIN & address of MSC)

SMSC --> MSC (delivery attempt using resolved IMSI/MIN and to MSC
indicated in HLR response)
<-- MSC

The whole messaging in SMS operates over the air interface but specifically uses SS7.. a specialised signalling network common in telecommunications. Given that SMS messages are small, there is no need to use a data channel to send the message.. instead the traffic channel, normally used to manage cell handover and other admin functions is used to allow SMS messages to be sent over it... so a phone user can be on a call while sending or receiving a message.

referring to above.. any MO message will route through the MSC of the current network (and roaming network) and onto the subscribers home SMSC (even if he is roaming.. the messages always go to his native SMSC)

The SMSC then carries out a 2-stage delivery of the message.. the first is the HLR lookup whch serves two purposes.. one to resolve the directory number of the destination mobile into a MIN or IMSI (IMSI International Mobile Subscriber Identifier is always used for GSM.. ANSI (CDMA/TDMA) use MIN with some networks possibly using IMSIs). The second function is to obtain a switch address for the destination mobile.. this tells us where the subscriber is.

The second delivery stage is the actual delivery itself which addresses the message to the IMSI or MIN and routes it to the MSC address as obtained from the HLR.. this will either succeed or fail depending on coverage and other possible fail scenarios.

If the attempt fails.. then the SMSC will retry again later on or when it receives a network alert from the mobile (routed by the HLR and/or MSC), it can immediately retry the message and get it delivered.

Prepaid operates on the exact same model with the exception that the MO MSC stage or SMSC MO and/or MT stages will perform credit adjustments rejecting the message if no credit is available

For socket programming.. try google and search for that..
Posted by milo

In SS& network there is no Physical to Application layer.
But the Analogy is same in SS7.The layers in SS7 are MTP Layer-1.MTP-Layer-2,MTP-Layer-3
SCCP layer,TCAP layer,ISUP or INAP or MAP layers(simelar to application layer in OSI).
And More over Regarding SMS,
----->SDP----->SCP----->SMSC(short Messeage Service Centre)---->destination mobile terminal.

This is General flow.
MSC-Mobile switching centre
SCp-Service control point
SDP-Service data point

With regards

Posted by meetvetri

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