Elements of SS7
--> SSP : Signal System Point
--> STP : Signal Transfer Point
--> SCP : Signal Control Point
Signal Switching Point
SSP is the local exchange in the telephone network.
Convert signaling from the voice switch into SS7 signalling messages
Perform database access by sending database queries to computer systems located centrally to the network.
Signal Transfer Point
STP serves as a router in the SS7 network.
Switches SS7 messages received from various SSPs.
Used for traffic measurement and usage measurements.
Signal Control point
Serves as an interface to telephone company databases.
Performs protocol conversion from SS7 to X.25
It maintains databases of various applications like
Call management services database.
Line information database
Business service database
Links
Associated Link(A): Link between SSP and STP/SCP.
Bridge Link(B) : Link between two different networks.
C Link : Links that connects the mated STPs
Diagonal Link(D) : Interconnecting two mated Pair of STPs.
Extended Link(E) : SSP of one network to STP of another network.
Fully Associated Link(F) : Directly connect two signallin end points.
Signalling Units pass through the Signalling Link
There are three types of Signalling Units
1) Fill in signal units (FISUs)
2) Link status signal units(LSSUs)
3) Messages signal units(MSUs)
FISUs :
Their purpose is to occupy the link at those times when there are no LSSUs or MSUs to send.
They undergo error checking.
Constant monitoring of link quality in the absence signalling traffic.
LSSUs :
Communicate information between the nodes on either end of the link LSSUs are used primarily to
Signal the initiation of link alignment
The quality of received signalling traffic and the status of the processors at either end of the link.
MSUs:
All signalling associated with call setup and tear down
Database query and response
SS7 Networking Management
MSUs are the basic envelope within which all addressed signalling information is placed.
Signalling System No. 7
SS7 meets rapid convergence of voice and data.
Growth of VOD, especially VOIP.
High volume.
Efficiency :
Out of band links at 64kbps
Shorter information transfer time
Ability to fall back to the originating end of the call
Service enabling :
Free phone services such as 1800 numbers
Automatic call back and calling number delivery
Automatic calling card services
Wireless services such as roaming
Network reliability :
Carries extensive network management messages
Network architecture
Security
SS7 Protocols :
MTP ( Message Transfer Part ) Level 1 :
MTP Level is known as the signalling data link.
MTP ( Message Transfer Part ) Level 2 :
The MTP Level 2 together with MTP Level 1, provides signalling link for reliable transfer of signalling messages between two directly connected signalling points.
This Layer ensures that messages are sent point to point error free and in sequence.
MTP ( Message Transfer Part ) Level 3 :
MTP Level 3 provides the functions and procedures related to messages routing and network management.
This layer takes control of
routing messages between various signalling points in the network,
Load sharing,
route failure management.
SCCP :
SCCP provides enhancements to the MTP Level 3 to provide connection less and connection-oriented network services as well as to address translation capabilities.
SCCP is used as the transport layer for TCAP based services such as freephone (800/888), Calling card, Wireless roaming and personel communications services(PCS).
Window for external applications to interact with the network.
Signalling Connection Control Part (SCCP), a routing protocol in SS7 protocol suite in layer 4 end to end routing for TCAP messages to their proper database.
--> SSP : Signal System Point
--> STP : Signal Transfer Point
--> SCP : Signal Control Point
Signal Switching Point
SSP is the local exchange in the telephone network.
Convert signaling from the voice switch into SS7 signalling messages
Perform database access by sending database queries to computer systems located centrally to the network.
Signal Transfer Point
STP serves as a router in the SS7 network.
Switches SS7 messages received from various SSPs.
Used for traffic measurement and usage measurements.
Signal Control point
Serves as an interface to telephone company databases.
Performs protocol conversion from SS7 to X.25
It maintains databases of various applications like
Call management services database.
Line information database
Business service database
Links
Associated Link(A): Link between SSP and STP/SCP.
Bridge Link(B) : Link between two different networks.
C Link : Links that connects the mated STPs
Diagonal Link(D) : Interconnecting two mated Pair of STPs.
Extended Link(E) : SSP of one network to STP of another network.
Fully Associated Link(F) : Directly connect two signallin end points.
Signalling Units pass through the Signalling Link
There are three types of Signalling Units
1) Fill in signal units (FISUs)
2) Link status signal units(LSSUs)
3) Messages signal units(MSUs)
FISUs :
Their purpose is to occupy the link at those times when there are no LSSUs or MSUs to send.
They undergo error checking.
Constant monitoring of link quality in the absence signalling traffic.
LSSUs :
Communicate information between the nodes on either end of the link LSSUs are used primarily to
Signal the initiation of link alignment
The quality of received signalling traffic and the status of the processors at either end of the link.
MSUs:
All signalling associated with call setup and tear down
Database query and response
SS7 Networking Management
MSUs are the basic envelope within which all addressed signalling information is placed.
Signalling System No. 7
SS7 meets rapid convergence of voice and data.
Growth of VOD, especially VOIP.
High volume.
Efficiency :
Out of band links at 64kbps
Shorter information transfer time
Ability to fall back to the originating end of the call
Service enabling :
Free phone services such as 1800 numbers
Automatic call back and calling number delivery
Automatic calling card services
Wireless services such as roaming
Network reliability :
Carries extensive network management messages
Network architecture
Security
SS7 Protocols :
MTP ( Message Transfer Part ) Level 1 :
MTP Level is known as the signalling data link.
MTP ( Message Transfer Part ) Level 2 :
The MTP Level 2 together with MTP Level 1, provides signalling link for reliable transfer of signalling messages between two directly connected signalling points.
This Layer ensures that messages are sent point to point error free and in sequence.
MTP ( Message Transfer Part ) Level 3 :
MTP Level 3 provides the functions and procedures related to messages routing and network management.
This layer takes control of
routing messages between various signalling points in the network,
Load sharing,
route failure management.
SCCP :
SCCP provides enhancements to the MTP Level 3 to provide connection less and connection-oriented network services as well as to address translation capabilities.
SCCP is used as the transport layer for TCAP based services such as freephone (800/888), Calling card, Wireless roaming and personel communications services(PCS).
Window for external applications to interact with the network.
Signalling Connection Control Part (SCCP), a routing protocol in SS7 protocol suite in layer 4 end to end routing for TCAP messages to their proper database.
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