Mt1310 Unit 7 Essay

SIGNALING SYSTEM 7
The hardware and software functions of the SS7 protocol are divided into functional abstractions called “levels”. These levels map loosely to the Open Systems Interconnect (OSI) 7 layer model defined by the international standards organisation .
• Messsage transfer part
• Isdn user part
• Telephone user part
• Signaling connection control part
• Transaction capabilities applications part

SS7 Protocol Stack
The hardware and software functions of the SS7 protocol are divided into functional abstractions called "levels." These levels map loosely to the Open Systems Interconnect (OSI) 7-layer model defined by the International Standards Organization (ISO).
• Message Transfer Part
The Message Transfer Part (MTP) is divided into three levels. The lowest level, MTP Level 1, is equivalent to the OSI Physical Layer. MTP Level 1 defines the physical, electrical and functional characteristics of the digital signalling link. Physical interfaces defined include E-1 (2048 kb/s; 32 64 kb/s channels), DS-1 (1544 kb/s; 24 64kb/s channels), V.35 (64 kb/s), DS-0 (64 kb/s) and DS-0A (56 kb/s).
Level 2 implements flow control, message sequence validation and error checking. When an error occurs on a signalling link, the message (or set of messages) is retransmitted. MTP Level 2 is equivalent to the OSI Data Link Layer.
MTP Level 3 provides message routing between signalling points in the SS7 network. MTP Level 3 reroutes traffic away from failed links and signalling points and controls traffic when congestion occurs. MTP Level 3 is equivalent to the OSI Network