SS7

Question 2

SS7 Protocol Stack

Answer 2

ISUP | TCAP

ISUP | SCCP

MTP3 (Network)

MTP2 (Data Link)

MTP1 (Physical)

Question 3

Three signaling points in the SS7 network.

Answer 3

• SSP (Service Switching Point)
• STP (Signaling Transfer Point)
• SCP (Service Control Point)

Question 4

SS7 Basic Call Setup Messages

Answer 4

• IAM (Initial Address Message)
• ACM (Address Complete Message)
• ANM (Answer Message)

Question 5

SS7 Signaling Units (SU)

Answer 5

• MSU (Message Signal Units)
• LSSU (Link Status Signal Units)
• FISU (Fill-in Signal Units)

Question 6

SCCP

Answer 6

• Signaling Connection Control Part
• Routes using point code and subsystem number or a global title.

Question 7

SSN

Answer 7

• Subsystem Number
• Addresses a specific application on a node
• SSNs are one octet in length

Question 8

MTP

Answer 8

• Message Transfer Part
• Reliably transfers messages over the links in a linkset.

Question 9

ISUP

Answer 9

• ISDN User Part
• ISUP addresses a switch at the other end of its trunk connections using a DPC

Question 10

GTT

Answer 10

• Global Title Translations

• The Global Title Translation provides the SSN of the database and point code of the SCP that interfaces that database application.

Question 11

A Link

Answer 11

• Access link
• Connects a signaling end point (e.g. an SCP or SSP) to an STP

Question 12

B Link

Answer 12

• Bridge link
• Connects an STP to another STP
• Distinction between “B” links and “D” links are rather arbitrary

Question 13

C Link

Answer 13

• Cross link
• Connect STPs performing identical functions into a mated pair
• Normally only used due to link failure(s)

Question 14

D Link

Answer 14

• Diagonal link
• Connects a secondary (e.g. Local or regional) STP pair to a primary (e.g. inter-network gateway) STP pair in a quad-link configuration
• Distinction between “B” links and “D” links are rather arbitrary

Question 15

E Link

Answer 15

• Extended link
• Connects an SSP to an alternate STP in case the “home” STP cannot be reached via an “A” link
• “E” links are not usually provisioned unless the benefit of a marginally higher degree of reliability justifies the added expense

Question 16

F Link

Answer 16

• Fully Associated Link
• Connects two signaling end points (i.e., SSPs and SCPs)
• “F” links are not usually used in networks with STPs