SS7 (Signaling System 7): Advantages and Disadvantages

This page covers the advantages and disadvantages of SS7. It mentions SS7 advantages or benefits and SS7 disadvantages or drawbacks. It also describes SS7 or CCS7 basics.

What is SS7 or CCS7?

Introduction:

• SS7 stands for Signaling System Number 7.
• It uses telephone signaling protocols in the majority of exchanges around the world.
• It creates a smart telephone network that converges normal telephone users, VOIP users, and PSTN users.
• The SS7 network consists of CO or SSP, STP, and SCP as shown in the figure.
• Digital signals on the network exist which are independent from voice circuits.
• One signaling link serves the existence of several voice circuits on the network.
• Suitable for various communication services e.g. telephony, text, data and internationally standardized.
• Supports high signaling data rates viz. 56 Kbps and 64 Kbps

Following are the useful terminologies related to the SS7 network.

• SSP (Signal Switching Point) or CO (Central Office): It functions as an SS7 compliant telephone exchange which performs origination, termination, and switching of calls.
• STP (Signal Transfer Point): They are packet switches of the SS7 network. They perform routing functionalities. It allows exchanges to exchange signaling informations with each other.
• SCP (Signal Control Point): They are databases that take care of advanced call processing features.
• Tandem (Trunk Automatic Exchange): It allows connection between two exchanges not having a direct trunk between them.
• Trunk: The link between two exchanges is known as a trunk.

As depicted in the figure, a typical SS7 network is composed of CO or SSP, STP, SCP, and tandem.

Benefits or Advantages of SS7 | CCS7

Following are the benefits or advantages of SS7 or CCS7:

• It enables better voice circuit utilization.
• Signaling links are always available even during the existing calls.
• One signaling system controls complex messages i.e. several services/features.
• It offers high reliability compared to voice transmission.
• It is possible to route call-independent messages such as SMS, database queries, OAM (Operation and Maintenance) messages, etc.
• Expansion of services does not require replacement of old equipment with newer ones.
• It helps in performing services which include automatic caller ID, call hold, blocking of subscriber numbers, automatic redirect, conference calls, prepaid calls, conversion of telephone numbers, etc.
• It enables high-speed connection setup and transfer of data without any loss or duplication.
• The SS7 network is a link between the circuit-switched network and the IP protocol-based communication network. Hence, a packet-switched network can also be used.
• Unlike CAS (Channel Associated Signaling), there is no interference between signaling tones by the network and the frequency of human speech patterns.

Drawbacks or Disadvantages of SS7 | CCS7

Following are the disadvantages of SS7 or CCS7:

• It uses more complicated switches.
• There is no inherent testing of the speech path by call setup signaling. As a result, it requires explicit call continuity checks or elaborate continuity test procedures are needed.
• It increases cost due to the use of an additional subnetwork.
• The CCS7 (Common Channel Signaling System) should have a very low error rate in order to function as desired.
• CCS links can lead to a single point of failure because in CCS7 a single link can control thousands of voice circuits. As a result, if a single link fails and no alternate routes are found, thousands of calls could be lost.