The Signalling System 7 (SS7) protocol stack is a group of signalling standards that enable the various components of the PSTN to talk to one another. It's essential because it allows for more complex services like call forwarding, caller ID, and messaging to function amongst various telecommunications networks.
Originally created in the 1970s, the SS7 Protocol stack has
become integral to today's sophisticated communication systems. In this article, we'll take a look at the SS7 Protocol stack as a whole and discuss its components and major advantages of SS7 Protocol.
Table of Content:
Overview of SS7 Protocol Stack
How the SS7 protocol works
Signalling network
Message transfer
Call setup
Call teardown
Components of SS7 protocol
Signalling points
Signal transfer points
Service control points
Signalling transfer points
Signalling link
Advantages of SS7 protocol
Faster call setup
More reliable than traditional signaling methods
Supports advanced features
Increased security and fraud protection
SecGen: Your Trusted Partner in Ensuring Secure Telecom Networks
How does the SS7 protocol work?
The Signalling System 7 (SS7) protocol allows for the establishment of a signalling network, which in turn allows for the establishment of communication between various network parts in the PSTN. The network's ability to set up and disconnect calls, forward calls, and display caller ID are all made possible via digital signalling.
Signaling network: Three types of nodes make up the SS7 protocol's signalling network: signalling points (SPs), signal transfer points (STPs), and service control points (SCPs).
An SP is a device that creates or deletes a signalling packet, while an STP is a device that sends and receives packets between SPs. To manage more complex services like call forwarding and call filtering, SCPs are used.
Separate from the voice network, both physically and logically, is the SS7 protocol signalling network. The network's dependability and throughput are both improved by this partitioning, as signalling messages will no longer interfere with voice traffic.
Message transfer: A packet-switched network is used to carry SS7 protocol messages. For easier transmission between SPs and STPs, each message is divided into many packets. When two nodes employ the SS7 protocol stack, they establish a connection before exchanging data.
Any time an SP starts a signalling exchange, it will forward the message to the closest STP. According to the message's contents, the STP sends it to its intended recipient. It might be another SP, an SCP, or an STP.
Call setup: Setting up a call relies heavily on the SS7 protocol. When a user makes a call, signalling messages are sent from the calling subscriber's SP to the calling service provider's SP via the SS7 protocol. Call details such as phone number dialled, calling party number, and service type are conveyed in the signalling messages.
To convey the called party's number to the receiving SP, the calling SP uses the SS7 protocol. If the call can be completed, the terminating SP will utilize the SS7 protocol to inform the originating SP; otherwise, it will return an error message.
To connect the calling party's SP to the called party's SP, the SS7 protocol is utilized if the call can be completed. Voice data can be sent over that line when a connection is made.
Call teardown: When the call is complete, the SS7 protocol tears down the connection between the originating and terminating SPs. The SS7 protocol is also used to transmit billing information and to update network databases with call records.
Components of SS7 protocol
Multiple parts of the Signalling System 7 (SS7) protocol create a signalling network between various PSTN network nodes. The numerous aspects of a signalling system are denoted by their respective abbreviations: SPs (signal points), STPs (signal transfers), SCPs (service control points), SCTPs (signalling links).
Signaling points: Signalling nodes are nodes in a network that either start or stop the transmission of signals. SPs are any network nodes part of the SS7 protocol's signalling infrastructure, including switches and routers. Each SP is assigned a unique point code to send and receive signaling messages.
Signal transfer points: The function of signal transfer points in a network is to forward signalling packets from one SP to another. STPs are responsible for delivering messages to their intended recipients by determining their final destination based on the destination point code included in the message. Screening and filtering capabilities are another security feature offered by STPs.
Service control points: Network nodes known as service control points allow for more nuanced management of services including call routing, caller ID, and messaging. Information used to perform services, including service logic and database data, is stored in SCPs.
Calls are routed appropriately after being routed through the SCP, which uses service logic and database information to make that determination.
Signaling transfer points: Network nodes called "signalling transfer points" connect SS7 with other signalling protocols. SCTPs allow for interoperability between various telecommunications networks by facilitating communication between signalling protocols.
Signaling links: Connecting nodes in the SS7 protocol signalling network are signalling linkages. Between SPs and STPs, signalling messages are transmitted via signalling links. Depending on the parameters of the network, the signalling links could be T1/E1 lines or high-speed data links.
Advantages of SS7 protocol
The Signalling System 7 (SS7) protocol is superior to older signaling techniques. Some significant benefits of the SS7 protocol are as follows:
Faster call setup: The SS7 protocol allows quicker call setup, a crucial benefit. Signalling channels used by the SS7 protocol are isolated from the audio channels used for phone calls. With faster signalling messages going both ways, calling can be initiated in less time.
More reliable than traditional signaling methods: The SS7 protocol is more trustworthy than previous signalling systems. Typically, signalling messages in older systems were transmitted along with voice data. Call quality may suffer due to delays, dropped calls, and other problems. The SS7 protocol uses independent signalling channels to expeditiously and reliably transmit signalling messages.
Supports advanced features:
The SS7 protocol allows for additional previously unavailable capabilities with older signalling techniques. The SS7 protocol, for instance, allows for sophisticated call routing features like rerouting calls based on caller ID, time of day, and other parameters. Call forwarding, call waiting, and conference calling are all possible with the SS7 protocol.
Increased security and fraud protection: Telecom networks are more protected from fraud thanks to the SS7 protocol. The SS7 protocol employs sophisticated authentication and encryption methods to avoid hacking and network intrusion.
Call screening and filtering tools are also supported, which might be useful for preventing the network from being used to make fraudulent phone calls.
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