What are the abbreviations of SSP, MTP and NRZ in network knowledge?

No.7 signaling

No.7 signaling: also known as common channel signaling. That is, a signaling mode that transmits a group of session signaling on a high-speed data link in a time-division manner, which is usually used between offices.

The No.7 signaling system used in China is called China No.7 signaling system. Signaling Network No.7 is an out-of-band data communication network, which is superimposed on the operator's switching network and is an important part of the support network. Complete local, long-distance and international automatic and semi-automatic telephone connections between fixed telephone networks or ISDN networks; Providing local, long-distance and international telephone call services between switches in the mobile network, as well as related mobile services, such as short messages; Providing intelligent network services and other value-added services for fixed networks and mobile networks; Provide transmission and collection of operation management and maintenance information.

Signaling network No.7 is roughly composed of the following parts: the signaling point is the node that processes control messages in SS7 signaling network, the signaling point that generates messages is the source signaling point of messages, and the signaling point that receives messages is the destination signaling point of messages. There are three types of signaling points:

1. Service switching point (SSP) A service switching point is the origin or termination point of signaling messages, which is essentially a local switching system (or switching center CO), and it initiates or receives incoming calls.

2. The signal transmission point (STP) completes the function of the router, looks at the messages sent by SSP, and then switches each message to the appropriate place through the network. STP connects other signaling points with the network to form a larger network.

3. The service control point (SCP) is a typical server to access the database. SCP is the control center of intelligent network service, which is responsible for executing service logic, providing call processing function, receiving query information and database sent by SSP, sending call processing instructions to SSP after verification, receiving call list generated by SSP and processing accordingly.

In No.7 signaling network, ISUP signaling (ISDN user part) messages are used to establish voice relay circuits between voice exchanges in the management release central office, and provide information exchange required by voice and non-voice services to support basic bearer services and supplementary services. For example, ISUP signaling messages can carry calling ID, calling party phone number, user name, etc. TCAP signaling (transaction capability application part) messages are used to support telephone services, such as toll-free calls, local number portability, card services, mobile roaming and authentication services. TCAP mainly includes mobile application part (map) and operation and maintenance management part (OMAP). MAP provides programs such as roaming and channel switching in mobile services, while OMAP only provides formal testing programs for MTP routing and SCCP routing.

Message transfer part of MTP message transfer part

Information Transmission Part (MTP) is a SS7/C7 protocol, which is mainly used to transmit signaling information and perform related functions, such as error control and signaling link security. In addition, MTP also supports reliable network routing. MTP consists of two parts: MTP Layer 2 (MTP2) and MTP Layer 3 (MTP3), and their functions correspond to Layer 2 and Layer 3 of OSI 7 reference model respectively.

Layer 2 of information transmission part is located at Layer 2 of SS7 protocol stack. It is mainly responsible for the reliable transmission of signaling units on a single signaling link, and realizes the reliability of MTP2 through retransmission technology.

Layer 3 of information transmission part is the network layer in SS7 protocol stack. MTP3 sends SS7 signaling information to public network nodes through destination code, and sends information to appropriate signaling entities through eight-bit service information. As one of SS7 protocols, MTP3 is also considered as a part of ATM B-ICI interface. In SS7 protocol stack, MTP3 is located between MTP2 and user parts (ISUP, TUP, SCCP and TCAP). Among them, B-ISUP is an application layer protocol running on MTP3.

MTP3 is divided into two parts: SMH (signaling message processing) and SNM (signaling network management). SNM is mainly responsible for the management of MTP; SHM mainly deals with the identification, distribution and routing of signaling information. The function and process of signaling system are defined in MTP3, which is used for signaling information processing and signaling network management. The signaling information processing part includes the actual transmission of signaling information and the process of transmitting guiding information to the correct signaling link or user part; The signaling network management part includes controlling the routing process of signaling information and the configuration of signaling network functions, wherein the configuration is based on predetermined information and the status of signaling network functions.

MTP3 provides a connectionless information transmission system for transmitting information on the network. MTP3 has many link protection features to support the automatic rerouting function of signaling information at fault signaling transmission points. MTP3 also includes some management functions, such as congestion control on signaling links.

M2UA: User Adaptation Layer (M2UA) is a protocol for accessing MTP2 functional services through stream control transmission protocol (SCTP). MTP3 User Adaptation Layer (M3UA) is a protocol that supports the transmission of any SS7 MTP3 user signaling (such as ISUP, SCCP and TUP information) on the IP network.

nonreturn to zero code

Non-return-to-zero system (NRZ) is a data stream in which a continuous data pulse "1" lasts for several clock pulses without returning to a "0" state.

Non-return-to-zero code (NRZ) is a signal that maintains a constant voltage level when there is no signal transition (no return to zero voltage level) in a bit interval.