Types of switching technology
Port switching
Port switching technology first appeared in slot-type hubs. The backplane of this type of hub is usually divided into multiple Ethernets. Network segment (each network segment is a broadcast domain), without bridge or routing connection, the networks are not connected to each other. After the large main module is inserted, it is usually allocated to a network segment of a backplane. Port switching is used to distribute and balance the ports of the Ethernet module among multiple network segments of the backplane; according to the degree of support, port switching It can also be subdivided into:
·Module exchange: The entire module is migrated to the network segment.
·Port group exchange: Usually the ports on the module are divided into several groups, and each group of ports allows network segment migration.
·Port-level switching: support each port to migrate between different network segments. This kind of switching technology is based on the first layer of OSI, and has the advantages of flexibility and load balancing capabilities; if configured properly, it can also perform customer errors to a certain extent, but it does not change the characteristics of the shared transmission medium. It can be called a real exchange.
Frame switching
Frame switching is currently the most widely used LAN switching technology. It provides a parallel transmission mechanism through micro-segmentation of traditional transmission media to reduce conflict areas. Obtain high bandwidth. Generally speaking, the implementation technology of each company’s products will be different, but the processing methods for network frames are generally as follows: The first 14 bytes of the network frame will transmit the network frame to the corresponding port.
·Store and forward: Check and control errors by reading network frames.
The exchange speed of the former method is very fast, but it lacks more advanced control of network frames, lacks intelligence and security, and cannot support the exchange of ports with different speeds. Therefore, various manufacturers focus on the latter technology.
Some manufacturers even decompose the network frame and divide the frame into fixed-size cells. The cell processing is extremely easy to implement with hardware, and the processing speed is fast. At the same time, it can complete advanced control functions (such as the United States). MADGE's LET hub) such as priority control.
Cell exchange
ATM technology represents the future direction of the development of network and communication technology, and is also a "good medicine" to solve many problems in current network communication. ATM uses a fixed length of 53 Cell exchange of bytes. Since the length is fixed, it is easy to implement in hardware. ATM uses dedicated non-differentiated connections and runs in parallel. Multiple nodes can be established at the same time through a switch, but it will not affect the communication capabilities between each node. ATM also allows multiple virtual links to be established between the source node and the target node to ensure sufficient bandwidth and fault tolerance. ATM uses statistical time-division circuits for multiplexing, which can greatly improve channel utilization. The bandwidth of ATM can reach 25M, 155M, 622M and even several Gb transmission capacity.
Switching technology function
Media gateway access function
The media gateway function is an endpoint/network connected to the IP network A relay or a collection of several endpoints, it is an interface device between a packet network and an external network, and provides the function of media stream mapping or transcoding. For example, PSTN/ISDN IP relay media gateway, ATM media gateway, user media gateway and integrated access gateway, etc., support MGCP protocol and H.1248/MEGACO protocol to realize resource control, media processing control, signal and event processing, and connection Various complex functions such as management, maintenance management, transmission and security.
Call control and processing function
Call control and processing function is one of the important functions of softswitch, which can be said to be the soul of the entire network. It can provide control functions for the establishment, hold and release of basic service/multimedia service calls, including call processing, connection control, intelligent call trigger detection, and resource control. Supports basic two-party call control functions and multi-party call control functions. Multi-party call control functions include special logic relationships for multi-party calls, and call members' joining/exiting/isolation/auditing, etc.
Service provision function
In the process of network evolution from circuit switching to packet switching, softswitch must be able to realize all that PSTN/ISDN switches provide Services, including basic services and supplementary services, should also cooperate with existing intelligent networks to provide intelligent network services, or cooperate with third parties to provide a variety of value-added services and intelligent services.
Interworking function
The next-generation network is not an isolated network, especially in the evolution of the existing network to the next-generation network. It is inevitable to achieve collaborative work, interconnection and smooth evolution with existing networks. For example, the signaling gateway can be used to realize the intercommunication between the packet network and the existing No. 7 signaling network; the signaling gateway can be used to intercommunicate with the existing intelligent network to provide users with a variety of smart services; the H.323 protocol can be used to achieve communication with existing networks. Intercommunication of IP telephone network with H.323 system; SIP protocol can be used to realize intercommunication with future SIP network system; SIP or BICC protocol can be used to interconnect with other softswitch equipment; H.248 terminal and SIP in IP network can also be provided Interworking between the terminal and the MGCP terminal.
Protocol function
Softswitch is an open, multi-protocol entity, so it must adopt various standard protocols and various media gateways and application servers , The terminal communicates with the network to maximize the protection of user investment and give full play to the role of the existing communication network. These protocols include H.323, SIP, H.248, MGCP, SIGTRAN, RTP, INAP, etc.
Resource management function
The softswitch should provide resource management functions to centrally manage various resources in the system, such as resource allocation, release, Configuration and control, resource status detection, resource usage statistics, setting resource usage thresholds, etc.
Charging function
The softswitch should have the functions of collecting detailed call bills and double counting, and be able to transmit the call bills to the corresponding billing center according to the needs of the operator.
Authentication and authorization functions
The softswitch shall support local authentication functions, which can authenticate and authorize users and media gateways within the jurisdiction of the Prevent the access of illegal users/devices. At the same time, it should be able to connect with the certification center, and can send the user and media gateway information in the jurisdiction area to the certification center for access authentication and authorization, so as to prevent illegal users and equipment from accessing.
Address resolution function
Softswitch equipment should be able to complete the conversion function of E.164 address to IP address, alias address to IP address, and also Complete the redirection function. For the number analysis and storage function, the softswitch is required to support the storage of 20 digits of the calling number and 24 digits of the called number, and the ability to analyze the 10-digit number and then select the route, and the ability to add or delete numbers at any position.
Voice processing function
The softswitch equipment should be able to control whether the media gateway uses voice signal compression, and provide a selectable voice compression algorithm. The algorithm should be at least Including G.729, G.723.1 algorithm, optional G.726 algorithm. At the same time, it is possible to control whether the media gateway adopts echo cancellation technology, and to set the size of the voice packet buffer area to reduce the impact of jittery voice quality.