Overview of B-ISDN network
B-ISDN (Broadband Integrated Services Digital Network) is a broadband communication network, and broadband means high-speed information transmission. The information rate on the N-ISDN subscriber line can reach 160kbit/s, but the information transmission rate on the B-ISDN subscriber line can be as high as 155.520Mbit/s (or 622.Mbit/s).
B-ISDN differs from N-ISDN not only in the information transfer rate, but also in the technical essence of the two. B-ISDN is based on ATM technology, and N-ISDN is mainly based on circuit switching technology, so there are big differences between the two networks. In B-ISDN, users can completely request different bandwidths at different moments, and can make requirements in terms of real-time and reliability, that is, B-ISDN can truly support a variety of different services, even though these services The required transmission rate, delay and reliability requirements are very different.
B-ISDN users-network interface reference configuration
There are two kinds of users in B-ISDN-network interface: public UNI and dedicated UNI. B-ISDN user-network interface reference configuration includes 5 functional groups and 4 reference points. The five functional groups are B-NT1 (Type 1 broadband network terminal), B-NT2 (Type 2 broadband network terminal), B-TA (Broadband terminal adapter), B-TE1 (Type 1 broadband terminal equipment, namely B-ISDN standard terminal), B-TE2 (type 2 broadband terminal equipment, that is, non-B-ISDN standard terminal); the four reference points are TB, SB,UB and R.
B-NT1 is the terminal equipment of the physical transmission line, which mainly completes the function of the physical layer. B-NT2 completes the low-level functions such as the physical layer, as well as high-level functions such as centralization, switching, multiplexing/splitting, and OAM. The corresponding physical device can be a dedicated ATM switch (customer premises ATM switch). B-TE1 is the standard terminal of B-ISDN. It is the terminal at the user interface of SB or TB, that is, via SB or T The B reference point is connected to the B-ISDN network, and it executes all terminal protocols from the low-level to the high-level. B-TE2 is a non-B-ISDN standard terminal, it must be connected to B-ISDN (SB interface) through B-TA for protocol conversion and rate adaptation, which is the R user interface Terminal.
Mode
The main feature of B-ISDN is the compatible mode of synchronous transfer mode (STM) and asynchronous transfer mode (ATM), which supports a wide range of voice, Image and data application. ATM can not only integrate voice, data, image and other services into one network, but it also has the advantages of realizing dynamic bandwidth allocation and multimedia communication. ATM broadband switching is the key and core to realize B-ISDN. It is a fast packet switching, packet-oriented transfer mode.
B-ISDN business
B-ISDN uses a brand-new network to replace various existing business networks, such as telephone networks and data networks. This single integrated service network can transmit various types of information and support various types of services, such as voice, video on demand, TV broadcasting, dynamic multimedia e-mail, etc.
Business features
(1) Different services require different transmission rates and bandwidths.
(2) Different businesses behave differently in emergencies.
(3) Different businesses have different real-time requirements.
(4) Different services have different requirements for transmission reliability.
The B-ISDN network must be able to support services with different characteristics.
Types of services
According to the requirements of services for network resources, five types of services are defined: constant bit rate (CBR: constant bit rate) service, real-time variable bit rate (rt -VBR: real-time variable bit rate) service, non-real-time variable bit rate (nrt-VBR: non-real-time variable bit rate) service, unspecified bit rate (UBR: unspecified bit rate) service and available bit rate (ABR: available bit rate) business.
Development driving factors
Broadband Integrated Services Digital Network (B-ISDN) was developed under certain business requirements and technological advancement, including the following factors p>
1 Demand for broadband services.
2 Integrating the two switching methods of circuit and packet into a connected broadband network.
3 The need to allocate interactive services and distributed services together.
4 Requires flexibility for users and network operators at the same time.
5 High-speed transmission, switching and signal processing availability development needs.
6 Data processing and image processing multimedia terminal technology development needs.
B-ISDN emphasizes ISDN's broadband and multimedia communications. It is a fast-band service and other ISDN services that can provide higher than 1.544Mbit/s or 2.048Mbit/s, and has the ability to adapt to various business logic Intelligent communication networks such as, maintenance and network management are a broader ISDN concept. The key to its business integration is to use a unified information unit and a single structure connection to achieve multimedia communication, and use a multi-purpose user-network interface to provide multiple services