[Telecommunications ATM business]
1. Business description
ATM is the English abbreviation of ASYNCHRONOUS TRANSFER MODE (asynchronous transfer mode), which is based on packet switching technology. The developed fast packet switching technology uses statistical time division multiplexing technology and comprehensively absorbs the advantages of high efficiency of packet switching and high speed of circuit switching. In view of the shortcomings of relatively low packet switching rate, circuit switching is almost independent of protocol processing. Features: high-performance hardware devices are used to improve processing speed and achieve high-speed transmission. ATM uses unique ATM cells for data transmission, and each ATM cell is 53 bytes. , can transmit voice, data, image and video services. It can provide high-speed data transmission channels between 256K and 622M.
2. Business characteristics
1. Flexibility: Dynamically allocate circuit bandwidth as needed. A physical transmission channel can be dynamically divided into several sub-channels. Each sub-channel can provide different speed business.
2. High rate: ATM simplifies protocol control, has low delay, and has a transmission rate of N*2MBPS to 622MBPS, which can meet various business requirements for LAN and WAN communications.
3. Multi-service: As a multi-service access platform, the ATM network can meet the requirements of digital services with different transmission rates such as data, voice, and image.
4. Reliability: The ATM network provides a good quality assurance mechanism, which can ensure the realization of broadband real-time services such as video on demand.
5. Security: The bandwidth occupied by users is independent of each other, completely eliminating unsafe factors such as illegal intrusion caused by shared bandwidth.
3. Business positioning
ATM networks can be used in finance, aviation, economics and trade, meteorology, government agencies, customs, broadcasting, commerce, education, construction, medical and other fields. The main applications are There are:
1. High-speed LAN interconnection;
2. High-quality video conferencing;
3. Remote teaching;
4. Remote medical diagnosis;
5. Remote collaborative work;
6. Multimedia communication;
7. Video on demand (VOD) and TV on demand;
8. Various services with timing and optional bandwidth.
IV. Business types
The types of data transmission services provided by networks composed of ATM technology include: ATM permanent virtual connection service (ATM PVC service), ATM switching virtual connection service ( ATM SVC service), frame-in-frame bearer service (FRBS), circuit emulation service.
Currently, according to the geographical scope of business provision, it can be subdivided into local ATM business, domestic ATM business, international and Hong Kong, Macao and Taiwan ATM business.
Domestic ATM services can directly reach provincial capital cities and some prefecture-level cities.
Countries and regions where international and Hong Kong, Macao and Taiwan ATM services are accessible: Hong Kong, Taiwan, Japan, the United States, Singapore and other countries.
5. ATM service levels
At present, the ATM network can open the following four service levels to users: constant bit rate (CBR) service, real-time variable bit rate (RT-VBR) ) services, non-real-time variable bit rate (NRT-VBR), and unlimited bit rate (UBR) services.
1. The characteristics of CBR service are connection-oriented, fixed bit rate, and timing relationship between communication endpoints. Transmission can be continued at a peak cell rate (PCR) throughout the entire connection process, and the communication terminal can transmit at a cell rate equal to or less than (PCR) at any time and period. The main applications require fixed-bandwidth connections, such as voice services, image services that require strict timing, and circuit simulation services.
2. The characteristics of RT-VBR service are connection-oriented, variable bit rate, and timing relationship between communication endpoints.
The bandwidth occupied by communication endpoints changes with the terminal information sending rate at different times. The ATM network guarantees SCR for communication terminals and requires communication terminals not to send information at a rate greater than the peak cell rate (PCR). RT-VBR services are mainly used for services that require strict time sensitivity (requiring strict delay and delay changes), such as image services.
3. The characteristics of NRT-VBR service are connection-oriented, variable bit rate, and no timing relationship between communication endpoints. The bandwidth occupied by the communication endpoint changes with the rate at which the terminal information is sent at different times. The ATM network guarantees SCR to the communication terminal and requires the communication terminal to send information at a rate not greater than the peak cell rate (PCR). NRT-VBR services mainly apply sudden services that do not have strict requirements on delay and delay changes, such as data transmission, E-MAIL, FAX and other services.
4. UBR business features are connection-oriented, with variable bit rates. The bandwidth occupied by communication endpoints changes with changes in the terminal information sending rate and available bandwidth at different times. The ATM network requires communication terminals to send information at a rate no greater than the peak cell rate (PCR). UBR services are mainly suitable for services that do not have high requirements on service quality and transmission rate, such as data backup.
VI. Service provision methods
1. The port types provided to users include:
ATM: E1 (2M), E3 (34M), STM- 1 (155M), IMA (N*2M, Nlt; =8);
FR: channelized E1, non-channelized E1, V.35;
Circuit simulation: channel E1, unchannelized E1, V.35.
2. The rates (SCR) provided to users include:
256K, 512K, 1M, 2M, 3M, 4M, 5M, 6M, 7M, 8M, 9M, 10M, 13M, 15M, 17M, 19M, 21M, 23M, 25M, 27M, 29M, 31M, 34M, 40M, 45M, 50M, 55M, 60M, 65M, 70M, 75M, 80M, 85M, 90M, 95M, 100M, 110M, 120M, 130M, 140M.
The various service levels provided to users use constant cell rate (SCR) as the main service parameter, and the values ??of peak cell rate (PCR) and burst size (MBS) are determined according to the SCR value.
7. Implementation method
(1) Frame Relay extended access
For areas that are not temporarily covered by the ATM network, the Frame Relay network can be used For extended access, ATM switches and Frame Relay switches have multiple interconnection relays to achieve service interoperability. Commonly used interfaces on the client side include V.24, V.35, G.703, etc.
(2) XDSL dedicated line access
XDSL is the general term for digital user loop technologies based on copper wires such as ADSL, VDSL, HDSL, etc. X represents letters such as A, V, H, etc. Among them, ADSL uplink can reach up to 1Mbps and downlink can reach 8Mbps, which is an asymmetric digital user loop technology; VDSL uplink can reach up to 19.2Mbps and downlink can reach up to 55Mbps, which is an asymmetric digital user loop technology; HDSL uplink and downlink have the highest Up to 2Mbps, it is a symmetrical digital user loop technology.
The user side can access the ATM network at a higher rate through XDSL equipment and twisted pair copper wires. The access range of ADSL and HDSL can reach 3~5 kilometers, and the access range of VDSL is within 800 meters. Commonly used interfaces include: V.35, G.703, Ethernet port, etc.
(3) Use the transmission network to extend access
For users with long distances (generally beyond 4 kilometers), high speeds (more than 2Mbps) or high link reliability requirements , you can use the transmission equipment to connect through optical fiber and access. The user-side transmission equipment is responsible for providing a transparent channel and does not encapsulate the ATM protocol.
You can go to the business hall to inquire specifically about the charging status.