Comprehensive Explanation of ATM access knowledge

ATM access is also a very common access technology, so I have studied a comprehensive introduction to the ATM access technology. I will share it with you here, I hope to help you understand ATM.

I. Introduction to ADSL Technology

Asypolicric Digital Subscriber Line (ADSL) is an Asymmetric Digital user Line. Its primary feature is that its upstream and downstream speeds are not symmetric, that is, the upstream and downstream speeds are not equal, the high downlink rate and relatively slow uplink rate of ADSL technology are very suitable for Internet browsing. ADSL uses the unique modulation technology to generate three information channels over this telephone line:
A high-speed downstream channel with a speed of 32 kbps-8 mbps for users to download information;
A 32 kbps-1mbps upstream channel for uploading output information;
An ordinary old-fashioned telephone service channel for general telephone services;
The three channels can work simultaneously at a distance of 3 KM-5 KM in a pair of Copper Twisted Pair wires.

Ii. ADSL Access Mode

ADSL technology uses a large number of existing copper twisted pair wire resources of the telecommunications company and stable ADSL modulation technology to provide broadband access functions, it provides a low-cost, high-speed, and stable access platform for high-speed Internet access and broadband application development. The remote adsl cpe (adsl modem) accesses the local DSLAM through the ATMPVC through the copper cable, and converts the ADSL frame into a standard ATM cell on the DSLAM, the ATM access cells penetrate through the ATM Backbone Network to access the Broadband Access Server (BRAS). The BRAS end the Frame Conversion from the CPE into an IP packet and send it to the INTERNET.

Iii. ADSL business functions

ADSL supports the uplink speed of 32 Kbps to 1 Mbps on a copper line and the downlink speed of 32 Kbps to 8 Mbps. The valid transmission distance is within 3-5 kilometers. ADSL can dynamically adjust the user access speed based on the quality of twisted pair copper wires and the distance between transmission. These features make ADSL an ideal technology for high-speed surfing, on-demand video streaming (IAV), and remote LAN access, in these applications, the user downloads much more information than the uploaded information (sending instructions. Currently, we have two main types of ADSL Services:

1. Individual users are provided with a high-speed Internet access platform based on the technical characteristics of ADSL. users use virtual dialing software to dial the Broadband Access Server and assign a random IP address to the user.

2. Provide INTERNET leased line access for commercial users. Users have fixed IP addresses assigned to them by telecom companies. Commercial users can develop various online commercial applications through the high-speed access platform of ADSL. Compared with the ddnleased line, the ADSL leased line features low equipment cost and simple maintenance.

The Application of ADSL is far from the above two types. Using the stability of ADSL and its seamless connection with ATM, you can develop high-level applications of adsl over atm, such as local interconnection (point-to-point or point-to-point) and leased line interconnection. The advantages of the adsl over atm service are:
1. Flexible. The combination of ADSL and ATM can flexibly carry various high-level information and provide users with various services;
2. scalability. The ADSL system based on ATM access can be seamlessly connected to the core network of ATM access, so as to provide users with high-speed access channels;
3. Economic. The price of devices that use ADSL to provide broadband access services to users is much lower than that of ddnleased lines;
4. manageability: the use of ADSL for ATM access to the user end requires fewer devices, the device settings are simple, and the maintainability is strong.

Iv. Traditional ATM access methods and features

As a high-speed connection-oriented network exchange technology, ATM (asynchronous transmission mode) has become a mature, advanced, and stable high-speed WAN networking technology. There are two traditional ATM access methods:
1. Use SDH or frame relay network as remote user access, and use the interconnection between local devices to convert atm cells.
2. Connect the 155M access terminal to the local ATM device as a fiber-to-the-home device, and enable ATM access at the user access end.
The main features of traditional ATM access are:
1. Line switching and group switching are supported.
2. video, voice, and data are transmitted simultaneously on a regular line.
3. Guaranteed Service Quality for multiple businesses and allocated bandwidth as needed.
4. Fiber-to-the-home is required for access, resulting in high investment costs and long construction periods.
5. the user end must use an atm cpe, such as a router with an ATM interface card. The equipment is expensive.

V. Access methods and features of traditional local interconnection

Local interconnection is the lan to lan Service. Traditional local interconnection can be divided into two types: narrowband and broadband. Narrowband local interconnection is based on DDN to provide users with a channel with fixed bandwidth and low speed to achieve interconnection of LAN in different regions. Narrowband interconnection provides users with a secure, stable, but relatively low-speed Interconnection channel. The devices required for narrowband interconnection are the DTU or leased line MODEM that communicates with the local DDN device. The user's interconnection devices are like bridges or routers. With the increasing number of applications between users' LANs, bandwidth insufficiency becomes the main issue of narrowband interconnection.

The same city interconnection of broadband is mainly based on 10 m interconnection of man or M interconnection. The implementation of Broadband Interconnection is to connect both ends of the user to the Metropolitan Area Network's access layer through optical fiber, and allocate the same VLAN number between two different access points of the metropolitan area network to implement TRUNCK interconnection between metropolitan networks. This interconnection feature provides high-speed Interconnection, security and stability, simple equipment maintenance, and provides services such as voice, image, and data. Similarly, if you use a broadband network for local interconnection, you need to lay optical fiber cables. There are also disadvantages such as high investment costs and long construction periods.

6. using ADSL for ATM Access

The communication between the adsl cpe and the local device DSLAM is completed using ADSL frames, while the communication between the DSLAM and the ATM is a standard ATM cell communication. The ADSL Network is a data network carried by the ATM as the backbone. Using the seamless connection between ADSL and the ATM access network, the adsl over atm service can be developed and can be accessed as a remote user through the ATM. ADSL's high-speed downlink speed and medium-Speed Uplink speed are very suitable for users with high requirements on the downlink speed, while the uplink data volume is relatively small. For example, some branches of a large company can communicate with the headquarters, and the branch has a large amount of data to download from the headquarters, while the Branch's upstream traffic is relatively less. The high-speed Interconnection provided by adsl over atm access meets the high-speed Interconnection requirements of users and reduces the investment in local construction. Using ADSL as the access for ATM users, the user-side device only needs one adsl modem and does not need to add other devices for easy maintenance and remote monitoring.

7. using ADSL for local interconnection and leased line access

The interconnection between the local and LAN services is the interconnection between the LAN and LAN services. the interconnection between the LAN and LAN involves both the interconnection of bridges and routes. According to the technical characteristics of ADSL, you can achieve local interconnection between ADSL and users, between ADSL and LAN users in multiple forms. The main implementation methods include:

1. Using the seamless connection between ADSL and the ATM network, through the configuration of PVC on the ATM access device (VP exchange or PVC exchange), the same city interconnection between ADSL users is realized. This interconnection service can be implemented in the form of a bridge or a route. The configuration of the ADSL client device can be flexibly interconnected through a bridge or a route based on the connection failure. Supports one-to-multiple-point communication. Due to the limitations of ADSL technology, the total uplink transmission rate of the master port in the point-to-multiple-point communication is up to 1 M.
The bandwidth access server BRAS of the ADSL Network is used to achieve the same city interconnection between ADSL users and the same city interconnection between ADSL and LAN Access Users. The implementation method is to create a specific VR for each connected user group in BRAS, end all the user PVC or VLAN that need to be interconnected on this VR, routing on VR enables communication between different subnets. The interconnection between ADSL and ADSL users can be a bridge or a routing method, and the interconnection between ADSL users and LAN users can be a routing method. The ADSL client device is flexibly configured as a bridge or a route based on the inaccessible access mode. It supports one-to-multiple-point communication. The user's main port can be connected through a man or other means.

2. An external PVC Termination Device, for example, CISCO7206, is added to an ATM device. By terminating the PVC or VLAN of an ADSL user on this device, you can flexibly develop various services of ADSL, including services such as local ADSL interconnection and ADSL leased line Internet access. This interconnection mode can be implemented by means of bridges and routes. the user-side MODEM can be flexibly set to a bridge or a routing mode based on the disconnected interconnection mode, and supports one-to-multiple-point communication mode.

3. As the access to the frame relay circuit, many Frame Relay networks currently use the ATM network as the core. Therefore, after the ADSL Network is connected to the ATM network, it can be used as an access method for Frame Relay leased lines, connect to each other through RFC1483 BRIDGE.

8. advantages of using ADSL in ATM access and local interconnection

Using ADSL for ATM access has the following advantages:
1. ADSL can provide high-speed access for remote users. You only need to install an adsl modem on the user end, without complicated ATM access equipment, which reduces investment and simplifies maintenance.
2. ATM users connected by ADSL can access the INTERNET, and the network provides a transparent transmission channel.
3. Based on different user needs, users can be provided with a variety of QOS levels to better utilize network resources.
4. using ADSL for local interconnection access, the access method is flexible, and the Network Bridge or network routing mode is supported. One-to-multiple-point communication mode is supported; the copper cable can provide users with high-speed, downlink, and medium-Speed Uplink interconnection. The existing copper resources can be fully utilized for ADSL Access, which can ensure high-speed access and stable communication while saving investment costs.
5. Compared with the traditional DDN/FR leased line, the investment of local and client devices can be reduced by 10 times.

9. using ADSL for access through ATM and local interconnection should pay attention to the problem. using ADSL for access through ATM and local interconnection has many advantages, providing users with one more choice for access, note the following:

1. the user's access point must be within the valid communication range of 3 km-5 km of the ADSL local device.
2. You must use the adsl modem with the routing function as the client access device when using the routing method as the local interconnection.
3. The communication quality of ADSL depends on the line quality. To ensure the stability of user communication, an external line with good line quality must be used (with low attenuation and no underfloor ).
4. the user must get out of the misunderstanding that fiber access is better than copper access. As long as the communication bandwidth and failure rate can be guaranteed, the access method used is the same.
5. During the construction of adsl dslam, ATM-based upstream instead of IP upstream must be used. For those using IP upstream, city network switches can only be used to achieve local interconnection.
6. The impact of ADSL as a leased line access on traditional DDN/FR services is viewed based on Syndrome identification.
7. correctly handle the charges for using ADSL as a leased line access.

10. using ADSL for ATM access or local interconnection

Compared with the traditional ATM access method, the investment cost is reduced by 200 to 300 times, and the construction period is short. This is a good way for the company's branches to connect to the headquarters, both telecom operators and users have benefited a lot. Telecom operators can make full use of the original telephone copper resources, without re-deploying optical fiber, but also provide users with a maximum downstream bandwidth of 6 m. for users, they can save on purchasing expensive atm cpe. At present, these access methods have been tested, and the results are satisfactory. If UNI is used for interconnection between the ATM switch and the frame relay network, the ing between the frame relay and the ATM access can be realized through the frame relay switch, so that the communication between the ADSL user and the frame relay can be realized and the network scale can be expanded. The ADSL Network can gradually replace the original DDN network as the main access method for ATM and frame relay.

1. Optical fiber access technology leads the communication storm
2. Next-generation wireless access technology
3. Unlocking the mystery of redundant routing automatic switching in Broadband Access Networks
4. Wireless Access Point learning notes
5. Wireless Access networks will become the future development trend