IP technology and ATM Technology

With the development of routing technology, IP technology and ATM technology are constantly improved, and have become the main force of routing exchange technology. At the same time, many people are very optimistic about the prospects of these two technologies, I believe that it will play a more important role in the future. ATM is the main representative Technology in the communication field in the last century, while IP is the goal and direction of network convergence in this century and the future. In view of the transition from traditional networks to IP networks, ATM and IP addresses must be combined to ultimately achieve the development requirements of converged networks.

1. Background

ATM technology was proposed by China Telecom at the end of 1980s. It is a network technology developed to realize the B-ISDN of broadband integrated data service network for various services including voice, data and image. The essence of ATM technology is the synthesis of circuit switching and group switching. Therefore, the ATM technology is flexible and can occupy resources as needed at any time. For specific services, the transmission rate varies with the Information arrival rate. It can adapt to any type of business, regardless of the speed, burstable size, real-time requirements, and quality requirements, they can provide satisfactory services. The original idea of ATM is to create a unified platform for future communication systems. The ATM Forum that develops ATM specifications has been accommodating new content to the ATM through various means to ensure the initial goal of the ATM. However, this causes the complexity of ATM technology exceptions and the process of standardization is slow. In addition, expensive equipment prices are also a major factor that affects the popularization of ATM technology. Therefore, ATM is generally limited to the Construction of telecom backbone networks.

IP technology originated in 1960s and was initially used only for the establishment of computer LAN. Over the past decade, with the rapid popularization of the Internet, IP technology has become a de facto standard for interconnection of open systems. In essence, IP technology is a data transmission technology that directly relies on the IP grouping header information to determine the packet forwarding path without establishing connections in advance. The main features of the IP technology are: the IP protocol is a network-Level Interconnection protocol, which is easy to achieve the interconnection of different network, it is particularly suitable for non-real-time short message communication such as email and Information Retrieval. It has a unified addressing system and high network scalability. It adopts the modular structure of independent services and supports various applications, it is easy to add new businesses. The biggest advantage of IP technology is that it can run on any media and network, and can ensure the intercommunication between different networks, that is, "IPovereverything ". With the development of broadband IP technology, various services, including voice, data, and images, can be transmitted over the IP network. The so-called "EverythingonIP" situation has emerged, IP services will soon become the mainstream of communication services. However, during the development of IP technology, it also encountered problems such as router bottlenecks and difficult to guarantee service quality.

Both ATM and IP are promising technologies, but they encounter some problems in their respective development processes. If we combine these two technologies and use the ATM network to provide high-speed direct data links for IP users, we can make full use of the resource advantages of the ATM network to develop the IP user services on the ATM, it can also solve problems encountered in the development of IP networks and further promote the development of IP services.

2 Classification of IP and ATM Integration Technology

At present, the technology of Combining IP and ATM is mainly divided into two categories: overlapping technology and integration technology. When overlapping technology is used, IP addresses are stacked on the ATM layer. The ATM endpoint uses the ATM address selection protocol to select a route for the IP packet. The advantage of overlapping technology is that it adopts standard signaling standard of ATM Forum/ITU-T, and is compatible with standard ATM network and business; its disadvantage is that it is less efficient to transmit IP packets. When integrated technology is adopted, the ATM layer is regarded as the Peer layer of the IP layer. The ATM endpoint only needs to be identified by an IP address. In the ATM network, the existing network layer routing protocol is used to select a route for the IP Group, A non-standard ATM signaling protocol is used when a connection is established. When integrated technology is adopted, the Address Resolution Protocol is not required, but the complexity of the ATM switch is increased, making the ATM switch look more like a multi-protocol router. The advantage of the integration technology is that the efficiency of IP packet transfer is relatively high, and the Address Resolution Protocol is not required; the disadvantage is that it is more difficult to integrate with the standard ATM technology.

3 overlapping Technology

Overlapping technologies are implemented in three ways: CIPOA (ClassicalIPoverATM), LANE (LAN Emulation), and MPOA (Multi-protocol over ATM ).

CIPOA (traditional IP technology on ATM)

The IETF workgroup defines and regulates CIPOA in RFC1483 (multi-protocol encapsulation on AAL5) and RFC1577 (ClassicalIPandARPoverATM) files. The basic idea of CIPOA is to use the capability of IP addresses to accommodate low-layer network technologies and support the IP protocol on the ATM network. It inherits the basic idea of IP, and only regards the ATM network as an exclusive subnet that is in the same status as the physical subnets such as Ethernet and ring-based network. Since the CIPOA specification only supports the IP protocol, it applies to the Internet and lan that only use the IP protocol. With this specification, you can directly run existing IP-based network protocols (such as TCP and UDP) and IP-based application protocols (such as WWW, FTP, and NFS) on an ATM network ).