Packet Switching Types: ATM, Frame Relay, TCP/IP, X.25

Transmission: SONET T-Carrier

Services: [3G] [4G] [Bluetooth] [I-Mode] [WAP] [Wireless and packet switching]

ATM

ATM stands for Asynchronous Transfer Mode. Pretty catchy, eh? ATM, sometimes called cell relay, is a high speed multiplexing and switching technology for data. An advanced packet switching scheme, ATM makes all its packets one length. These uniformly small packets or cells let data flow smoothly, like a collection of images on movie film, all moving through the projector at a constant frame rate. ATM also boasts improved error control compared to conventional packet switching, as well as numerous other features that now make it a core technology of data networks world wide. ATM can run over SONET or T-Carrier. Check out all the ATM info in the free .pdf files below.

(1) Click here for a nice introduction to ATM by Davis (203K, 7 pages in .pdf)

Ordering information for ATM for Public Networks by Ronald H. Davis (external link to Amazon.com)

(2) More intense, electronic engineering student stuff, in this introduction to ATM by Lucent's M.R, Karim (16 pages, 198K in .pdf)

More info and ordering information for ATM Technology and Services Delivery, first edition, by M. R. Karim, Lucent (external link to Prentice Halll)

(3) A different discussion, this time on ATM and the challenges of high speed switching. Good stuff (223K, 24 pages in .pdf)

Ordering information for Edwin Coover's ATM Switches (external link to Amazon.com)

The F.C.C. definition

A definition by the F.C.C.: Cell relay is a high-bandwidth, low-delay, switching and multiplexing packet technology. Its combination of simplified error and flow control, fixed-length cells which allow high-speed switching, and procedures for allocating network bandwidth enable it to support voice, data, image, and video traffic. Asynchronous transfer mode (ATM) is the international standard implementation of cell relay. It is defined to work over different physical media and at speeds ranging from 45-622 Mbps, with extensions to lower and higher speeds possible. Vendors are beginning to produce ATM network equipment and carriers are beginning to assemble ATM networks. Current service offerings are developmental in nature, however, and it is expected to take several years for the technology to mature. Significant infrastructure investments by carriers will be required to make ATM widely available.

Comments by Professor Levine on related matters

Because of the growing interest in packet speech and data transmission and switching via the Internet (VoIP, etc.) there is now a question regarding the competition between ATM and TCP/IP packet transmission. Some people say that BISDN should include VoIP and other TCP/IP packet services for data, as well as ATM. In some cases, all of these formats are used together (TCP/IP packets are cut into 48 octet pieces which are transmitted via ATM, and the ATM cells are transmitted in the payload of a SONET/SDH multiplexing format) to provide backward compatability with existing transmission systems, and this leads to very high overhead and degrades the system performance somewhat. There is also a question about whether either of both of these packet formats should always be transmitted as the payload of SONET/SDH multiplexing. Some people suggest that ATM and SONET/SDH be phased out and TCP/IP or other IP packet formats be used alone. As a result of all of these alternatives being considered, the term BISDN is not used very much today (compared to 5 or 10 years ago).

What exactly is ISBDN? The term usually refers to Broadband Integrated Services Digital Network or B-ISDN. I do not follow this subject closely. The main aspect of BISDN that has been developed and published as a standard is the use of ATM multiplexing and routing for high bit-rate data services; BISDN refers to use of ATM. BISDN appears to have very little relationship to ordinary (circuit-switched 64 kb/s channel) ISDN systems, although there are some so-called "broadband" or "wideband" ISDN circuit switched services such as 384 kbit/s (sometimes called a "six-pack" because it uses six channels of 64 kb/s each).

There is also a research project in Europe called BISON (like the animal) related to automatic methods for network design and repair. It is sometimes confused with BISDN. There is a report (pdf document) on the Internet regarding BISON at

http://www.cs.unibo.it/bison/deliverables/DUP.pdf

Packet Switching Types: ATM, Frame Relay, TCP/IP, X.25

Transmission: SONET T-Carrier

Services: [3G] [4G] [Bluetooth] [I-Mode] [WAP] [Wireless and packet switching]