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]

SONET

Sonet stands for Synchronous Optical Network, a high speed transmission technology designed to send traffic over fiber optic cable, but now also used over coax. [More here] That compares to the older and more well known T-Carrier system, which started in 1963, an inherently slower technique since it was built for copper cables, noisy, error producing, bandwidth limited metallic lines. Like T-1, SONET is a transmission standard, one that carries other protocols to their destination. So circuit switched voice traffic, X.25 network data packets, ATM cells, and TCP/IP based internet traffic all moves over the road that SONET provides. SONET also sports modern network features including bandwidth management, real time monitoring of the system, survivable networking, and universal connectivity. Sound like so much mush? Not really. Nathan Muller says SONET will provide communications' transport mechanism for the next three to four decades; all modern telephone companies are building their new networks with it. Read the files below for more information.

Russell explains why the present telephone network is configured the way it is and introduces SONET. (11 pages, 275K, .in .pdf)

Ordering information for the book this file is from: Signaling System #7 by Travis Russell, McGraw Hill (external link to Amazon.com) is here; I am puzzled by the reviews at Amazon on this book. I think this selection is quite clear, moves logically, and is well written. What am I missing?

Some quick SONET specifics by Bates from the title below (6 pages 146K)

Ordering information for The Broadband Telecommunications Handbook by Regis J. Bates (external link to Amazon.com)

Although often daunting, some patents explain technology fairly well. You can't be a beginner to understand them, but the intermediate or advanced reader should use them as a resource.

http://www.uspto.gov (external link)

Here's one SONET detail explained in the following patent:

Upgraded telecommunication network 5,293,376

"The basic module or first level of the SONET signal is called the Synchronous Transport Signal-Level 1 (STS-1). The STS-1 has a bit rate of 51.84 Mb/sec and is synchronous. The STS-1 signal is formed from a sequence of repeating frames. The STS-1 frame structure is illustrated in FIG. 2. The STS-1 frame structure can be drawn as 90 columns by 9 rows of 8-bit bytes. The order of transmission of the bytes is row by row, from left to right across the columns, with one entire frame being transmitted every 125 .mu.s. The 125 .mu.s frame period supports digital voice signal transport encoded using 1 byte/125 .mu.s=64 kb/s. The first three columns of the STS-1 frame contain section and line overhead bytes. The remaining 87 columns form the STS-1 Synchronous Payload Envelope (SPE). The SPE carries SONET payloads including 9 bytes of path overhead. The STS-1 can carry a clear channel DS3 signal (44.736 Mb/s) or, alternatively, a plurality of lower-rate signals such as DS0, DS1, DS1C, and DS2 by dividing the Synchronous Payload Envelope into a plurality of fixed time slots. For example, 648 DS0 signals fit into the SPE of an STS-1 signal."

"Higher rate SONET signals are obtained by byte interleaving N frame aligned STS-1 signals to form an STS-N signal in accordance with conventional SONET technology. An STS-N signal may be viewed as having a repetitive frame structure, wherein each frame comprises the overhead bits of N STS-1 frames and N synchronous payload envelopes. For example, three STS-1 signals may be multiplexed by a multiplexer into an STS-3 signal. The bit rate of the STS-3 signal is three times the bit rate of an STS-1 signal and the structure of each frame of the STS-3 signal comprises three synchronous payload envelopes and three fields of overhead bits from the three original STS-1 signals. When transmitted using optical fibers, the STS-N signal is converted to optical form and is designated as the OC-N signal."

Resources

[More here] Tom: I think SONET does not depend on a specific media, that is, it can run over coax, fiber optic cable, or perhaps even radio. The medium need only support the minimum bandwidth for the SONET standard: a 51.84 Mb/sec transmission rate called STS-1. This can also be accomplished with Coaxial and I beleive vendors like Lucent use coaxial connections on their class 5 switches. A little more on this.

The current Nortel product (DMS Super Node) uses a Spectrum Peripheral Module (SPM) to supply its SONET interface. This is an optical interface. On the other hand the Lucent product (5ESS) uses a Digital Networking Unit SONET (DNUS). This uses a Coaxial interface. The Lucent may have the capability to do optical interfaces and on that the note, the administrative, communication, and switching modules are connected via optical interfaces, but the DNUS interface is currently using coaxial. At least in my organization, or should I say it was that way yesterday.

Thanks, Andrew Glover

[back to text]

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]