ntt protocol boosts sonet/sdh for Internet, lans
By STEPHEN HARDY
Asynchronous Transfer Mode (atm) has another challenger compatible with Synchronous Optical Network/Synchronous Digital Hierarchy (sonet/sdh) transmission, thanks to Nippon Telegraph & Tel-ephone Corp. (ntt--Tokyo). The Japanese telecommunications giant has announced a new protocol suite, called "multiple access protocol over sonet/sdh" (mapos), which provides frame-based transfer and multiple access capabilities over sonet/sdh networks. The protocol could also be used in local area network (lan) applications, according to the company.
ntt claims the new protocol uses bandwidth more efficiently than atm and is more scalable than Gigabit Ethernet. The former claims rest on the protocol`s small overhead requirements (see figure), the fact that it does not have to conform to atm`s 53-byte cells with 5-byte headers, and its maximum frame size of 64-bytes. The scalability claim is based on the current sonet/sdh hierarchy, which extends beyond the speeds currently envisioned for Gigabit Ethernet.
The company also says that mapos differs from atm in that it does not require special patches to accommodate Internet protocol transmission.
The focal point of a mapos-based network is a frame switch developed by ntt. The switch can be used as a hub of a wide area or Internet network, or connected directly with an end-user`s workstation. This latter capability opens the door to the use of sonet/sdh for lan applications over either fiber or copper, according to ntt.
ntt is leasing the technology to interested parties. The first customer is Central Systems Research (csr). The Tokyo-based company plans to unveil the coreswitch-80 mapos frame switch and three network interface cards, with an eye toward the Internet exchange, Internet service provider, and large corporate network markets. The products should be available next month. q