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To: Doug who wrote (1072)	12/11/1997 9:04:00 PM
From: Tim Bagwell	Read Replies (1) \| Respond to of 12623

are all Fibre protocols based on 512 byte cells or do they include larger Frames Doug, All protocols are different. SONET for example uses a base frame that consists of 8000 frames/sec of 810 bytes each. Of the 810 bytes 783 correspond to payload and leaving about 3% overhead for control and timing bits. This would correspond to an OC-1 rate. An OC-n rate would mux the number of bytes in each frame by n. Notice that 80008=64K bits/sec which corresponds to a telephone grade voice channel or a DS0 channel. So each byte of a frame could contain voice data. So 783 phone calls could be sent on an OC-1. Of course, by using compression and making use of dead time in a voice pattern they can mux in others (TDM) so the actual number of calls carried is much higher and will vary. The large number of bytes is a disadvantage for routing. ATM is more efficient because it has a cell size of only 53 bytes of which 5 are overhead. Routing info is included in 24 bits of each and every ATM cell. There are many other types of protocols in use. how far are we from elctro/optical IP switching or is it a no can do since digit based protocols & frequency are in a two seperate domains* That's the problem -- the cell rates are too fast for conventional optical switches. The better optical switches are electro-mechanical so that speeds are limited. Electro-optic switch technology exists but is still at a research stage and the switches aren't a whole lot faster. Consequently, optical switching is limited to simple reconfiguration operations. The optical switch or an optical router is the holy-grail of the all-optical-network (AON) making it at least a decade away at best. It's not even clear that AON is preferred to good ole' electronic switching. Incidentally,