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ICSA 745 Transmission Systems Emerged Technologies

ICSA 745 Transmission Systems Emerged Technologies. Nirmala Shenoy Department of Information Technology Rochester Institute of Technology. Emerged Technologies. Scope TI / E1 Carrier Systems X.25 ISDN SS7 FDDI. Emerged Technologies. Coverage Purpose of the technology

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ICSA 745 Transmission Systems Emerged Technologies

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  1. ICSA 745 Transmission SystemsEmerged Technologies Nirmala Shenoy Department of Information Technology Rochester Institute of Technology update 12/15/2001

  2. Emerged Technologies • Scope • TI / E1 Carrier Systems • X.25 • ISDN • SS7 • FDDI update 12/15/2001

  3. Emerged Technologies • Coverage • Purpose of the technology • Typical topology • Layers • PDU • Any other aspects • Conclusions update 12/15/2001

  4. T1/E1 Carriers Systems • Purpose • Up to 1960s telephone networks were analog • 1962 – digital trunks • 1980 – T1 digital carrier lines were introduced • T – telephone carrier line – copper based update 12/15/2001

  5. T1 / E1 Carrier System • Purpose • Initially to carry digitized voice at 64 kbps • Voice was carried as digital signals – DS • DS was primarily based on PCM & ADPCM • Time Division Multiplexing schemes • T1 was the North American Carrier • E1 was the European Carrier update 12/15/2001

  6. T1 / E1 Carrier System • Purpose • T1 – can accommodate 24 64kbps voice channels – bw – 1.544 Mbps • E1 – can accommodate 32 64kbps voice channels – bw – 2.048Mbps • E1 is similar to T1, but not compatible to T1 update 12/15/2001

  7. T1 / E1 Carrier System • Multiplexing hierarchy- T1 • DS0 – one 64kbps channel for one voice user • DS1- 24, 64kbps channels used by T1 • DS2 – 96, 64kbps channels used by T2 • 7DS2 can be multiplexed into DS3 • 6DS3 can be multiplexed into DS4 • T1 uses DS1, but DS1 signals can be transmitted over any carrier. update 12/15/2001

  8. T1 / E1 Carrier System • Topology – similar for T1 and E1 • Typically point to point • Multiple links via cross connect switch update 12/15/2001

  9. T1 / E1 Carrier System • Protocol Layer • Both T1 and E1 are in the Physical layer of the seven layer OSI model • Define connectors, signaling conventions, framing formats, etc update 12/15/2001

  10. T1 / E1 Carrier System • Protocol Data Unit – T1 • Each voice channel gets 8 bits • 24 channels make a frame = 125sec frame • A frame has 192 bits • 193rd bit is a framing bit – synchronization • Synchronization requires 12 bits which are spread over 12 frames update 12/15/2001

  11. T1 / E1 Carrier System • Protocol Data Unit – T1 • Signaling • A & B bit signaling – in band signaling • Done by bit robbing from payload • Off-hook, on-hook, ringing • 8th bit for every 6th and 12th frame • 8th bit is unreliable • 56 kbps update 12/15/2001

  12. T1 / E1 Carrier System • Protocol Data Unit – E1 • Each voice channel gets 8 bits • 32 channels make a frame = 125sec frame • A frame has 256 bits • 32nd byte used for control • Out-of-band signaling update 12/15/2001

  13. T1 / E1 Carrier System • Conclusions • Limited management operations • multiplexing schemes not easy • Bit stuffing problems • Stepping stones to more robust technologies • Sonet/SDH update 12/15/2001

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