update 12/15/20011 ICSA 745 Transmission Systems Emerged Technologies Nirmala Shenoy Department of Information Technology Rochester Institute of Technology

update 12/15/20012 Emerged Technologies Scope –TI / E1 Carrier Systems –X.25 –ISDN –SS7 –FDDI

update 12/15/20013 Emerged Technologies Coverage –Purpose of the technology –Typical topology –Layers –PDU –Any other aspects –Conclusions

update 12/15/20014 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 12/15/20015 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 12/15/20016 T1 / E1 Carrier System Purpose –T1 – can accommodate 24 64kbps voice channels – bw – Mbps –E1 – can accommodate 32 64kbps voice channels – bw – 2.048Mbps –E1 is similar to T1, but not compatible to T1

update 12/15/20017 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 12/15/20018 T1 / E1 Carrier System –Topology – similar for T1 and E1 –Typically point to point –Multiple links via cross connect switch

update 12/15/20019 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/ 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 –193 rd bit is a framing bit – synchronization –Synchronization requires 12 bits which are spread over 12 frames

update 12/15/ 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 8 th bit for every 6 th and 12 th frame 8 th bit is unreliable 56 kbps

update 12/15/ 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 –32 nd byte used for control Out-of-band signaling

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