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TELECOMMUNICATIONS SYSTEMS AND TECHNOLOGY

TELECOMMUNICATIONS SYSTEMS AND TECHNOLOGY. PART 4-1. SONET & SDH. SONET/SDH. SONET (USA PROPOSAL/STANDARD) S YNCHRONOUS O PTICAL NET WORKING (ORIGINATED BY BELLCORE  THE RESEARCH ARM OF THE RBOCS ) AND THEREAFTER IN CONJUNCTION WITH ANSI

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TELECOMMUNICATIONS SYSTEMS AND TECHNOLOGY

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  1. TELECOMMUNICATIONS SYSTEMS AND TECHNOLOGY PART 4-1

  2. SONET & SDH

  3. SONET/SDH • SONET (USA PROPOSAL/STANDARD) SYNCHRONOUS OPTICAL NETWORKING (ORIGINATED BY BELLCORE THE RESEARCH ARM OF THE RBOCS) AND THEREAFTER IN CONJUNCTION WITH ANSI • SDH (EUROPEAN PROPOSAL/STANDARD) SYNCHRONOUS DIGITAL HIERARCHY ( CCITT  ITU)

  4. A COMMUNICATIONS LINK • WHEN DATA IS TRANSMITTED OVER A • COMMUNICATIONS MEDIUM, VARIOUS TASKS • MUST BE PROVIDED ON THE LINK (THIS IS THE • DIFFERENCE BETWEEN A DUMB WIRE/GLASS AND AN • INTELLIGENT WIRE/GLASS – LINK) • THESE INCLUDE: • FRAMING OF THE DATA • ERROR CHECKING • LINK MANAGEMENT

  5. FOR OPTICAL COMMUNICATIONS THESE FUNCTIONS HAVE BEEN STANDARDIZED BY THE ANSI T1X1.5 COMMITTEE AS SYNCHRONOUS OPTICAL NETWORKING (SONET) AND BY THE ITU AS SYNCHRONOUS DIGITAL HIERARCHY (SDH). • ANSI: AMERICAN NATIONAL STANDARDS INSTITUTE • ITU: INTERNATIONAL TELECOMMUNICATION UNION • FORMERLY KNOWN AS: • CCITT: INTERNATIONAL TELEGRAPH AND TELEPHONE • CONSULTATIVE COMMITTEE

  6. USEFUL LINKS ANSI HOME PAGE: http://www.ansi.org/ ITU HOME PAGE: http://www.itu.int/home/index.html ITU TELECOM PAGE: http://www.itu.int/ITU-T/

  7. SONET Vs SDH • THERE ARE A LOT OF SIMILARITIES BETWEEN SONET AND SDH, THERE ARE SOME SIGNIFICANT • DIFFERENCES, ESPECIALLY IN TERMINOLOGY. • SONET IS A SUBSET OF SDH AND IT IS EASIER TO • INTRODUCE THE TOPIC FROM A SONET POINT OF VIEW • AS UNDERSTANDING SONET MAKES IT EASIER TO • UNDERSTAND SDH • FOR EXAMPLE CERTAIN ASPECTS OF SDH EXIST TO MAINTAIN COMPATIBILITY WITH SONET

  8. HISTORY 1. PRE-1960’S INDIVIDUAL ANALOG LINES BETWEEN SWITCHING OFFICES

  9. HISTORY 2. 1962 AT&T DS-1 T1-CARRIER DIGITAL SERVICE CHANNEL BANK RESIDES IN C.O.

  10. HISTORY 3. POST 1962 • AS TIME ELAPSED: • THE VOLUME OF LONG DISTANCE CALLS INCREASED • SUBSTANCIALLY • THE NUMBER OF T-CARRIER CIRCUITS REQUIRED • INCREASED EQUALLY • THE CAPACITY DEMAND (BANDWITH) INCREASED • AS WELL

  11. HISTORY 4. LATE 1970’S • OPTICAL COMMUNICATIONS BECAME FEASIBLE, ALLOWING HIGHER SPEED COMMUNICATIONS • (HIGHER TROUGHPUT/BANDWITH – A SYSTEM CAN CARRY MANY MORE TELEPHONE CALLS) • ONE OF THE FIRST COMMERCIAL FIBER COMMUNICATIONS SYSTEM WAS INSTALLED IN CHICAGO IN 1977 AND OPERATED AT 45 MBPS (DS-3 RATE  T3-CARRIER)

  12. HISTORY Multiplexer Multiplexer Two optical fibers (Tx and Rx) MULTPLEXER RESIDES IN C.O.

  13. HISTORY • ORIGINALLY, THE TELEPHONE COMPANIES LOOKED AT OPTICAL COMMUNICATIONS AS SIMPLY A REPLACEMENT FOR THE OLDER WIRE OR MICROWAVE COMMUNICATIONS USED FOR YEARS • VENDORS OF OPTICAL COMMUNICATIONS EQUIPMENT USED THEIR PROPRIETARY FRAMING TECHNIQUES. ONCE AN OPTICAL FIBER VENDOR WAS SELECTED, NO CHOICE REMAINED FOR THE VENDOR OF ALL THE EQUIPMENT IN THAT OPTICAL NETWORK

  14. HISTORY • STANDARDS IN OPTICAL COMMUNICATIONS • BECAME APPARENT • ANSI WORK STARTED IN 1985 WITH THE CCITT • (NOW CALLED ITU) INITIATING A STANDARDIZATION EFFORT IN 1986 • FROM THE VERY BEGINNING CONFLICT BETWEEN ANSI (US PROPOSALS) AND THE ITU (EUROPEAN PROPOSALS) EXISTED

  15. HISTORY • THE US WANTED A DATA RATE CLOSE TO 50 MBPS IN ORDER TO CARRY DS-1 (1.544 MBPS) AND DS-3 (44.736 MBPS) SIGNALS. • THE EUROPEANS NEEDED A SPECIFICATION WHICH WOULD CARRY E1 (2.048 MBPS), E3 (34.368 MBPS), AND 139.264 MBPS SIGNALS EFFICIENTLY. SO THEY REJECTED THE 50 MBPS PROPOSAL AND DEMANDED A BASE SIGNAL RATE CLOSE TO 150 MBPS.

  16. HISTORY EVENTUALLY A COMPROMISE WAS REACHED WHICH ALLOWED THE US SPECIFICATION KNOWN FORMALLY AS SYNCHRONOUS OPTICAL NETWORKING (SONET) WHOSE DATA RATES ARE A SUBSET OF THE ITU SPECIFICATION, KNOWN FORMALLY AS SYNCHRONOUS DIGITAL HIERARCHY (SDH).

  17. HISTORY ANSI HAS A REPORT WHICH OUTLINES THE MAJOR DIFFERENCES BETWEEN SONET AND SDH [T1RPT36]

  18. SONET/SDH GOALS • TO ENHANCE SERVICES AND EXISTING TECHNOLOGIES (THE FIRST STANDARDS FOR OPTICAL COMMUNICATIONS WERE FOCUSED ON HANDLING VOICE CIRCUITS SUCH AS DS-1’s/E1’s AND DS-3’s/E3’s) • TO PROVIDE A COMMON CONNECTIVITY INTERFACE AMONG THE LOCAL EXCHANGES AND THE LONG DISTANCE CARRIER

  19. SONET/SDH GOALS • ABILITY OF DIFFERENT CARRIERS TO INTERCONNECT • CONTINUE THE MULTIPLEXING STRUCTURE TO GROW INTO GIGABITS/SEC • PROVIDE IMPROVEMENTS FOR THE SUPPORT OF OPERATIONS, ADMINISTRATION, AND MAINTENANCE (OAM) • UNIFY THE U.S, EUROPEAN, AND JAPANESE DIGITAL SYSTEMS, ALL BASED ON THE 64 KBPS PCM CHANNELS (COMBINED IN DIFFERENT (AND INCOMPATIBLE) WAYS)

  20. SONET/SDH BENEFITS • COMMUNICATION OVER OPTICAL FIBER • (OPTICAL TRANSMISSION BETWEEN EO’s IS IMMUNE • TO ELECTRICAL INTERFERENCE) • FIBER OPTIC STRANDS (DIAMETER IS CLOSE TO THAT • OF A HUMAN HAIR = 125 MICROMETERS) ARE MUCH • SMALLER AND LIGHTER THAN COPPER WIRE • ONLY TWO FIBER STRANDS ARE NEEDED FOR FULL • DUPLEX OPERATION AS OPPOSED TO 4 COPPER WIRES

  21. SONET/SDH BENEFITS • LIGHT PULSES CAN OPERATE AT MUCH HIGHER RATES • THAN THAT OF AN ELECTRICAL SYSTEM • WITH COPPER, THE HIGHEST RATE IN THE US IS THE • DS-3 RATE AT 44.736 Mbps • WITH SONET THE RATE STARTS AT 51.84 Mbps

  22. SONET MUX RATES

  23. SONET MUX RATES OC-1 OPTICAL CARRIER/LEVEL 1 (51.84 Mbps) OC-N = (N x 51.84) Mbps

  24. STS-1: SYNCHRONOUS TRANSPORT SIGNAL/LEVEL 1, (51.84 Mbps) OC-1 OPTICAL CARRIER/LEVEL 1 (51.84 Mbps), (STS-1 = OC-1)

  25. SONET/SDH BENEFITS • SONET’S LIGHT SIGNAL CAN TRAVEL MUCH FURTHER • WITHOUT REPEATER THAN ELECTRICAL SIGNALS CAN • OVER COPPER • WHILE A DS-3 CIRCUIT NEEDS A REPEATER EVERY • 450 FEET, A SONET CIRCUIT WILL NEED A REPEATER • AFTER 87.5 MILES • THE BIT ERROR RATE (BER) FOR SONET (BER = 1 X 10-10) • IS MUCH LOWER THAN THAT OF ELECTRICAL SIGNALS • OVER COPPER (BER = 1 X 10-6)

  26. SONET/SDH BENEFITS • SONET DATA RATES ARE INTEGER MULTIPLES OF • THE OC-1 DATA RATE. • OC-N STRUCTURE  OC-N = (N x 51.84) Mbps • THIS MULTIPLICITY RULE DOES NOT APPLY IN THE DS-N WORLD – TO CREATE THE HIGHER ELECTRICAL RATES, ONE CANNOT COMBINE, IN A LINEAR FASHION THE LOWER RATE, SIGNALS • SONET INTERLEAVES LOWER RATE SIGNALS TO CREATE HIGHER RATE SIGNALS WITH THE NEW FRAME • STRUCTURE BEING THE BYTE-INTERLEAVED LOWER • FRAME RATES

  27. SONET/SDH BENEFITS FOR EXAMPLE: OC-3 = 155.52 Mbps OC-9 GIVES (9/3 = 3  3 x 155.52 Mbps = 466.56 Mbps) OC-12 GIVES (12/3 = 4  4 x 155.52 Mbps = 622.08 Mbps) OC-192 GIVES (192/3 = 64  64 x 155.52 Mbps = 9953.28 Mbps)

  28. SONET/SDH BENEFITS • SONET IS DESIGNED TO INTERFACE TO ANY EXISTING • DIGITAL SIGNALS AS WELL AS ANY FUTURE ONES SO • ALLOWING FOR EASE OF CURRENT AND FUTURE • MIGRATION • SONET IS DESIGNED TO SIMPLIFY THE NETWORK (LESS • NUMBER OF EQUIPMENT NEEDS – BECAUSE OF THE • LINEAR RELATIONSHIP OF FRAMES GOING UPWARD INTO • THE HIERARCHY) • AS A RESULT, SONET ALLOWS FOR SIMPLER NETWORK • MANAGEMENT

  29. SONET E1 IS THE EUROPEAN T1 (32 8-BIT A-LAW PCM CHANNELS PER FRAME + 1 F-BIT PER FRAME)

  30. SONET TERMINOLOGY • THE END-TO-END CONNECTION THROUGH A SONET/SDH NETWORK IS ALWAYS CALLED THE “PATH” • THE CONNECTION BETWEEN MAJOR NODES, SUCH AS MULTIPLEXERS (ADD/DROP MULTIPLEXERS, SONET MULTIPLEXERS) IS CALLED A “LINE” • THE LINK BETWEEN AN ADD/DROP MULTIPLEXER (ADM) AND A REGENERATOR (REPEATER), OR BETWEEN TWO REGENERATORS, IS CALLED A “SECTION”

  31. SONET TERMINOLOGY SONET MUX SONET MUX

  32. SONET LAYER STRUCTURE • SONET USES A LAYERED ARCHITECTURE TO DESCRIBE • ITS OPERATION • PHYSICAL LAYER  LOWEST LAYER • SECTION LAYER • LINE LAYER • PATH LAYER  HIGHEST LAYER

  33. SONET LAYER STRUCTURE

  34. PHYSICAL LAYER • THE PHYSICAL LAYER DEALS WITH THE TRANSPORT OF • SONET INFORMATION ACROSS THE PHYSICAL MEDIUM • THE LAYER IS RESPONSIBLE FOR CONVERTING • ELECTRICAL STS-N SIGNALS TO OC-N OPTICAL SIGNAL • AND VICE VERSA • THE LAYER DOES NOT ADD ANY OVERHEAD TO THE • SONET SIGNAL

  35. SECTION LAYER • THE SECTION LAYER PROVIDES FRAMING AND • MAINTENANCE FUNCTION BETWEEN TWO PIECES • OF SECTION TERMINATING EQUIPMENT (STE) • THIS SECTION IS THE SMALLEST PORTION OF THE • END-TO-END SONET CONNECTION, AND GENERALLY • REFERS TO THE LINKS BETWEEN REGENERATORS • THE SECTION LAYER HAS ITS OWN OVERHEAD IN • THE SONET SIGNAL (SONET FRAME STRUCTURE)

  36. LINE LAYER • THE LINE LAYER DEALS WITH THE COMMUNICATIONS • BETWEEN SONET LINE TERMINATING EQUIPMENT • (LTE) • THE LTE FUNCTIONS INCLUDE MULTIPLEXING AS • WELL AS LINE MAINTENANCE AND PROTECTION • THE LINE LAYER ALSO HAS ITS OWN OVERHEAD IN • THE SONET SIGNAL (SONET FRAME STRUCTURE)

  37. PATH LAYER • THE PATH LAYER DEALS WITH COMMUNICATIONS • BETWEEN PATH TERMINATING EQUIPMENT (PTE). • PTE MAPS VARIOUS TYPES OF TRAFFIC INTO SONET • FRAMES FOR TRANSPORT, AND REMOVES THAT • TRAFFIC FROM THE SONET FRAME AT THE OTHER • END OF THE PATH • THE PATH LAYER ALSO HAS ITS OWN OVERHEAD • IN THE SONET SIGNAL.

  38. SONET LAYER STRUCTURE • EACH PIECE OF SONET EQUIPMENT PROCESSES ITS • ASSOCIATED OVERHEAD LAYER. • PTE PROCESSES PATH OVERHEAD • LTE PROCESSES LINE OVERHEAD • STE PROCESSES SECTION OVERHEAD • THIS LAYERED STRUCTURE LETS US DEFINE SPECIFIC • FUNCTIONS FOR EACH PART OF THE SONET OVERHEAD, • SO IF WE NEED TO CHANGE THAT FUNCTIONALITY, • WE ONLY HAVE TO CHANGE ONE PART OF THE • OVERHEAD (MODULAR DESIGN)

  39. SONET LAYER STRUCTURE • ALTHOUGH EACH SONET OVERHEAD IS SEGREGATED • BY LAYERS, EACH LAYER REQUIRES THE SERVICES • OF ALL THE LAYERS BELOW IT TO PERFORM ITS • FUNCTIONS. SO BEFORE A PTE PROCESSES ITS • OVERHEAD, THE SECTION AND LINE OVERHEAD MUST • BE PROCESSED • PROCESSING MAY BE ACCOMPLISHED BY SEPARATE • LTE, STE, AND PTE OR A SINGLE PIECE OF EQUIPMENT, • SUCH AS A SONET MULTIPLEXER

  40. SONET LAYER STRUCTURE • A SONET MULTIPLEXER IS A PTE AND OPERATES AT ALL • 4 SONET LAYERS (TAKES DS-3/E1/ATM CELLS IN AND • PUTS OUT AN OC-N SIGNAL OUT) • SONET MULTIPLEXER IS ALSO CALLED A TERMINAL • MULTIPLEXER, OC MULTIPLEXER, BYTE INTER-LEAVED • MULTIPLEXER • THE ADD/DROP MULTIPLEXER (ADM) IS AN LTE

  41. SONET MULTIPLEXER ATM DS3 E1 ATM DS3 E1 DS3 ADD DS3 DROP DS3 ADD DS3 DROP ADD/DROP MUX ADD/DROP MUX

  42. SONET MULTIPLEXER • THE ADD/DROP MULTIPLEXERS (ADMS) ARE LTE • HOWEVER SINCE ADMS CAN ADD OR DROP SIGNALS, • THEY SERVE TWO PURPOSES: • FROM THE PERSPECTIVE OF THE TRAFFIC JUST • PASSING THROUGH HERE, THESE ADMS ARE • FUNCTIONING AS LTE • BUT FOR THE DS3 THAT IS DROPPED AND FOR THE • ONE THAT IS ADDED, THESE ADMS ARE PTE

  43. SONET LAYER STRUCTURE SONET MUX ADM REPEATER

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