SONETWhat is SONET?Physical ComponentsSONET ProtocolsProtocols (Cont)Protocol HierarchySignal HierarchyByte MultiplexingSTS-1 Frame FormatMultiplexingConcatenationSTS-3c Frame FormatLocation of SPE in STS-1Scrambling: IntroductionScrambling (Cont)ScramblingAutomatic Protection SwitchingSONET TopologySONET vs SDHSummaryHomeworkAdditional ReferencesRaj JainThe Ohio State University1SONETSONETRaj JainProfessor of CIS The Ohio State UniversityColumbus, OH 43210These slides are available at:http://www.cse.ohio-state.edu/~jain/cis777-99/Raj JainThe Ohio State University2What is SONET?What is SONET?Synchronous optical networkStandard for digital optical transmission (bit pipe)Developed originally by Bellcore. Standardized by ANSI T1X1Standardized by CCITT  Synchronous Digital Hierarchy (SDH)You can lease a SONET connection from carriersCity A City BCarriersRaj JainThe Ohio State University3MultiplexerRepeaterAdd-DropMultiplexerRepeaterMultiplexerTerminalsTerminalsSection Section Section SectionLine LinePathPhysical ComponentsPhysical ComponentsSection = Single run of fiberLine = Between multiplexersRaj JainThe Ohio State University4SONET ProtocolsSONET ProtocolsSynchronous Optical NetworkCity A City BNetworkDatalinkPhysicalTransportLineSectionPhotonicPathRaj JainThe Ohio State University5Protocols (Cont)Protocols (Cont)Photonic Layer: Characteristics of fibers, transmitters, receivers and encoding (ANSI T1.106-1988)Section Layer: Transmission across a single link. Framing, scrambling, and error monitoring.Line Layer: Signaling between multiplexer switches. Frame synchronization. Multiplexing of data in to SONET frames.Path Layer: End-to-end signaling issues. Mapping DS3, FDDI, BISDN into SONET payload.Raj JainThe Ohio State University6Protocol HierarchyProtocol HierarchyPathLineSectionPhotonicPathLineSectionPhotonicTerminal RegeneratorSTS MultiplexerTerminalPhotonic PhotonicSectionSectionLineEnvelopeSTS-N BlockFrameLightRaj JainThe Ohio State University7Signal HierarchySignal HierarchyANSIDesignationOpticalSignalCCITTDesignationData Rate(Mbps)Payload Rate(Mbps)STS-1 OC-1 51.84 50.112STS-3 OC-3 STM-1 155.52 150.336STS-9 OC-9 STM-3 466.56 451.008STS-12 OC-12 STM-4 622.08 601.344STS-18 OC-18 STM-6 933.12 902.016STS-24 OC-24 STM-8 1244.16 1202.688STS-36 OC-36 STM-12 1866.24 1804.032STS-48 OC-48 STM-16 2488.32 2405.376STS-96 OC-96 STM-32 4976.64 4810.176STS-192 OC-192 STM-64 9953.28 9620.928Synchronous Transport Signal Level n = STS-n = n  51.84 MbpsSTM=Synchronous Transport Module, OC=Optical Carrier levelRaj JainThe Ohio State University8Byte MultiplexingByte MultiplexingAlso known as byte interleavingEasier to view in two dimensionB2 A2 C1 B1 A1C2A1A2B1B2C1C2A3B3C3A1A2A3B1B2B3C1C2C3C3C2C1B3B2B1A3A2A1Raj JainThe Ohio State University9STS-1 Frame FormatSTS-1 Frame FormatOverhead = Header. 810 Bytes/125 s = 51.84 Mbps87 ColumnsOverhead3 ColumnsSectionOverhead3 RowsPath Overhead90 ColumnsSynchronous Payload Envelope9 RowsLineOverhead6 RowsRaj JainThe Ohio State University10MultiplexingMultiplexing155.52 Mbps51.84 Mbps 51.84 Mbps51.84 MbpsOverheadSTS-1PayloadOverheadSTS-1PayloadOverheadSTS-1Payload1 ByteRaj JainThe Ohio State University11STS-3c PayloadConcatenationConcatenation155.52 Mbps51.84 Mbps 51.84 Mbps51.84 MbpsOverheadSTS-1PayloadOverheadSTS-1PayloadOverheadSTS-1PayloadOverheadRaj JainThe Ohio State University12STS-3c Frame FormatSTS-3c Frame Format2430 Bytes/125 s = 155.54 Mbps261 ColumnsOverhead9 ColumnsSectionOverhead3 RowsPath Overhead270 ColumnsSynchronous Payload Envelope9 RowsLineOverhead6 RowsRaj JainThe Ohio State University13Location of SPE in STS-1Location of SPE in STS-1SPE supplied by the user  Can arrive at any time  SPE can straddle two successive STS framesPathOverhead3 ColumnsFrame 0 9 RowsFrame 19 Rows87 Columns87 Columns9 RowsRaj JainThe Ohio State University14Scrambling: IntroductionScrambling: IntroductionTwo Methods:1. Add random sequence2. Divide by a number and send quotient. Similar to CRC.Both implemented by shift-registers. Analyzed using polynomials. 1+x6+x7DataDataInDCQSFrameSyncBitClockSSDCSDCQS S S1 2 3 4 5 6 7Raj JainThe Ohio State University15Scrambling (Cont)Scrambling (Cont)Set-Reset Synchronous scrambler: Add a fixed random bit pattern. Need to tell where to start adding  Need to synchronize.Self-synchronous scrambler: Divide by a fixed number. No need for synchronization. Errors multiply.Example: Send 12 using divider 3 Send 4. 1-bit error  Received 5  15  2-bit error in data.Scrambler Descrambler11001001111101Raj JainThe Ohio State University16ScramblingScramblingSONET uses NRZ coding. 1 = Light On, 0 = Light Off.Too many 1’s or 0’s  Loss of bit clocking informationAll bytes (except some overhead bytes) are scrambledPolynomial 1 + x6 + x7 with a seed of 1111111 is used to generate a pseudo-random sequence, which is XOR’ed to incoming bits.1111 1110-0000 0100-0001 … 010If user data is identical to (or complement of) the pseudo-random sequence, the result will be all 0’s or 1’s.Raj JainThe Ohio State University17Automatic Protection SwitchingAutomatic Protection Switching100 ms or more is “loss of signal” 2.3 ms or less is not “loss of signal”In-between is up to implementationsMost implementations use 13-27 ms  Higher speed lines  maintain sync for more bits APS allows switching circuits on faultMay take up to 50 ms to completeWastes entire links as standby.Protection by routers works faster than by SONETRaj JainThe Ohio State University18SONET TopologySONET TopologyTwo fibers: Working + ProtectionOn a fault, faulty cable is isolated and ring heals itself.Four Fibers: Two working + Two protection  Bi-directional operation  Traffic sent over shortest pathMuxSurvivableRingMuxMuxMuxRaj JainThe Ohio State University19SONET vs SDHSONET vs SDHANSI vs ITU-TBits 5,6 of SPE/VC pointer are different [RFC2171]Synchronous payload envelope (SPE) vs Virtual Container (VC)Network element vs Network node interfaceSection vs regenerator sectionLink vs multiplex sectionRaj JainThe Ohio State University20SummarySummarySONETSDHSTS-n, STM-nSTS-3cRaj JainThe Ohio State University21HomeworkHomeworkRead Chapter 8 of Black’s Emerging Technologies, 2nd Ed.Raj JainThe Ohio State University22Additional ReferencesAdditional ReferencesChapter 9 of FDDI Handbook by Raj