SONETWhat is SONET?Physical ComponentsSONET ProtocolsProtocols (Cont)Protocol HierarchySignal HierarchyByte MultiplexingSTS-1 Frame FormatMultiplexingConcatenationSTS-3c Frame FormatLocation of SPE in STS-1Scrambling: IntroductionScrambling (Cont)ScramblingSONET vs SDHSummaryHomeworkRaj JainThe Ohio State University1SONETSONETRaj JainProfessor of CIS The Ohio State UniversityColumbus, OH 43210http://www.cse.ohio-state.edu/~jain/Raj JainThe Ohio State University2What is SONET?What is SONET?Synchronous optical networkStandard 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 ComponentsSection = Single run of fiberLine = Between multiplexersRaj JainThe Ohio State University4SONET ProtocolsSONET ProtocolsSynchronous 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 MultiplexingAlso known as byte interleavingEasier to view in two dimensionB2 A2 C1 B1 A1C2A1A2B1B2C1C2A3B3C3A1A2A3B1B2B3C1C2C3C3C2C1B3B2B1A3A2A1Raj JainThe Ohio State University9STS-1 Frame FormatSTS-1 Frame FormatOverhead = 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 Format2430 Bytes/125 ms = 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-1SPE 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 University16ScramblingScramblingSONET uses NRZ coding. 1 = Light On, 0 = Light Off.Too many 1’s or 0’s Loss of bit clocking informationAll bytes (except some overhead bytes) are scrambledPolynomial 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 … 010If 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 University17SONET vs SDHSONET vs SDHANSI vs ITU-TBits 5,6 of SPE/VC pointer are different [RFC2171]Synchronous payload envelope (SPE) vs Virtual Container (VC)Network element vs Network node interfaceSection vs regenerator sectionLink vs multiplex sectionRaj JainThe Ohio State University18SummarySummarySONETSDHSTS-n, STM-nSTS-3cRaj JainThe Ohio State University19HomeworkHomeworkRead chapter 9 of FDDI Handbook by Raj
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