SONET Technology Primer by Gary Nicholl Gary Nicholl

Transcription

1 SONET Technology Primer by Gary Nicholl Gary Nicholl

2 Agenda SONET Introduction SONET and Signaling SONET Multiplexing SONET Overhead SONET OAM Summary 2

3 Introduction - What is SONET? SONET - Synchronous Optical NETwork (ANSI) SDH - Synchronous Digital Hierarchy (ITU) Set of physical layer standards for communication over fiber optic (and electrical) links. Note: The material in this presentation is applicable to both SONET and SDH, but for simplicity only SONET terminology is used. 3

4 What does SONET Provide? TDM multiplexing onto high capacity fiber systems. Standard bit rate, frame format, optical specifications to ensure multi-vendor interoperability. Fast restoration (50ms) schemes for both linear (pt-pt) and ring topologies. Operations, Administration, Maintenance & Provisioning (OAM&P) - provision connections - performance monitoring - detect/isolate failures 4

5 SONET Network Overview Synchronization Network ST1 OAM Network ST2 Provisioning ADM Monitoring DS1 DS3 OC-Nc (IP) ADM ADM ADM ADM ADM ADM DS1 DS3 OC-Nc (IP) SONET Transport Network Synchronization Network OAM&P Network 5

6 SONET Terminology Line Path Line Section Section Section Section PTE (Mux,ADM ) STE (REG) LTE (ADM) STE (REG) PTE (Mux,ADM ) Path Termination Section Termination Line Termination Section Termination Path Termination Service (DS1, DS3 ) Mapping Demapping STE= Section Terminating Equipment LTE = Line Terminating Element PTE = Path Terminating Equipment REG = Regenerator MUX = Terminal Multiplexer ADM = Add/Drop Multiplexer DCS = Digital Cross-Connect System Service (DS1, DS3 ) Mapping Demapping 6

7 Signal Hierarchy and Line Rates Synchronous Transport Signal Line Rate Mbits/s Optical Carrier STS OC-1 STS OC-3 STS OC-12 STS OC-48 STS OC-192 7

8 STS-1 Frame Format 9 rows x 90 columns Top row first, transmitted from from left to right 125 us frame 810 bytes / frame Mb/s data rate (810 x 64 kb/s) STS-1 SPE (87 Columns/bytes) Section Overhead (3 Byte/Rows, 3 Columns) Line Overhead (6 Byte/Rows, 3 Columns) A1 A2 C1 B1 D1 H1 B2 D4 D7 E1 D2 H2 K1 D8 F1 D3 H3 K2 D9 D10D11D12 Z1 D5 Z2 D6 J1 B3 C2 G1 F2 H4 Z3 Z4 Z5 Order of Transmission 1 2 Path Overhead (9 Rows x 1 Column) 8

9 STS-1 Synchronization & s STS-1 SPE floats within STS-1 Frame Start of SPE (J1) indicated by pointer bytes (H1/H2) Accounts for difference between STS-1 SPE and STS-1 Frame rates Can tolerate up to 300ppm offset (1 pointer adjustment/4 frames) STS-1 Frame (9 rows / 90 columns) A1 A2 C1 B1 D1 E1 D2 F1 D3 H1 B2 D4 H2 K1 D5 H3 K2 D6 D7 D8 D9 D10D11D12 Z1 Z2 J1 B3 C2 G1 F2 H4 Z3 Z4 Z5 STS-1 SPE (9 rows/ 87 columns) 9

10 STS-N Frame Format SOH (3 Byte/ Rows) LOH (6 Byte/ Rows) TOH (3 Byte/Columns) A1 A2 C1 A1 A2 C1 A1 A2 C1 B1 D1 H1 B2 D4 D7 E1 D2 H2 K1 D8 F1 D3 H3 K2 D9 D10D11D12 Z1 D5 Z2 STS-N = N x byte interleaved STS-1s D6 STS-1#1 STS-1#N J1 J1B3 J1B3C2 B3C2G1 C2G1F2 G1F2H4 F2H4Z3 H4Z3 Z4 Z3Z4 Z5 Z4Z5 Z Interleave Order (125 µs) STS- SPE (87 Byte/Columns) 10

11 SONET Concatenation (STS-Nc) A1 A2 C1 A1 A2 C1 A1 A2 C1 B1 E1 F1 D1 D2 D3 H1 H2 H3 B2 K1 K2 D4 D5 D6 D7 D8 D9 D10D11D12 Z1 Z2 STS POH (1 Byte/Row) STS-1#N STS-1#1 1 Column (N/3)-1 Columns J1 B3 C2 G1 F2 H4 Z3 Z4 Z5 Fixed Stuff STS-Nc Payload Capacity (N x 780 bytes) OC-3c = Mb/s OC-12c = Mb/s OC-48c = Gb/s OC-192c = Gb/s STS-Nc SPE ( N x 87 Byte/Columns) 11

12 SONET Multiplexing Payload IP/ATM P O H STS Envelope STS-3c SPE (155 Mbps) STS Transport Overhead STS-N Facility DS3 Broadband SONET (DS3 or Greater) STS-1 SPE (51 Mbps) Wideband SONET (Channelized STS-1) D S D 1 S D 1 S D 1 S 1 V TV 1.5T V 1.5T V 1.5T 1.5 Payload VT Envelope STS Envelope P O H P O H STS-1 SPE (51 Mbps) Byte Interleave S T S N 12

13 More SONET Multiplexing TOH (3 Byte/ Columns) SOH (3 Byte/ Rows) LOH (6 Rows) A1 A2 C1 A1 A2 C1 A1 A2 C1 B1 D1 H1 B2 D4 D7 STS POH (9 Rows) F1 D3 H3 K2 D9 D10D11D12 Z1 E1 D2 H2 K1 D5 D8 Z2 D6 J1 B3 C2 G1 F2 H4 Z3 Z4 Z5 STS- SPE (87 Byte/Columns) STS- SPE (87 Byte/Columns) Interleave Order (125 µs) 3 N STS-1 Frames for STS-N Signal If DS3 Mapped DS3 Fills SPE If STS SPE Mapped 1 VT Subframe per Column 1 2 DS3 (M13 or Clear Channel) V-4 R S V-3 R S V-2 R S V-1 V-5 S DS1 Payload VT 1.5 Superframe and 500 ms VT 1.5 SPE One Sub-Frame Per STS-1 Frame 500 µs 375 µs 250 µs 125 µs 13

14 IP/ATM Mapping into SONET IP packets and ATM cells are mapped into SONET today! Packet/Cell octets aligned with SONET byte boundaries Cell/Packet boundaries can cross SONET STS-N frame boundaries Frame n Frame n+1 A1A2 TOH J1 B3 C2 G1 F2 H4 Z3 Z4 Z5 Fixed Stuff A1A2 TOH J1 B3 C2 G1 F2 H4 Z3 Z4 Z5 Fixed Stuff 14

15 SONET Overhead Layers Line Path Line Section Section Section Section PTE (ADM, DSLAM, REG ADM or DCS REG PTE (ADM, DSLAM, Path Termination Section Termination Line Termination Section Termination Path Termination Service (DS1, DS3 ) Mapping Demapping PTE = Path Terminating Element MUX = Terminal Multiplexer REG = Regenerator ADM = Add/Drop Multiplexer DCS = Digital Cross-Connect System Service (DS1, DS3 ) Mapping Demapping 15

16 SONET Overhead Byte Designations Transport Overhead Path Overhead Section Overhead Line Overhead A1 B1 A2 Orderwire E1 Trace/ STS ID J0/Z0 F1 Section Data Communication Channel D1 D2 D3 H1 B2 H2 K1 H3 K2 Line Data Communication Channel D4 D5 D6 D7 D8 D9 D10 D11 D12 Sync Status/ S1/Z1 REI/ M0 or M1/Z2 Orderwire Trace J1 B3 Signal Label C2 Path Status G1 F2 Indicator H4 Z3 Z4 Tandem Connection Z5 16

17 Bytes TOH POH SOH A1 B1 H1 A2 Orderwire E1 H2 T/G STS ID J0/Z0 F1 Section Data Comm. Channel D1 D2 D3 H3 Trace J1 B3 Signal Label C2 Path Status G1 2 bytes for framing (F628) reside in all STS-1s framer typically searches for A1/A2 boundary set by h/w B2 K1 K2 F2 LOH Line Data Comm. Channel D4 D5 D6 D7 D8 D9 D10 D11 D12 Sync S1/Z1 REI M0 or M1/Z2 Order wire Indicator H4 Z3 Z4 Tandem Connection Z5 17

18 Performance Monitoring TOH POH SOH LOH A1 B1 H1 B2 H2 K1 H3 K2 Line Data Comm. Channel D4 D5 D6 D7 D8 D10 D11 D12 Sync S1/Z1 A2 Orderwire E1 REI M0 or M1/Z2 T/G STS ID J0/Z0 F1 Section Data Comm. Channel D1 D2 D3 D9 Order wire Trace J1 B3 Signal Label C2 Path Status G1 F2 Indicator H4 Z3 Z4 Tandem Connection Z5 Separate checks for Section, Line and Path BIP = Bit Interleaved Parity Simple even parity scheme Parity calculated over all corresponding bit positions in previous frame. set by h/w B1: 1 x byte / STS-N B2: N x bytes / STS-N B3: 1 x byte / SPE B1/B3 do not scale well with N! 18

19 Section (B1) Example Even parity calculated over all bit 1s from previous STS-N frame. Even parity calculated over all bit 8s from previous STS-N frame. B1 Byte A1 A2 C1 A1 A1 B1A2 A2 E1C1 C1 F1 B1 B1 D1E1 E1 D2F1 F1 D3 D1 D1 H1D2 D2 H2D3 D3 H3 H1 H1 H3 B2H2 H2 K1H3K2 B2 B2 K1 K2 D4K1D5K2D6 D4 D4 D5 D6 D7D5D8D6D9 D7 D7 D8 D9 D10D8 D11 D9 D12 D10 D10D11D12 Z1D11 Z2D12 Z1 Z1 Z2 Z2 A1 A2 C1 A1 A1 B1A2 A2 E1C1 C1 F1 B1 B1 D1E1 E1 D2F1 F1 D3 D1 D1 H1D2 D2 H2D3 D3 H3 H1 H1 H3 B2H2 H2 K1H3K2 B2 B2 K1 K2 D4K1D5K2D6 D4 D4 D5 D6 D7D5D8D6D9 D7 D7 D8 D9 D10D8 D11 D9 D12 D10 D10D11D12 Z1D11 Z2D12 Z1 Z1 Z2 Z2 Frame n Frame n+1 19

20 Line (B2) Example Even parity calculated over all bit 1s from previous STS-1 frame - LOH. Even parity calculated over all bit 8s from previous STS-1 frame - LOH. B2 Byte H1 B2 D4 D7 D10 Z1 H2 K1 D5 D8 D11 Z2 H3 K2 D6 D9 D12 H1 B2 D4 D7 D10 Z1 H2 K1 D5 D8 D11 Z2 H3 K2 D6 D9 D12 Frame n Frame n+1 20

21 Data Communication Channel (DCC) TOH POH SOH LOH A1 B1 H1 B2 H2 K1 H3 K2 Line Data Comm. Channel D4 D5 D6 D7 A2 Orderwire E1 D8 T/G STS ID J0/Z0 F1 Section Data Comm. Channel D1 D2 D3 D9 Trace J1 B3 Signal Label C2 Path Status G1 F2 Indicator H4 Z3 Out-of-Band communications channel Used to transmit OAM data to/from Network Management system Separate Section and Line channels D1-D3-192 kb/s OSI/CMIP D4-D kb/s OSI/CMIP D10 D11 D12 Sync S1/Z1 REI M0 or M1/Z2 Order wire Z4 Tandem Connection Z5 21

22 Automatic Protection Switching () TOH POH SOH A1 B1 H1 B2 A2 Orderwire E1 H2 K1 T/G STS ID J0/Z0 F1 Section Data Comm. Channel D1 D2 D3 H3 K2 Trace J1 B3 Signal Label C2 Path Status G1 F2 K1/K2 - Automatic Protection Switching () Bit mapped communication channel between LTEs for controlling protection switching. Under control of s/w on line card Used on P link only LOH Line Data Comm. Channel D4 D5 D6 D7 D8 D9 D10 D11 D12 Sync S1/Z1 REI M0 or M1/Z2 Order wire Indicator H4 Z3 Z4 Tandem Connection Z5 LTE W P K1/K2 Channel LTE 22

23 Reverse signaling SOH LOH A1 B1 H1 B2 H2 K1 H3 K2 Line Data Comm. Channel D4 D5 D6 D7 D8 D10 D11 D12 Sync S1/Z1 TOH A2 Orderwire E1 REI M0 or M1/Z2 T/G STS ID J0/Z0 F1 Section Data Comm. Channel D1 D2 D3 D9 Order wire POH Trace J1 B3 Signal Label C2 Path Status G1 F2 Indicator H4 Z3 Z4 Tandem Connection Z5 LTE-LTE Signaling Indicates to upstream LTE of downstream failure. RDI - Remote Defect Indicator (hard failure - K2) REI - Remote Error Indicator (B2 bit errors - M1) set by h/w LTE L Fail L-RDI (k2) B2 errors L-REI (M1) LTE 23

24 Path Trace TOH POH SOH LOH A1 B1 H1 B2 H2 K1 H3 K2 Line Data Comm. Channel D4 D5 D6 D7 D8 D10 D11 D12 Sync S1/Z1 A2 Orderwire E1 REI M0 or M1/Z2 Trace J0/Z0 F1 Section Data Comm. Channel D1 D2 D3 D9 Order wire Trace J1 B3 Signal Label C2 Path Status G1 F2 Indicator H4 Z3 Z4 Tandem Connection Z5 J1- Path Trace. End-End path connectivity check 64 byte (SONET) or 16 byte (SDH) repeating message. Inserted continuously at source, checked against expected value by receiver message typically set by user J0 - Section Trace. Not defined yet (old STS ID byte) 24

25 Signal Label TOH POH SOH A1 B1 A2 Orderwire E1 Trace J0/Z0 F1 Section Data Comm. Channel D1 D2 D3 Trace J1 B3 Signal Label C2 Describes contents of payload (e.g. DS1, ATM, FDDI etc.) fixed value, set by application C2 Byte H1 H2 H3 Path Status G LOH B2 K1 K2 Line Data Comm. Channel D4 D5 D6 D7 D8 D9 D10 D11 D12 Sync S1/Z1 REI M0 or M1/Z2 Order wire F2 Indicator H4 Z3 Z4 Tandem Connection Z5 HEX VALUE PAYLOAD 00 Unequipped 01 Equipped Nonspecific payload 02 Virtual Tributaries 04 DS Mb/s 13 ATM 14 DQDB 15 FDDI 16 Scrambled POS (Proposed) CF Unscrambled POS 25

26 Path Status SOH A1 B1 TOH A2 Orderwire E1 Trace J0/Z0 F1 POH Trace J1 B3 G1 Byte Performs function of REI & RDI for PTE LOH Section Data Comm. Channel D1 D2 D3 H1 B2 H2 K1 H3 K2 Line Data Comm. Channel D4 D5 D6 D7 D8 D9 D10 D11 D12 Sync S1/Z1 REI M0 or M1/Z2 Order wire Signal Label C2 Path Status G1 F2 Indicator H4 Z3 Z4 Tandem Connection Z5 G1 Byte REI-P RDI-P UD REI-P: G1 bits 1-4 RDI-P: G1 bits 5-7 Undefined: G1 bit 8 26

27 Order wire TOH POH SOH A1 B1 H1 B2 A2 Orderwire E1 H2 K1 Trace J0/Z0 F1 Section Data Comm. Channel D1 D2 D3 H3 K2 Trace J1 B3 Signal Label C2 Path Status G1 F2 64kbps voice channels used for craftsperson communication between equipment locations mobile phones commonly used instead LOH Line Data Comm. Channel D4 D5 D6 D7 D8 D9 Indicator H4 Z3 D10 D11 D12 Sync S1/Z1 REI M0 or M1/Z2 Order wire Z4 Tandem Connection Z5 27

28 s TOH POH SOH A1 B1 A2 Orderwire E1 T/G STS ID J0/Z0 F1 Section Data Comm. Channel D1 D2 D3 Trace J1 B3 Signal Label C2 Payload bytes H1-H3 Align SPE within STS frame set/controlled by h/w H1 H2 H3 Path Status G1 B2 K1 K2 F2 LOH Line Data Comm. Channel D4 D5 D6 D7 D8 D9 D10 D11 D12 Sync S1/Z1 REI M0 or M1/Z2 Order wire Indicator H4 Z3 Z4 Tandem Connection Z5 28

29 Misc Bytes TOH POH SOH LOH A1 B1 H1 B2 H2 K1 H3 K2 Line Data Comm. Channel D4 D5 D6 D7 D8 D10 D11 D12 Sync S1/Z1 A2 Orderwire E1 REI M0 or M1/Z2 T/G STS ID J0/Z0 F1 Section Data Comm. Channel D1 D2 D3 D9 Order wire Trace J1 B3 Signal Label C2 Path Status G1 F2 Indicator H4 Z3 Z4 Tandem Connection Z5 F1: Customer communications channel. Not used much. F2: same as F1. S1: Sync status byte. Indicates synchronization quality of OC- N signal. H4: Multi-frame byte. Only used for VT payloads. Z3/4: bytes. Allocated for future undefined uses. Z5: Tandem connection. New function. Not used much. 29

30 OAM - The Big Picture? Network Management 3 Data Communications Channel (DCC) LOS LOF B1 B2 1 ADM ADM ADM ADM ADM 2 K1/K2 K1/K2 K1/K2 K1/K2 Three Steps: 1) Detect failure (, B1, B2, B3) 2) Service restoration (50ms) - fast local signaling (K1/K2) 3) Fault isolation and repair - signaling to centralized network management location (DCC) 30

31 Is SONET the only way? 4x140M London Supy Channel (SCM) Bristol 4x140M MUX LTE REG REG REG LTE MUX #1 #2 #N OAM 50km LOS Error counts BER Tx Laser Bias Rx Optical power ALS OAM 565Mb/s Optical Line System Installed 1985, Mercury Communications, London-Bristol 5B6B Block Coded - 678Mb/s line rate Sophisticated single-ended OAM features 31

32 To Wrap Up! TDM multiplexing onto high capacity fiber systems. Standard bit rate, frame format, optical specifications to ensure multi-vendor interoperability. Fast restoration (50ms) schemes for both linear (pt-pt) and ring topologies. Operations, Administration, Maintenance & Provisioning (OAM&P) - provision connections - performance monitoring - detect/isolate failures 32

33 Summary SONET provides standardization, interoperability, and OAM SONET is complex to implement largely due to requirement to support legacy traffic SONET is widely deployed However, there is no magic about SONET 33

34 Acronyms ADM: Add-Drop Multiplex : Automatic Protection Switching BIP: Bit Interleaved Parity BITS: Building Integrated Timing Supply OC: Optical Carrier POH: Path Overhead POS: Packet Over SONET PTE: Path Terminating Entity SDH: Synchronous Digital Hierarchy SONET: Synchronous Optical Network SPE: Synchronous Payload Envelope STE: Section Terminating Entity STM: Synchronous Transport Module STS: Synchronous Transport Signal TOH: Transport Overhead VT: Virtual Tributary 34

35 References Telcordia (Bellcore) GR-253-CORE ANSI T1.105 and T1.106 ITU-T G.707 and G.783 SONET, Walter J. Goralski, McGraw-Hill Series on Computer Communications Broadband Networking, ATM, SDH, and SONET, Mike Sexton, Andy Reid, Artech House 35

36 Backup Material 36

37 SONET STS-1 s 0 us H1 H2 H3 Start of STS-1 SPE 9 Rows STS-1 SPE 125 us 9 Rows H1 H2 H3 STS-1 Path Overhead 250 us Transport Overhead 37

38 Bytes (H1, H2) - Channelized Consider STS-3 3 STS-1 bit steams of Mbps STS-3 H1 H1 H1 H2 H2 H2 Transport Overhead (TOH) x STS-1's H1 H2 SPE 810 Path Overhead (POH) 38

39 Bytes (H1, H2) - Concatenated (STS-Nc) Consider STS-3c (c = concatenated) Single bit stream of Mbps H1 c c H2 c c STS-3c SPE STS-3c SONET Frame Transport Overhead (TOH) 2430 Path Overhead (POH) 39

40 Using s to Accommodate Timing Offsets/Jitter Positive Stuff Negative Stuff Byte After H3 Ignored, Or H3 Holds Extra Byte To Shorten/Lengthen Frame H1, H2 Values Indicate Changes - Maximum Every 4 Frames Requires Close (Not Exact - up to 300ppm offset) Clock Synchronization Among Elements 40

41 SONET Multiplexing Hierarchy STS-1 signals can be wideband or broadband Wideband = Channeled with VT 1.5s containing DS1s Broadband = High rate DS3 and concatenated STS-1s VT mapped STS-1s are designed for transport and switching of sub-sts-1 rate payloads STS-1s can be concatenated to create higher speed payloads STS-3c, STS-12c, STS-48c, STS-192c (future) For data applications, etc.. STS-1s are multiplexed together to create the transmitted payload STS-N = N multiplexed STS-1s Can intermix broadband and wideband STS-1s within STS-Ns N is currently defined as 1, 3, 12, 48,

42 Automatic Protection Switching Uses K1 and K2 bytes of Line Overhead Needs 2 or more fibers Allows network to react to failed lines, interfaces, or poor signal quality Can be provisioned for a 1:1 or 1:n facility For 1:1 each working facility is backed up or protected For 1:n one protection facility exists for n-working fibers Section Line H1 c c H2 c c K1 K2 STS-3c SPE STS-3c SONET Frame 2430 Transport Overhead (TOH) Path Overhead (POH) 42

43 - Diagram ADM/Router Working facility ADM/Router Protection facility 1:1 Protection Working facility Protection facility 1:N Protection 43

44 Automatic Protection Switching - K1, K2 - all bits of K1 + bits 1-5 or K2 K1 byte: Switch priority - K1 bits 1-4 Channel requesting switch action - K1 bits 5-8 K2 byte: Carries the Line "Alarm Indication Signal" and Line "Remote Defect Indicator" 44