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SONET Technology Primer

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Presentation on theme: "SONET Technology Primer"— Presentation transcript:

1 SONET Technology Primer
by Martin Schulman

2 Topics To Be Covered Motivation & History
Termination Equipment And Frame Formats Electrical And Optical Encoding Topologies And Redundancy PPP Over SONET Relationship To Other Standards NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

3 <1984 NA Digital Telephony
Fiber Optic Transmission Systems DS1 M13 M13 DS1 DS1 Cross Connect Switches Leased Line Fiber DS3 Central Office M13 Central Office DS3 No Guaranteed Timing Synchronization Key System Aspects: M13 Building Blocks Asynchronous Operation Electrical DS3 Signals Proprietary Fiber Systems Brute Force Cross Connect AT&T Network/Western Electric Equipment DS1 Central Office NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

4 Post-Divestiture Dilemmas
Switches Leased Line LAN Services Data Services Different Carriers, Vendors DS1 M13 Internal DS3 Cross Connect Faster Fiber Coming: Need “Mid-Span Meet” Support New Services Allow Other Topologies Standardize Redundancy Common OAM&P Scalable Cross Connect Support Other Topologies, Protect Fibers NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

5 SONET Concept Developed By Bellcore
The Standards Process Divestiture CCITT Expresses Internet in SONET SONET/SDH Standards Approved Exchange Carriers Standards Associate (ECSA) T1 Committee Formed British and Japanese Participation in T1X1 ANSI T1X1 Approves Project CCITT XVIII Begins Study Group CEPT Proposes Merged ANSI/CCITT Standard Bellcore Proposed SONET Principles To ANSI T1X1 1984 1985 1986 1987 1988 SONET Concept Developed By Bellcore Standard That Almost Wasn’t >400 Technical Proposals Rate Discussions AT&T vs. Bellcore International Changes For Byte/Bit Interleaving, Frames, Data Rates Phase I, II, III Separate APS, etc. US T1X1 Accepts Modifications ANSI Approves SYNTRAN NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

6 SONET Defined Synchronous Optical Network
Set of Layer 1 Standards For Communication over Fiber Optic (and Electrical) Links In Order To Facilitate: Fiber Optic Link Speed Increases Variety Of Topologies and Grooming Functions Operations, Administration, Maintenance, and Provisioning (OAM&P) When Used As Telephony Carrier Equipment And CPE Interconnect NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

7 Equipment Types All Perform Electro-Optical Conversion
Path Sections PTE Repeaters All Perform Electro-Optical Conversion Section Termination (STE) Line Termination (LTE) Path Termination (PTE) Data Between PTE May Traverse Multiple LTE, STE Line SONET End Device - I.e. Telephony Switch, Router PTE NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

8 STS-1 Frame Format Frame Transmission
90 Bytes Or “Columns” 9 Rows Each Small Rectangle Represents One Byte Transmitted MSB First Frame Transmission Top Row First, Sent Left To Right 125 ms/Frame 810 Bytes/Frame 51.84 Mbps Rate Frame Contains One Payload NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

9 Section Overhead (SOH)
=0xF6 A2 =0x28 J0/Z0 STS-ID Rcv SOH Xmt SOH B1 BIP-8 E1 Orderwire F1 User D1 Data Com D2 Data Com D3 Data Com A1,A2 - Framing Bytes J0/Z0 - Section ID, Reserved BIP-8 - Bit Interleaved Parity E1 Orderwire - Craft Voice Interface Between Sections F1 User - Proprietary Management D1-D Kbps OSI/CMIP Channel Section Overhead 9 Bytes Total Originated And Terminated By All Section Devices (Regenerators, Multiplexers, CPE) Other Fields Pass Unaffected NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

10 Line Overhead (LOH) Line Overhead 18 Bytes Total
Pointer H2 Pointer H3 Pointer Act B2 BIP-8 K1 APS K2 APS Xmt LOH Rcv LOH D4 Data Com D5 Data Com D6 Data Com Rcv SOH Xmt SOH Xmt SOH Rcv SOH D7 Data Com D8 Data Com D9 Data Com D10 Data Com D11 Data Com D12 Data Com S1 Sync M0 REI E1 Orderwire Line Overhead 18 Bytes Total Originated And Terminated By All Section Devices (Regenerators, Multiplexers, CPE) LOH+SOH=TOH (Transport OH) H1-3 - Payload Pointers BIP-9 Bit Parity K1, K2 - Automatic Protection Switching D4-D kbps OSI/CMIP S1 - Time Sync Indicator M0 - Return Error Indicator E1 Orderwire - Craft Voice Interface Between Sections NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

11 Path Overhead (POH) Path Overhead
J1 Trace PTE STE PTE B3 BIP-8 J1- Repeated ID String BIP-8 - Parity C2 - Payload Type Indicator G1 - End End Path Status F2 - User H4 - Use Depends On Payload Z3-5 - Future Growth Frame N Frame N Frame N+1 C2 Sig Label Frame N+1 G1 Path Stat Path Overhead H1,H2 Point To Beginning - Beginning Floats Within Frame 9 Bytes (1 Column) Spans Frames Originated And Terminated By All Path Devices (I.e. CPE, Switches) STE Can Relocate Payload F2 User H4 Indicator Z3 Growth Z4 Growth Z5 Tandem NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

12 SPE Synchronous Payload Envelope Contains POH + Data
First Byte Follows First Byte Of POH Wraps In Subsequent Columns May Span Frames Up To Single Data Signal - Enough for DS3 Defined Payloads Virtual Tributaries (For DS1, DS2) DS3 SMDS ATM PPP More... NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

13 Accommodating 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) Clock Synchronization Among Elements NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

14 Clock Synchronization
BITS BITS Level 1: 10-11 Level 2: 1.6x10-8 Level 3: 4.6x10-6 Level 4: 32x10-6 PTE Primary Reference Backup Reference Building Integrated Timing System Hierarchical Clocking Distribution Normally All Synch’d To Stratum 1 (Can Be Cesium/Rubidium Clock) Dedicated Link Or Recovered Fallback To Higher Stratum In Failure (Temperature Controlled Crystal) BITS PTE NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

15 N Individual STS-1 Frames
STS-N Frame Format 90xN Bytes Or “Columns” N Individual STS-1 Frames Composite Frames Byte Interleave STS-1’s Clock Rate = Nx51.84 Mbps Examples STS Mbps STS Mbps STS Mbps STS Gbps STS Gbps NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

16 STS-Nc Frame Format Composite Frames
90xN Bytes Or “Columns” Transport Overhead Composite Frames Same TOH Structure And Data Rates As STS-N Not All TOH Bytes Used First H1, H2 Point To POH Single Payload In Rest Of SPE Accommodates FDDI, E4, etc. Examples Only 1 BIP-8 for section layer (B1) Only One DCC (D1-D3) Only Two E1, E2 Orderwires Only One User (F1) Only One APS (K1 and K2) Only One DCC (D4-D12) NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

17 Transmission Encoding
Electrical Transmission Standard STS-1: B3ZS (BPV), 450’ STS-3: Coded Mark Inversion, 225’ Useful Intra-Office Connection Scrambling Ensures Ones Density Does Not Include A1, A2, C1 Bytes Output Is NRZ Encoded 1+x6+x7 E O OC-N Is Optical Carrier STS-N Long Reach: 40 km 1310 or 1550 nm SM Intermediate Reach: 15 km Short Reach:Long Reach 2 km 1310 nm MM NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

18 Network Elements Nonstandard, Functional Names TM: Terminal Mux
D+R MN MN TM ADM DCC DS1s D+R MN MN D+R DS1s Nonstandard, Functional Names TM: Terminal Mux ADM: Add-Drop Mux DCC: Digital Cross Connect (Wideband and Broadband) MN: Matched Node D+R: Drop and Repeat NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

19 Topology Building Blocks
ADM ADM 2 Fiber Ring 4 Fiber Ring DCC ADM DCC ADM Each Line Is Full Duplex Each Line Is Full Duplex ADM ADM ADM ADM DCC ADM DCC ADM ADM ADM Uni- vs. Bi- Directional All Traffic Runs Clockwise, vs Either Way NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

20 SONET Processing Hardware
OAM&P OSI Node Manageability Is Required Well Defined Protocols, Alarms: Loss of Signal: All 0’s Loss Of Frame: Cannot Find A1,A2 Alarm Indication Signal - Line: Remote Side Sees LOS or LOF Remote Defect Indication - Line: Remote Seeing Above Alarms Alarm Indication Signal - Path: Indication To Downstream Devices Of A Problem Remote Defect Indication - Path: Indication To Upstream Devices Of A Problem SONET Processing Hardware DCC Links Hardware Error Detection Hardware Error Signaling NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

21 APS Line Protection Switching Path Protection Switching
ADM ADM ADM ADM ADM ADM Line Protection Switching Path Protection Switching Uses TOH Trunk Application Backup Capacity Is Idle Supports 1:n, N=1-14 Uses POH Access Line Applications Duplicate Traffic Sent On Protect 1+1 Automatic Protection Switching Line Or Path Based Revertive vs. Non-Revertive Mechanism For Intentional Cutover Restoration Times ~ 50 ms K1, K2 Bytes Signal Change Common Uses: 2 Fiber UPSR or ULSR, 4 Fiber BPSR NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

22 Packet Over SONET (POS)
Special Data Scrambler 1+ x43 Polynomial Protects Against Transmitted Frames Containing Synch Bytes Or Insufficient Ones Density Standard PPP Encapsulation Magic Number Recommended No Addres and Control Compression No Protocol Field Compression PPP FCS Byte Stuff Scrambling SONET Framing Standard CRC Computation OC3 May Use CRC-16 Other Speeds Use CRC-32 SONET Framing OC3, OC12, OC48, OC192 Defined C2 Byte = 0x16 With Scrambling C2 Byte = oxCF Without (OC-3) NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

23 Technology Relationships
Synchronous Digital Hierarchy (SDH) International Diffs - Terms, OH Fields Rates: STS-N -> STM-N/3 For N>=3 SDL Proposal Fix HDLC For High Speed Use Pt-Pt Links Without SONET Overhead WDM/DWDM: More Capacity - Optical Routing For Redundancy No Access To Lower-Level (I.e. DS1 Signals) NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

24 Acronyms ADM: Add-Drop Multiplex APS: 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 NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

25 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 RFC-1619 and Successor NANOG, May 23-25 Copyright © 1999, Juniper Networks, Inc.

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