SONET Technology Primer by Martin Schulman NANOG May

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

<1984 NA Digital Telephony DS 1 M 13 Fiber Optic Transmission Systems • Switches • Leased Line M 13 DS 1 Cross Connect Fiber DS 3 Central Office Key System Aspects: • M 13 Building Blocks • Asynchronous Operation • Electrical DS 3 Signals • Proprietary Fiber Systems • Brute Force Cross Connect • AT&T Network/Western Electric Equipment NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. Central Office M 13 No Guaranteed Timing Synchronization DS 3 DS 1 Central Office Slide 3 COMPANY CONFIDENTIAL

Post-Divestiture Dilemmas • Switches • Leased Line • LAN Services • Data Services Different Carriers, Vendors Faster Fiber Coming: • Need “Mid-Span Meet” • Support New Services • Allow Other Topologies • Standardize Redundancy • Common OAM&P • Scalable Cross Connect NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. M 13 DS 1 Internal DS 3 Cross Connect Support Other Topologies, Protect Fibers Slide 4 COMPANY CONFIDENTIAL

The Standards Process Divestiture CCITT Expresses Internet in SONET British and Japanese Participation in T 1 X 1 Exchange Carriers Standards Associate (ECSA) T 1 Committee Formed ANSI T 1 X 1 Bellcore Proposed Approves SONET Principles Project To ANSI T 1 X 1 1984 1985 CCITT XVIII Begins Study Group 1986 SONET/SDH Standards Approved CEPT Proposes Merged ANSI/CCITT Standard 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, III Separate APS, etc. NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. US T 1 X 1 Accepts Modifications ANSI Approves SYNTRAN Slide 5 COMPANY CONFIDENTIAL

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

Equipment Types 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 NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. Line SONET End Device - I. e. Telephony Switch, Router PTE Slide 7 COMPANY CONFIDENTIAL

STS-1 Frame Format 90 Bytes Or “Columns” 9 Rows Each Small Rectangle Represents One Byte 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. Transmitted MSB First Slide 8 COMPANY CONFIDENTIAL

Section Overhead (SOH) Rcv SOH Xmt SOH A 1 =0 x. F 6 A 2 =0 x 28 J 0/Z 0 STS-ID B 1 BIP-8 E 1 Orderwire F 1 User D 1 D 2 D 3 Data Com 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. • A 1, A 2 - Framing Bytes • J 0/Z 0 - Section ID, Reserved • BIP-8 - Bit Interleaved Parity • E 1 Orderwire - Craft Voice Interface Between Sections • F 1 User - Proprietary Management • D 1 -D 3 - 192 Kbps OSI/CMIP Channel Slide 9 COMPANY CONFIDENTIAL

Line Overhead (LOH) H 1 Pointer Xmt LOH Xmt SOH Rcv LOH Rcv SOH Xmt SOH Rcv SOH B 2 BIP-8 H 2 H 3 Pointer Act K 1 APS K 2 APS D 4 D 5 D 6 Data Com D 7 D 8 D 9 Data Com D 10 D 11 D 12 Data Com Line Overhead • 18 Bytes Total • Originated And Terminated By All Section Devices (Regenerators, Multiplexers, CPE) • LOH+SOH=TOH (Transport OH) NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. S 1 M 0 E 1 Sync REI Orderwire • H 1 -3 - Payload Pointers • BIP-9 Bit Parity • K 1, K 2 - Automatic Protection Switching • D 4 -D 12 - 576 kbps OSI/CMIP • S 1 - Time Sync Indicator • M 0 - Return Error Indicator • E 1 Orderwire - Craft Voice Interface Between Sections Slide 10 COMPANY CONFIDENTIAL

Path Overhead (POH) PTE STE Frame N+1 Path Overhead • H 1, H 2 Point To 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 NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. J 1 Trace B 3 BIP-8 C 2 Sig Label G 1 Path Stat F 2 User H 4 Indicator Z 3 Growth • J 1 - Repeated ID String • BIP-8 - Parity • C 2 - Payload Type Indicator • G 1 - End Path Status • F 2 - User • H 4 - Use Depends On Payload • Z 3 -5 - Future Growth Z 4 Growth Z 5 Tandem Slide 11 COMPANY CONFIDENTIAL

SPE Synchronous Payload Envelope • Contains POH + Data • First Byte Follows First Byte Of POH • Wraps In Subsequent Columns • May Span Frames • Up To Single 49. 536 Data Signal Enough for DS 3 NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. Defined Payloads • Virtual Tributaries (For DS 1, DS 2) • DS 3 • SMDS • ATM • PPP • More. . . Slide 12 COMPANY CONFIDENTIAL

Accommodating Jitter Positive Stuff Negative Stuff Byte After H 3 Ignored, Or H 3 Holds Extra Byte To Shorten/Lengthen Frame H 1, H 2 Values Indicate Changes - Maximum Every 4 Frames Requires Close (Not Exact) Clock Synchronization Among Elements NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. Slide 13 COMPANY CONFIDENTIAL

Clock Synchronization BITS PTE • Level 1: 10 -11 • Level 2: 1. 6 x 10 -8 • Level 3: 4. 6 x 10 -6 • Level 4: 32 x 10 -6 Primary 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) NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. Backup Reference BITS PTE Slide 14 COMPANY CONFIDENTIAL

STS-N Frame Format 90 x. N Bytes Or “Columns” N Individual STS-1 Frames Composite Frames • Byte Interleave STS-1’s • Clock Rate = Nx 51. 84 Mbps NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. Examples STS-1 51. 84 Mbps STS-3 155. 520 Mbps STS-12 622. 080 Mbps STS-48 2. 48832 Gbps STS-191 9. 95323 Gbps Slide 15 COMPANY CONFIDENTIAL

STS-Nc Frame Format 90 x. N Bytes Or “Columns” Transport Overhead Composite Frames • Same TOH Structure And Data Rates As STS-N • Not All TOH Bytes Used • First H 1, H 2 Point To POH • Single Payload In Rest Of SPE • Accommodates FDDI, E 4, etc. NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. Examples Only 1 BIP-8 for section layer (B 1) Only One DCC (D 1 -D 3) Only Two E 1, E 2 Orderwires Only One User (F 1) Only One APS (K 1 and K 2) Only One DCC (D 4 -D 12) Slide 16 COMPANY CONFIDENTIAL

Transmission Encoding Electrical Transmission Standard • STS-1: B 3 ZS (BPV), 450’ • STS-3: Coded Mark Inversion, 225’ • Useful Intra-Office Connection Scrambling • Ensures Ones Density • Does Not Include A 1, A 2, C 1 Bytes • Output Is NRZ Encoded 1+x 6+x 7 E O OC-N Is Optical Carrier STS-N Long Reach: 40 km 1310 or 1550 nm SM Intermediate Reach: 15 km 1310 or 1550 nm SM Short Reach: Long Reach 2 km 1310 nm MM NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. Slide 17 COMPANY CONFIDENTIAL

Network Elements D+R DS 1 s TM ADM MN MN DCC DS 1 s D+R Nonstandard, Functional Names TM: Terminal Mux ADM: Add-Drop Mux DCC: Digital Cross Connect (Wideband Broadband) MN: Matched Node D+R: Drop and Repeat NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. Slide 18 COMPANY CONFIDENTIAL

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

OAM&P OSI Node DCC Links Hardware Error Detection Hardware Error Signaling SONET Processing Hardware NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. Manageability Is Required Well Defined Protocols, Alarms: • Loss of Signal: All 0’s • Loss Of Frame: Cannot Find A 1, A 2 • 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 Slide 20 COMPANY CONFIDENTIAL

APS ADM ADM Line Protection Switching Uses TOH Trunk Application Backup Capacity Is Idle Supports 1: n, N=1 -14 ADM ADM Path Protection Switching 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 • K 1, K 2 Bytes Signal Change • Common Uses: 2 Fiber UPSR or ULSR, 4 Fiber BPSR NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. Slide 21 COMPANY CONFIDENTIAL

Packet Over SONET (POS) Standard PPP Encapsulation • Magic Number Recommended • No Addres and Control Compression • No Protocol Field Compression PPP FCS Byte Stuff Standard CRC Computation • OC 3 May Use CRC-16 • Other Speeds Use CRC-32 NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. Special Data Scrambler • 1+ x 43 Polynomial • Protects Against Transmitted Frames Containing Synch Bytes Or Insufficient Ones Density Scrambling SONET Framing • OC 3, OC 12, OC 48, OC 192 Defined • C 2 Byte = 0 x 16 With Scrambling • C 2 Byte = ox. CF Without (OC-3) Slide 22 COMPANY CONFIDENTIAL

Technology Relationships u Synchronous Digital Hierarchy (SDH) International Diffs - Terms, OH Fields v Rates: STS-N -> STM-N/3 For N>=3 v u SDL Proposal Fix HDLC For High Speed Use v Pt-Pt Links Without SONET Overhead v u WDM/DWDM: More Capacity - Optical Routing For Redundancy v No Access To Lower-Level (I. e. DS 1 Signals) v NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. Slide 23 COMPANY CONFIDENTIAL

Acronyms u u u u 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. Slide 24 COMPANY CONFIDENTIAL

References Telcordia (Bellcore) GR-253 -CORE u ANSI T 1. 105 and T 1. 106 u ITU-T G. 707 and G. 783 u SONET, Walter J. Goralski, Mc. Graw-Hill Series on Computer Communications u RFC-1619 and Successor u v http: //search. ietf. org/internet-drafts/draft-ietf-pppext-pppoversonetupdate-04. txt NANOG, May 23 -25 Copyright © 1999, Juniper Networks, Inc. Slide 25 COMPANY CONFIDENTIAL