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Advances in Optical Networks: SONET

Advances in Optical Networks: SONET. By Sean Goggin April 19, 2005. Overview. Fundamentals of Optical Networks SONET SDH Future of SONET. Fundamentals of Optical Networks. Fiber Optic Medium Variants of Fiber and Optical Networks Multiplexing Methods Optical Network Equipment

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Advances in Optical Networks: SONET

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  1. Advances in Optical Networks:SONET By Sean Goggin April 19, 2005

  2. Overview • Fundamentals of Optical Networks • SONET • SDH • Future of SONET Advances in Optical Networks: SONET

  3. Fundamentals of Optical Networks • Fiber Optic Medium • Variants of Fiber and Optical Networks • Multiplexing Methods • Optical Network Equipment • Topologies of Optical Networks Advances in Optical Networks: SONET

  4. Fiber Optic Medium • Core • Medium Where Light Travels • Cladding • Reflects Light Back into the Core • Buffer Coating • Protective Coating Advances in Optical Networks: SONET

  5. Single-Mode Small Core Approximately 9 Microns Uses IR Laser Light Transmitter Greater then 10 Miles* Most Expensive Multi-Mode Large Core Approximately 62.5 Microns Uses Light Emitting Diode Transmitter Less then 10 Miles* Least Expensive *Without Regeneration Variants of Fiber Optic Advances in Optical Networks: SONET

  6. Types of Multiplexing • Time Division Multiplexing (TDM) • Simplest Implementation • Uses Single Wavelength • Wavelength Division Multiplexing (WDM) • Complex Implementation • Multiple Wavelengths on a Single Fiber to Increase Bandwidth Advances in Optical Networks: SONET

  7. Opaque Weak Signals are Boosted with a Repeater Optical-Electronic-Optical (OEO) Repeater Incurs Pricey Conversion Delay All-Optical (Pure) Weak Signals are Boosted with a Amplifier Erbium-Doped Fiber Amplifier (EDFA) Complete Photonic Boost Types of Optical Networks Advances in Optical Networks: SONET

  8. OEO Repeater Advances in Optical Networks: SONET

  9. Erbium Doped Fiber Amplifier Advances in Optical Networks: SONET

  10. Optical Network Equipment • Repeaters (OEO) & Amplifiers (EDFA) • Optical Crossconnects (OXC) • Photonic Switch with N Full-Duplex Ports • Optical Add-Drop Multiplexer (OADM) • Wavelengths Can Be Added and Removed from the Photonic Flow • Ex: Remove Traffic for Inbound T1 and Traffic for Outbound T1 • Needed for WDM Advances in Optical Networks: SONET

  11. Optical Add-Drop Multiplexer Advances in Optical Networks: SONET

  12. Topologies • Ring Topology • Data Moves in One Direction around 1st Ring • If Failure Occurs, Traffic is Rerouted in Opposite Direction on 2nd Ring • Each Ring is ½ Total Capacity • Self-Maintaining • Mesh Topology • Locations are Linked to 2 or More Other Locations • If a Link Fails, Traffic is Rerouted around the Failure • Requires Routes to be Established Before Failure Advances in Optical Networks: SONET

  13. Ring Topology Advances in Optical Networks: SONET

  14. Mesh Topology Advances in Optical Networks: SONET

  15. Sample of Optical Network Advances in Optical Networks: SONET

  16. Telecom Terminology • Synchronous Optical Network (SONET) • Asynchronous Transfer Mode (ATM) • Digital Signal (DS) • Synchronous Transport Signal (STS) • Optical Carrier (OC) Advances in Optical Networks: SONET

  17. Telecom Circuits • Digital Signal Levels • DS-0: 64 Kb Transmission Channel • DS-1(T1): 1.5 Mb; Formed of 24 DS-0 • DS-3(T3): 44.7 Mb; Formed of 672 DS-0 • Synchronous Transport Signals Channels • STS-1: 52 Mb; Formed of 28 DS-0 or a Single DS-3 • STS-3: 155 Mb; Formed of 84 DS-0 or 3 DS-1 • Electric Signal is Converted to an Optical Signal it Becomes OC Advances in Optical Networks: SONET

  18. SONET Connections Advances in Optical Networks: SONET

  19. Background of SONET • Conceived by MCI During the Mid-1980’s • Designed from the Ground-Up to Hasten the Adoption of Optical Technology • Capacity and Distance Increased Rapidly Due to Technological Developments • Increased Purity of Fiber Optic Cable • Longer Distance without Regeneration • Iron, Nickel, and Hydroxyl Ions Cause Impurities • 1970’s 20dB/km Loss, Today .2 dB/km Loss Advances in Optical Networks: SONET

  20. Development of Laser Technology • Lasers Yield Higher Energy then LEDs Allowing for Longer Distance Before Regeneration • Development of Pure-Optical Technology • Eliminating Optical-Electronic-Optical Conversion for Regeneration & Routing Increase Speed • Possibility to Breach 10 Gb Barrier • Wave Division Multiplexing & Dense Wave Division Multiplexing • Using Multiple Wavelengths Capacity Can Be Increased Upwards of 92 Times the Capacity of a Single Wavelength Advances in Optical Networks: SONET

  21. ANSI Transmission Standard • United States • Canada • Korea • Taiwan • Hong Kong • SDH used in Rest of the World • Interoperable with SONET Advances in Optical Networks: SONET

  22. Description • Physical-Layer Standard • Four-Layer Protocol Stack • TDM Creates Synchronous Channels • Multiplex Many Types of Traffic into Uniform Streams onto Fiber Optic Cabling • Used Primarily as Backbone for ATM Advances in Optical Networks: SONET

  23. Not Well Suited for Data Because of Native 64 kilobit “chunks” • Utilizes Ring Topology for Reliability • Low Maintenance do to Automatic Protection Switching (APS) • Operations, Provisioning, Monitoring and Maintenance Functions are Done Uniformly and Efficiently Advances in Optical Networks: SONET

  24. Typical SONET Ring is Single Wavelength Opaque Network (Circa 2000) • Entire Ring Must Operate at the Same Speed • Adding Capacity to Rings Takes a Long Time and Typically Constitute a New Ring Due to Convenience • Recent use of IP Over SONET Advances in Optical Networks: SONET

  25. Four-Layers of SONET • Photonic: STS Electrical Data is Converted into OC Light Pulses and Vice Versa • Section: Operates between Optical repeaters, Helping to Transmit STS Frames • Line: Synchronizes and Multiplexes Multiple Streams into One Stream, Invokes APS When Required • Path: Used for End-to-end Communications and Control Advances in Optical Networks: SONET

  26. STS-1 Frame • Section, Line, and Path Stack Layers are Overheard in the basic STS-1 Frame • Frame is comprised of 9 Rows by 90 Columns = 810 bytes • 1st 3 Columns of Each Row Addresses Section and Line Overhead (27-Bytes) • 4th Column of Each Row Addresses Path Overhead (9-Bytes) • 86 Columns are Payload (774-Bytes) Advances in Optical Networks: SONET

  27. Advances in Optical Networks: SONET

  28. Section Overhead • 9-Bytes • Supports • Performance Monitoring (STS-N Signal) • Local Orderwire • Data Communication Channels • Framing Advances in Optical Networks: SONET

  29. Line Overhead • 18-Bytes • Supports • Locating the Payload in the Frame • Multiplexing or Concatenating Signals • Performance Monitoring • Automatic Protection Switching (APS) • Line Maintenance Advances in Optical Networks: SONET

  30. Path Overhead • 9 Evenly Distributed Path Overhead Bytes per 125 Microseconds • Supports • Performance Monitoring of Payload • Signal Label • Path Status • Path Trace Advances in Optical Networks: SONET

  31. SONET Virtual Tributaries • SONET is Capable of Accommodating Large and Small Capacities • STS-1 Frame Payload Can be Sub-Divided to Create Virtual Tributaries (VT) • Services Below DS3 are Transported via VTs in SONET • VTs are Multiplexed to Reach Capacity of STS Payload Advances in Optical Networks: SONET

  32. SONET Multiplexing Hierarchy Advances in Optical Networks: SONET

  33. ATM Over SONET • Data-Link Layer Standard • Voice Packets are Synchronous and Continuous, Data Packets are Asynchronous and Burst • ATM Dynamically Allocates “Cells” to Voice and Data on Synchronous and Continuous Connection • Provides Routing, Quality of Service (QoS), and Flexible Traffic Engineering Advances in Optical Networks: SONET

  34. Advances in Optical Networks: SONET

  35. ATM Cell • ATM Cell is 53-Bytes = 48-Bytes User Data + 5-Byte Header • Fixed-Size Cell is More Manageable and Easy to Hardware Route • Cell Header Contains Information Pertaining to the Cell’s Path, Priority, and Other Useful Information Advances in Optical Networks: SONET

  36. ATM Cell Header • General Flow Control (GFC, 4-bit) • Used for Local Functions, i.e. Identifying Multiple Stations that Share an ATM Interface. Typically not Used, Set to a Default Value • Virtual Path Identifier (VPI, 8-bit) • Used with the VCI, to Identify Next Destination of a Cell as it Passes through a Series of Routers on the Way to the Destination • Virtual Channel Identifier (VCI, 16-bit) • Used with the VPI, to Identify Next Destination of a Cell as it Passes through a Series of Routers on the Way to the Destination Advances in Optical Networks: SONET

  37. Payload Type (PT, 3-bit) • First Bit Indicates Whether the Cell Contains User or Control Data. If Cell Contains User Data, the Second Bit Indicates Congestion, and the Third Bit Indicates Whether the Cell is the Last in a Series of Cells • Congestion Loss Priority (CLP, 1-bit) • Indicates Whether the Cell Should be Discarded if it Encounters Extreme Congestion as it Moves through the Network • Header Error Control (HEC, 8-bit) • Checksum Calculated Only on the Header Itself Advances in Optical Networks: SONET

  38. ATM Header Advances in Optical Networks: SONET

  39. Problems with ATM • “Cell Tax” 53-Byte ATM Cells are too Small for Most Data Traffic • Ex: Requires Two 53-Byte ATM Cells to Transfer the Smallest IP Data Packet (64-Bytes) • 5-Byte Tax for Every 48-Bytes of Data for ATM vs. 1,500-Bytes with Minimal Overhead in Ethernet (Best Case) • IP over ATM losses 20% of SONET Rate Advances in Optical Networks: SONET

  40. IP Over SONET • Transports IP Utilizing Point-to-Point Protocol (PPP) and High-level Data Link Control (HDLC) • PPP Provides Multi-Protocol Encapsulation, Error Control, and Link Initialization Control • HDLC Frames the PPP-Encapsulated IP Datagrams into the STS-1 Frame’s Payload • Requires STS-3c (3 Multiplexed STS-1) Advances in Optical Networks: SONET

  41. Promising Future • WDM Allows ATM and IP to Coexist on SONET • Pure-IP Networks Adopting Rapidly • ISPs (AOL) • Carriers (Sprint, GTE, Level 3, Qwest) • Telephony Traffic Remains Static, IP Traffic Increasing 7% to 20% Per Month • Cheaper then ATM Advances in Optical Networks: SONET

  42. Issues to be Addressed • Generating Traffic for STS-3 (155 Mbps) • PPP Establishes Direct Link • No Addressing Capabilities • No Routing Capabilities • PPP has No Flow Control • Additional Router Buffer Maybe Necessary • Multiple Links Need to Be Provisioned in Event of Link Failure Advances in Optical Networks: SONET

  43. Without ATM’s Layer-2 QoS, QoS Must be Added at Layer-3 • Multi-Protocol Label Switching (MPLS) Utilized for QoS, Processor Intensive? • HDLC Poor Scaling Hampers Connections Above OC-48 • Lucent Proposes Simplified Data Link (SDL) Advances in Optical Networks: SONET

  44. SDH • Synchronous Digital Hierarchy (SDH) Published in 1989 by CCITT • Addressing Synchronization of ANSI and CCITT Standards, Establishing a World Standard • 32 64-kb Channels (E0) are Multiplexed into a 2 Mbps E1 Signal • 21 E1 are Multiplexed into a STM-0 (52 Mbps) Advances in Optical Networks: SONET

  45. SONET vs. SDH • 1.5 Mbps DS1 vs. 2 Mbps E1 • 52 Mbps STS-1 vs. 155 Mbps STM-1 • Multiplexing Smaller Connections into Larger is Similar to SONET • SDH can Accommodate SONET By Changing SONET Signal from Bit-Interleaving to Byte-Interleaving. Advances in Optical Networks: SONET

  46. SDH Connections Advances in Optical Networks: SONET

  47. Connection Comparison Advances in Optical Networks: SONET

  48. Future of SONET • 10 Gb Barrier • OC-768 • Tunable Lasers • SONET and Metro Ethernet • Which is Best for MAN? • IP Over SONET vs. IP Over Fiber • Fiber Infrastructure without SONET Advances in Optical Networks: SONET

  49. Advances in Optical Networks: SONET

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