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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

Advances in Optical Networks:SONET

By

Sean Goggin

April 19, 2005

overview
Overview
  • Fundamentals of Optical Networks
  • SONET
  • SDH
  • Future of SONET

Advances in Optical Networks: SONET

fundamentals of optical networks
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

fiber optic medium
Fiber Optic Medium
  • Core
    • Medium Where Light Travels
  • Cladding
    • Reflects Light Back into the Core
  • Buffer Coating
    • Protective Coating

Advances in Optical Networks: SONET

variants of fiber optic
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

types of multiplexing
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

types of optical networks
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

oeo repeater
OEO Repeater

Advances in Optical Networks: SONET

erbium doped fiber amplifier
Erbium Doped Fiber Amplifier

Advances in Optical Networks: SONET

optical network equipment
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

optical add drop multiplexer
Optical Add-Drop Multiplexer

Advances in Optical Networks: SONET

topologies
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

ring topology
Ring Topology

Advances in Optical Networks: SONET

mesh topology
Mesh Topology

Advances in Optical Networks: SONET

sample of optical network
Sample of Optical Network

Advances in Optical Networks: SONET

telecom terminology
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

telecom circuits
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

sonet connections
SONET Connections

Advances in Optical Networks: SONET

background of sonet
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

slide20
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

slide21
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

description
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

slide23
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

slide24
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

four layers of sonet
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

sts 1 frame
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

section overhead
Section Overhead
  • 9-Bytes
  • Supports
    • Performance Monitoring (STS-N Signal)
    • Local Orderwire
    • Data Communication Channels
    • Framing

Advances in Optical Networks: SONET

line overhead
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

path overhead
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

sonet virtual tributaries
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

sonet multiplexing hierarchy
SONET Multiplexing Hierarchy

Advances in Optical Networks: SONET

atm over sonet
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

atm cell
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

atm cell header
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

slide37
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

atm header
ATM Header

Advances in Optical Networks: SONET

problems with atm
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

ip over sonet
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

promising future
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

issues to be addressed
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

slide43
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

slide44
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

sonet vs sdh
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

sdh connections
SDH Connections

Advances in Optical Networks: SONET

connection comparison
Connection Comparison

Advances in Optical Networks: SONET

future of sonet
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