Transcript Click

Advances in Optical Networks:
SONET
By
Sean Goggin
April 19, 2005
Overview
•
•
•
•
Fundamentals of Optical Networks
SONET
SDH
Future of SONET
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
2
Fundamentals of Optical
Networks
•
•
•
•
•
Fiber Optic Medium
Variants of Fiber and Optical Networks
Multiplexing Methods
Optical Network Equipment
Topologies of Optical Networks
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
3
Fiber Optic Medium
• Core
– Medium Where Light
Travels
• Cladding
– Reflects Light Back
into the Core
• Buffer Coating
– Protective Coating
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
4
Variants of Fiber Optic
• Single-Mode
– Small Core
Approximately 9
Microns
– Uses IR Laser
Light Transmitter
– Greater then 10
Miles*
– Most Expensive
Tuesday, April 19, 2005
• Multi-Mode
– Large Core
Approximately 62.5
Microns
– Uses Light Emitting
Diode Transmitter
– Less then 10 Miles*
– Least Expensive
*Without Regeneration
Advances in Optical Networks:
SONET
5
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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
6
Types of Optical Networks
• Opaque
– Weak Signals are
Boosted with a
Repeater
– Optical-ElectronicOptical (OEO)
Repeater
– Incurs Pricey
Conversion Delay
Tuesday, April 19, 2005
• All-Optical (Pure)
– Weak Signals are
Boosted with a
Amplifier
– Erbium-Doped
Fiber Amplifier
(EDFA)
– Complete Photonic
Boost
Advances in Optical Networks:
SONET
7
OEO Repeater
Processor
Strong
Optical
Signal
Optical
Transceiver
Optical
Transceiver
Weak
Optical
Signal
Electronic
Circuit
Pathway
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
8
Erbium Doped Fiber Amplifier
Pump Laser
Strong
Optical
Signal
Filter
Tuesday, April 19, 2005
ErbiumDoped
Fiber
Advances in Optical Networks:
SONET
Coupler
Weak
Optical
Signal
9
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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
10
Optical Add-Drop Multiplexer
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
11
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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
12
Ring Topology
Internet
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
13
Mesh Topology
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
14
Sample of Optical Network
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
15
Telecom Terminology
•
•
•
•
•
Synchronous Optical Network (SONET)
Asynchronous Transfer Mode (ATM)
Digital Signal (DS)
Synchronous Transport Signal (STS)
Optical Carrier (OC)
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
16
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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
17
SONET Connections
Megabits
OC
STS
SONET Channels
Per Second
Level
Level
DS-1
DS-3
52 OC-1
STS-1
28
1
155 OC-3
STS-3
84
3
622 OC-12
STS-12
336
12
2,488 OC-48
STS-48
1,344
48
9,953 OC-192
STS-192
5,376
192
39,812 OC-768
STS-768
21,504
768
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
18
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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
19
– 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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
20
• ANSI Transmission Standard
– United States
– Canada
– Korea
– Taiwan
– Hong Kong
• SDH used in Rest of the World
– Interoperable with SONET
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
21
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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
22
• 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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
23
• 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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
24
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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
25
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)
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
26
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
27
Section Overhead
• 9-Bytes
• Supports
– Performance
Monitoring (STS-N
Signal)
– Local Orderwire
– Data Communication
Channels
– Framing
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
28
Line Overhead
• 18-Bytes
• Supports
– Locating the Payload
in the Frame
– Multiplexing or
Concatenating Signals
– Performance
Monitoring
– Automatic Protection
Switching (APS)
– Line Maintenance
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
29
Path Overhead
• 9 Evenly Distributed
Path Overhead Bytes
per 125 Microseconds
• Supports
– Performance
Monitoring of Payload
– Signal Label
– Path Status
– Path Trace
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
30
SONET Virtual Tributaries
• SONET is Capable of Accommodating
Large and Small Capacities
• STS-1 Frame Payload Can be SubDivided to Create Virtual Tributaries (VT)
• Services Below DS3 are Transported via
VTs in SONET
• VTs are Multiplexed to Reach Capacity of
STS Payload
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
31
SONET Multiplexing Hierarchy
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
32
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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
33
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
34
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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
35
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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
36
• 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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
37
ATM Header
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
38
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 (64Bytes)
– 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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
39
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)
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
40
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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
41
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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
42
• 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)
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
43
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)
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
44
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 BitInterleaving to Byte-Interleaving.
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
45
SDH Connections
Megabits
SDH
STM
Per Second
Level
Level
52
SDH Channels
E1
E4
STM-0
21
155 SDH-1
STM-1
63
1
622 SDH-4
STM-4
252
4
2,488 SDH-16
STM-16
1,008
16
9,953 SDH-64
STM-64
4,032
64
39,812 SDH-256
STM-256
16,128
256
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
46
Connection Comparison
Mbps
OC Level STS Level SDH Level
52 OC-1
STS-1
155 OC-3
STS-3
SDH-1
622
1244
2488
4976
OC-12
OC-24
OC-48
OC-96
9953 OC-192
19906 OC-384
39812 OC-768
Tuesday, April 19, 2005
STM Level
STM-0
STM-1
STS-12
STS-24
STS-48
STS-96
SDH-4
SDH-8
SDH-16
SDH-32
STM-4
STM-8
STM-16
STM-32
STS-192
STS-384
STS-768
SDH-64
SDH-128
SDH-256
STM-64
STM-128
STM-256
Advances in Optical Networks:
SONET
47
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
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
48
Tuesday, April 19, 2005
Advances in Optical Networks:
SONET
49