Transcript Optical Networks: The Platform for the Next Generation

Optical Networks: The Platform
for the Next Generation Internet
Andrea Fumagalli
Dept. of Electrical Engineering
University of Texas at Dallas
[email protected]
01/18/2000
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Optical Networks
Team:
James Cai
Isabella Cerutti
Jing Li
Marco Tacca
Luca Valcarenghi
University of Texas at Dallas
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Outline
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The Optical Layer
Static/Semi-Static Ligthpath Networks
Dynamic Ligthpath Networks
Optical Packet Switching
Current Projects and Testbeds
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The Optical Layer
The Optical Layer
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Optical fiber
Optical Amplifiers (OA)
Wavelength Routing Nodes (WRN)
The ITU Optical Layer
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Optical Fiber
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Three transmission windows
– first: 800-900 nm (Multimode)
– second: 1240-1340 nm (Singlemode)
– third:1500-1650 nm (Singlemode)
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Potentially available bandwidth in each
window ~ 20 THz
Effective bandwidth limited by the device
characteristics
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Semiconductor Optical Amplifiers
(SOA)
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Broadband gain characteristics (work
both at 1300 nm and 1550 nm)
Maximum bandwidth up to 100 nm
Gain fluctuation, polarization dependent,
high coupling loss
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Doped Fiber Amplifiers
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Erbium-Doped Fiber Amplifiers (EDFA)
– Conventional (C)  band ~1530-1565 nm
– Long (L)  band ~1570-1605 nm (soon)
– Total available bandwidth ~ 70 nm (i.e., 80x2
channels at 10Gb/s)
 High gain with no crosstalk, small noise figure,
low loss
 Gain function of , bigger dimensions
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Praseodymium-Doped Fiber Amplifiers
(PDFA)
– amplify at 1300 nm (not yet available)
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Wavelength Routing Nodes (WRN)
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OADM (Optical Add Drop Multiplexer)
F-OXC (Fiber Optical Crossconnect)
WT-OXC (Wavelength Translating Optical
Crossconnect)
WR-OXC (Wavelength Routing Optical
Crossconnect)
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WRN Schematic Representation
F-O XC
OADM
Node A
Node A
From node B
From node B
To C
To C
Drop Add
Drop Add
WR-OXC
WT-O XC
Node A
Node A
From node B
From node B
Drop Add
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To C
To C
To D
To D
Drop Add
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WRN Functions
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OADM usually 2x2 F-OXC with  adding
and dropping
F-OXC fiber switching with  adding and
dropping
WT-OXC wavelength and fiber switching
with  conversion
WR-OXC wavelength and fiber switching
without  conversion
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ITU and Optical Layer
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International Telecommunications Union
agency of United Nations devoted to
standardize international communications
Optical Layer defined by ITU inside the
ISO-OSI Data Link layer (Rec. G.805)
OL provides lightpaths to higher layers
lightpath: point-to-point all-optical
connection between physically nonadjacent nodes
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Optical Layer (OL)
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Consists of:
– Optical Channel (OC) layer or lightpath layer
 end-to-end route of the lightpaths
– Optical Multiplex Section (OMS) layer 
point-to-point link along the route of a
lightpath
– Optical Amplifier Section (OAS) layer  link
segment between two optical amplifier
stages
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Inter-layer Design Issues
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Issues in establishing, e.g., a lightpath
– OC layer  routing, protection, and
management
– OMS layer  monitoring, multiplexing
– OAS layer  regeneration, amplification
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Optical Network Techniques
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Static/Semi-static Lightpath
Dynamic Lightpath
Optical Packet Switching
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Static/Semi-Static Lightpath
Networks
Static/Semi-Static Ligthpath
Networks
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Design issues
The RWA problem
OL protection issues
Multicast in WDM networks
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Design Issues
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Optical layer dimensioning
Routing and Wavelength Assignment
(RWA) problem:
given a physical topology and a set of
end-to-end lightpaths demands determine
a route and a  assignment for each request
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Fault protection
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Optical Layer Dimensioning
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Each fiber can carry up to 128 ’s each
operating at 10 Gb/s [Chabt et al. ‘98]
The Optical Layer is given a lightpath
demand matrix
Demands are obtained by models applied
to the IP layer
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RWA Problem
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Static Lightpath Establishment (SLE)
(with no  conversion at the nodes) is a
NP-complete problem [Chlamtac ‘92]
Need for either approximate or heuristic
solutions
Joint optimization with the spare capacity
assignment  global network resources
optimization
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Global Network Optimization
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Given the lightpath demand matrix find
contemporary the solution of the RWA
problem for working and protection ’s
Objective:
minimize the total required network
resources (e.g., -mileage, number of OXCs
and so on) while guaranteeing network
resilience from a single network fault
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OL Protection Techniques
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End-to-end Path
– Shared-Path Protection (SPP)
– Dedicated-Path Protection (DPP)
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WDM Self-Healing Ring (WSHR)
– Shared-Line-switched WSHR (SL-WSHR) or
WDM SPRING (Shared Protection RING)
– Dedicated-Path-switched WSHR (DPWSHR) or Unidirectional Path-Protected
Ring (UPPR)
– Shared-Path-switched WSHR (SP-WSHR)
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OL Protection Schemes
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Multi-WSHR Approach
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Wavelength Minimum Mileage (WMM)
problem:
Minimize -mileage (product between the
number of required channels in every link
and its length) for a given set of traffic
demands in a generic mesh topology using
WSHRs
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Practical constraints:
– maximal ring size, maximal number of rings
per link and per node
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WMM Sub-problems
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Ring Cover (RC):
– select the rings to cover each link carrying a
working lightpath
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Working Lightpath (WL) routing:
– route the working lightpath for each traffic
demand
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Spare Wavelength (SW) assignment:
– protect each working lightpath using the
selected rings
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WMM Solution
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Modular solutions
– Assume a ring cover, find optimal path
routing
– Assume a path routing, find optimal ring
cover
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Joint solution (here)  global optimum
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Results
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Practical Constraints:
– Maximum ring size of
8 nodes
– At most 2 ring per link
– At most 4 rings per
node
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ILP versus SA
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C= set of rings, SRA= Shortest Ring Algorithm,
SR= Shortest Ring, SP= Shortest Path
Uniform traffic, SL-WSHR
Pentium based Processor 166MHz
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Multicast in WDM Networks
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Pros
– Built-in multicast-capability: optical coupler and
optical splitter
– Provide high bandwidth
– Multiple wavelengths can support multiple multicast
groups
– Virtual network topology can be reconfigured by
crossconnect or wavelength converter (in the semistatic lightpath case)
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Multicast in WDM Networks
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Cons
– Global topology of the network is needed
– Reconfiguration delay is rather slow (it implies
utilization of static/semi-static lightpath)
– The number of multicast groups supported is limited
by the number of wavelength per fiber
– Not suitable for receiver oriented multicast (dynamic
reconfiguration)
– Optical amplifier is needed to compensate the power
loss due to optical splitting
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Building Light-tree to Implement
Multicast
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A light-tree rooted at the source and covering
all the destinations is build using a dedicated
wavelength
From upper layer’s point of view, it is one hop
from source to all the destinations
Optical signal is not converted to electrical
format at intermediate node, so that fewer
transmitters and receivers are needed
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Dynamic Ligthpath Networks
Dynamic Ligthpath Networks
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Dynamic routing and channel assignment
Network scenario and layering
Multi-token WDM networks
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Dynamic Lightpath
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Reconfigurable networks
WT-OXC, WR-OXC, and active
components used
More expensive than fixed networks
Adaptable to varying lightpath requests
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Dynamic Routing and Channel
Assignment
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Logical connection (lightpath) requests
arrive randomly
Network state:
all active connections with their optical
path (route and wavelength assignment)
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Real time algorithm needed to
accommodate each request
Blocking and fairness issues
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Network Scenario
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Ring and interconnected rings are among
the most used topologies
Several ring based results in the literature
Acceptable management complexity as
opposed to arbitrary network topology
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Network Layering
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Network Layers
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Physical Layer
– consists of the physical connections of the
network
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Interconnected Ring Layer
– adapts the static nature of the physical layer
to the dynamic nature of the traffic
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Logical Layer
– furnishes higher connectivity among the
routers enhancing the load balancing and
the fault-tolerance
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Open Issues
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Ring placement
Intra- and inter-ring dynamic lightpath
allocation
Load balancing
Scheduling of the packets and routing
table lookups at the routing nodes
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Intra-ring Dynamic Lightpath
Allocation
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Tell-and-go mechanism for setting up
lightpaths
On-line routing and wavelength
assignment [ONRAMP]
Tell-and-go with multi-token [CFC98]
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Multi-token WDM Ring Structure
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Nodes connected using virtual multi-channel
rings
Multi-token control
– simple and fast technique supporting dynamic
lightpath allocation
– short format for information bearing tokens
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Multi-token Control
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One token per channel
Token transmitted on the control channel
Token control for on demand lightpath
establishment
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Optical Packet Switching
Optical Packet Switching
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Enabling technologies
Routing node structure
Proposed solutions
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Optical Packet Switching
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Optical Time Division Multiplexing
Switches optically route packets based
on the header
Required high speed switches, tunable
optical delays, packet header recognition
mechanisms
Experimental phase
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Enabling Technologies
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Multiplexing (bit and packet interleaving)
techniques
Synchronization techniques
Delay lines  buffering
Demultiplexing techniques
Optical logical gates
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Routing Node Structure
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Routing Node Functions
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Synchronization
– utilization of variable delay lines
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Header Recognition
– performed either optically or electronically while the
remainder of the packet is optically buffered
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Buffering
– feed-forward and feed-back delay lines structures
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Routing
– deflection or hot-potato either with or without small
input and output buffer
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Proposed Solutions
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COntention Resolution by Delay lines
(CORD)
Asynchronous Transfer Mode Optical
Switching (ATMOS)
Multi-token packet switched ring
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CORD
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By UMas, Stanford, GTE Labs in 1996
Two nodes with ATM-sized packets at two
different ’s
Headers carried on distinct subcarrier ’s
Each node generates packet to any node
Use of delay lines for contention resolution
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ATMOS
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11 laboratories in Europe involved
Objectives:
– Developing optical ATM switching
capabilities
– Demonstrating optical store and forward
routing node
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Combination of WDM and TDM
Cell-routing demonstrations carried out at
2.5 Gb/s
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Multi-Token Packet Switched
Ring
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Multi-Token Inter-Arrival Time (MTIT)
Access Protocol
Supports IP directly over WDM
Achieves a bandwidth efficient
multiplexing technique in WDM ring
Protocol efficiency grows with the number
of ’s and is packet length independent
High throughput and low access delay
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Packet Switching Performance
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More channels, lower the access delay
More channels, higher the achievable
throughput
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Current Projects and Testbeds
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High Speed Connectivity Consortium
SuperNet Broadband Local Trunking
Optical Label Switching for IP over WDM
SuperNet Network Control&Management
NGI-ONRAMP
CANARIE
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Conclusion
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WDM technology is going to provide a
number of solutions over time:
– Static lightpaths
– Dynamic lightpaths/Burst switching
– Packet switching
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In order to achieve end-to-end QoS for
Internet traffic not only bandwidth counts:
– Traffic grooming for self-similar traffic
– Flow switching for dynamic configurations
– Access and backbone adaptation
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References (I)
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R. Ramaswami and K.N. Sivarajan, Optical Networks:
a practical prospective, Morgan Kaufmann Publishers
Inc., 1998
T.E. Stern and K. Bala, Multiwavelength Optical
Networks. A Layered Approach., Addison-Weslwy, May
1999
htttp://www.darpa.mil/ito/
N. Ghani and S. Dixit, “Channel Provisioning for
Higher-Layer Protocols in WDM Networks”, in
Proceedings of SPIE All-Optical Networking 1999:
Architecture, Control and Management Issues, Boston,
September 19-21, 1999
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References (II)
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I. Chlamtac, A. Ganz, and G. Karmi, “Lightpath
communications: a novel approach to high bandwidth
optical WAN’s”, IEEE Transactions on Communication,
v. 40, pp. 11171-1182, July 1992
M.W. Chabt et al., “Toward Wide-Scale All-Optical
Transparent Networking: the ACTS Optical PanEuropean Network (OPEN) Project”, IEEE JSAC, v. 16,
pp.1226-1244, Sept. 1998
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References (III)
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A. Fumagalli, I. Cerutti, M. Tacca, F. Masetti, R.
Jagannathan, and S. Alagar, “Survivable Networks
Based on Optimal Routing and WDM Self-Healing
Rings”, in Proceedings of IEEE INFOCOM ‘99, March
21-25, 1999
A. Fumagalli, L. Valcarenghi, “Fast Optimization of
Survivable WDM Mesh Networks Based on Multiple
Self-healing Rings”, in Proceedings of SPIE All-Optical
Networking 1999: Architecture, Control and
Management Issues, Boston, September 19-21, 1999
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References (IV)
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A. Fumagalli, J. Cai, I. Chlamtac, “A Token Based
Protocol for Integrated Packet and Circuit Switching in
WDM Rings”, in Proceedings of Globecom ‘98
A. Fumagalli, J. Cai, I. Chlamtac, “The Multi-Token
Inter-Arrival Time (MTIT) Access Protocol for
Supporting IP over WDM Ring Network”, in
Proceedings of ICC ‘99
J. Aracil, D. Morato and M. Izal, “Analysis of Internet
Services for IP over ATM networks”, IEEE
Communications Magazine, December 1999
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References (V)
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J. Beran, Statistics for Long-Memory Processes,
Chapman & Hall, 1994
I. Norros, “On the use of Fractional Brownian Motion in
the theory of Connectionless Networks”, IEEE JSAC,
13(6), August 1995.
J. Manchester, J. Anderson, B. Doshi and S. Dravida,
“IP over SONET”, IEEE Communications Magazine,
May 1998.
P. Newman, G. Minshall, T. Lyon and L. Huston, “IP
Switching and Gigabit Routers”, IEEE Communications
Magazine, January 1997.
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References (VI)
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Bill St. Arnaud et al., “Architectural and engineering
issues for building an optical Internet”,
http://www.canet2.net
A. Viswanathan, N. Feldman, Z. Wang and R. Callon,
“Evolution of Multiprotocol Label Switching”, IEEE
Communications Magazine, May 1998.
S. Keshav and R. Sharma, “Issues and trends in router
design”, IEEE Communications Magazine, May 1998.
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