01/18/2000 1

Optical Networks: The Platform for the Next Generation Internet

Andrea FumagalliDept. of Electrical Engineering

University of Texas at Dallas

andreaf@utdallas.edu

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Optical NetworksTeam:James Cai

Isabella Cerutti

Jing Li

Marco Tacca

Luca Valcarenghi

University of Texas at Dallas

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Outline

The Optical Layer Static/Semi-Static Ligthpath Networks Dynamic Ligthpath Networks Optical Packet Switching Current Projects and Testbeds

The Optical Layer

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The Optical Layer

Optical fiber Optical Amplifiers (OA) Wavelength Routing Nodes (WRN) The ITU Optical Layer

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Optical Fiber Three transmission windows

– first: 800-900 nm (Multimode)– second: 1240-1340 nm (Singlemode)– third:1500-1650 nm (Singlemode)

Potentially available bandwidth in each window ~ 20 THz

Effective bandwidth limited by the device characteristics

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Semiconductor Optical Amplifiers (SOA)

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 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

Praseodymium-Doped Fiber Amplifiers (PDFA)– amplify at 1300 nm (not yet available)

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Wavelength Routing Nodes (WRN)

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

Drop Add

Node A

From node B

To C

Drop Add

F-OXC

Node A

From node B

To C

OADM

WT-OXC

Node A

From node B

Drop Add

To D

To C

WR-OXC

Node A

From node B

Drop Add

To D

To C

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WRN Functions 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 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 non-adjacent nodes

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Optical Layer (OL) 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

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

Static/Semi-static Lightpath Dynamic Lightpath Optical Packet Switching

Static/Semi-Static Lightpath Networks

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Static/Semi-Static Ligthpath Networks Design issues The RWA problem OL protection issues Multicast in WDM networks

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Design Issues

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 Fault protection

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Optical Layer Dimensioning

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 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 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 End-to-end Path

– Shared-Path Protection (SPP)– Dedicated-Path Protection (DPP)

WDM Self-Healing Ring (WSHR)– Shared-Line-switched WSHR (SL-WSHR) or

WDM SPRING (Shared Protection RING)– Dedicated-Path-switched WSHR (DP-

WSHR) 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 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 Practical constraints:

– maximal ring size, maximal number of rings per link and per node

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WMM Sub-problems Ring Cover (RC):

– select the rings to cover each link carrying a working lightpath

Working Lightpath (WL) routing:– route the working lightpath for each traffic

demand Spare Wavelength (SW) assignment:

– protect each working lightpath using the selected rings

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WMM Solution

Modular solutions– Assume a ring cover, find optimal path

routing– Assume a path routing, find optimal ring

cover Joint solution (here) global optimum

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Results

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

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 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 semi-static lightpath case)

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Multicast in WDM Networks

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

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

Dynamic Ligthpath Networks

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Dynamic Ligthpath Networks

Dynamic routing and channel assignment Network scenario and layering Multi-token WDM networks

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Dynamic Lightpath

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

Logical connection (lightpath) requests arrive randomly

Network state:all active connections with their optical

path (route and wavelength assignment) Real time algorithm needed to

accommodate each request Blocking and fairness issues

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Network Scenario

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 Physical Layer

– consists of the physical connections of the network Interconnected Ring Layer

– adapts the static nature of the physical layer to the dynamic nature of the traffic

Logical Layer– furnishes higher connectivity among the routers

enhancing the load balancing and the fault-tolerance

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Open Issues

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

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 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

One token per channel Token transmitted on the control channel Token control for on demand lightpath

establishment

Optical Packet Switching

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Optical Packet Switching

Enabling technologies Routing node structure Proposed solutions

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Optical Packet Switching

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

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 Synchronization

– utilization of variable delay lines Header Recognition

– performed either optically or electronically while the remainder of the packet is optically buffered

Buffering– feed-forward and feed-back delay lines structures

Routing– deflection or hot-potato either with or without small

input and output buffer

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Proposed Solutions

COntention Resolution by Delay lines (CORD)

Asynchronous Transfer Mode Optical Switching (ATMOS)

Multi-token packet switched ring

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CORD 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 11 laboratories in Europe involved Objectives:

– Developing optical ATM switching capabilities

– Demonstrating optical store and forward routing node

Combination of WDM and TDM Cell-routing demonstrations carried out at

2.5 Gb/s

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Multi-Token Packet Switched Ring 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 More channels, lower the access delay More channels, higher the achievable

throughput

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Current Projects and Testbeds

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 WDM technology is going to provide a number of

solutions over time:– Static lightpaths– Dynamic lightpaths/Burst switching– Packet switching

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) 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)

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 Pan-European Network (OPEN) Project”, IEEE JSAC, v. 16, pp.1226-1244, Sept. 1998

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References (III)

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)

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)

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)

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.