01/18/ Optical Networks: The Platform for the Next Generation Internet Andrea Fumagalli Dept. of Electrical Engineering University of Texas at Dallas

01/18/ Optical Networks Team: James Cai Isabella Cerutti Jing Li Marco Tacca Luca Valcarenghi University of Texas at Dallas

01/18/ Outline n The Optical Layer n Static/Semi-Static Ligthpath Networks n Dynamic Ligthpath Networks n Optical Packet Switching n Current Projects and Testbeds

The Optical Layer

01/18/ The Optical Layer n Optical fiber n Optical Amplifiers (OA) n Wavelength Routing Nodes (WRN) n The ITU Optical Layer

01/18/ Optical Fiber n Three transmission windows –first: nm (Multimode) –second: nm (Singlemode) –third: nm (Singlemode) n Potentially available bandwidth in each window ~ 20 THz n Effective bandwidth limited by the device characteristics

01/18/ Semiconductor Optical Amplifiers (SOA) n Broadband gain characteristics (work both at 1300 nm and 1550 nm) n Maximum bandwidth up to 100 nm n Gain fluctuation, polarization dependent, high coupling loss

01/18/ Doped Fiber Amplifiers n Erbium-Doped Fiber Amplifiers (EDFA) –Conventional (C) band ~ nm –Long (L) band ~ 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 n Praseodymium-Doped Fiber Amplifiers (PDFA) –amplify at 1300 nm (not yet available)

01/18/ Wavelength Routing Nodes (WRN) n OADM (Optical Add Drop Multiplexer) n F-OXC (Fiber Optical Crossconnect) n WT-OXC (Wavelength Translating Optical Crossconnect) n WR-OXC (Wavelength Routing Optical Crossconnect)

01/18/ WRN Schematic Representation

01/18/ WRN Functions n OADM usually 2x2 F-OXC with adding and dropping n F-OXC fiber switching with adding and dropping n WT-OXC wavelength and fiber switching with conversion n WR-OXC wavelength and fiber switching without conversion

01/18/ ITU and Optical Layer n International Telecommunications Union agency of United Nations devoted to standardize international communications n Optical Layer defined by ITU inside the ISO-OSI Data Link layer (Rec. G.805) n OL provides lightpaths to higher layers n lightpath: point-to-point all-optical connection between physically non- adjacent nodes

01/18/ Optical Layer (OL) n 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

01/18/ Inter-layer Design Issues n Issues in establishing, e.g., a lightpath –OC layer  routing, protection, and management –OMS layer  monitoring, multiplexing –OAS layer  regeneration, amplification

01/18/ Optical Network Techniques n Static/Semi-static Lightpath n Dynamic Lightpath n Optical Packet Switching

Static/Semi-Static Lightpath Networks

01/18/ Static/Semi-Static Ligthpath Networks n Design issues n The RWA problem n OL protection issues n Multicast in WDM networks

01/18/ Design Issues n Optical layer dimensioning n 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 n Fault protection

01/18/ Optical Layer Dimensioning n Each fiber can carry up to 128 ’s each operating at 10 Gb/s [Chabt et al. ‘98] n The Optical Layer is given a lightpath demand matrix n Demands are obtained by models applied to the IP layer

01/18/ RWA Problem n Static Lightpath Establishment (SLE) (with no conversion at the nodes) is a NP-complete problem [Chlamtac ‘92] n Need for either approximate or heuristic solutions n Joint optimization with the spare capacity assignment  global network resources optimization

01/18/ Global Network Optimization n Given the lightpath demand matrix find contemporary the solution of the RWA problem for working and protection ’s n 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

01/18/ OL Protection Techniques n End-to-end Path –Shared-Path Protection (SPP) –Dedicated-Path Protection (DPP) n 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)

01/18/ OL Protection Schemes

01/18/ Multi-WSHR Approach n 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 n Practical constraints: –maximal ring size, maximal number of rings per link and per node

01/18/ WMM Sub-problems n Ring Cover (RC): –select the rings to cover each link carrying a working lightpath n Working Lightpath (WL) routing: –route the working lightpath for each traffic demand n Spare Wavelength (SW) assignment: –protect each working lightpath using the selected rings

01/18/ WMM Solution n Modular solutions –Assume a ring cover, find optimal path routing –Assume a path routing, find optimal ring cover n Joint solution (here)  global optimum

01/18/ Results n Practical Constraints: –Maximum ring size of 8 nodes –At most 2 ring per link –At most 4 rings per node

01/18/ ILP versus SA n C= set of rings, SRA= Shortest Ring Algorithm, SR= Shortest Ring, SP= Shortest Path n Uniform traffic, SL-WSHR n Pentium based Processor 166MHz

01/18/ Multicast in WDM Networks n 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)

01/18/ Multicast in WDM Networks n 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

01/18/ Building Light-tree to Implement Multicast n A light-tree rooted at the source and covering all the destinations is build using a dedicated wavelength n From upper layer’s point of view, it is one hop from source to all the destinations n Optical signal is not converted to electrical format at intermediate node, so that fewer transmitters and receivers are needed

Dynamic Ligthpath Networks

01/18/ Dynamic Ligthpath Networks n Dynamic routing and channel assignment n Network scenario and layering n Multi-token WDM networks

01/18/ Dynamic Lightpath n Reconfigurable networks n WT-OXC, WR-OXC, and active components used n More expensive than fixed networks n Adaptable to varying lightpath requests

01/18/ Dynamic Routing and Channel Assignment n Logical connection (lightpath) requests arrive randomly n Network state: all active connections with their optical path (route and wavelength assignment) n Real time algorithm needed to accommodate each request n Blocking and fairness issues

01/18/ Network Scenario n Ring and interconnected rings are among the most used topologies n Several ring based results in the literature n Acceptable management complexity as opposed to arbitrary network topology

01/18/ Network Layering

01/18/ Network Layers n Physical Layer –consists of the physical connections of the network n Interconnected Ring Layer –adapts the static nature of the physical layer to the dynamic nature of the traffic n Logical Layer –furnishes higher connectivity among the routers enhancing the load balancing and the fault-tolerance

01/18/ Open Issues n Ring placement n Intra- and inter-ring dynamic lightpath allocation n Load balancing n Scheduling of the packets and routing table lookups at the routing nodes

01/18/ Intra-ring Dynamic Lightpath Allocation n Tell-and-go mechanism for setting up lightpaths n On-line routing and wavelength assignment [ONRAMP] n Tell-and-go with multi-token [CFC98]

01/18/ Multi-token WDM Ring Structure n Nodes connected using virtual multi-channel rings n Multi-token control –simple and fast technique supporting dynamic lightpath allocation –short format for information bearing tokens

01/18/ Multi-token Control n One token per channel n Token transmitted on the control channel n Token control for on demand lightpath establishment

Optical Packet Switching

01/18/ Optical Packet Switching n Enabling technologies n Routing node structure n Proposed solutions

01/18/ Optical Packet Switching n Optical Time Division Multiplexing n Switches optically route packets based on the header n Required high speed switches, tunable optical delays, packet header recognition mechanisms n Experimental phase

01/18/ Enabling Technologies n Multiplexing (bit and packet interleaving) techniques n Synchronization techniques n Delay lines  buffering n Demultiplexing techniques n Optical logical gates

01/18/ Routing Node Structure

01/18/ Routing Node Functions n Synchronization –utilization of variable delay lines n Header Recognition –performed either optically or electronically while the remainder of the packet is optically buffered n Buffering –feed-forward and feed-back delay lines structures n Routing –deflection or hot-potato either with or without small input and output buffer

01/18/ Proposed Solutions n COntention Resolution by Delay lines (CORD) n Asynchronous Transfer Mode Optical Switching (ATMOS) n Multi-token packet switched ring

01/18/ CORD n By UMas, Stanford, GTE Labs in 1996 n Two nodes with ATM-sized packets at two different ’s n Headers carried on distinct subcarrier ’s n Each node generates packet to any node n Use of delay lines for contention resolution

01/18/ ATMOS n 11 laboratories in Europe involved n Objectives: –Developing optical ATM switching capabilities –Demonstrating optical store and forward routing node n Combination of WDM and TDM n Cell-routing demonstrations carried out at 2.5 Gb/s

01/18/ Multi-Token Packet Switched Ring n Multi-Token Inter-Arrival Time (MTIT) Access Protocol n Supports IP directly over WDM n Achieves a bandwidth efficient multiplexing technique in WDM ring n Protocol efficiency grows with the number of ’s and is packet length independent n High throughput and low access delay

01/18/ Packet Switching Performance n More channels, lower the access delay n More channels, higher the achievable throughput

01/18/ Current Projects and Testbeds n High Speed Connectivity Consortium n SuperNet Broadband Local Trunking n Optical Label Switching for IP over WDM n SuperNet Network Control&Management n NGI-ONRAMP n CANARIE

01/18/ Conclusion n WDM technology is going to provide a number of solutions over time: –Static lightpaths –Dynamic lightpaths/Burst switching –Packet switching n 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

01/18/ References (I) n R. Ramaswami and K.N. Sivarajan, Optical Networks: a practical prospective, Morgan Kaufmann Publishers Inc., 1998 n T.E. Stern and K. Bala, Multiwavelength Optical Networks. A Layered Approach., Addison-Weslwy, May 1999 n htttp:// n 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

01/18/ References (II) n 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 , July 1992 n 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 , Sept. 1998

01/18/ References (III) n 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 n 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

01/18/ References (IV) n A. Fumagalli, J. Cai, I. Chlamtac, “A Token Based Protocol for Integrated Packet and Circuit Switching in WDM Rings”, in Proceedings of Globecom ‘98 n 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 n J. Aracil, D. Morato and M. Izal, “Analysis of Internet Services for IP over ATM networks”, IEEE Communications Magazine, December 1999

01/18/ References (V) n J. Beran, Statistics for Long-Memory Processes, Chapman & Hall, 1994 n I. Norros, “On the use of Fractional Brownian Motion in the theory of Connectionless Networks”, IEEE JSAC, 13(6), August n J. Manchester, J. Anderson, B. Doshi and S. Dravida, “IP over SONET”, IEEE Communications Magazine, May n P. Newman, G. Minshall, T. Lyon and L. Huston, “IP Switching and Gigabit Routers”, IEEE Communications Magazine, January 1997.

01/18/ References (VI) n Bill St. Arnaud et al., “Architectural and engineering issues for building an optical Internet”, n A. Viswanathan, N. Feldman, Z. Wang and R. Callon, “Evolution of Multiprotocol Label Switching”, IEEE Communications Magazine, May n S. Keshav and R. Sharma, “Issues and trends in router design”, IEEE Communications Magazine, May 1998.