when will commercial optical packet switching happen n.
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  1. (WHEN) WILL COMMERCIALOPTICAL PACKET SWITCHINGHAPPEN? Masataka Ohta Graduate School of Information Science and EngineeringTokyo Institute of Technology Network Architecture GroupNew Generation Network Research CenterNational Institute of Information and Communication Technology

  2. What am I? • Radio Amateur • ready to depend on electronics, if necessary • Information Scientist & Engineer • HPC -> CG -> UNIX -> Internet • Author of 3 RFCs (character encoding & DNS) • ready to modify Internet Protocols, if necessary • recent ID: End to End NAT • Working on Photonic Internetworking • only for these 10 years

  3. My Position on the Topic • Will Commercial Optical Packet Switching Happen? • Yes. • When Commercial Optical Packet Switching Happen? • as soon as the demand arises • However, Optical Packet Switching over λ Switching is Commercially Impossible.

  4. Which is better IP over WDMfor Optical Packet Switching? TCP/UDP IPv4 Ethernet λ SW/GMPLS IPv4 WDM WDM

  5. Commercial Difficulty ofWavelength Routing • 10Gbps is too fast for most applications • 10Gbps is slow enough for electric processing • Commercial electric switches is more capable and may be less expensive than optical MEMS switches • 10Gbps or 40Gbps optical packet switching is commercially hopeless

  6. Commercial Voltaire QDR 4700Infiniband Switch Router • Maximum configuration per 19U chassis • 40Gbps*324 ports (6.5W – 12W per port) • 51.8Tbps of non-blocking bandwidth • combining 2 (4?) chassis • Latency 100~300ns • Fully commercialized with hot swappable modules and redundant management blades • Internal packet format is similar to IPv6

  7. Still,Optical is Better than Electrical • Not because Optical Devices are faster • These days, electrical devices are really fast • But because Optical Devices handle a lot more Wideband Signals • Many optical devices can handle 1Tbps or faster data as easily as 10Gbps ones • Key to success of WDM is • Wide bandwidth of fiber and EDFA

  8. Many Wavelengths enablesWideband 1Tbps Packets • To Encode a Packet • Simultaneously modulate 100 Wavelengths each at 10Gbps • Wavelength • Wavelength • time • time Single Wavelength Packets Multiple Wavelength Packets

  9. At 1Tbps,Optical Buffering is Trivially Easy! • Buffering 1Tbps Packets is 100*100 = 10,000 Times or more Easier than that of 10Gbps Packets, because: • 100 times less or even less number of buffers are necessary to achieve the equivalent speed • implies 100 times less powerconsumption • buffers need 100 times shorter fiber delay lines • loss & dispersion by FDLs negligible • TCP slow start of most access is negligible

  10. Very Small Amount of Buffer is Required at the Backbone • Backbone Traffic is Poisson, if • backbone speed is much faster than access • 1Tbps backbone is much faster than most, if not all, access • Paced TCP is used • Exceptional hosts with exceptionally fast access should use paced TCP • An Optical Buffer with 15 or 31 Fiber Delay Lines is Enough

  11. Timing Considerations • 1Tbps is fast enough • to make fiber delay lines short • 1500B, typical MTU of the Internet, packet is 12ns long or 3.6m long in vacuum • 1Tbp is slow enough • to allow for electric control • FPGA 2ns, external SERDES enables finer control • SRAM for L3 route look up 3.3ns • to allow for optical switching

  12. IPv4 Address 22bit 2bit 8bit RAM0 (4MW*18bit) 18bit 1 x 0 14bit X X X RAM1 (4MW*18bit) X X 8:1 MUX (4bit) Pipelined Full /24 Route Lookupwith Full /32 for 16K /22s

  13. Commercially Available100ps Optical Switch Power consumption of 0.125W (± 2.5V @ 50Ω)

  14. Optical Packet Format ofMany Wavelength Packetsfor Almost-all Optical Switches Wavelengths to be processed, updated & switched electrically Header Payload Wavelength Wavelengths to be switched optically Time

  15. Routing Table Control Logic Original Header Electric Optical Modified Header ADM ADM Buffer ADM ADM Buffer ADM ADM Buffer Structure of an Optical Packet Switch with Many-Wavelength Packets

  16. A Bad News for IEEE (at least IEEE802) and IETF • To make routers as optical as possible • the number of wavelengths containing header SHOULD be minimal • with 500B average packet and 100 wavelengths, a wavelength contains only 5B in average • Ethernet address is long, header is tooo long • IPv4 is fine, but IPv6 CAN’T be supported • IPv6 header is INDEFINITELY (1280B) long

  17. Wasted Bandwidth Wavelength Wavelength Time Time : Payload : Header Dividing a Header into Wavelengths with more OEOs

  18. MUX MUX ... ... MUX MUX Dummy packets to suppress EDFA surge MUX Structure of an Optical Buffer with FDL and MUXes

  19. Extinction Ratio?8:1 MUX with Improved Extinction Ratio 2:1 2:1 2:1 2:1 2:1 2:1 2:1 2:1 2:1 2:1 2:1 2:1 2:1 2:1 2:1 A 15 FDL buffer for 8 input ports needs15*15+31=256 switches

  20. Estimated Performance with Simulation • Packet Drop Probability: 0.0017% • with 15 Fiber Delay Lines (longest one is 833m long with exponentially increased length) • 100 wavelengths each at 10Gbps • 65% Poisson load • packet length uniformly distributed 1B~1500B • 2ns of minimum packet interval • Effective speed is 433Gbps

  21. Commercially AvailableFiber Delay Line From Catalogue of General Photonics Corporation

  22. Estimated Power Consumption • Optical switches of 1Tbps*8port switch will consume • 256W • assuming extinction ratio improved MUXes with 256*8=2048 2:1 50Ω traveling wave optical switches with Vπ=5V • Switch drivers consume additional power • Control logic and EDFAs consume some more power

  23. Effect of Dispersion • Dispersion Causes Delay Differences between Wavelengths for ULH transport minimum interval for switching wave length time separate switching is impossible Effect of Dispersion on Switch Intervals between Many-Wavelength Packets

  24. Experiments onMany-Wavelength Packets • Switching and 87Km Transmission of 10Gbps*16 wavelength packets • all wavelengths carry different content • H. Furukawa, N. Wada, H. Harai, Y. Awaji, M. Naruse, H. Otsuki, T. Miyazaki, K. Ikezawa, A. Toyama, N. Itou, H. Shimizu, H. Fujinuma, H. Iiduka, E. Kong, P. Chan, R. Man, G. Cincotti, and K. Kitayama, "Field Trial of IP over 160 Gbit/s Colored-Optical-Packet Switching Network with Transient-Response-Suppressed EDFA and 320 Gbit/s Throughput Optical Packet Switch Demonstrator,'' in OFC 2007 Post Deadline (PDP4), March 2007. • 1.28Tbps 128-wavelength packet switching • four different data patterns for 128 wavelengths • Wada, N. Kataoka, T. Makino, N. Takezawa, K. Nashimoto, and T. Miyazaki, "Field Demonstration of 1.28T bit/s/port, Ultra-wide Bandiwdth Colored Optical Packet Switching with Polarization Independent High-speed Switch and All-optical Hierarchical Label Processing," ECOC 2007 Post Deadline (PD3.1), Sep. 2007.

  25. Experiments on Optical Buffers • 16 Fiber Delay Lines • with SOA switches • K. Habara, H. Sanjo, H. Nishizawa, Y. Yamada, S. Hino, I. Ogawa, and Y. Suzaki, “Large-Capacity Photonic Packet Switch Prototype Using Wavelength Routing Techniques,” IEICE Transactions on Communications, Vol. E83-B, No. 10, pp. 2304-2311, Oct. 2003. • 31 Fiber Delay Lines • with PLZT switches • H. Furukawa, H. Harai, N. Wada, N. Takezawa, K. Nashimoto, T. Miyazaki, “A 31-FDL Buffer Based on Trees of 1x8 PLZT Optical Switches,” ECOC 2006 Technical Digest, Sep. 2006 (Paper No. Tu4.6.5).

  26. Where is the Commercial Demand? • 100G Ethernet will be enough for WAN for the time being • LAN! • Data Centers • Real (not for LINPACK only) Supercomputers for Fluid Dynamics need much bandwidth • 64bps for 1FLOPS or so, 640Pbps for 10PFLOPS • On LAN, loss & dispersion are negligible • 10Tbps over a fiber not difficult with large MTU

  27. Conclusions • Many-wavelength packets is a promising technology • Cost: λ SW >>MW Ethernet >> MW IPv4 • routers can be constructed with commercially available optical and electrical devices • Commercial demands are arising • Being truly optical, the faster, the easier • the less W/bps & $/bps (more commercial)