* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Generalized Multiprotocol Label Switching: An Overview of Routing
Super-resolution microscopy wikipedia , lookup
Nonimaging optics wikipedia , lookup
Vibrational analysis with scanning probe microscopy wikipedia , lookup
Ellipsometry wikipedia , lookup
Ultrafast laser spectroscopy wikipedia , lookup
Optical flat wikipedia , lookup
Dispersion staining wikipedia , lookup
Photon scanning microscopy wikipedia , lookup
Nonlinear optics wikipedia , lookup
Diffraction grating wikipedia , lookup
Magnetic circular dichroism wikipedia , lookup
3D optical data storage wikipedia , lookup
Harold Hopkins (physicist) wikipedia , lookup
Astronomical spectroscopy wikipedia , lookup
Fiber-optic communication wikipedia , lookup
Optical rogue waves wikipedia , lookup
Optical tweezers wikipedia , lookup
Optical coherence tomography wikipedia , lookup
Anti-reflective coating wikipedia , lookup
X-ray fluorescence wikipedia , lookup
Silicon photonics wikipedia , lookup
TTM1: Approaches to Optical Internet Packet Switching David K. Hunter and Ivan Andonovic Abstract • Increased capcity demands WDM • Next evolution after WDM: Optical switching (OPS) Introduction • There is a ”mismatch” between the capacity available through use of WDM and processing capacities of routers. • IP routers have the following tasks: – Routing: Build connectivity through establishing routing tables in a network. Different protocols used to spread information (e.g. OSPF, IS-IS) – Forwarding: Decide output port interface – Switching: Transport a packet to the correct output port – Buffering: If contention, store packet temporarily Optical Packet Switching • Transmission and switching in the optical domain, but forwarding and routing in the electronical domain. • The next step would be to process packet headers (forwarding) in the optical domain. Then only the actual routing is left for the elctronical domain. Optical Packet Switching • (At least) two alternative approaches to OPS: – Fixed Length Packets (FLP) – Variable Length Packets (VLP) – (But additionally one could distinguish between Asynchronous or Syncronous (Slotted) transport). The design of Optical Packet Switches • Three principal sub-blocks (Note: This is a slotted network): – Input interface: Alignment of packets i time. Why? – Switching core: Transports packets to the correct output port – Output interface: Header insertion The design of Optical Packet Switches • Packet format defined in the KEOPS project – – – – Sync.pattern. Why? Guard time. Why? More sync: payload sync. Why? More guard. Why? Wavelength in Contention Resolution Two possible multiplexing schemes: • Scattered Wavelength Path (SCWP) – Packets are spread on random (”scattered”) free wavelengths. • Shared Wavelength Path (SHWP) – Each path (=”virtual connection”) in the optical packet layer is assigned a particular wavelength. Wavelengths may be shared by many paths. (But packets belonging to a path will not change to another wavelength). Wavelength in Contention Resolution – Using SCWP there is one large buffer per fiber for all wavelengths. Buffer depth per wavelength is size of buffer divided by number of wavelengths. – Using SHWP there is one buffer per wavelength. Comparison of buffer depth for achieving PLR 10-9 Wavelength in Contention Resolution • Broadcast and Select Switch (KEOPS) – Wavelength encoder. N wavelength converters, one for each input. Encoding each packet on a fixed wavelength with a unique wavelength for each input. – Buffer and broadcast section. Number of FDLs and a space switch stage. Electronically controlled selection (full signal?). – Wavelength selector block. N demultiplexers, followed by electronically controlled selection. • All packets available at all outputs => support multicast Wavelength in Contention Resolution WASPNET design: • No large splitting losses as in KEOPS B&S • Core components are Tuneable Wavelength Converters (TWCs), and 2N x 2N Arrayed Waveguide Grating (AWG). Pluss N*N space switch. Variable-Length Optical Packet Switching – S stages, D in/outputs in every stage except first (N inputs) and last (N outputs); and D FDLs. – Delay line granularity of each stage is N times that of the next stage. – Brute force algoritme controlling the switch is computationally intensive. Delay lines in units of packet granularity Conclusions • At the start of OPS (year 2000) Most OPS approaches assumed fixed length packets and synchronous operation of switches. • If the goal is to carry variable length packets (as in Ethernet) asynchronous operation may be necessary. • Use of wavelength dimension to resolve contention is also shown to be useful.