Wavelength Routed Networks Wavelength Assignment Wavelength Conversion Cost Implications Network Modeling

Ring Network WDM de-mux SDH equipment

Equivalent Topology A B C D

Traffic Matrix ABCDABCD ABCDABCD Shows amount of traffic between two nodes. Units here are in fibre bandwidth.

Traffic Allocation ABCDABCD ABCDABCD A B C D

Optical Layer WDM de-mux SDH equipment

Optical Layer OPTICAL PATHS SDH HIGHER LAYER PROTOCOLS

General Network A B D C E F

Optical Layer Issues (1) Transparency Format independence bit rate independence Wavelength reuse non-overlapping paths

Optical Layer Issues (2) Reliability provision of alternate paths Virtual Topology Topology seen by higher layers Circuit Switching Dynamic topology

Wavelength Routing Nodes Other nodes Local traffic Control

Types of wavelength router No wavelength conversion single wavelength from transmitter to receiver Fixed wavelength conversion At every node the output wavelengths are a fixed permutation of the input wavelengths Limited conversion input wavelengths can be changed to a fixed subset of output wavelengths Full conversion

Electronic vs Optical XC E: RegenerativeO: Transparent point to point linksglobal links fixed formatformat independent bandwidth smallerbandwidth larger routing easyrouting hard (in general) detailed monitoringlow level monitoring

Network Design (1) Optical Layer Functionality Protection Management Dimensioning Physical fibre links Number of wavelengths Protocols

Network Design (2) Timescales slow for bandwidth management fast for packet switching Scaleability Can we make the network N times bigger Local vs Global information Can the network operate without global knowledge Blocking

Scaling P vs NP vs E computations Polynomial time Non-deterministic Polynomial time Exponential

Scaling examples

Network Design Goals Maximum available bandwidth Minimum cost Flexibility, Reliability, Upgradability..... Restrictions Finance Node Locations Physics / Engineering

Traffic Modeling Traffic Matrix difficult to predict in detail can be useful in upgrading networks Permutations Maximum Load Maximum traffic for minimum resource Statistical

Blocking To allow or not to allow allow more blocking means less resource needed also means less network availability don  t allow need more network resource will always allow 100% network use

Network Types Static no switching initial design critical Dynamic incorporate switches need for  on-line  design/optimization

Static Networks The network is defined by the set of possible light paths between each pair of nodes In general, the network need not be symmetric In order for nodes i and j to communicate we need to select two wavelengths, one from i to j and the other from j to i Summarize all possibilities in connection matrix Implementation details are not yet included

Connectivity Matrix {1,2}{2}{3} {1}{3}{2,3} {2}{1,3}{2} Receiver Transmitter

Graphical Representation Node 1 Node 2 Node 3

Lightpath Collision 2 sub-network Node 1 Node 2 Node 3 Connect 1-1 Connect 3-3 Collision

Permutations Each set of node wavelength assignments defines a tuning of the network Because of light path collisions, not all tunings are legal Each legal tuning enables a single permutation Consider a single tuning giving two permutations at least one receiver must be able to connect to two transmitters since the receiver wavelength is fixed the two transmitters have the same wavelength but this is a light path collision

Wavelength Estimate Let W = number of wavelengths n = number of nodes Then the number of possible tunings is W 2n The number of permutations is n! So W 2n > n! or W >(n!) 1/2n Using Stirling's formula for n! ~ (n/e) n (2  n) 1/2 this can be written (for large n) W > (n/e) 1/2 (2  n) 1/4n The simple upper bound is W = n

Wavelength Estimate

Other Results For offline static routing: For wide-sense non-blocking:

Blocking Estimate

Non-blocking Estimate

Siemens SURPASS non-blocking and switching granularity Integrated packet fabrics (RPR, MPLS) Multi service platform: 2M, 155M, STM-1/4/16/64, 40Gbit/s, GFP for 10/100BT, GbE, 10GbE, SAN interfaces (FICON, Fi-ber Channel) GFP mapping and LCAS for optimal scalability of Ethernet Services Support of concatenated services (VC-4-4c, VC-4-16c, VC-4-64c) A variety of STM-64 interfaces, including "WDM" variants Extensive protection mechanisms (SNCP, MSP, BSHR, Hardware) including RPR traffic steering web site ctionid=0&sdc_secnavid=0&sdc_3dnvlstid=&sdc_countryid=180&sdc_ mpid=0&sdc_unitid=999&sdc_conttype=4&sdc_contentid= &sd c_langid=1&Ðweb site