Wayne D. Grover Tutorial for DRCN 2005 Island of Ischia (Naples), Sunday October 16, 2005 DRCN 2005 Tutorial T3 p-Cycles: Fast, simple and efficient new options for network survivability at optical and MPLS layers Department of Electrical and Computer Engineering

2 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ p-cycles Ring-to-mesh evolution Incremental mesh design, reoptimization Demand uncertainty Ultra-long haul, optical bypass node recovery, oversubscription Multiple classes of service (QoP) Provisioning strategies Dynamic demands Topology evolution Availability analysis SRLG effects Optical & IP Transport Networking Disaster recovery TRLabs / U of A Network Systems Research Group

3 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Acknowledgements: Students involved in the research Demetrios Stamatelakis Anthony Sack Adil Kodian Gangxiang Shen John Doucette Grace Shi Dominic Schupke Matthieu Clouqueur

4 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Background and Motivation “ Ring “ A msec restoration times B. Complex network planning and growth C. High installed capacity for demand-served D. Simple, low-cost ADMs E. Hard to accommodate multiple service classes F. Ring-constrained routing “Mesh” G. Slower restoration times H. Exact capacity planning solutions I. Well under 100% redundancy J. Relatively expensive DCS/OXC K. Easy / efficient to design for multiple service classes L. Shortest-path working routing Shopping list: “A, D, H, I, L (and K) please” And, especially for transparent optical networks, fully preconnected protection paths are a great advantage

5 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ “ring-like speed” “mesh-like efficiency” Relative Characteristics of Known Schemes Restoration Time Capacity Redundancy 1+1 APS, Rings p-Cycles Mesh Span Restoration Shared Backup Path Protection (SBPP) True Mesh Path Restoration 100% redundancy

6 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ p-Cycles : an example p-cycle (no failures) A working path is not constrained to follow the p-cycle. Working paths may traverse the native shortest paths of the facility graph.

7 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ p-Cycles Reaction to an “on-cycle” failure is logically identical to a unit-capacity BLSR loopback reaction loopback “on-cycle” spans have both working and spare capacity like a BLSR an “on-cycle” failure

8 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ p- Cycles - a “straddling span” failure Reaction to a straddling span failure is to switch failed signals onto two protection paths formed from the related p-cycle Break-in Straddling spans have two protected working signal units and have no spare capacity

9 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ A lot ! Re-consider the example: It consumes 13 unit-hops of spare capacity It protects one working channel on 13 spans and two working channels on each of 9 other spans i.e., spare / working ratio = 13 / (13*1 + 9*2 ) = 42% How much difference can this make ? A fully-loaded Hamiltonian p-cycle reaches the redundancy limit, 1/(d-1) x2

10 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ p -Cycle Capacity Design… If span i fails, p-cycle j provides one unit of restoration capacity If span i fails, p-cycle j provides two units of restoration capacity i j i j

11 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Basic (non-joint) p-cycle Design Model Min cost of spare capacity =1 if span k in cycle j (parameter) P=set of candidate cycles, index j Number of unit copies of cycle j to build as a p-cycle (solution variable). x ij =2 if span i straddles cycle j. x ij =1 if span i on-cycle to cycle j. x ij =0 if neither of above.

12 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ AMPL Model to Implement p-Cycle SCP (1) # p-cycle SCP IP Model for AMPL # This is an AMPL model for determining the minimum-cost p-cycle network design. # This model optimizes p-cycles only... working capacity is provided as inputs. # SETS #**************************** set SPANS; # Set of all spans. set CYCLES; # Set of all candidate cycles. # PARAMETERS #**************************** param Cost{j in SPANS}; # Cost of each unit of capacity on span j. param Work{j in SPANS}; # Number of working links placed on span j. param Xpi{p in CYCLES, i in SPANS} default 0; # Number of paths a single copy of cycle p provides for restoration of failure of span i (2 if straddling span, 1 if on-cycle span, 0 otherwise). param pCrossesj{p in CYCLES, j in SPANS} := sum{i in SPANS: i = j and Xpi[p,j] = 1} 1; # Equal to 1 if cycle p passes over span j, 0 otherwise. i.e. if Xpi[p,j] = 1, then cycle p crosses span j.

13 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ AMPL Model to Implement p-Cycle SCP (2) Continued….. # VARIABLES #**************************** var p_cycle_usage{p in PCYCLES} >=0 integer, <=10000; # Number of copies of p-cycle p used. var spare{j in SPANS} >=0 integer, <=10000; # Number of spare links placed on span j. # OBJECTIVE FUNCTION #**************************** minimize sparecost: sum{j in SPANS} Cost[j] * spare[j]; # CONSTRAINTS #**************************** subject to full_restoration{i in SPANS}: Work[i] <= sum{p in PCYCLES} Xpi[p,i] * p_cycle_usage[p]; subject to spare_capacity_placement{j in SPANS}: spare[j] = sum{p in PCYCLES} pCrossesj[p,j] * p_cycle_usage[p];

14 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Working span capacities arising from one unit of demand on each node-pair: Total working capacity: 158 units Design Example

15 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Design Solution: 53.8 % overall redundancy A1A1 B1B1 C1C1 D2D2 E2E2 Total protection capacity:85 units Redundancy:53.8% Optimal configuration dynamically computable or self-organized p-Cycle Copies Total:7

16 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ In optimal designs, individual (unit capacity) p-cycles are often Hamiltonian, but protected networks based entirely on a single Hamiltonian p-cycle some are not optimal in general ! x 2 x 1 With this cycle set, redundancy is lower than if we used any single Hamiltonian Important observation re: role of Hamiltonian p-cycles

17 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Optimal Spare capacity design - Typical Results “Excess Sparing” = Spare Capacity compared to Optimal Span-Restorable Mesh i.e., “mesh-like” capacity

18 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Understanding why p-cycles are so efficient... 9 Spares cover 9 Workers 9 Spares cover 29 working channels on 19 spans Spare Working Coverage UPSR or BLSR p-Cycle …with same spare capacity “the clam-shell diagram”

19 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Further comparing p-cycles to rings

20 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ ADM-like nodal device for p-cycle networking

21 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Other Results: COST239 European Study Network Pan European optical core network 11 nodes, 26 spans Average nodal degree = 4.7 Demand matrix –Distributed pattern –1 to 11 lightpaths per node pair (average = 3.2) 8 wavelengths per fiber wavelength channels can either be used for demand routing or connected into p-cycles for protection Copenhagen London Amsterdam Berlin Paris Brussels Luxembourg Prague Vienna Zurich Milan

22 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Corroborating Results... Schupke et al… ICC % redundancy for 100% span restorability

23 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Exact comparison of Mesh and p-cycle network design

24 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ (Non-joint) Circumference- and Hop-limited Designs (Broadnets ’04) p-cycle threshold occurs about 3 or 4 hops higher than for the corresponding span-restorable mesh.

25 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ A possible point of confusion about p-cycles Coincidentally named “protection cycles” per Ellinas et. al. are not the same as p-cycles Ellinas’s method of “protection cycles” is based on oriented cycle double covers of the graph: they operate exclusively in an on-cycle way. The result is logical ring-like protection at exactly the 100% redundancy lower limit for rings. Every span will have exactly matching working and protection fibers. p-cycles can involve spans that have 2 working and zero protection fibers (or channels)

26 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ To illustrate…Bi-directional Cycle Covers Even-degree nodeOdd degree node Consider the problem of “covering” all spans at a node with conventional bi-directional rings, without causing a span overlap... At an even degree node… there is no problem

27 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Bi-directional Cycle Covers Even-degree nodeOdd degree node Now consider the same problem of covering at an odd-degree nodec At an odd degree node… no bi-directional ring cover exists that does not involve a span overlap

28 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ But with Unidirectional (Oriented) Cycle Covers Even-degree nodeOdd degree node …you can always cover both even and odd nodes without the equivalent of a ring span overlap... examples of undirectional ring covers... Equivalent to the bidirectional cover The unidirectional ring cover avoids any double-coverage ! (A mirror image set provides bidirectional W,P)

29 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Summary: Important Features of p-Cycles Working paths go via shortest routes over the graph p-Cycles are formed only in the spare capacity Can be either OXC-based or based on ADM-like nodal devices a unit-capacity p-cycle protects: –one unit of working capacity for “on cycle” failures –two units of working capacity for “straddling” span failures Straddling spans: –there may be up to N(N-1)/2 -N straddling span relationships –straddling spans each bear two working channels and zero spare –-> mesh capacity efficiency Only two nodes do any real-time switching for restoration –protection capacity is fully pre-connected –switching actions are known prior to failure –-> BLSR speed “pre-configured protection cycles”  p - cycles

30 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Approaches to p-Cycle Network Design (non-joint)(joint) Route all lightpath requirements via shortest-paths Heuristic algorithm(s) for p-cycle formation I.L.P. solution for p-cycle formation enumerate graph cycles working routes & working capacity p-cycles & spare capacity enumerate eligible working routes enumerate graph cycles “all in one” I.L.P. solution working routes & working capacity p-cycles & spare capacity

31 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Motivation for Joint Design example of the effect this can have: 2 spares 2 working channel-hops 12 spares in total TOTAL Capacity = 14 route length = 2 2 λ route length = 2+ε 1 spare 2+ε working 6 spares in total TOTAL Capacity = 8+ ε 2 λ  i.e., joint optimization will more fully exploit opportunities for straddling span efficiencies

32 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Comments : Non-joint problem: –several easy heuristic algorithms –however, optimal solution is quite fast too –no real difficulties here Joint design problem: –I.L.P more complex to solve (coupled integer decision variables and constraint systems) Idea: use I.L.P. but with reduced number of “preselected” candidate cycles –need some a priori view as to what makes a candidate cycle a promising as p-cycle

33 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Jointly optimized p-cycle network design Objective Function: –Minimize { total cost of working and spare capacity } Subject To: –A. All lightpath requirements are routed. –B. Enough WDM channels are provisioned to accommodate the routing of lighpaths in A. –C. The selected set of p-cycles give 100% span protection. –D. Enough spare channels are provisioned to create the p-cycles needed in C. –E. Integer p-cycles decision variables, integer capacity

34 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Pre-selection Heuristics: A Priori p-Cycle Efficiency: AE(p) AE (p) measures a cycle’s potential to provide protection relationships for working channels S S,p = 3 S C,p = 9 AE(p) = 1.67 S S,p = 4 S C,p = 10 AE(p) = 1.80

35 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Preselection Criteria: (1) Topological Score (TS) Credit rules: +1 for an “on-cycle” protection relationship +2 for a “straddling span” protection relationship Examples TS 6 spans, all on-cycle (equiv. To a ring) TS= 6 7 spans on-cycle 2 straddlers TS = 7 + 2*2 = 11 “on-cycle” “straddlers” By itself TS tends to like large cycles (Hamiltonian maximizes TS): no regard to corresponding cost of the cycle

36 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Preselection Criteria: (2) a Priori Efficiency (AE) AE is defined as: TS j Cost of cycle j ExamplesAE TS= 6 Cost = 6 hops --> AE = 1 Note: all rings have AE = 1 TS= 11 Cost = 7 hops --> AE = 1.57 Preselection hypothesis: choose a “small” number of elite cycle candidates based on AE Let I.L.P. formulation assemble final design

37 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Demand-weighted p-Cycle Efficiency: E w (p) Ew(p) measures a cycle’s actual efficiency in providing protection relationships for uncovered working channels AE(p) = 1.67 E w (p) = AE(p) = 1.67 E w (p) = 3.67 X p,i = 1 if on cycle X p,i = 2 if straddler w i = working on i c i = unit cost of i

38 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Benefits of Preselection by AE Metric (non-joint design) COST239 non-joint designs: Solution quality vs. No. candidate p-cycles in design 500 cycles 2000 cycles

39 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Benefits of AE Metric Pre-Selection (Joint Design) 200 cycles 2000 cycles COST239 joint designs: Solution quality vs. No. candidate p-cycles in design

40 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ How Much Does Joint Design Improve Efficiency? jointnon-joint COST-239 COST-239 Joint design uses 5% more working capacity, and 43% less spare capacity for total network capacity reduction of 13%. (4 p-cycles)(7 p-cycles) working spare

41 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Self-organization of the p-cycles... p-cycles certainly could be centrally computed and configured. –based on the preceding formulation However, an interesting option is to consider if the network can adaptively and continually self-organize - a near-optimal set of p-cycles within itself, - for whatever demand pattern and capacity configuration it currently finds.

42 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Self-organization of the p-cycles Based on an extension / adaptation of SHN™ distributed mesh restoration algorithm –“DCPC” = distributed cycle pre-configuration protocol Operates continually in background –Non-real time phase self-organizes p-cycles –Real time phase is essentially BLSR switching –p-cycles in continual self-test while in “storage” Centralized “oversight” but not low-level control –Method is autonomous, adaptive Networks actual state on the ground is the database

43 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Key concepts of DCPC protocol Node roles: –Cycler node state, Tandem node state DCPC implemented as event-driven Finite State Machine (FSM) Nodal interactions are (directly) only between adjacent nodes –Indirectly between all nodes (organic self-organization) –via “statelets” on carrier / optical signal overheads Three main steps / time-scales / processes –Each nodes act individually, “exploring” network from its standpoint as cycler node. –All nodes indirectly compare results –Globally best p-cycle is created

44 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Overview of DCPC protocol

45 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ How DCPC discovers “best p-cycles” (1)

46 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ How DCPC discovers “best p-cycles” (2)

47 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ DCPC Performance studies

48 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ IP/MPLS Restoration with p-Cycles IP Networks are already “Restorable” Restoration occurs when the Routing protocol updates the Routing Tables This update can take a Minute or more - Packets are lost until this happens Speed-up of IP Restoration is needed Not losing packets would be great too Also some control over capacity / congestion impacts needed p-cycles proposed as “fast” part of a fast + slow strategy that retains normal OSPF-type routing table re-convergence

49 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ MPLS/IP p -Cycle Properties p-Cycles are Virtual Circuits –Consume Zero Capacity until used –Well suited to MPLS-like Emerging Standards p-Cycles are Pre-planned –Centrally or Distributed (~DCPC) –Designed prior to Failure –At Failure, a p-Cycle requires no time to Setup or Use p-Cycles can restore Node and Span Failures

50 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ (1)Network setup: logical p-cycle establishment in routing tables. –p-cycles are established as “virtual circuits” using MPLS or a small number of “reserved” IP addresses (2) Real-time phase: nodal p-cycle behavior: –encapsulation, –deflection, –re-introduction MPLS/IP-layer p-cycles

51 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Insertion of an IP packet into a p-cycle –If the packet’s normal routing table entry indicates forwarding into a now-dead port, encapsulate the packet with the “p-cycle address” for dead neighbour router, route encapsulated packet (I.e, into p-cycle) –The IP packet is encapsulated in a p-cycle packet and routed along the p-cycle Operation of IP-layer p-cycles

52 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ IP Packet p-Cycle Packet Encapsulation Routing Table p-cycle Packet Operation of IP-layer p-cycles

53 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Insertion of an IP packet into a p-cycle… –The p-cycle packet packet contains the IP packet two new fields: –The ID of the p-cycle on which the packet belongs –The cost of the original pre-failure path for the IP packet Operation of IP-layer p-cycles

54 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Router Processing of a p-cycle packet arrival –(a) the router checks if it has a routing entry (with a functional port) for the encapsulated IP packet’s destination; if no, continue the packet along the p-cycle –(b) If yes to (a), test ; is cost of local “continuing route” option >= cost in p-cycle packet (I.e., from the encapsulation point); If yes, continue along the p-cycle. If no, remove the IP packet from the p-cycle packet and route it “normally” from this node. Operation of IP-layer p-cycles

55 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Operation of IP-layer p-cycles Failed Link Router Data De-Encapsulation Data Encapsulation Router p-cycle (a) On-Cycle Failure (1 restoration Path) (b) Straddling Failure (2 Restoration paths)

56 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Capacity Planning for IP/MPLS p-cycles Integer Program Formulation –chooses a set of p-cycles to restore all Span failures –Failed working demands may be re-routed over all available p-cycles –User-defined input constraint on number of p-cycles in the design –Objective: Minimize the Max Restoration-induced total flow on any span (i.e., min (max (oversubscription)) –subject to: The maximum over-subscription is over all Span Failures Every span failure is “covered” Hop count limit is respected Design limiting number of p-cycles

57 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ /12 3/6 Pre-Failure flow 4.5/6 10.5/12 4.5/6 “Straddling” Failure Flow lost = 3 Split 1.5 units each way around p-cycle Max subscription = 10.5/12 = /6 “On-Span” Failure Flow lost = 9 9 units around p-cycle Max (over-) subscription = 12/6 = 2 Installed capacity Controlled restoration-induced “over-subscription” of capacity

58 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Integer Program design results Run in “Bellcore” network –Minimally provisioned to be fully mesh- span restorable Some sample results

59 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ This set of five p-cycles producing  20% over- subscription for any IP span restoration Allowed 15 design p-cycles,  max over-subscription goes to  2% Sample Result

60 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Extension of p-cycles into node-encircling p-cycles for network recovery from node failures (especially router or LSR node failures)

61 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ An Attractive Two-layer Strategy (?) WDM layer: p-cycles protect against router failure MPLS layer: node- encircling p-cycles protect against router failure What actually fails ? Routers, LSRs Lambdas, fibers, ducts Survivability Measure Node- encircling MPLS p- Cycles p-Cycles Total resource cost may be very low for both span and node protection, especially if MPLS-layer p- Cycles employ oversubscription-based planning and/or the common pool capacity principle.

62 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Node Encircling p-Cycles. Each Node has a p-Cycle dedicated to its failure For each Node, a p-Cycle is chosen which includes all logically “Adjacent” Nodes but not the Protected Node Router Failure Restoration using “Node-Encircling” p-Cycles Node- Encircling p- cycle Other Nodes Encircled Node

63 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Node encircling p-Cycles are virtual Circuits or LSPs predefined by LSR router table entries no capacity used until needed can be planned on controlled oversubscription design basis by logically encircling the node, a single structure intercepts and protects all transiting flows Router Restoration using “Node-Encircling” p-Cycles Node Failure

64 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ –An “encircling” p-cycle for node k includes all nodes that are logically adjacent (directly connected) to node k but not node k itself. –“Encircling” p-cycles may be visually (graphically) apparent as such, may require a Figure 8, and / or may be non-apparent, I.e., logically, but not graphically encircling. A special case of “Figure-8’ing” is when the Figure 8 loop is logically required to go down and back the same span, to include one or more degree 2 sites. –The important property is that the encircling structure “intercepts” all transiting flows through the subject node. –Examples of each case follow... Key concept / extension of “node encircling” p-cycles

65 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Possible types of Node Encircling p-Cycles Simple, Apparent Simple, Non-Apparent Non-Simple (Segment) Non-Simple (Figure “8”)

66 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Sample result illustrating MPLS layer capacity vs worst tolerable oversubscription factor tradeoff in node protection with NEPCs Worst-case individual oversubscription factor (full loads, worst case span, worst case node failure) 

67 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ An “encircling” p-cycle for node k includes all nodes that are logically adjacent (directly connected) to node k but not node k itself. “Encircling” p-cycles may be visually (graphically) apparent as such, may require a “Figure 8,” and / or may be non-apparent, I.e., logically, but not graphically encircling. –A special case of “Figure-8’ing” is when the Figure 8 loop is logically required to go down and back the same span, to include one or more degree 2 sites. The important property is that the encircling structure “intercepts” all transiting flows through the subject node. –Examples of each case follow... Extension of basic p-cycles to “node encircling” p-cycles

68 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Router Node Restoration using node encircling p-Cycles Simple, Apparent Simple, Non-Apparent Non-Simple (Segment) Non-Simple (Figure “8”)

69 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Outline: A survey of recent research progress p-Cycles: key concepts and properties Node encircling p-cycles (for MPLS over WDM) Dual failure survivability Multi-QoP design of p-Cycle networks Protected Working Capacity Envelope Concept (PWCE) Adaptive PWCE Failure Independent Path-protecting (FIPP) p-cycles Some references

70 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Approaches to p -Cycle Network Design for high R 2

71 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Results for Susceptibly-limited static p-cycles design (COST-239) Dual failure Restorability Additional Relative Spare Capacity Cost Reconfiguration σ max =4 σ max =13 σ max =9 smaller σ max

72 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Results for post-failure reconfiguration of p-Cycles Relative Spare Capacity Cost Static R 1 =100% Reconfiguration R 2 =100% Vulnerable working capacity protected only Fraction of p-cycles changeable in form Only additional p-cycles 100%5%0%

73 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Straddling Protection Principle for Dual Failure Protection in p-cycles

74 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Dispersal Protection Principle for Dual Failure Protection in p-cycles

75 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Sample Results 7n11s Test Network 9n16s Test Network No extra spare capacity required over the all-gold design even if 20% of all demands are offered platinum protection Full Dual Failure Survivability (All Platinum Capacity) designs can be achieved with ~300 Redundancy above All-Gold 25n50s Test Network

76 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Outline: A survey of recent research progress p-Cycles: key concepts and properties Node encircling p-cycles (for MPLS over WDM) Dual failure survivability Multi-QoP design of p-Cycle networks Protected Working Capacity Envelope Concept (PWCE) Adaptive PWCE Failure Independent Path-protecting (FIPP) p-cycles Some references

77 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Define Some terms... QoP - is like QoS but refers to different “Quality of Protection” service classes. R1 - a class of service path that is assured of single span failure restorability -the average level of single failure restorability of a network as a whole R2 - a class of service path that is assured of restorability to any dual span failure - the average level of dual failure restorability of a network spare capacity - the shared but idle standby capacity of a mesh network that is used to protect services from different failure scenarios

78 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Economy Bronze Silver Gold No restoration attempt and possible preemption to satisfy Gold-class (and possibly also Silver-class) restorability requirements No restoration attempt if affected by a failure Best effort restoration after restoration of class Gold Assured restoration in any single span-failure scenario (R 1 service) Platinum Assured restoration to any dual span-failure scenario (R 2 service) Basic multi-QoP paradigm “multi-QoP” service paradigm Gold and silver may both preempt economy service capacity but silver only does so after all of gold’s requirements are met.

79 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Network Design Model … Minimize {total cost of capacity installed} subject to: - (a) all gold, silver, bronze and economy service demands are routed and assigned working capacity. - (b) on any span failure working capacity assigned to gold service paths is 100% restorable - (c) on every other span the sum of the spare capacity plus and economy capacity is sufficient to support the largest restoration flows needed for (b) - (d) (optionally) capacity is modular

80 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Test networks Net-A (20 nodes, 40 spans) Net-B (25 nodes, 50 spans) Net-C (30 nodes, 60 spans) Multi-QoP demand scenarios: –20 demands total between each node pair (55% = 11 lightpaths, 30% = 6 lightpaths, 15% = 3 lightpaths)

81 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Four multi-QoP Scenarios... All designs based on span restoration mechanism with hop limit of five Designs are “ jointly optimized” : (-> routing of gold and economy paths are synergistic decisions.) Mathematical model minimizes total capacity cost

82 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Sample Results (Study of multi-QoP Design... (Results for network 25n50s1) Conventional “all gold” design “working” “spare”

83 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ , 15,30 mix “gold” “silver” “economy” true spare capacity

84 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ ,30,55 mix “gold” “silver” “economy” true spare capacity

85 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ ,55,15 mix “gold” “silver” “economy” true spare capacity

86 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ ,30,15 mix true spare capacity

87 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Restorability of “gold” class (always 100%)

88 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Best efforts restorability of silver class (~45%) (~98%) (~10%) (~15%)

89 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Proportions of gold and silver restorability derived from economy

90 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Consider the 55,15, 30 Mix again... There is no spare capacity needed. (!) Restoration requirements for the 55% gold service class are fully met by preemption of economy class services. Silver class services enjoy ~ 40-50% best efforts restorability. Any given economy service path can still only expect to be disrupted in 12 to 14 % of all failures.

91 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Multi-QoP Mesh Design: Important points... Gold class always 100% restorable No spare capacity perse, except with maximum imbalance of gold and economy Best efforts restorability changes greatly depending in economy percentage Virtually all gold & silver restoration is obtained by economy preemption --> All capacity is earning revenue at some level or other.

92 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Outline: A survey of recent research progress p-Cycles: key concepts and properties Node encircling p-cycles (for MPLS over WDM) Dual failure survivability with p-cycles Multi-QoP design of p-Cycle networks Protected Working Capacity Envelope Concept (PWCE) Adaptive PWCE Failure Independent Path-protecting (FIPP) p-cycles Some references

93 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Problem Automatic routing and provisioning of optical network survivable services Optical network service provisioning

94 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Existing paradigm for automated provisioning of protected services: Shared Backup Path Protection (SBPP): –all nodes maintain synchronized global state database –for every new demand: find a working path find a disjoint backup path arrange / coordinate sharability of spare channels with all other shared backup arrangements in the network –disseminate the changes to all nodes in the network Observations / concerns –state updates are on the time-scale of the individual connections –abrupt onset / discovery of blocking

95 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ SBPP-based Service Provisioning: Concept I want to establish a protected connection to node 11 Spare capacity sharing I want to establish a protected connection to node 2 To arrange each backup path full shareability and routing information is needed. This is a large amount of volatile changing data in a large dynamic network. Global state consistency seems to limit scalability in both network size and speed of provisioning? Same basic mechanisms of the Internet itself. Network state dissemination on the time scale of the connections themselves.

96 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Example of SBPP: “Provisioning Protection” Green-blue protection sharing Green-red sharing To arrange each backup path full shareability and routing information is needed. This is a large amount of volatile changing data in a large dynamic network. Global state consistency seems to limit scalability in both network size and speed of provisioning? Same basic mechanisms of the Internet itself. Network state dissemination on the time scale of the connections themselves.

97 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ The PWCE Alternative: “Provisioning over Protected Capacity” Under a locally-acting survivability mechanism such as span restoration, p-cycles, or optical segment equivalents, we provision over protected capacity. If the working path can be routed it is protected. User-Network interface simply specifies protected, unprotected, best-efforts, service class. Each configuration of spare capacity defines a corresponding envelope for dynamic operations. If dynamic traffic is statistically stationary there is no state dissemination. The network envelope dimensions serve stochastic demand analogously to how a trunk group serves Erlang traffic. Reconfiguration (adaptation) of the envelope and any state change dissemination occurs only on the time scale of the non-stationary evolution of the demand pattern, not the per- connection time scale. Approach to limits of the operating envelope is observable and graceful. OSPF routing cost changes and central re-optimization of spare capacity can “stretch the envelope.” Total Capacity Reserve Network Protected Operating Envelope Demand

98 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Protected working Capacity Envelope (PWCE): –Based on span protection built into the network any distribution or allocation of total capacity to spare capacity mathematically defines a protected working envelope. –nodes maintain only OSPF topology view –for every new demand: find a working path - done –if all working channels used on a span, send a single LSA to withdraw the span from the OSPF topology view. Properties –state updates required only on the time-scale at which the statistics of the random demand evolve. –network visibility to monitor operating point in the envelope. –Graceful degradation, and can adapt the PWCE to “stretch the envelope.”

99 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Protected Working Capacity Envelope Total deployed capacity Initial network No per-connection protection path establishment No complicated online protection capacity sharing Protection capacity Protecting network Working capacity Working network Protected services Protecting

100 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Working capacity= Working network i.e., PWCE Protection capacity= Protecting network p-Cycle Protected Working Capacity Envelope Total deployed capacity=16 16 Initial network No per-connection establishment of protection paths No online spare capacity sharing computation

101 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Network State Database Comparison SBPP link state database Link ID Deployed capacity in channels Used capacity in channels Free capacity in channels Working channels Protection channels Protection channel sharing relationship Channel ID List of sharing working paths SBPP Connection database Connection ID Source node ID Working path Destination node ID List of links on the path List of channels used on the links Protection path List of links on the path List of channels used on the links PWCE link state database Link ID Envelope capacity in channels Link connectivity PWCE Connection database Connection ID Source node ID Working path Destination node ID List of links on the path

102 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Design of a Protected Working Capacity Envelope Model A Model BModel C Model D Model E Model FModel G Model H Envelope Volume Maximization Envelope Shaping Considerations PWCE (G, T i, D ref )= {w 0 i, s i }

103 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ An Example- Model D (span-wise total capacities are given) Sets: S: set of spans of network, index i or k P: set of eligible cycles of the network, index j Parameters:

104 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Model D (cont’) Parameters: Sets: S: set of spans of network, index i or k P: set of eligible cycles of the network, index j

105 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Model D (cont’) Parameters: l k : structuring weight on span k (for envelope shaping) T k : total deployed capacity on span k  : weighting factor to mediate the trade-off between structuring and volume maximization Variables: w 0 k : PWCE capacity on span k s k : spare capacity on span k : a scalar variable associated with the structuring effort n j : number of unit copies of cycle j to be configured as p-cycles njnj

106 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Model D (cont’) Objective: p-cycles to ensure working envelope capacity fully restored p-cycles not exceed the spare capacity budget on each span Envelope capacity is structured to follow a nominal shaping Constraints:

107 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Model D (cont’) The sum of working and spare capacity does not exceed the total span capacity

108 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ On average around 10 times difference SBPP PWCE Total Network State Database Comparison

109 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Control & State Synchronization Signaling Comparison On average around 40 times difference SBPP PWCE

110 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Blocking Performance Comparison PWCE

111 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Key Observation Blocking probability Restoration speed Signaling and state database low 200~300ms SBPP 60~80ms PWCE

112 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Adaptive Protected Working Capacity Envelope “stretching the envelope” and redesigning the envelope 

113 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Adaptive Protected Working Capacity Envelope Total deployed capacity=16 16 Initial network Working capacity= Working network Protection capacity=4 Protecting network

114 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Adaptive Protected Working Capacity Envelope Total deployed capacity=16 16 Initial network New envelope Working capacity= Working network Protection capacity=4 Protecting network New working capacity= New PWCE New protection capacity= Protecting network

115 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Adaptive PWCE: Redesign and Reconfiguration Envelope capacity decrease Envelope capacity increase Protection capacity Free envelope capacity Used envelope capacity

116 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ APWCE Reconfiguration Model Capacity utilization on span i in the Nth envelope Envelope capacity on span i in the Nth envelope Nth round PWCE (N+1)th round PWCE Span M

117 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Performances of SBPP, PWCE and APWCE under non-stationary random demand Blocking probability threshold: 0.08

118 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Summary of PWCE / APWCE Blocking about as good as SBPP in the same total capacity. Network state databases and state update signaling vastly reduced Protection times reduced. –Protection also becomes full pre-cross-connected User simplicity increased (“route it and mark it protected”). –Needs simple OSPF topology view of non-exhausted spans only. This is static in an envelope that is well configured to a certain stationary random demand pattern. Over statistically stationary epochs there is zero signalling for protection establishment and efficiency –No protection related signaling on per-connection timescale –No dependency on network size –No or rapidity of provisioning. Brief signaling activity to update OSPF edge weights (stretching) or to reoptimize the envelope only now and then as the entire demand pattern evolves with time.

119 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Outline: A survey of recent research progress p-Cycles: key concepts and properties Node encircling p-cycles (for MPLS over WDM) Multi-QoP design of p-Cycle networks Dual failure survivability Protected Working Capacity Envelope Concept (PWCE) Adaptive PWCE Failure Independent Path-protecting (FIPP) p-cycles Some references

120 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Some Properties of basic (span-protecting) p-cycles Failure independent ? (fault isolation) Path protecting ? (efficiency and end-node control) Fully pre-cross-connected ? (transparency!) “Ring speed”? Inherently node-failure protecting ? No (fault isolation is assumed) No (paths are protected span by span) YES No (other methods used)

121 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Properties of SBPP Failure independent ? Path protecting ? Fully pre-cross-connected ? “Ring speed”? node-failure protecting ? NoYES YesNo NoYES (Basic p-cycles)SBPP

122 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Motivation for “FIPP” p-Cycles Basic p-cycles 1.Span-protecting 2.NEPC technique for node-protection 3.Assume failure localization to spans Advantages of SBPP 1.path-protecting 2.Failure-independent end-node detection and activation Transparent optical networks 1.Highly desirable if protection paths or structures are “fully pre-connected”

123 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Q. How could p-cycles be extended to path protection ? Without giving up the fully pre-connected property of backup paths for transparent optical networks ! Why this problem is hard : the “mutual capacity” issue A prior attempt:  “Flow p-cycles” (Shen, Grover, JSAC, Oct 2003)

124 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Flow protecting p-cycles … Succeed in extending basic concepts of p-cycles to include node protection and path restoration levels of spare capacity efficiency but they are also –Failure specific in response –Require fault sectionalization –Are not end-node activated

125 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Key concept of “FIPP” p-Cycles (1) FIPP p-cycles address (or avoid) the mutual capacity problem, leading to simple, failure-independent, end-node control without giving up pre- connectedness by adapting a property of SBPP :  SBPP spare channel sharing principle: “Only allow working paths that are all mutually risk-disjoint to share spare channels in their backup routes.”

126 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Key concept of “FIPP” p-Cycles (2) FIPP concepts: (1): Define the protection structures as p-cycles on the end-nodes of the set of protected paths. (2): “Only allow working paths that are all mutually risk-disjoint to share protection structures.” Or more generally; (3): Any set of working paths with mutually disjoint backup routes on the FIPP p-cycle can for a compatible set of end-to-end protected paths.

127 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Conceptually …. (a group of seven mutually disjoint routes between selected end-node pairs) NETWORK

128 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Conceptual Diagram a FIPP p-cycle protecting all seven O-D pairs (all straddlers) x2

129 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Conceptual Diagram FIPP p-cycle protecting mixture of straddling and on-cycle routes x2 x1 x2 x1

130 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ FIPP p-cycle network design approaches 1.Let route groupings suggest the FIPP cycles –Enumerate candidate sets of “Compatible” Routes –Choose optimal set of groups and associated FIPP p-cycles 2.Load candidate cycles with compatible route sets –Enumerate candidate cycles (same as basic p-cycle design) –Represent route choices for each O-D pair –Write ILP model for full restorability at min spare capacity. 3.Heuristics based of candidate FIPP cycle “loading.” (A PAPER ON THE DESIGN THEORY AND ALGORITHMS IS TO BE PRESENTED AT DRCN 2005)

131 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Example of an actual FIPP p-Cycle (from Design Results) x1 x2 x1 x2 x1 x2 8 spare channels protect 13 end- to-end service paths (more remain possible to be loaded)

132 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Full Solution for COST239 with 1000 Eligible Cycles: Example solution is exactly as capacity efficient as SBPP Five pre-defined structures protect a whole network

133 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Summary: Properties of FIPP Failure independent ? Path protecting ? Fully pre-cross-connected ? “Ring speed”? node-failure protecting ? “Structural” aspect of protection and provisioning NoYESYES YesNoYES NoYESYES YESNoYES (Basic p-cycles)SBPP FIPP p-cycles

134 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Literature (on p-cycles and related PWCE) Grover, W. D., "p-Cycles," Chapter 10 in Mesh-based Survivable Networks: Options and Strategies for Optical, MPLS, SONET and ATM Networking, Prentice Hall PTR, Upper Saddle River, New Jersey, A. Sack, W. D. Grover, "Hamiltonian p-Cycles for Fiber-Level Protection in Homogeneous and Semi-Homogeneous Optical Networks," IEEE Network, Special Issue on Protection, Restoration, and Disaster Recovery, vol. 18, no. 2, March/April 2004, pp W.D. Grover, "The Protected Working Capacity Envelope Concept: An Alternative Paradigm for Automated Service Provisioning," IEEE Communications Magazine, January 2004, pp A. Kodian, A. Sack, W. D. Grover, “p-Cycle Network Design with Hop Limits and Circumference Limits,” Proceedings of the First International Conference on Broadband Networks (BROADNETS 2004), San José, California, USA, October 2004, pp (presentation) D. K. Leung, W.D. Grover, “Capacity Design of p-Cycle Networks in the Face of Demand Forecast Uncertainty,” Proc. of 9th OptoElectronics and Communications Conference and 3rd International Conference on Optical Internet (OECC/COIN 2004), Yokohama, Japan, July 12-16, A. Schupke, W.D. Grover, M. Clouqueur, “Strategies for Enhanced Dual Failure Restorability with Static or Reconfigurable p-Cycle Networks,” Proc International Conference on Communications (ICC 2004), Paris, France, June G. Shen, W.D. Grover, "Exploiting forcer structure to serve uncertain demands and minimize redundancy of p-cycle networks," Proceedings of OptiComm 2003, Dallas, Texas, October 13-17, 2003, pp (presentation) F. J. Blouin, A. Sack, W. D. Grover, H. Nasrallah, "Benefits of p-Cycles in a Mixed Protection and Restoration Approach," Proceedings of the Fourth International Workshop on the Design of Reliable Communication Networks (DRCN 2003), Banff, Alberta, Canada, October 2003, pp J. Doucette, D. He, W. D. Grover, O. Yang, "Algorithmic Approaches for Efficient Enumeration of Candidate p-Cycles and Capacitated p-Cycle Network Design," Proceedings of the Fourth Intl Workshop on the Design of Reliable Communication Networks (DRCN 2003), Banff, October 2003, pp (presentation) A. Kodian, W. D. Grover, J. Slevinsky, D. Moore, "Ring-Mining to p-Cycles as a Target Architecture: Riding Demand Growth into Network Efficiency," Proceedings of the 19th Annual National Fiber Optics Engineers Conference (NFOEC 2003), Orlando, September 2003, pp (presentation) G. Shen, W. D. Grover, "Extending the p-Cycle Concept to Path Segment Protection for Span and Node Failure Recovery," IEEE JSAC Optical Communications and Networking Series, vol. 21, no.8, Oct. 2003, pp M. Clouqueur, W.D. Grover, "Mesh-Restorable Networks with Enhanced Dual-Failure Restorability Properties," to appear in Photonic Network Communications, Kluwer Academic Publishers, accepted August D.A. Schupke, M.C. Scheffel, W.D. Grover, Configuration of p-Cycles in WDM Networks with Partial Wavelength Conversion, Photonic Network Communications, Kluwer Academic Publishers, vol 6, Issue 3, pp W.D. Grover, J. Doucette, M. Clouqueur, D. Leung, D. Stamatelakis, "New Options and Insights for Survivable Transport Networks," IEEE Communications Magazine, vol.40, no.1, January 2002, pp

135 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Literature Grover, W.D.; Stamatelakis, D., “Bridging the ring-mesh dichotomy with p-cycles,” Second International Workshop on the Design of Reliable Communication Networks (DRCN), Munich, Germany, April , Grover, W.D.; Stamatelakis, D., "IP Layer Restoration and Network Planning Based on Virtual Protection Cycles," IEEE JSAC Special Issue on Protocols and Architectures for Next Generation Optical WDM Networks, vol.18, no.10, October, 2000, pp Grover, W.D.; Stamatelakis, D., "Theoretical Underpinnings for the Efficiency of Restorable Networks Using Pre- configured Cycles ("p-cycles")," IEEE Transactions on Communications, vol.48, no.8, August 2000, pp Grover, W.D.; Stamatelakis, D., "Rapid Restoration of Internet Protocol Networks using Pre-configured Protection Cycles," Proc. 3rd Can. Conf. On Broadband Research (CCBR'99), Nov. 7-9, Ottawa, 1999, pp Grover, W.D.; Stamatelakis, D., "Cycle-oriented distributed pre-configuration: ring-like speed with mesh-like capacity for self-planning network restoration," in Proc. IEEE International Conf. Commun. (ICC '98), Atlanta, June 8-11, 1998, pp Schupke, D.A.; Grover, W.D.; Clouqueur, M., "Strategies for Enhanced Dual Failure Restorability with Static or Reconfigurable p-Cycle Networks," IEEE International Conference on Communications (ICC), Paris, France, June 20-24, Schupke, D.A.; Scheffel, M.C.; Grover, W.D.,"Configuration of p-Cycles in WDM Networks with Partial Wavelength Conversion," Photonic Network Communications, Kluwer Academic Publishers, vol. 6, no. 3, pp , November Schupke, D.A.; Scheffel, M.C.; Grover W.D., "An Efficient Strategy for Wavelength Conversion in WDM p-Cycle Networks," Fourth International Workshop on the Design of Reliable Communication Networks (DRCN), Banff, Alberta, Canada, October 19-22, Grover, W.D. "p-Cycles, Ring-Mesh Hybrids and "Ring-Mining:” Options for New and Evolving Optical Networks," Invited Paper, Proc. Optical Fiber Communications Conference (OFC 2003), Atlanta, March 24-27, 2003, pp Grover, W.D. "Understanding p-Cycles, Enhanced Rings, and Oriented Cycle Covers" (invited paper), 1st Int’l Conference on Optical Communications and Networks (ICOCN’02), Singapore, Nov.11-14, 2002, pp Grover, W:D.; Doucette, J. E., "Advances in Optical Network Design with p-Cycles: Joint optimization and pre-selection of candidate p-cycles," Proceedings of the IEEE-LEOS Summer Topical Meeting on All Optical Networking, Mont Tremblant, Quebec, July 15-17, Grover, W:D.; Doucette, J. E.; Clouqueur, M.; Leung, D.; Stamatelakis, D."New Options and Insights for Survivable Transport Networks," IEEE Communications Magazine, vol.40, no.1, January 2002, pp Schupke, D.A.; Grover, W.D.; Gruber, C.G.; Stamatelakis, D., "p-Cycles: Network Protection with Ring-speed and Mesh- efficiency,“ Invited Talk, 1 st COST270 Workshop on Reliability of Optical Networks, Systems and Components, Dubendorf, Switzerland, December 12-13, 2001.

136 © Wayne D. Grover 2005 Patents Issued or Pending Presented at DRCN_ Related web sites W. Grover home pages with publications for download Web site for book on mesh-based survivable networks (contains chapters on p-cycles and on ring-mesh evolution and covers PWCE concept.): p-Cycles web forum prepared by TRLabs Network Systems group:

Wayne D. Grover Tutorial for DRCN 2005 Island of Ischia (Naples), Sunday October 16, 2005 DRCN 2005 Tutorial T3 p-Cycles: Fast, simple and efficient new options for network survivability at optical and MPLS layers Department of Electrical and Computer Engineering