10/6/2003Kevin Su Traffic Grooming for Survivable WDM Networks – Shared Protection Kevin Su University of Texas at San Antonio

10/6/2003Kevin Su Outline Introduction Motivation System Model –Grooming Node Architecture –Network Model Proposed Schemes –Protection-at-lightpath (PAL) level –Mixed protection-at-connection (MPAC) level –Separated protection-at-connection (SPAC) level Heuristic Algorithms Performance Evaluation

10/6/2003Kevin Su Introduction WDM: stands for wavelength division multiplexing, it is a technology that divides the bandwidth of an optical fiber into many non-overlapping wavelengths, so that multiple communication channels can operate simultaneously on different wavelengths. –Increases the transmission capacity of optical fibers. –Allows simultaneously transmission of multiple wavelengths within a single fiber. –Up to 320 wavelengths per fiber; per wavelength, 10Gb/s, STS-192 (OC-192), today; expected to grow to 40Gb/s, STS-768(OC-768), soon.

10/6/2003Kevin Su Introduction Traffic Grooming: refers to problem of efficiently packing low- speed connections onto high-capacity lightpaths to better utilize network resourses. –The bandwidth requirement of a typical connection request is between STS-1 (51.84 Mb/s) and STS-192(full wavelength) Protection: is a proactive procedure in which spare capacity is reserved during connection setup. –Working path: a path that carries traffic during normal operation –Backup path: a path over which the connection is rerouted when a working path fails –Single Failure (single-fiber failure, single-node failure) –Dedicated Protection –Shared Protection

10/6/2003Kevin Su Introduction

10/6/2003Kevin Su Motivation Survivable Traffic Grooming –Efficiently utilize the network resources (traffic grooming) –A failure of a network element can cause the failure of several lightpaths, thereby leading to large data and revenue loss (protection) Static Case Dynamic Case

10/6/2003Kevin Su Grooming Node Architecture

10/6/2003Kevin Su Network Model A network is represented as a weighted, directed graph G=(V, E, C, λ, P) –V: set of nodes –E: set of unidirectional fibers (referred to links) –C: the cost function for each link –λ: the number of wavelengths on each link –P: number of grooming ports at each node Connection request is represented as a quadruple –s: source node –d: destination node –B: bandwidth requirement – : holding time

10/6/2003Kevin Su Proposed Schemes - PAL Protection-at-lightpath (PAL) level provides end-to-end protection w.r.t. lightpath. Under PAL, a connection is routed through a sequence of protected lightpath, or p-lightpath. A p-lightpath has a lightpath as working path and link-disjoint path as backup path Working path consumes a grooming-add port at the source node and a grooming-drop port at the destination node Backup path doesn’t consume any grooming port and wavelengths along a backup path are only reserved When working path fails, backup path is set up as a lightpath by utilizing the grooming ports previously used by the working path Two p-lightpaths can share wavelengths along common backup links if their working paths are link-disjoint.

10/6/2003Kevin Su Proposed Schemes - PAL Initial network configuration Edge represents bidirectional fiber, each fiber has 2 wavelengths Wavelength capacity STS-192, every node has 3 grooming ports c1 ; c2 ; c3

10/6/2003Kevin Su Proposed Schemes - PAL After provisioning c1 c1 ; c2 ; c3

10/6/2003Kevin Su Proposed Schemes - PAL After provisioning c2 c1 ; c2 ; c3

10/6/2003Kevin Su Proposed Schemes - PAL After provisioning c3 c1 ; c2 ; c3

10/6/2003Kevin Su Proposed Schemes – MPAC Mixed Protection-at-Connection (MPAC) level provides end-to-end protection w.r.t. connection. Under MPAC, a connection is routed via link-disjoint working path and backup path, each of which traverses a sequence of lightpaths. A lightpath traversed by a working path utilizes a portion of its capacity to carry traffic during normal operation A lightpath traversed by a backup path reserves part of its capacity for that backup path “Mixed” means that capacity of one wavelength can be utilized by both working paths and backup paths.

10/6/2003Kevin Su Proposed Schemes - MPAC After provisioning c1 c1 ; c2 ; c3

10/6/2003Kevin Su Proposed Schemes - MPAC After provisioning c2 c1 ; c2 ; c3

10/6/2003Kevin Su Proposed Schemes - MPAC After provisioning c3 c1 ; c2 ; c3

10/6/2003Kevin Su Proposed Schemes – SPAC Separated Protection-at-Connection (MPAC) level provides end-to- end protection w.r.t. connection. Under SPAL, a connection is routed via link-disjoint working path and backup path. A working path traverses a sequence of lightpath. A backup path traverses a sequence of links, each of which has judiciously reserved a number of wavelengths as backup resourses “Separated” means that the capacity of a wavelength can be utilized by either working paths or backup paths, but not both.

10/6/2003Kevin Su Proposed Schemes - SPAC After provisioning c1 c1 ; c2 ; c3

10/6/2003Kevin Su Proposed Schemes - SPAC After provisioning c2 c1 ; c2 ; c3

10/6/2003Kevin Su Proposed Schemes - SPAC After provisioning c3 c1 ; c2 ; c3

10/6/2003Kevin Su Proposed Schemes

10/6/2003Kevin Su Heuristic Algorithm It is NP-complete to provision a connection request with shared protection. The Author proposed heuristic for MPAC, SPAC, PAL MPAC –Backup-sharing measuring Every lightpath is associated with a conflict set to identify the sharing potential between paths. conflict set for lightpath can be represented as an integer set { } where represents the amount of traffic that will be rerouted on lightpath when link e fails. The amount of backup capacity reserved on lightpath is thus –Route computation Enumerates K candidate working paths For each candidate working path, computes a disjoint minimal-cost path as backup path based on some cost function Selects the path pair of minimal cost

10/6/2003Kevin Su Heuristic Algorithm SPAC (the same as MPAC except) –Different backup-sharing measurement –Different cost function in route computation PAL –Different backup-sharing measurement –Route computation Extend a stand shortest-path algorithm such that every hop along the resultant shortest path corresponds to a p-lightpath, which can be either an exisiting p- lightpath or a new p-lightpath consisting of fresh wavelength links and free grooming ports

10/6/2003Kevin Su Performance Evaluation Connection-arrival process is Poisson process Connection-holding time follows a negative exponential distribution Capacity of wavelength is STS-192 # of connection requests follows the distribution STS-1: STS-3: STS-12: STS-48: STS-192 = 300: 20: 6: 4 :1 Load (in Erlang) is defined as connection-arrival rate times average holding time times a connection’s average bandwidth normalized in the unit of STS-192 Number of grooming ports is set as # of wavelengths times its nodal degree times a scalar ( implies that any incoming wavelength to the W-Fabric can be dropped to the G-Fabric) The number of alternate paths K = 2 Measurement metrics –Bandwidth-blocking Ratio –Resource-Efficiency Ratio

10/6/2003Kevin Su Network Topology 24-node example network topology

10/6/2003Kevin Su Performance Evaluation

10/6/2003Kevin Su Performance Evaluation

10/6/2003Kevin Su Performance Evaluation BBR versus network offered load with k =1,2 and 3

10/6/2003Kevin Su Conclusion and Future Work Investigate the survivable traffic-grooming problem in dynamic case –PAL, MPAC, SPAC –Findings: It is beneficial to groom working paths and backup paths separately as in PAL and SPAC Separately protecting each individual connection yields the best performance when the number of ports is suffcient Protecting each specific lightpath achieves the best performance when the # of grooming ports is moderate or small Future work –Considering the residual connection holding time

10/6/2003Kevin Su References C. Ou, K. Zhu, H. Zang, L. H. Sahasrabuddhe, and B. Mukherjee. “Traffic Grooming for Survivable WDM Networks – Shared Protection”. Accepted to IEEE Journal of Selected Area in Communication H. Zhu, H.Zang, K. Zhu, and B. Mukherjee, “A novel, generic graph model for traffic grooming in heterogeneous WDM mesh networks” IEEE/ACM Trans. Neworking, vol.11 pp , Apr. 2003