Traffic Grooming for Survivable WDM Networks

1
Traffic Grooming for Survivable WDM Networks
Shared Protection

• Kevin Su
• University of Texas at San Antonio

2
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

3
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.

4
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) ---0---
• ---0------0---
• Dedicated Protection
• Shared Protection

5
Introduction
6
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

7
Grooming Node Architecture
8
Network Model

• A network is represented as a weighted, directed
  graph
• G(V, E, C, ?, P)
• V set of nodes
• E set of unidirectional fibers (referred to
  links)
• C the cost function for each link
• ? the number of wavelengths on each link
• P number of grooming ports at each node
• Connection request is represented as a quadruple
  lts, d, B, gt
• s source node
• d destination node
• B bandwidth requirement
• holding time

9
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 doesnt 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
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
• c1lt0,2,STS-12, t1gt c2 lt 0,3,STS-3, t2gt c3
  lt4,3,STS-48, t3gt

11
Proposed Schemes - PAL

• After provisioning c1
• c1lt0,2,STS-12, t1gt c2 lt 0,3,STS-3, t2gt c3
  lt4,3,STS-48, t3gt

12
Proposed Schemes - PAL

• After provisioning c2
• c1lt0,2,STS-12, t1gt c2 lt 0,3,STS-3, t2gt c3
  lt4,3,STS-48, t3gt

13
Proposed Schemes - PAL

• After provisioning c3
• c1lt0,2,STS-12, t1gt c2 lt 0,3,STS-3, t2gt c3
  lt4,3,STS-48, t3gt

14
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.

15
Proposed Schemes - MPAC

• After provisioning c1
• c1lt0,2,STS-12, t1gt c2 lt 0,3,STS-3, t2gt c3
  lt4,3,STS-48, t3gt

16
Proposed Schemes - MPAC

• After provisioning c2
• c1lt0,2,STS-12, t1gt c2 lt 0,3,STS-3, t2gt c3
  lt4,3,STS-48, t3gt

17
Proposed Schemes - MPAC

• After provisioning c3
• c1lt0,2,STS-12, t1gt c2 lt 0,3,STS-3, t2gt c3
  lt4,3,STS-48, t3gt

18
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.

19
Proposed Schemes - SPAC

• After provisioning c1
• c1lt0,2,STS-12, t1gt c2 lt 0,3,STS-3, t2gt c3
  lt4,3,STS-48, t3gt

20
Proposed Schemes - SPAC

• After provisioning c2
• c1lt0,2,STS-12, t1gt c2 lt 0,3,STS-3, t2gt c3
  lt4,3,STS-48, t3gt

21
Proposed Schemes - SPAC

• After provisioning c3
• c1lt0,2,STS-12, t1gt c2 lt 0,3,STS-3, t2gt c3
  lt4,3,STS-48, t3gt

22
Proposed Schemes
23
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

24
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

25
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
  connections 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

26
Network Topology

• 24-node example network topology

27
Performance Evaluation
28
Performance Evaluation
29
Performance Evaluation
BBR versus network offered load with k 1,2 and 3
30
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

31
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
  2004.
• 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.285-299, Apr. 2003