Dynamic Routing and Wavelength Assignment Scheme for Protection against Node Failure

1
Dynamic Routing and Wavelength Assignment Scheme
forProtection against Node Failure
11/16

• Ying Wang1 , Tee Hiang Cheng1,2 and Biswanath
  Mukherjee3
• 1School of Electrical and Electronic Engineering,
  Nanyang Technological University, Singapore
• 2Lightwave Department, Institute for Infocomm
  Research, Singapore
• 3 Department of Computer Science, University of
  California, Davis, California 95616

2
Outline

• There are few studies on the design of optical
  networks that could survive single node failures.
• We design a dynamic RWA scheme that will set
  up a primary path as well as a node-disjoint
  shared protection path for each connection.
• We propose a novel scheme that uses three vectors
  to convey incomplete information of link state.
• Finally, we get the experiment results of some
  criteria.

3
Introduction

• Optical network is prone to failures hence,
  network survivability is a major concern of
  network operators.
• Resiliency is generally achieved by means of
• Protection and Restoration.
• In a typical protection scheme against node
  failure, the primary and backup paths need to be
  node-disjoint in any intermediate node along
  their routes.
• node-disjoint requirement can also protect
  against a
• link failure.

4
Introduction (contd.)

• Most of the RWA problem studies related to
  protection and restoration in the optical layer
  focus on off-line computation.
• These problems are pertaining to network
  planning
• or static provisioning.
• DLE (Dynamic Lightpath Establishment)
• The primary and backup paths need to
• be calculated at the same time and
  wavelength
• channels need to be allocated for both
  paths.

5
Network Information Scenarios

• We consider three possible ways in which network
  status information can be stored and disseminated
  and the effect on capacity efficiency.
• Full Information Scenario (FIS)
• Partial Information Scenario (PIS)
• No Sharing of Information Scenario (NSIS)

6
Full Information Scenario (FIS)

• Having a centralized RWA server that stores all
  the information about the network and computes
  the primary and backup paths for any new
  wavelength demand.
• scalability problem

7
Partial Information Scenario (PIS)

• PIS is to disseminate the network information to
  every node in the network such that each ingress
  node can make a RWA decision based on the network
  information it posses.
• Only essential network information can be
  disseminate.
• Uses three vectors to describe the state of
  each link.
• - Wavelength Channel Availability Vector
  Wavi
• - Backup Wavelength Channel Reservation
  Vector Wres
• - Conflict Vector CN

8
No Sharing of Information Scenario (NSIS)

• When ingress nodes make a routing and wavelength
  assignment decision, it has no information of
  existing primary and backup lightpaths , so it
  cannot share any wavelength channels on the
  backup lightpath with others
• It will result in the worst capacity
  efficiency and can be
• used as a benchmark

9
ILP solution

• Values given
• N Set of nodes in the network
• E Set of unidirectional fiber links in the
  network
• W Set of wavelengths channel on each fiber
  link
• s Source node of a lightpath
• d Destination node of a lightpath
• Sijw Assume the value of 1 if wavelength
  channel w is
• free on link ij zero otherwise
• The variables are
• Pijw Assume the value of 1 if the primary
  lightpath uses
• wavelength channel w on link ij zero
  otherwise
• Bijw Assume the value of 1 if the backup
  lightpath uses
• wavelength channel w on link ij zero
  otherwise
• Zijw The cost of using wavelength channel w
  on link ij in
• the backup lightpath

10
ILP solution (contd.)

• The ILP formulation is as follows

11
ILP solution (contd.)
12
Experiment Result

• Capacity Efficiency
• Effectiveness of PIS with Different Number of
• Wavelength Channels per Link
• Capacity Comparison between Node Failure
• and Link Failure Protection

13
Capacity Efficiency

• The saving in the total number of wavelength
  channels used between NSIS and FIS varies from
  18 to 23, the saving in total wavelength
  channel usage between NSIS and PIS is from 10 to
  15. The result seems reasonable.

14
Effectiveness of PIS with Different Number of
Wavelength Channels per Link

• The results lead us to conclude that there exists
  an
• optimal number of wavelengths to aggregate
  beyond
• which, the network will suffer a significant
  drop in
• capacity efficiency.

15
Capacity Comparison between NodeFailure and Link
Failure Protection

• The simulation results also show that for most
  meshed
• topologies, less than 7 extra capacity is
  needed to
• provide node and link failure protection
  compared to link
• failure protection.