Extending the p-Cycle Concept to Path-Segment Protection

1
Extending the p-Cycle Concept to Path-Segment
Protection

• Gangxiang Shen, Wayne D. Grover
• gshen,grover_at_trlabs.ca
• URL http//hey.to/gxshen

2
Outline

• Background and Motivation
• Concept of Flow p-Cycles
• Flow p-Cycle Design Model
• Test Methods and Results
• Operational Aspects and Potential Applications
• Conclusions

3
Basic Approaches to Transport Network
Survivability
4
Background Span-Protecting p-Cycles

• Characteristic Ring-like switching speed and
  mesh-like capacity efficiency

5
Comparison between Ring and p-Cycle Protection
Ring network
p-Cycle
Spare Capacity
Protection Coverage
Able to restore 9 spans
Able to restore 19 spans
6
The Unique Position Span p-Cycles Occupy
Path rest, SBPP
Speed
Span (link)rest.
200 ms
BLSR
50 ms
100
50
200
Redundancy
7
Motivation

• All the studies so far on p-cycles consider
  span-protecting p-cycles, so it is natural to
  ask
• Q. is there is a path protection equivalent to
  p-cycles? --
• A. Yes the answer is Flow p-Cycles !

8
Concept of Flow p-Cycles

• Characteristic
• Protect spans that span p-cycles can protect as
  well as spans that span p-cycles cannot protect
  (example span 6-7 below)
• Intermediate node failure restoration (example
  node 7)
• Path restoration like spare capacity efficiency,
  11 path protection like switching speed

9
The Position Flow p-Cycles Occupy
Path rest, SBPP
p -cycles BLSR speedmesh efficiency
Speed
Span (link)rest.
200 ms
BLSR
50 ms
100
50
200
Redundancy
10
Various Flow-to-Cycle Relationships

• Related basic concepts
• Intersecting and non-intersecting
• Intersection nodes
• Intersection flow segment
• Straddling and on-cycle flow relationship

11
Mutual Capacity Consideration

• Single span-failure causes multiple flow-failures
  simultaneously
• Flow-based restoration is required

12
Flow p-Cycle Design Model for 100 Span Failure
Restoration

• Objective minimize total spare capacity
• Constraints
• Affected flows upon a span failure must be fully
  restored
• Number of cycle copies to build is set by the
  largest span failure-specific simultaneous use
  for unit copies of cycle
• The spare capacity on a span must be enough to
  support the number of copies of each p-cycle that
  overlies the span

13
Test Networks
14
Result Performance Comparison between Various
Protection Schemes
15
Operational Aspects and Protocol
16
Applications of the General Concept
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Conclusions

• Flow p-cycle concept was proposed and evaluated
• Flow p-cycle method achieves path restoration
  like spare capacity efficiency and 11 path
  protection like restoration speed

18
Future Work

• Identify the impacts from the network details and
  demand patterns
• Further consider operational aspects and develop
  control protocol
• Implement some applications of the general
  concept
• Consider an evolutional scheme, pre-configured
  segments p-segments
• Compare to ordinary node-encircling p-cycles
  for node protection.

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Main References

• 1 W. D. Grover and D. Stamatelakis,
  Cycle-oriented distributed preconfiguration
  Ring-like speed with mesh-like capacity for
  self-planning network restoration, in Proc. of
  IEEE ICC98, 1998, pp. 537-543.
• 2 D. Stamatelakis, W. D. Grover, IP layer
  restoration and network planning based on virtual
  protection cycles, IEEE Journal on Selected
  Areas in Communications, vol.18, no.10, October
  2000, pp. 1938 - 1949.
• 3 D. A. Schupke, C. G. Gruber, and A.
  Autenrieth, Optimal configuration of p-cycles in
  WDM networks, in Proc. of IEEE ICC02, 2002.
• 4 W. D. Grover, and J. E. Doucette, Advances
  in optical network design with p-cycles Joint
  optimization and pre-selection of candidate
  p-cycles, to appear in Proc. of the IEEE-LEOS
  Summer Topical Meeting on All Optical Networking,
  2002.
• 5 M. Herzberg and S. Bye, An optimal
  spare-capacity assignment model for survivable
  network with hop limits, in Proceedings of IEEE
  GLOBECOM94, 1994, pp. 1601-1607.
• 6 R. R. Iraschko, M.H. MacGregor, and W.D.
  Grover, Optimal capacity placement for path
  restoration in STM or ATM mesh-survivable
  networks, IEEE/ACM Transactions on Networking,
  vol. 6, no. 3, June 1998, pp. 325-336.

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Literature Survey on Span-Protecting p-Cycles

• 1998, Grover and Stamatelakis first proposed
  p-cycles concept and developed self-organized
  protocol 1
• 2000, application of p-cycles to IP/MPLS layer
  2 including node-encircling p-cycles
• 2002, application to DWDM networks 3
• 2002, studies on joint optimization of p-cycle
  network designs 4

21
Evolution of Survivability Schemes

• First Generation
• Pre-configured dedicated protection facilities
• Fast restoration speed
• Bad spare capacity redundancy
• Example various ring-based techniques like 11,
  UPSR, BLSR
• Second Generation
• Pre-planned but not pre-configured protection
  routes and shared spare capacities
• Good spare capacity redundancy
• Slow restoration speed
• Example mesh-based restoration schemes like
  span, path, SBPP

22
Evolution of Survivability Schemes (cont)

• Third Generation
• Pre-configured cycles
• Fast restoration speed
• Good spare capacity redundancy
• Example p-cycles
• Future Generation
• Pre-configured segments
• Fast restoration speed
• Good spare capacity redundancy
• Example p-segments

23
Comparison between Mesh (SBPP) Restoration and
p-Cycle Protection
Mesh restorable network
p-Cycle
Two-way talk Generalized adaptive
reconfiguration
No two-way talk Immediate action Fully
pre-prepared action
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Cycle Preselection Strategy

• D is set of nonzero demand pairs (i.e., flows)
  on the traffic matrix
• Sr is set of spans traversed by the working path
  between demand pair r
• P(j) denotes cycle j in cycle set P
• k enumerates spans on cycle P(j) and ck
  represents the cost of span k
• gr denotes number of traffic demand units of the
  working flow between demand pairs r
• lr denotes length of the working flow of demand
  pair r

25
Flow p-Cycle Design Model II 100 Span and Node
Failure Restoration

• Objective minimize total spare capacity
• Constraints
• Affected flows upon a span failure must be fully
  restored
• Affected flows upon an intermediate node failure
  must be fully restored
• Number of cycle copies to build is set by the
  largest span failure-specific simultaneous use
  for unit copies of cycle
• Number of cycle copies to build is set by the
  largest node failure-specific simultaneous use
  for unit copies of cycle
• The spare capacity on a span must be enough to
  support the number of copies of each p-cycle that
  overlies the span

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Concept of Multi-QoP

• R0 restorability this is a wholly best-effort
  class with no assured restorability
• Rs restorability this class is assured by design
  of restorability against any span failure, but
  receives only best efforts with no guarantee for
  node failure
• Rsn restorability this class enjoys assured
  restorability against any span failure or failure
  of an intermediate node other than its own
  end-nodes.

27
Flow p-Cycle Design Model III Design to Support
Multi-QoP

• Objective minimize total spare capacity
• Constraints
• Affected Rs and Rsn flows upon a span failure
  must be fully restored
• Affected Rsn flows upon an intermediate node
  failure must be fully restored
• Number of cycle copies to build is set by the
  largest span failure-specific simultaneous use
  for unit copies of cycle
• Number of cycle copies to build is set by the
  largest node failure-specific simultaneous use
  for unit copies of cycle
• The spare capacity on a span must be enough to
  support the number of copies of each p-cycle that
  overlies the span

28
Flow p-Cycle Design Model IV Maximal Node
Recovery under a Spare Capacity Budget

• Objective maximize overall node failure
  restorability
• Constraints
• Affected flows upon a span failure must be fully
  restored
• The restored traffic flows of a demand pair never
  exceeds its total lost traffic flows upon an
  intermediate node failure
• Number of cycle copies to build is set by the
  largest span failure-specific simultaneous use
  for unit copies of cycle
• Number of cycle copies to build is set by the
  largest node failure-specific simultaneous use
  for unit copies of cycle
• The spare capacity on a span must be enough to
  support the number of copies of each p-cycle that
  overlies the span
• Total spare capacity should not exceed a budget

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Result II Impact of Cycle Preselection
Strategies and Number of Cycles of Flow p-Cycles
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Result III Impact of Physical Distance Limit of
Cycle Circumference of Flow p-Cycles
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Result IV Performance on Node Failure Recovery
(1)
Rs 100 span failure restoration Rsn 100 span
and intermediate node failure restoration
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Result IV Performance on Node Failure Recovery
(2)
Normalized spare capacity for 100 span failure
restoration
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Result IV Performance on Node Failure Recovery
(3)
100 Rs services
100 Rsn services
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Publications

• 1 Wayne D. Grover, Gangxiang Shen, "Extending
  the p-cycle concept to path-segment protection,"
  to appear in ICC2003, Anchorage, Alaska, USA,
  May, 2003.
• 2 Gangxiang Shen, Wayne D. Grover, "Capacity
  requirements for network recovery from node
  failure with dynamic path restoration," to appear
  in OFC2003, Atlanta, Georgia, USA, March, 2003.
• 3 Gangxiang Shen, Wayne D. Grover, Extending
  the p-cycle concept to path-segment protection
  for span and node failure recovery, submitted to
  IEEE JSAC special issue (Optical communications
  and networking series 2003).