1 st COST270 Workshop on Reliability of Optical Networks, Systems and Components December 13, 2001 - EMPA, Dubendorf, Switzerland Dominic Schupke Claus Gruber Munich University of Technology Institute of Communication Networks Wayne Grover Demetrios Stamatelakis TRLabs, University of Alberta p-Cycles: Network Protection with Ring-speed and Mesh-efficiency
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1 st COST270 Workshop on Reliability of Optical Networks, Systems and Components December 13, 2001 - EMPA, Dubendorf, Switzerland Dominic Schupke Claus.
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1st COST270 Workshop onReliability of Optical Networks, Systems and Components
December 13, 2001 - EMPA, Dubendorf, Switzerland
Dominic SchupkeClaus Gruber
Munich University of Technology Institute of Communication Networks
Wayne GroverDemetrios Stamatelakis
TRLabs, University of Alberta
p-Cycles: Network Protectionwith Ring-speed and Mesh-efficiency
• Motivation• Basics• p-Cycles in WDM Networks• Self-organization of p-Cycles• p-Cycles in IP Router Restoration
(Overview)• Summary
Outline
Background and Motivation
“ Ring “A. 50 msec restoration timesB. Complex network planning
and growthC. High installed capacity for
demand-servedD. Simple, low-cost ADMsE. Hard to accommodate
multiple service classes F. Ring-constrained routing
“Mesh”G. Up to 1.5 sec restoration
timesH. Simple, exact capacity
planning solutions
I. well under 100% redundancy
J. Relatively expensive DCS/OXCK. Easy / efficient to design for
multiple service classesL. Shortest-path routing
“ Shopping list” : A, D, H, I, L (and K) please...keep
the rest
• For meshed networks• Pre-reserved protection paths (before failure) • Based on cycles, like rings• Also protects straddling failures, unlike rings• Local protection action, adjacent to failure (in
the order of some 10 milliseconds)• Shared capacity
Understanding why (optimally planned) p-cycles are so efficient...
9 Spares cover 9 Workers
9 Spares
cover 19 Workers
Spare
Working Coverage
UPSR or
BLSR
p-Cycle…same spare
capacity
“the clam-shell diagram”
Further comparing p-cycles to rings
ADM-like “capacity-slice” nodal device for p-cycle networking
nodal redundancy =
spare 1
working 1
: 3 25%
R
k
example k R
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.
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
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
Overview of DCPC protocol
How DCPC discovers “best p-cycles” (2)
How DCPC discovers “best p-cycles” (1)
DCPC Performance studies
Illustrating the Real time phase
Adapting p-cycles to the IP-layer …
IP Network Restoration
• 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
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)
• 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
p-Cycles are Virtual Circuits/Protection Structures which can redirect Packets around Failures– Plain IP is Connectionless but p-Cycles can be realized with