Microsoft PowerPoint - IMEC_WSokt02_vFinalSpeaker: Didier COLLE (IMEC)
– IMEC, TILab, SIRTI, T-SYSTEMS, AGH, NTUA, UPC, CISCO, TELLIUM
Outline • Introduction
• Single Layer Recovery • Recovery Interworking techniques • Multilayer survivability strategies • Network dimensioning: approach & assumptions • Network design: results • Conclusions
The Next-Generation Internet
a
de
cb
The impact of network failures
Cable
1101011000110101011
= 320 Tbps
Conclusion: a single cable cut can lead to a dramatic amount of lost traffic
5 billion telephone lines (= 64 kpbs)
56 900 full CD’s per second
Some failure rates
Source: Sirti
Statistics for the year 2000 for an Optical Cable Network of 30359 km
Cause Number of failures Percentage of failures Damage due to thirds 19 61% Rodents 6 29% Malice 3 10% Materials degradation 1 3% Natural events 1 3% Installation Defects 1 3% Total 31
Hard Failures: service interruption
Cause Number of failures Percentage of failures Materials degradation 484 58% Damage due to thirds 145 18% Natural events 128 17% Rodents 54 7% Total 811
Soft Failures: service degradation
0 2 000 4 000 6 000 8 000
10 000 12 000 14 000 16 000 18 000 20 000
2001 2002 2003 2004 2005 2006 Year
Voice Traffic Transaction Traffic IP Traffic Oslo
Stockholm
Copenhagen
Amsterdam
Dublin
3
3.1
3.2
3.3
3.4
3.5
3.6
IP protected
3
3.1
3.2
3.3
3.4
3.5
3.6
IP protectedIP protectedIP protectedIP protected
AELT (total traffic) - STM-1 h/y
0 10 20 30 40 50 60 70 80 90
2001 2002 2003 2004 2005 2006
IP unprotected IP protected
0 10 20 30 40 50 60 70 80 90
2001 2002 2003 2004 2005 2006
IP unprotected IP protected IP unprotected IP protected IP unprotectedIP unprotectedIP unprotected IP protectedIP protectedIP protected
IP traffic distance independent increased AELT
Expected Loss of Traffic, Averaged over all connections
Although IP traffic not highly revenue generating, probably intolerable not to protect it
Outline • Introduction • Single Layer Recovery
– Protection in the Optical layer – Recovery in the IP-MPLS layer
• Recovery Interworking techniques • Multilayer survivability strategies • Network dimensioning: approach & assumptions • Network design: results • Conclusions
Protection in the Optical Layer
IP-MPLS
a
de
cb
Recovery in the IP-MPLS layer
IP-MPLS
Link in OTN network (= optic fiber)
a
de
cb
Link in OTN network (= optic fiber)
Lightpath through OTN network
a
de
cb
– Large granularity few recovery actions – Close to root failure
No delay due to failure propagation No need to dealn with complex secondary failures
– Known to be fast (at least protection) – BUT: cannot recover from all failures
• IP-MPLS recovery – For sure, better failure coverage – MPLS protection (making use of pre-established backup LSPs) can
also be fast – BUT:
• Can be confronted with complex secondary failure scenarios • Fine granularity many recovery actions • During recovery increased usage of capacity decreased QoS
• Conclusion: combine recovery at both layers
Outline • Introduction • Single Layer Recovery • Recovery Interworking techniques
– Uncoordinated – Hold-off timer – Summary
Without coordination
Link in OTN network (= optic fiber)
Lightpath through OTN network
a
de
cb
de
cba
de
cb
Link in OTN network (= optic fiber)
Lightpath through OTN network
a
de
cb
A IS
A IS
Hold-off timer
Link in OTN network (= optic fiber)
Lightpath through OTN network
a
de
cb
Optical protection fails
Timer expires start recovery
Timer expires start recovery
Timer expires start recovery
Recovery Interworking • Hold-off timer
– adds a delay – but avoids unnecessary switch-over or route flaps in IP-MPLS – when needed? In case failure detection based on:
• AIS signals (e.g., PoS interfaces) • HELLO protocol (e.g., GbE interfaces):
– when HELLO interval too small – some examples:
» RFC3209: default 3.5*5ms < 50 ms for optical protection --> problem » In test-bed experiments: 5*80 ms (default: 4*100 ms)
• Alternative: Recovery Token – WHAT? Optical protection fails --> send recovery token signal to
IP-MPLS layer – PRO? Avoids unnecessary delay – CONTRA? Requires standardisation of recovery token signal
Outline • Introduction • Single Layer Recovery • Recovery Interworking techniques • Multilayer survivability strategies
– Static recovery techniques – Dynamic recovery techniques
• Network dimensioning: approach & assumptions • Network design: results • Conclusions
Static recovery techniques
Link in OTN network (= optic fiber)
Optical protection path for lightpath carrying IP spare cap
Lightpath through OTN network
a
de
cb
IP spare capacity optically unprotected
Common pool strategy: IP spare capacity pre- emptible by the optical recovery provide capacity only once
Dynamic recovery techniques
Link in OTN network (= optic fiber)
Lightpath through OTN network
a
de
cb
– WHAT? Provide in advance sufficient spare capacity in IP-MPLS layer
– Strategies: • Double protection • IP spare capacity optically unprotected • Common pool strategy
– ATTENTION! Potential problems (physical disjointness of IP-MPLS spare capacity and pre-emption), except in case of double protection
• Dynamic recovery techniques – WHAT? In case of a failure, automatically reconfigure the logical IP-
MPLS network by means of the Intelligent Optical Networking (ION) functionality
– Strategies: • ION global reconfigurations: in all conditions optimise the logical IP-
MPLS network. • ION local reconfigurations: in case of a failure, only up- or downgrade
the capacity of existing logical IP-MPLS links.
Outline • Introduction • Single Layer Recovery • Recovery Interworking techniques • Multilayer survivability strategies • Network dimensioning: approach & assumptions
– Cost model – Escalation strategy
• Network design: results • Conclusions
IP router
Optical Node Cost: OXC-ports, WDM-muxes, etc (in €/)
Trib. Interface Cost: OXC-ports, router line-cards, etc (in €/)
First try to recover as much traffic as
possible by dedicated optical channel
protection
Outline • Introduction • Single Layer Recovery • Recovery Interworking techniques • Multilayer survivability strategies • Network dimensioning: approach & assumptions • Network design: results
– Network scenario – Cost comparison of survivability strategies – ION global versus local reconfiguration strategies
• Conclusions
Trento
Torino
Genova
Milano
Venezia
Bologna
Roma
Cagliari
Napoli
ReggioC
Palermo
Bari
Firenze
Pescara
Outline • Introduction • Single Layer Recovery • Recovery Interworking techniques • Multilayer survivability strategies • Network dimensioning: approach & assumptions • Network design: results
– Network scenario – Cost comparison of survivability strategies – ION global versus local reconfiguration strategies
• Amount of reconfigurations
Outline • Introduction • Single Layer Recovery • Recovery Interworking techniques • Multilayer survivability strategies • Network dimensioning: approach & assumptions • Network design: results • Conclusions
Conclusions • Cost comparison
– Static multilayer survivability strategies: • double protection > IP spare unprotected > common pool
– Dynamic multilayer survivability strategies: • ION local reconfigurations < common pool • ION global (almost) most expensive strategy
• ION local reconfigurations strategy very promising – Cheapest strategy – Easy strategy to implement and to operate – Requires less reconfigurations in a failure situation
• Improved QoS during reconfigurations