ITU-T Workshop on Security Seoul (Korea), May 2002 Telecommunication network reliability Dr. Chidung LAC

france telecom R&D 2 ITU-T Workshop on Security Seoul (Korea), May 2002 Outline Dependability and survivability Availability assessment Recovery mechanisms Physical layer ATM network IP level From random non-intentional to provocated failures

france telecom R&D 3 ITU-T Workshop on Security Seoul (Korea), May 2002 Dependability and survivability (1/2) Quality of Service Accessibility Service continuity SecurityEase of useBilling AvailabilityPerformances Degraded state Nominal state Survivability

france telecom R&D 4 ITU-T Workshop on Security Seoul (Korea), May 2002 Dependability and survivability (2/2) Unavailability Reliability Maintenance support Maintainability Traffic engineering System capacity Offered traffic Grade of service Failures Congestion Abnormal situations Natural disasters (Safety) Man-made events (Security) Dependability Network elements

france telecom R&D 5 ITU-T Workshop on Security Seoul (Korea), May 2002 Availability assessment methodology Identification of elements contributing to the services unavailability (equipments, cable infrastructure, OAM errors, …) Block diagram representation (series, parallel) of these elements taking into account network architecture (redundancy, …) Allocation of a failure rate and a repair time MTTR to each element Estimated values from equipments vendors ( ) Use of field data (, MTTR) Service unavailability and failure rate assessment

france telecom R&D 6 ITU-T Workshop on Security Seoul (Korea), May 2002 Availability assessment : example (1/2) Optical distribution frame Amplifier ADM Optical fiber WDM ADM

france telecom R&D 7 ITU-T Workshop on Security Seoul (Korea), May 2002 Availability assessment : example (2/2) ADM block diagram representation Unavailability and failure rate calculation U Board i = Board i * MTTR Board i U Serial system = U Board j U Parallel system = U Board k U ADM Serial system = i Parallel system = U 2 U 1 ADM

france telecom R&D 8 ITU-T Workshop on Security Seoul (Korea), May 2002 Pre-WDM networks protection Automatic protection switching

france telecom R&D 9 ITU-T Workshop on Security Seoul (Korea), May 2002 Pre-WDM self-healing rings (1/2) Unidirectional rings

france telecom R&D 10 ITU-T Workshop on Security Seoul (Korea), May 2002 Pre-WDM self-healing rings (2/2) Bidirectional rings

france telecom R&D 11 ITU-T Workshop on Security Seoul (Korea), May 2002 Pre-WDM meshed networks restoration Failure Around the failure Failure End-to-end Failure Local-destination

france telecom R&D 12 ITU-T Workshop on Security Seoul (Korea), May 2002 WDM rings protection 2-fiber bidirectional rings

france telecom R&D 13 ITU-T Workshop on Security Seoul (Korea), May 2002 WDM meshed networks (1/2) Link protection Dedicated approach Shared approach Failure or Failure

france telecom R&D 14 ITU-T Workshop on Security Seoul (Korea), May 2002 WDM meshed networks (2/2) Path protection

france telecom R&D 15 ITU-T Workshop on Security Seoul (Korea), May 2002 ATM network (1/2) ATM v/s SDH-SONET Bandwidth on-demand v/s no dynamic bandwidth control Bursty traffic v/s switched services, private lines Logical v/s physical path structure Variations of VPs and VCs capabilities (from 0 to the physical link rate) v/s fixed capacities Non-hierarchy v/s hierarchy path capacity Separation of capacity allocation and physical route assignment for VPs and VCs OAM bandwidth with allocation on demand delay reduction for restoration message exchange, quicker detection of system degradation Faster detection of soft failure

france telecom R&D 16 ITU-T Workshop on Security Seoul (Korea), May 2002 ATM network (2/2) Automatic protection switching VPs or VCs used as links (protection units) 1+1 : connection switching by the receiver side node (from working to backup link) 1:1 : switching done both by the transmitter side and the receiver side nodes Self-healing network Distributed control restoration scheme More effective resource utilization Dynamic planned scheme : flooding algorithm to locate restoration routes Preplanned scheme : predetermination of the optimal alternate route and pre-assignement of a backup VP to each VP

france telecom R&D 17 ITU-T Workshop on Security Seoul (Korea), May 2002 IP level Recovery mechanisms proposed for MultiProtocol Label Switching Architecture used : Integrated Services with Resource Reservation Protocol (signaling protocol) Differentiated Services Main recovery modes : Link protection 1+1 and 1:1 Path protection Restoration/rerouting : on-demand establishment of Label Switched Paths

france telecom R&D 18 ITU-T Workshop on Security Seoul (Korea), May 2002 From random non-intentional to provocated failures Telcos poor experience in the domain Example of assessment difficulty : how to apply mathematical failure rate distribution ? Possible directions : Infrastructures protection : security reinforcement Logical intrusion : main challenge with actuals networks interfunctioning (operators networks, Internet, …) Behavior modelling : human factors applied to volontary acts Some initiatives : Critical Infrastructure Protection cascading effects due to interdependencies among different domains IEEE DIREN02, New York, June 2002

france telecom R&D 19 ITU-T Workshop on Security Seoul (Korea), May 2002 To probe further IEEE Communications – Issue on Survivable communication networks, August 1999 IEEE Communications – Issue on Resilience in communication networks, January 2002 IEEE Network – Issue on Network and service security, Nov/Dec 2002 ITU-T, Rec. E.800, Terms and definitions related to QoS and network performance including dependability Network reliability steering committee, Alliance for telecommunications industry solutions, T1A1.2 WG on Network Survivability Performance, Reliability/availability framework for IP-based networks and services, Draft technical report, July 2001