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Distributed Local Recovery from Multiple Link Failures in MPLS-TE Networks Andrea Fumagalli, Marco Tacca, Kai Wu, Sudheer Vinukonda, Priti Mahale Optical Networks Advanced Research (OpNeAR) Lab. F. G. Risk level. H. RLS2 (3). RLS6 (3). RLS1 (3). RLS5 (2). RLS0 (0). A. B. C. F4.
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Distributed Local Recovery from Multiple Link Failures in MPLS-TE Networks Andrea Fumagalli, Marco Tacca, Kai Wu, Sudheer Vinukonda, Priti Mahale Optical Networks Advanced Research (OpNeAR) Lab F G Risk level H RLS2(3) RLS6(3) RLS1(3) RLS5(2) RLS0(0) A B C F4 RLS 3 RLS 2 RLS7 (3) RLS8(3) RLS3(2) RLS4(1) F5 D E F6 A A B A D B A B B G F D E A B A B D E F3 Finding an RLS Local Recovery Risk Level and Risk Link Set (RLS) • Local Recovery – Fast ReRoute (FRR) • Restoration performed as close to point of failure as possible • Backup path pre-computed and pre-signaled • Global or local revert, make-before-break • 10s of ms recovery • Single failure assumption • Fast failure detection • Layer 2 (Sonet LOS etc.) • RSVP Hello • Risk = Failure Probability (Unavailability or Frequency of failure) • Risk level is a range of risk • RLS is a set of link associated with a risk level • Every failure scenario is represented by an RLS • Aggregation of SRLG’s • Defined at the IP/MPLS layer • Distributed by IGP extensions • Static or dynamic • Bottom up • From IP-to-optical mapping • Reliability information of all components • Network layer • IGP listener • Combined Fault Independent Approach Hybrid Approach Fault Dependent Approach • Step 1: For each local failure pattern, there is a list of suspect RLS’s • Ex: PLR=A, Failed Link=A-B (A-F and A-D work) • L=RLS0,RLS2,RLS3,RLS4,RLS5,RLS7 • Step 2: Identify the most possible RLS or set of RLS’s (logical RLS) • Step 3: Find the facilities belonging to the (logical) RLS, and select bypass tunnel for the facility against the (logical) RLS Local Recovery Procedure • Divide the suspect RLS list into logical RLS’s according to some rules • Shorten the (RLS) detection time by reducing the requirement on remote failure information • Increase the chance of finding a bypass tunnel by reducing the size of logical RLS • Identify the exact RLS that fails • (extra time) • Select bypass tunnels for all facilities • in the RLS • No need to identify exact RLS • Select bypass tunnels for all facilities in the RLS • There is no bypass tunnel to protect facility A-B that avoids all the links contained in the list of suspected RLS L for any Risk Level. • If the required Risk level is reduced to 2, Path=A-F-G-H-I-C-E-B (cost=6). With RL=1 Path=A-D-B (the longer path A-I-G-H-I-C-B also works) Simulation Setup Bypass tunnel selection – Monitoring time vs. Correct RLS Selection, Fault Dependent Bypass tunnel selection – Monitoring time vs. Correct RLS Selection, Hybrid Approach Summary • European Network • Random RLS generation • Proposed an RLS information model to incorporate multiple failures • Extended FRR to support fast local recovery against multiple failures • Investigated three approaches, fault dependent, fault independent and hybrid • Traded recovery time with recovery ratio