Enhanced Local Recovery in MPLS-TE Networks for Multiple Link Failures

1. 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