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Case for Segment Protection or Local Repair. M Vinod Kumar Tejas Networks. Agenda. Statistics Few Problem Statement What else can be taken care of? Other benefits Working of SPS-TE. Impact of Outage Times. Reason for Service Outage. Misconfiguration: Easily corrected
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Case for Segment Protection or Local Repair M Vinod Kumar Tejas Networks IEEE Interim, Seoul, Sept 08
Agenda • Statistics • Few Problem Statement • What else can be taken care of? • Other benefits • Working of SPS-TE
Reason for Service Outage • Misconfiguration: Easily corrected • Resource failure: Major cause of outage • Fiber cut: • 100 to 1000 times frequent than node failure • Metro – 13 cuts every 1000 mile per year • Long Haul – 4 cuts every 1000 mile per year • Node failure: • Software • Hardware
Fiber cut in USA, 1993 Cumulative Source: FCC
Diagnosis of 1993 fiber cuts in US 60% Dig-ups Source: D. Crawford, 1993
Now consider India • 10000 cuts per year! Annual Addition
Real Failure Numbers • With over 4,00,000 (4 lakh) rings, Indian Service Providers report multiple fiber cuts per day. • Provider-A report 15 planned cuts and 5 unplanned cuts per days • Provider-B report 8 cuts per day on an average • Service Providers know that certain links are more prone than others • Up-coming area • Rain/Flood/Rodent prone area
What About Other Countries? • All developing countries face similar problems that developed countries faced 10 years ago.
x To Router (Dual Home) x x Regional Aggregation x x x Metro Aggregation x x Access N:1 Requirement Aggregation nodes subtends multiple and diversely routed aggregation rings Aggregation node subtends multiple access ring Access ring is getting smaller
Requirements from Indian Service Provider Translated to Qay Requirements • Segment Protection models must include N:1 and should include 1:N and M:N including priority/pre-emption . • In case of 1:N model, higher priority tunnels/I-SID can pre-empt lower priority tunnels/I-SID, if required • In case of N:1 model, multiple segments can have priorities P1, P2, P3, P4 depending on the degree of protection switching needed. Typical carrier wants very fast switching (sub-50ms) of the traffic along pre-provisioned segment/path for degrees ranging between 3-10 • N:1 protection is like static routes for specific DA/VID combination with priorities P1, P2, P3 and P4 etc. In the event of the failure of P1 segment, traffic (DA/VID and associated I-SIDs) switches to P2 segment, provided it is ENABLED (Administrative Control) and healthy (Status = UP), otherwise move the traffic to P3.
Working of Segment Protection… IEEE Interim, Seoul, Sept 08
Present Scheme: Link Protection BEB#2 BEB#1 BCB BCB1 BCB2 TESI#1 BEB#4 TESI#2 BEB#3 • Single link failure between BCB1 and BCB2 can result in multiple TE protection switchover • In practice, many ESPs may be sharing a set of link (s) or/and node (s) BCB3
Proposed: Segment Protection BEB#2 BEB#1 BCB BCB1 BCB2 BEB#4 TESI#1 TESI#2 BEB#3 Have end-to-end protection along with local protection BCB3
Present Scheme: Group Failure BEB#2 BEB#1 BCB BCB1 BCB2 BEB#4 BEB#3 BCB3
Proposed: Segment Protection BEB#2 BEB#1 BCB BCB1 BCB2 BEB#4 TESI#1 TESI#2 BEB#3 Have end-to-end protection along with local protection BCB3
Present Scheme: One Link-disjoint Protection BEB#2 BEB#1 BCB BCB1 BCB2 BEB#4 BEB#3 BCB3
Proposed: Segment Protection BEB#2 BEB#1 BCB BCB1 BCB2 BEB#4 BEB#3 Inefficient to do global switching when there is cut Have end-to-end protection along with local protection BCB3
Present Scheme: Local Node Failure ESP#1 ESP#2
Proposed: Segment Protection ESP#1 ESP#2 Bypass a node or multiple nodes/links by properly configuring the MD and MEPs
Segment Protection in P-to-MP case p-to-mp TESI The tree branch can be protected independently
Segment Protection Can Scale to Multiple Domains MD#A MD#B • MD#C ESP#1 ESP#2 • PBB-TE (Qay) TESI as segments for Domain level protection
Summary: Requirements • Segment Protection Switching (SPS) shall offer n:1 • SPS should support m:n protection • Segment faults should be repairable through priority module • Priority module should take outage time impact into consideration • Segments shall be provisioned and dynamic after all provisioned segment fails • SPS should increase network utilization • Segment protection should prevent re-tracking of service • SPS should report if fault is on left or right side of the segment • SPS must tell if fault is in a service, collection of service, all the services, work segment or protect segment • Include explicit link failure along the Primary Segment • Include forwarding failure on a transit node along the Primary Segment. • Overlapping of Multiple segments should be allowed • Nesting of Segments should be allowed • SPS is more generic than IEEE 802.1Qay PBB-TE
Clarification on N:1 • Use pre-provisioned protection segments for rapid 50ms protection upto 3:1 • Use dynamic protection after 3:1 fails • Combination of pre- and dynamic provisioned protection segments
Working of SPS-TE • Link to SPS-TE