IEEE Interim, Seoul, Sept 08 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 Outage TimeImpacts Sub-50msNo outages, almost no TCP fallbacks, ms5% voiceband disconnects, gaming disruption, SS7 switch-over, video pixelization, FR and ATM re-routing 200ms-2sTCP/IP back-off 2s-10sTCP time-outs, webpage not available, router protocols gets affected, Circuit switched service disconnects 10s-5minAll sessions terminated, Routing table re-convergence

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 Source: FCC Cumulative

Diagnosis of 1993 fiber cuts in US Source: D. Crawford, % Dig-ups

Now consider India 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.

N:1 Requirement x x x Access Metro Aggregation Regional Aggregation x x x x x To Router (Dual Home) Access ring is getting smaller Aggregation node subtends multiple access ring Aggregation nodes subtends multiple and diversely routed aggregation rings

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.

IEEE Interim, Seoul, Sept 08 Working of Segment Protection…

Present Scheme: Link Protection TESI#1 TESI#2 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) BCB BCB1BCB2 BCB3 BEB#1 BEB#3 BEB#4 BEB#2

Proposed: Segment Protection TESI#1 TESI#2 BEB#1 BEB#3 BEB#4 BEB#2 BCB BCB1BCB2 BCB3 Have end-to-end protection along with local protection

Present Scheme: Group Failure BCB BCB1BCB2 BCB3 BEB#1 BEB#3 BEB#4 BEB#2

Proposed: Segment Protection TESI#1 TESI#2 BEB#1 BEB#3 BEB#4 BEB#2 BCB BCB1BCB2 BCB3 Have end-to-end protection along with local protection

Present Scheme: One Link-disjoint Protection BCB BCB1BCB2 BCB3 BEB#1 BEB#3 BEB#4 BEB#2

Proposed: Segment Protection BCB BCB1BCB2 BCB3 BEB#1 BEB#3 BEB#4 BEB#2 Inefficient to do global switching when there is cut Have end-to-end protection along with local protection

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

MD#A MD#B MD#C Segment Protection Can Scale to Multiple Domains 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

Thanks

Extra…

Working of SPS-TE Link to SPS-TE