ieee interim, seoul, sept 08 case for segment protection or local repair m vinod kumar tejas...
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IEEE Interim, Seoul, Sept 08
Case for Segment Protection or Local Repair
M Vinod KumarTejas Networks
Agenda
Statistics Few Problem Statement What else can be taken care of? Other benefits Working of SPS-TE
Impact of Outage Times
Outage Time Impacts
Sub-50ms No outages,
almost no TCP fallbacks,
50-200ms 5% voiceband disconnects, gaming disruption,
SS7 switch-over, video pixelization,
FR and ATM re-routing
200ms-2s TCP/IP back-off
2s-10s TCP time-outs, webpage not available, router protocols gets affected, Circuit switched service disconnects
10s-5min All 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, 1993Fiber Miles Till 1998
0
500
1000
1500
2000
2500
3000
3500
4000
1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998
Year
Fib
er
Mil
es
(in
10
00
s)
Series1
Source: FCC
Cum
ulat
ive
Diagnosis of 1993 fiber cuts in US
Source: D. Crawford, 1993
60% Dig-ups
Now consider India
10000 cuts per year!
Ann
ual A
dditi
on
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
MetroAggregation
RegionalAggregation
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
BCB1 BCB2
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
BCB1 BCB2
BCB3 Have end-to-end protection along with local protection
Present Scheme: Group Failure
BCB
BCB1 BCB2
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
BCB1 BCB2
BCB3Have end-to-end protection along with local protection
Present Scheme: One Link-disjoint Protection
BCB
BCB1 BCB2
BCB3
BEB#1
BEB#3
BEB#4
BEB#2
Proposed: Segment Protection
BCB
BCB1 BCB2
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#AMD#A MD#BMD#B
MD#CMD#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