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