Case for Segment Protection or Local Repair

1
Case for Segment Protection or Local Repair

• M Vinod Kumar
• Tejas Networks

2
Agenda

• Statistics
• Few Problem Statement
• What else can be taken care of?
• Other benefits
• Working of SPS-TE

3
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
4
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

5
Fiber cut in USA, 1993
Cumulative
Source FCC
6
Diagnosis of 1993 fiber cuts in US
60 Dig-ups
Source D. Crawford, 1993
7
Now consider India

• 10000 cuts per year!

Annual Addition
8
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

9
What About Other Countries?

• All developing countries face similar problems
  that developed countries faced 10 years ago.

10
N1 Requirement
Aggregation nodes subtends multiple and diversely
routed aggregation rings
Aggregation node subtends multiple access ring
Access ring is getting smaller
11
Requirements from Indian Service Provider
Translated to Qay Requirements

• Segment Protection models must include N1 and
  should include 1N and MN including
  priority/pre-emption .
• In case of 1N model, higher priority
  tunnels/I-SID can pre-empt lower priority
  tunnels/I-SID, if required
• In case of N1 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
• N1 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.

12
Working of Segment Protection
13
Present Scheme Link Protection
BEB2
BEB1
BCB
BCB1
BCB2
TESI1
BEB4
TESI2
BEB3

• 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
14
Proposed Segment Protection
BEB2
BEB1
BCB
BCB1
BCB2
BEB4
TESI1
TESI2
BEB3
Have end-to-end protection along with local
protection
BCB3
15
Present Scheme Group Failure
BEB2
BEB1
BCB
BCB1
BCB2
BEB4
BEB3
BCB3
16
Proposed Segment Protection
BEB2
BEB1
BCB
BCB1
BCB2
BEB4
TESI1
TESI2
BEB3
Have end-to-end protection along with local
protection
BCB3
17
Present Scheme One Link-disjoint Protection
BEB2
BEB1
BCB
BCB1
BCB2
BEB4
BEB3
BCB3
18
Proposed Segment Protection
BEB2
BEB1
BCB
BCB1
BCB2
BEB4
BEB3
Inefficient to do global switching when there is
cut Have end-to-end protection along with local
protection
BCB3
19
Present Scheme Local Node Failure
ESP1
ESP2
20
Proposed Segment Protection
ESP1
ESP2
Bypass a node or multiple nodes/links by properly
configuring the MD and MEPs
21
Segment Protection in P-to-MP case
p-to-mp TESI
The tree branch can be protected independently
22
Segment Protection Can Scale to Multiple Domains
MDA
MDB

• MDC

ESP1
ESP2

• PBB-TE (Qay) TESI as segments for Domain level
  protection

23
Summary Requirements

• Segment Protection Switching (SPS) shall offer
  n1
• SPS should support mn 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

24
Clarification on N1

• Use pre-provisioned protection segments for rapid
  50ms protection upto 31
• Use dynamic protection after 31 fails
• Combination of pre- and dynamic provisioned
  protection segments

25
Thanks
26
Extra
27
Working of SPS-TE

• Link to SPS-TE