1. Evolution of IP/OL Performance Management
Robert Doverspike, Jennifer Yates, Jorge Pastor, Martin Birk – AT&T Labs Research
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2. Outline Key Takeaways Evolution story for IP/OL Example problems
Performance Management – must consider interlayer (focus IP)
Evolution story for IP/OL
Architecture for Long Haul Networks
Example problems
Next chapter in evolution
Let’s get it right this time
Title

3. Key Takeaways Optical PM goals should focus on use in IP layer
Links in the IP layer form connections in the optical layer
Virtually all high rate connections are IP links (between either routers or Ethernet switches)
Perfect optical layer detection is a lofty goal, but
will fall short if architected in isolation
E.g., need to have strong inter-layer coordination
Why do we stress this for OL?
Inter-layer fault management has many flaws in practice, even after 15 years of SONET perfecting
Need adequate mechanisms across layers to handle scenarios when things go wrong or confusion reigns
Title

4. Evolution Story for Long Haul Networks
IP Layer
1st Generation
SONET Ring
Layer
Pt-Pt WDM Layer
Router
ADM
DCS/Intelligent Optical Switch
Degree-n OADM/WXC
WDM Terminal
Title

5. Evolution Story for Long Haul Networks
IP Layer
1st Generation
SONET Ring
Layer
DCS Layer
Pt-Pt WDM Layer
Router
ADM
DCS/Intelligent Optical Switch
Degree-n OADM/WXC
WDM Terminal
Title

6. Evolution Story for Long Haul Networks
IP Layer
2nd Generation
1st Generation
SONET Ring
Layer
Pt-Pt WDM Layer
ULH/WXC Layer
Router
ADM
DCS/Intelligent Optical Switch
Degree-n OADM/WXC
WDM Terminal
Title

7. Evolution Story for Long Haul Networks
IP Layer
3rd Generation
1st Generation
2nd Generation
SONET Ring
Layer
Pt-Pt WDM Layer
ULH/WXC Layer
Router
ADM
DCS/Intelligent Optical Switch
Degree-n OADM/WXC
WDM Terminal
Title

8. Some of the problems we’ve encountered
IP Layer X
SONET Ring
Layer
Ring switching impact on higher layers
Upper layer has timer – waits for lower layer to restore – Done!
Wrong! – not a simple decision on when to take IP link up and down
Title

9. Some of the problems we’ve encountered 1st Generation of IP/OL
IP Layer
PPP ACK; OSPF ping 
AIS-P BER-P CLR
AIS-P BER-P CLR X
SONET Ring
Layer
 LOS-L
LOS-L 
 AIS-P
SONET alarms received by upper layer are ambiguous and conflicting
Many error types in SONET: BER, AIS, P-LOS, clear during protection switching
Arrive at different times
Software bugs – routers don’t behave as expected
Inconsistencies in calculation of BER and IP layer holddown timer
Title

10. What is the source of these problems?
No standards for inter-layer interaction
Physical layer: testers need requirement scripts to test – no standard, no script
No industry requirement often means no testing, no sharing of behavior
Historically, L1 and L3 labs have been separate
Some members of Telecom community have integrated their labs
Software bugs – routers don’t behave as expected
No specification of common parameters and metric
Example: Router measures BER in fixed timer intervals
Router takes link down upon TCA (threshold exceeded)
Protection switching results in VERY short but high burst of error  Crosses router threshold even though it is << 10 ms!
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11. What is the source of these problems?
Shared Risk Groups still not well modeled
Single failure at lower layer results in multiple, scattered link failures at higher layer – network unprepared to restore
Example: portions of dual IP access links routed over same ring – both links taken down due to previous confusion LA NY SF
Washington
IP (logical) layer
Physical (fibre) layer LA NY SF
Washington
Common SRLG
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12. Identity Crisis 2nd Generation of IP/OL
High speed (2.5/10/40Gbs) IP links skip SONET ring/xconnect layer and instead route over long sequences of Point-to-point WDM systems, interconnected by O/E/O optical transponders
Should the Optical Path pretend to be a transparent (like dark fiber)
E.g., No AIS/BER TCA – re-transmit all LOS/LOP to Path Termination Points
How does one isolate faults for repair (OTs, Amplifiers, WDM Terms)?
OR: Should it display characteristics of SONET Section/Line/Path Fault Management Architecture?
However: then similar 1st Gen IP/SONET Ring confusion occurs
Practicality dictated that industry implemented a combination of both approaches
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13. ULH/WSC: The Final Solution? 3rd Generation of IP/OL
Use long-term model of all-optical path to IP layer link
Two major issues to resolve
What if intermediate OEO exists in near-term?
How do we model restoration at OL and how does IP layer interact?
IP layer responsible for deciding link health
Fast link layer detection (LOS)
GIGE and other signal are going to be transported over the 3rd Gen OL
Is the set of PM alarms and TCAs we inherit from SONET appropriate for 3rd Gen OL?
If not, which ones or new ones should we define?
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14. Some potential approaches
OL only passes simple alarms to the upper layer, e.g., LOS.
Upper layer makes its assessments of BER, packet coding violations, ACK failures
OL still does fault isolation for OEO components or amplifiers (e.g., to WDM Term or EMS or Fault OSS), but NOT passed up to IP layer
Where/how do we do this? Standards, Fora, vendor interactions, carrier requirements?
Repair process:
Need to correlate what fails in the OL with what fails in the IP layer (1 to many map)
Network discovery of IP/OL relationships (e.g., SRLG) across layers would facilitate fault correlation process
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