importance of interoperability testing · – combine multiple technologies (epon, gpon…) title:...

© UNIVERSITY of NEW HAMPSHIRE INTEROPERABILITY LABORATORY

1st International Workshop onCommunity Networks and FTTH/P/x1st International Workshop on1st International Workshop onCommunity Networks and FTTH/P/xCommunity Networks and FTTH/P/x

Importance of last mile Importance of last mile interoperabilityinteroperability

Eric LynskeyOctober 16, 2003

UNIVERSITY of NEW HAMPSHIRE

INTEROPERABILITY LABORATORY

Importance of last mile interoperability

OutlineOutlineOutline

• Conformance and interoperability

• Ethernet experiences

• Ethernet in the First Mile strategies

• Conclusions

• Conformance and interoperability

• Ethernet experiences

• Ethernet in the First Mile strategies

• Conclusions




What is conformance?What is conformance?What is conformance?

• Implement all mandatory portions of a standard– IEEE 802.3

• “shall” and “shall not” – mandatory

• “should” and “should not” – recommendations• “may” and “may not” – options

• State diagrams and associated variables, functions, etc…• Protocol Implementation Conformance Statement (PICS)

• Implement all mandatory portions of a standard– IEEE 802.3

• “shall” and “shall not” – mandatory

• “should” and “should not” – recommendations• “may” and “may not” – options

• State diagrams and associated variables, functions, etc…• Protocol Implementation Conformance Statement (PICS)




Verification of conformanceVerification of conformanceVerification of conformance

• PICS and spec. sheets– Not a guarantee of conformance

• Third party independent testing• Testing before and after system integration• Agreed upon test methodologies

• PICS and spec. sheets– Not a guarantee of conformance

• Third party independent testing• Testing before and after system integration• Agreed upon test methodologies

Spec sheetSpec Spec sheetsheet

IndependenttestingIndependentIndependenttestingtesting

IndependentreportIndependentIndependentreportreport




Test methodologiesTest methodologiesTest methodologies

• Different test tools provide different answers– Oscilloscopes, network analyzers, power meters…– Accuracy and repeatability of equipment– Testing algorithms can vary between vendors– More than one way to make a measurement

• Possible solution is to strictly define:– Test boards (probing problem)– Minimum requirements for test equipment– Test conditions

• Different test tools provide different answers– Oscilloscopes, network analyzers, power meters…– Accuracy and repeatability of equipment– Testing algorithms can vary between vendors– More than one way to make a measurement

• Possible solution is to strictly define:– Test boards (probing problem)– Minimum requirements for test equipment– Test conditions




What is interoperability?What is interoperability?What is interoperability?

• Two or more devices can establish, maintain, and tear down a connection under a given set of conditions while maintaining a certain level of performance.

• Interoperability at different layers– Protocol

– Physical

• Common and agreed upon set of guidelines

• Two or more devices can establish, maintain, and tear down a connection under a given set of conditions while maintaining a certain level of performance.

• Interoperability at different layers– Protocol

– Physical

• Common and agreed upon set of guidelines




10 GbE interoperability10 10 GbE GbE interoperabilityinteroperability

• 10 Gigabit Attachment Unit Interface (XAUI)– 4 lanes at 3.125 Gb/s with 8B/10B encoding

– Up to 50cm on standard FR-4 PCB

• Development of XAUI interoperability document– Joint effort between 10GEA and UNH – IOL

– Defined test channel, traffic, pass/fail condition

– Basis for technical feasibility study of XAUI

– Industry standard methodology for proof of interoperability

• 10 Gigabit Attachment Unit Interface (XAUI)– 4 lanes at 3.125 Gb/s with 8B/10B encoding

– Up to 50cm on standard FR-4 PCB

• Development of XAUI interoperability document– Joint effort between 10GEA and UNH – IOL

– Defined test channel, traffic, pass/fail condition

– Basis for technical feasibility study of XAUI

– Industry standard methodology for proof of interoperability




Verification of interoperabilityVerification of interoperabilityVerification of interoperability

• Public demonstrations– Trade shows, conferences

• Private demonstrations– Corporate laboratories, potential customers

– Third party independent testing

• Full and partial mesh interoperability

• Plugfests

• Public demonstrations– Trade shows, conferences

• Private demonstrations– Corporate laboratories, potential customers

– Third party independent testing

• Full and partial mesh interoperability

• Plugfests




Interoperability and conformanceInteroperability and conformanceInteroperability and conformance

• Standard defines interfaces and behaviors– Must conform to these requirements

– Not always clear what standards meant to say– Necessary to understand the importance of what standards do

not say

• Multiple implementations can and will exist– Different interpretations of standard– Similar interpretations but different implementations

• Interoperability is related to both the standard and its implementation

• Standard defines interfaces and behaviors– Must conform to these requirements

– Not always clear what standards meant to say– Necessary to understand the importance of what standards do

not say

• Multiple implementations can and will exist– Different interpretations of standard– Similar interpretations but different implementations

• Interoperability is related to both the standard and its implementation




Conformance ≠ InteroperabilityConformance Conformance ≠≠ InteroperabilityInteroperability

• Conform to multiple options– EPON forward error correction

– XAUI channel definition

• System vs. component conformance– Conformant components can be integrated into non-

conformant systems, thus creating interoperability problems

• Different features may not be interoperable

• Conform to multiple options– EPON forward error correction

– XAUI channel definition

• System vs. component conformance– Conformant components can be integrated into non-

conformant systems, thus creating interoperability problems

• Different features may not be interoperable




Interoperability ≠ ConformanceInteroperabilityInteroperability ≠≠ ConformanceConformance

• Multiple devices wrongly implement same feature

• Not all mandatory features affect interoperability

• Do all mandatory parts of standard need to be treated equally?

• Multiple devices wrongly implement same feature

• Not all mandatory features affect interoperability

• Do all mandatory parts of standard need to be treated equally?




Options inhibit interoperabilityOptions inhibit interoperabilityOptions inhibit interoperability

• Certain options are only useful if both ends of the link support it– Flow control, FEC

• Users must be aware of options in order to take advantage of them

• An increase in options leads to an increase in implementations, and therefore an increase in interoperability problems

• Certain options are only useful if both ends of the link support it– Flow control, FEC

• Users must be aware of options in order to take advantage of them

• An increase in options leads to an increase in implementations, and therefore an increase in interoperability problems




Standards not the final answerStandards not the final answerStandards not the final answer

• Standards don’t define everything– DBA, security, QoS

• Standards don’t always specify how/what to test

• Documented and agreed upon test metrics are necessary for agreed upon conditions for claims of interoperability and conformance

• Industry needs to pull together to create this documentation

• Standards don’t define everything– DBA, security, QoS

• Standards don’t always specify how/what to test

• Documented and agreed upon test metrics are necessary for agreed upon conditions for claims of interoperability and conformance

• Industry needs to pull together to create this documentation




• A one word description of Ethernet is “simple”

• Interoperability has contributed to the success of Ethernet

• As Ethernet moves into the access space, this trend of simplicity and interoperability must continue for the technology to be successful

• A one word description of Ethernet is “simple”

• Interoperability has contributed to the success of Ethernet

• As Ethernet moves into the access space, this trend of simplicity and interoperability must continue for the technology to be successful

Why do we need it?Why do we need it?Why do we need it?




How do we get it?How do we get it?How do we get it?

• Clearly document test plans that have achieved industry acceptance

• Test, test, and test again• Publicly demonstrate real interoperability and

conformance

• Walk into Best Buy, buy an EFM modem, plug it in, and it works!

• Clearly document test plans that have achieved industry acceptance

• Test, test, and test again• Publicly demonstrate real interoperability and

conformance

• Walk into Best Buy, buy an EFM modem, plug it in, and it works!




Gigabit Ethernet exampleGigabit Ethernet exampleGigabit Ethernet example

• Borrowed heavily from Fibre Channel

• Defined new Auto-Negotiation protocol– Handshaking protocol to determine HCD link

• Minor modifications to existing MAC (FD only)

• Conformance and interoperability issues

• Borrowed heavily from Fibre Channel

• Defined new Auto-Negotiation protocol– Handshaking protocol to determine HCD link

• Minor modifications to existing MAC (FD only)

• Conformance and interoperability issues




Gigabit Ethernet conformanceGigabit Ethernet conformanceGigabit Ethernet conformance

• Observed interoperability problem– On average, packet loss between two devices

transmitting randomly sized frames over low attenuation optical channel approaches 50%

• Cause is a conformance problem– Preamble defined as 7 bytes transmitted by the MAC

– PCS allows for reduction of preamble to 6 bytes

– Some devices do not accept 6 bytes of preamble

• Observed interoperability problem– On average, packet loss between two devices

transmitting randomly sized frames over low attenuation optical channel approaches 50%

• Cause is a conformance problem– Preamble defined as 7 bytes transmitted by the MAC

– PCS allows for reduction of preamble to 6 bytes

– Some devices do not accept 6 bytes of preamble




Interoperability case studyInteroperability case studyInteroperability case studyGigabit Ethernet Interoperability failures

0

5

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15

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25

Dec-97

Apr-98

Aug-98

Dec-98

Apr-99

Aug-99

Dec-99

Apr-00

Aug-00

Dec-00

Apr-01

Aug-01

Dec-01

Apr-02

Time

Perc

ent f

ailu

res




EFM ExampleEFM ExampleEFM Example

• Borrowing heavily from existing Ethernets– PCS, MAC, MAC Control

• New single fiber solutions• New MPCP sublayer

– Requires (de)registration, GATE and REPORT, timing

• New OAM sublayer– Requires handshaking

• New forward error correction• New Reconciliation Sublayer (preamble)

• Borrowing heavily from existing Ethernets– PCS, MAC, MAC Control

• New single fiber solutions• New MPCP sublayer

– Requires (de)registration, GATE and REPORT, timing

• New OAM sublayer– Requires handshaking

• New forward error correction• New Reconciliation Sublayer (preamble)




EFM preamble modificationsEFM preamble modificationsEFM preamble modifications

55 55 SPD 55 55 LLID LLID CRC8

Preamble DA SA Length/Type Data/Pad FCS

8-bytes 6-bytes 6-bytes 2-bytes 46-1500 bytes 4-bytes




EPON Conformance test toolEPON Conformance test toolEPON Conformance test tool

User-definedtest scripts

IntelligentAnalysis

ReportGenerator

Database ofResults

PC or equivalent Programmable hardware andtest equipment

TransmitEmulator

ReceiveEmulator

ComplexTriggeringCapability

ProcessingEngine

DeviceUnderTest




EPON Conformance test tool 2EPON Conformance test tool 2EPON Conformance test tool 2

8B/10BEncoderFEC10B/8B

DecoderMAC

Functions8B/10BEncoder

OLTFunctions

ONUFunctions

OAM/MAC Client

SERDES/PMD

Test vector generator

FEC block (optional)

Out toDUT




EFM OAM InteroperabilityEFM OAM InteroperabilityEFM OAM Interoperability

• Frame based protocol

• Optical channel not really an issue

• Potential issues– Discovery process

– Critical events

– Vendor extensions

• Frame based protocol

• Optical channel not really an issue

• Potential issues– Discovery process

– Critical events

– Vendor extensions




EFM P2P InteroperabilityEFM P2P InteroperabilityEFM P2P Interoperability

• Auto-Negotiation…DONE

• MAC, PCS, MAC Control, RS…DONE

• Potential issues– Distance

– Temperature

– Single fiber

• Need to define interoperability channel

• Auto-Negotiation…DONE

• MAC, PCS, MAC Control, RS…DONE

• Potential issues– Distance

– Temperature

– Single fiber

• Need to define interoperability channel




EFM EPON InteroperabilityEFM EPON InteroperabilityEFM EPON Interoperability

• MPCP– Registration of ONU onto EPON– P2P Emulation– GATE and REPORT messages

• Optical channel– Single fiber– Lengths, number of splits– Topology (tree, bus, hybrid)– FEC for operating at high BER with MPN penalty

• MPCP– Registration of ONU onto EPON– P2P Emulation– GATE and REPORT messages

• Optical channel– Single fiber– Lengths, number of splits– Topology (tree, bus, hybrid)– FEC for operating at high BER with MPN penalty




ConclusionsConclusionsConclusions

• EFM community has a lot of work to do even after the standard is complete– Prove the “unproven” technologies defined by EFM– Develop test methodologies for interoperability– Document what is not written in the standard– Test

• Development of interoperability group– Where is it placed – Combine multiple technologies (EPON, GPON…)

• EFM community has a lot of work to do even after the standard is complete– Prove the “unproven” technologies defined by EFM– Develop test methodologies for interoperability– Document what is not written in the standard– Test

• Development of interoperability group– Where is it placed – Combine multiple technologies (EPON, GPON…)

importance of interoperability testing · – combine multiple technologies (epon, gpon…) title:...

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