online diagnosis of network-on-chip

Online Diagnosis of Networks-on-Chip

Sebastian Klotz

Supervisor: Dipl.-Inf. Stefan Holst

Reliable NoC in the Many Core Era

6/15/2009

2

Agenda

1. Objectives of Online Diagnosis

2. System Level Fault Models

3. Control Fault Detection/Localization Methods

4. Data Fault Detection/Localization Methods

5. Conclusion

Reliable NoC in the Many Core Era - Online Diagnosis of Networks-on-Chip

3

Agenda





5. Conclusion


4

Objectives of Online Diagnosis

Online Diagnosis:

Detection and localization of faulty switches and inter-switch links

Fault classification Distinguish between transient, intermittent and permanent faults

Observe network behavior during operation

Provide service (input) for recovery mechanism


5

Agenda





5. Conclusion


6

NoC Switch Architecture

Switch Components:

First-In-First-Out

(FIFO) Buffer

Multiplexer (MUX)

Crossbar Switch

Router


N

S

E

W

SEW

N

RES

N

MUX

ER

PS W

WE R N

SWNR

MU

X

MUX

MUXMUX

Crossbar

Processor

Switch

Router

MUX

MUX

FIFO

FIFO

FIFO

FIFO

FIFO

7

System Level Fault Models

Control Faults:

Dropped Data

Fault

Direction Fault

Multiple Copies

in Space Fault

Multiple Copies

in Time Fault

Data Fault:

Corrupted

Data Fault

Goal: Route data from W

N

Fault-free case


N

S

E

W

SEWN

RES

N

MUX

ER

PS W

WE R N

SWNR

MU

X

MUX

MUXMUX

Crossbar

Processor

Switch

Router

MUX

MUX

FIFO

FIFO

FIFO

FIFO

FIFO

8

N

S

E

W

SEWN

RES

N

MUX

ER

PS W

WE R N

SWNR

MU

X

MUX

MUXMUX

Crossbar

Processor

Switch

Router

MUX

MUX

FIFO

FIFO

FIFO

FIFO

FIFO



N

Fault in Router, FIFO or MUX

Control Faults:

Dropped Data

Fault

Direction Fault

Multiple Copies

in Space Fault

Multiple Copies

in Time Fault

Data Fault:

Corrupted

Data Fault


9

N

S

E

W

SEWN

RES

N

MUX

ER

PS W

WE R N

SWNR

MU

X

MUX

MUXMUX

Crossbar

Processor

Switch

Router

MUX

MUX

FIFO

FIFO

FIFO

FIFO

FIFO



N

Fault in the Router

Control Faults:

Dropped Data

Fault

Direction Fault

Multiple Copies

in Space Fault

Multiple Copies

in Time Fault

Data Fault:

Corrupted

Data Fault


10

N

S

E

W

SEWN

RES

N

MUX

ER

PS W

WE R N

SWNR

MU

X

MUX

MUXMUX

Crossbar

Processor

Switch

Router

MUX

MUX

FIFO

FIFO

FIFO

FIFO

FIFO



N

Fault in the Router or MUX

Control Faults:

Dropped Data

Fault

Direction Fault

Multiple Copies

in Space Fault

Multiple Copies

in Time Fault

Data Fault:

Corrupted

Data Fault


11

N

S

E

W

SEWN

RES

N

MUX

ER

PS W

WE R N

SWNR

MU

X

MUX

MUXMUX

Crossbar

Processor

Switch

Router

MUX

MUX

FIFO

FIFO

FIFO

FIFO

FIFO



N

Fault in the FIFO Buffer

&

Control Faults:

Dropped Data

Fault

Direction Fault

Multiple Copies

in Space Fault

Multiple Copies

in Time Fault

Data Fault:

Corrupted

Data Fault

@t+1@t


12

N

S

E

W

SEWN

RES

N

MUX

ER

PS W

WE R N

SWNR

MU

X

MUX

MUXMUX

Crossbar

Processor

Switch

Router

MUX

MUX

FIFO

FIFO

FIFO

FIFO

FIFO


Control Faults:

Dropped Data

Fault

Direction Fault

Multiple Copies

in Space Fault

Multiple Copies

in Time Fault

Data Fault:

Corrupted

Data Fault


N

Routing is ok, but data is affected!

10100101

10101101


13

Agenda





5. Conclusion


14

Control Fault Detection/Localization

Distraction Detection

Switch Count (TTL)

Time-out Detection

Sequence Number

Trapped Packet Detection

S1[0,0]

S8[1,2]

S2[1,0]

S7[0,2]

[x,y]

- 3x3 Network-on-Chip / XY-Routing

S9[2,2]

S4[0,1]

S5[1,1]

S6[2,1]

S3[2,0]

1XXYY nDestinatioSwitchSwitchSource


15



Switch Count (TTL)

Time-out Detection

Sequence Number


S1[0,0]

S4[0,1]

S8[1,2]

S5[1,1]

S6[2,1]

S2[1,0]

S9[2,2]

S3[2,0]

S7[0,2]

SaN

[x,y]

Direction Faults – „Stuck-at N, E, S, W“ Multiple Copies in Space Faults

Ex. 1: Route from S4 [0,1]

S9 [2,2]


16

S1[0,0]

S4[0,1]

S8[1,2]

S5[1,1]

S6[2,1]

S2[1,0]

S9[2,2]

S3[2,0]

S7[0,2]

SaN

[x,y]



Switch Count (TTL)

Time-out Detection

Sequence Number




S9 [2,2]

S8[1,2]

from other Switches

=?

ComperatorSwitch Address

Source AddressDestination Address ErrorNo

1XXYY nDestinatioSwitchSwitchSource

nDestinatioSwitch XX SwitchSource YY

Distraction Detected!


17



Switch Count (TTL)

Time-out Detection

Sequence Number




S6 [2,1]

S1[0,0]

S4[0,1]

S8[1,2]

S5[1,1]

S6[2,1]

S2[1,0]

S9[2,2]

S3[2,0]

S7[0,2]

SaN

[x,y]

This stuck-at port fault cannot be

discovered; S3 acts like expected!


18



Switch Count (TTL)

Time-out Detection

Sequence Number




S4 [0,1]

S1[0,0]

S4[0,1]

S8[1,2]

S5[1,1]

S6[2,1]

S2[1,0]

S9[2,2]

S3[2,0]

S7[0,2]

SaE

[x,y]

8

SwitchSource YY No violation of XY-Routing!

Livelock!


19



Switch Count (TTL)

Time-out Detection

Sequence Number


Direction Faults - „Reflection“


S4 [0,1]

S1[0,0]

S4[0,1]

S8[1,2]

S5[1,1]

S6[2,1]

S2[1,0]

S9[2,2]

S3[2,0]

S7[0,2]

SaE

[x,y]

Idea:

Decrement „switch count field“ on each hop.Switch count field = „10,9,8,7,6,5,4,3,2,1,0“ !?

Drop packet

8

Livelock!


20



Switch Count (TTL)

Time-out Detection

Sequence Number


Dropped Data Faults


S4 [0,1]

S1[0,0]

S4[0,1]

S8[1,2]

S5[1,1]

S6[2,1]

S2[1,0]

S9[2,2]

S3[2,0]

S7[0,2]

SaE

[x,y]

ACK/NACK?

Idea:

Start timer whenever data leaves the source.Stop timer when reception is confirmed.Expiration of the timer indicates dropped data.


21

Duplicated Packet

Packet #4 missing



Switch Count (TTL)

Time-out Detection

Sequence Number


# 1# 2# 2# 3# 5

# 6

# 11# 10# 9# 8# 7

Sourcenode

Destination node

Network-on-Chip

DroppedDataFaults

MultipleCopiesFaults

Sequence Number

Watchdog Counter

Dropped Data Faults Multiple Copies in Space / Time Faults


22



Switch Count (TTL)

Time-out Detection

Sequence Number


N

S

E

W

PProcessor

Router

SaP Fault

ViolationindicatesSaP Fault!

Direction Faults - „Stuck-at Processor“

SwitchnDestinatio XYXY

Comparison that isperformed in the PE:


23

Agenda





5. Conclusion


24

Data Fault Detection/Localization

End-to-End (e2e)

Switch-to- Switch (s2s)

Code- Disjoint- Detection (cdd)

Detect Corrupted Data Faults

Perform Data Fault Detection by means of Error Detection and Correction (EDC) Codes.

ED:

Parity-Check Codes

Cyclic Redundancy Check (CRC) Codes

EDC:

Hamming Codes (SEC/DED)

SEC: Single Error CorrectionDED: Double Error Detection


25


End-to-End (e2e)



PE PE

Encoder Decoder

Switch A Switch B

Sender NI Receiver NI

Packet buffer

Queuing buffer

Credit signal

Data

Encode data at the sending node

Data Fault Detection at the destination

Clear localization is not possible

PE: Processing ElementNI: Network Interface


26


End-to-End (e2e)



DecoderSwitch B

PE PE

Encoder DecoderSwitch A

Sender NI Receiver NI

Packet buffer Circular

(queuing and retransmission)

buffers

Data

Decoder

ACK

NACK


Perform “checking” at ever switch input

Last switch and link is suspicious

PE: Processing ElementNI: Network Interface


27


End-to-End (e2e)



N

S

EW

P

FIFO

link error flag

Router

Po(Xo)

switch error flag

Xi

Xip

XoXop

Pi(Xi)


Perform “checking” at ever switch in- as well as output

Clear localization of the fault (switch/link)


28


Comparison of the Fault Localization capabilities:

End-to-End, Switch-to-Switch and Code-Disjoint-Detection

Sw1

D1 D2

Sw7

Sw6

Sw5Sw3S2

Sw2S1

Sw4

L1 L2

L3

L4 L5 L6

L9

L8

L7

I

II


Path II (S2 to D2 )

Fault in L5 :

e2e = {S2 , L4 , Sw3 , L5 , Sw4 , L6 , Sw5 ,L7 , Sw6 , L8 , Sw7 , L9, D2 }

s2s = {Sw3 , L5 }cdd = {L5 }

Path I (S1 to D1 )

Fault in Sw1 :

e2e = {S1 , L1 , Sw1 , L2 , Sw2 , L3 , D1 }s2s = {Sw1 , L2 }cdd = {Sw1 }

29

Agenda





5. Conclusion


30

Conclusion

Objectives of Online Diagnosis:

Fault Detection/Localization

Fault Classification (transient, intermittent & permanent)

Fault Modeling

Regard altered switch behavior (abstraction)

Classify models into either Control or Data Faults


Distraction Detection with different extensions


ED(C)

Detection / e2e, s2s and cdd

Localization


Thank you for your attention!

Reliable NoC in the Many Core Era

6/15/2009

online diagnosis of network-on-chip

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