The Next Generation of Networks is all about Hotspot Distributions and Cut-Through Circuits

.

The Cut-Through Mode

C: Cut Through

Check, etc. Q: Queue

D: Drop QoS classes

M.Zhanikeev -- [email protected] The NextGen of Networks is all about Hotspot Distributions and Cut-Through Circuits - http://bit.do/150421 - 2/18...

2/18

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Hotspots and Circuits

• hotspots are models based on power-law◦ hotspot flows: BigData transfer, VM migration, backup, etc.

• the old circuits vs packets argument is back◦ packets are more efficient, given a mixture of many ON/OFF voice flows◦ with hotspot traffic this is not true anymore


3/18

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Hotspots


4/18

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What are Hotspots?.Hotspots are.....

.

...samples of parallel streams ofrandom variables

• sets are: normal, popular, hot andflash

• example in CDNs: majority ofcontent is not popular (normal), some ismildly popular (pop), and only a fewitems are hot (hot) and can experienceshort-term viral events (flash)

• ... same for many other processes, likeFukuoka city in the figure (variableis area)


5/18

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Hotspot Generation

• setup tuple: ⟨n, np, nh,m, v⟩

0 10 20 30 40 50List of traffic sources

00.40.81.21.622.42.8

log( traffic volume)

0 10 20 30 40 50List of traffic sources

00.40.81.21.622.42.8

log( traffic volume)

Magnitude=2 Magnitude=10

Hotspots

Normal

Hotspot under a Flash event

• n total number of items

• np number of pop items

• nh number of hot/flashitems

• m magnitude of Flashevents for hot items

• v variance across parallelrandom streams -- setsare samples

• there is also d for Betasetup, but can be constant


6/18

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Hotspot Classification (1)

0 20 40 60 80 100Position in decreasing list of values

0

0.45

0.9

1.35

1.8

2.25

2.7

3.15

3.6

Val

ues a

s (1

+ lo

g( 1

+ x

))

Class DClass CClass BClass A • problem: the aboveparameters are notintiutive

• some form ofmeaningfulclassificationmight be helpful

• figure: one way is tomeasure how manylarge items in set

• good method, but stillhard to assign a singleletter to a distribution


7/18

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Hotspot Classification (2) commit!

100 200 300 400 500 600Average of head 50%

0

5

10

15

20

25

30

35

40

Ave

rage

of t

ail

50%

A

C

B

D

• head vs tail halves• simple letters for classes

• will use this for analysis


8/18

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Circuits


9/18

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Circuits in Practice

• a scheduling problem, circuit scheduler

• 1- vs 2-network designs

SWITCH

NOC

Storage Node A

Storage Node B

Step 1: Book session

Step 2: Transfer bulk

SWITCH

Storage Node A

Storage Node B

SWITCH

Booking segment

Bulk Segment


10/18

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Circuits vs Packets

• comparison of per-flow and per-packet overhead

Interference Overhead Isolation

Do Nothing HIGH ZERO NO

Network Virtualization HIGH HIGH NO (store -and -forward)

Traditional Scheduler LOW HIGH YES P2Px1N (1 network) HIGH VERY HIGH YES P2Px2N (2 networks) ZERO VERY HIGH YES Tall Gate (sensing) LOW HIGH YES


11/18

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Performance : Circuits vs ...

0 2 4 6 8Ordered list

0

0.45

0.9

1.35

1.8

2.25

log(

dur

atio

n)

Do Nothing Network VirtualizationTraditional SchedulerP2Px1N P2Px2N Tall Gate


0

0.8

1.6

log(

dur

atio

n)


0.6

1.2

1.8

2.4

log(

dur

atio

n)


1.5

1.8

2.1

2.4

log(

dur

atio

n)


1.65

1.95

2.25

2.55

log(

dur

atio

n)


1.2

1.6

2

2.4

log(

dur

atio

n)

Size: 10M..100M Size: 100M..500MSize: 500M..1G

Size: 10G..100GSize: 1G..10G Size: 10G..50G

2.4• simple models ofper-flow overhead

• separate analysis for bulksize

• p2p aremany-to-manymethods

• tall gate a method fordistributed scheduling ofcircuits


12/18

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Analysis


13/18

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Analysis Model

• a mixture of 100 hotspot dists (flowsize), flows above 500MB opt forcircuits but can go for packets if faster, congestion as x log n (x: line-rate time, n: number of

concurrent flows), packet/flow line ratio is 5:1, many many random simulations

NOC


14/18

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Performance : Hotspots (one)

2 3 4 5

Hotspot C (log of count)

2

3

4

5

Hots

pot D

(log

of c

ount

)

250300

1000

500

950

200

450

• a visualization

• only ≥ 500MB flows aremonitored

• diagonal: flow transfer rate• axes: counts for flow classesfor a given rate


15/18

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Performance : Hotspots (all)

2 3 4 5

Hotspot A (log of count)

2

3

4

5

Hots

pot B

(log

of c

ount

)

250300

1000

500

200

950

450

2 3 4 5


2

3

4

5

Hots

pot C

(log

of c

ount

)

250300

1000

500

200

950

450

2 3 4 5


2

3

4

5

Hots

pot D

(log

of c

ount

)

250300

1000

500

200

950

450

2 3 4 5

Hotspot B (log of count)

2

3

4

5

Hots

pot C

(log

of c

ount

)

250300

1000

500

950

200

450

2 3 4 5

Hotspot B (log of count)

2

3

4

5

Hots

pot D

(log

of c

ount

)

250300

1000

500

950

200

450

2 3 4 5

Hotspot C (log of count)

2

3

4

5

Hots

pot D

(log

of c

ount

)

250300

1000

500

950

200

450


16/18

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Wrapup

• with hotspots and 5:1 packet/flow ratio, Class D,C flows perform the best◦ that's good news -- networks are efficient under extreme hotspot distributions

• worst performing is Class A◦ using dedicated circuit lines is inefficient, better switch to all-packet lines


17/18

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That’s all, thank you ...


18/18

The Next Generation of Networks is all about Hotspot Distributions and Cut-Through Circuits

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