the switchboard traffic engineering problem for mixed contention/cut-through output channels

for Mixed Contention/Cut-Through

Marat Zhanikeev [email protected] maratishe.github.io

2016/11/18@PN研@KDDI研

The Switchboard

PDF: bit.do/161118

Traffic Engineering Problem

#STEP #TE #TrafficEngineering #OSPF #cut-through #contention #SDN Output Channels

.

Commutators are Back (as robots)• all the technology is already there, we just need to start using it• basically, switching robotics

◦ this paper proposed the Switchboard Traffic Engineering Problem(STEP)

Marat Zhanikeev -- [email protected] The Switchboard Traffic Engineering Problem for Mixed Contention/Cut-Through Output Channels 2/16...

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Cut-Through Mode as Basis for STEP

C: Cut Through

Check, etc. Q: Queue

D: DropQoSclasses


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STEP (1)• each outgoing port gets multiple slots, i.e. the n-by-m switchboard• can be implemented as multiple ethernet ports, fiber wavelengths, etc.

A switch 4-port switchPhysical Logical Switchboard

n×mswitchingmatrix

xth port,y slots n ports

m slots


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STEP (2) The Weight Setting Problem• 1st element: weights per slot, the same way as in the OSPF problem

• 2nd element: migrations of some slots to other outgoing ports

Switchboard

n×mswitchingmatrix

n portsm slots

Occupied/used slotEmpty slot

Migration(1:3 to 3:2)

w11 w21

wnm

wn1………

Weight setting


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Formulations (1) OSPF Cases

• unit demand as source s, destination d, volume v, time t, and sometimes opticalwavelength λ, can be written as Ti = ⟨s, d, v, t⟩

• traditional/OSPF : Ti = ⟨s, d, v⟩ → ⟨s, a, b, ..., d⟩• optimal w/out switching : Ti = ⟨s, d, v⟩ → ⟨s, λ⟩• optical with switching : Ti = ⟨s, d, v⟩ → ⟨s, λs, λa, λb, ...⟩• e2e circuits : Ti = ⟨s, d, v, t1, t2⟩ → ⟨s, λ, t⟩


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Formulations (2) The STEP Problem

• M load spread across n outgoing ports, each with m slots (n-by-m switchboard)

◦ unit of load is flowsize vi• load aggregated per slot xy : Lxy = max

{vi}xy, i ∈ xy

• fitness of the slot xy : Fxy = wxyLxy

• aggregate slots into ports as potential : Px =∑{Fj

Vj

}y, j ∈ x

• optimize (w/out migrations) : minimize max{P}xsubject of x ≤ n

• optimize (with migrations) : minimize a · max{P}x+ (1− a) ·

∑i∈m Ci

◦ .... subject of x ≤ n, a ≤ 1, m ≤ Q.


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Experiment (1) Setup

0 20 40 60 80 100Decreasing order

0

0.35

0.7

1.05

1.4

1.75

2.1

2.45

2.8

log(

val

ue)

Class AClass BClass CClass DClass E • hotspot distributions for

picking weights -- same asin OSPF, (i.e. large flows repel other flows)

• use WIDE packet traces forreal packets/flows

• otherwise, the same as inOSPF -- just optimize theweights


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Experiment (2) Results

0 1 2 3 4 5 6

X (port) + Y (slot) coordinate

9560

9600

9640

9680

9720

9760

9800

Load

ind

ex (l

og o

f hot

spot

)

1

1

1

2 2

2

3

3

3

44 4

5

5

5

1

1

1

2 2

2

3

3

3

44 4

5

5

5

Method : real

0 1 2 3 4 5 6

X (port) + Y (slot) coordinate

9560

9600

9640

9680

9720

9760

9800

Load

ind

ex (l

og o

f hot

spot

)

1

1

1

1

1

2

2

2

3

3

3

4

4

4

51

1

1

2

22

3

3

3

3

34

4

4

5

Method : optimal

Hotspot class : D

• real = based on real traces and notoptimized

• optimal is the optimized version ofthe switchboard

• visual effect: STEP spreads thetraffic across ports


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Experiment (3) Layouts (good)

0 2 4 6 8 10 12 14Decreasing order

0

2

4

6

8

10

log(

1 +

fitn

ess)

beforebefore#10.6hotclass#Emigrations#5

10.4

0

2.5

10

10.5

3.1

0

0

10.6

10.4

0

3.1

9.9

10.1

7.8

before


0

2

4

6

8

10

log(

1 +

fitn

ess)

afterafter#10.6 (diff#-0.1)hotclass#Emigrations#5

10.40

2.5010

00

3.10

10.4

00

10.600

0000

10.5

9.910.17.80

3.1

after


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Experiment (4) Layouts (bad)

0 2 4 6 8 10 12 14Decreasing order

0

2

4

6

8

10

log(

1 +

fitn

ess)

beforebefore#10.7

6.2

10

6.7

8.6

9.3

9.3

9.8

0

5.7

0

0

10.7

0

0

9.8

before


0

2

4

6

8

10

log(

1 +

fitn

ess)

afterafter#10.7 (diff#0)

6.2106.700

8.69.39.300

00

5.700

00

10.700

00

9.89.80

after


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Summary

• cut-through circuits are possible even under a large number of flows

• will work with 2+ independent outgoing ports• future steps: actually build a switching robot


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That’s all, thank you ...


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STEP is NOT a scheduling problem

Line =

outgoing

port

Overhead = contention

No. of flows

Line =

outgoing

port

Overhead

Scheduling

Traditional

Circuits


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Future NOC...

• ... will manage a pool of packet and circuit ports

NOC


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STEP in the Hotspot Context• version 1: map all heavy hitter flows as circuits• version 2: offer a paid service that some of the bulk transfer services canuse

ezis wolF

Decreasing flow size

TopNparameter

In Out

Switch

CircuitsPackets


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the switchboard traffic engineering problem for mixed contention/cut-through output channels

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