TOWARDS AN ELASTIC DISTRIBUTED SDN CONTROLLERAdvait Dixit, Fang Hao, Sarit Mukherjee, T.V. Lakshman, Ramana Kompella

Physical Network Infrastructure

SDN Control Plane

Distributed Control Plane

• Single point of failure• Performance bottleneck

Spatial Partitioning

Overload

Growing the Control Plane

Shrinking the Control Plane

Goals

•Build a distributed control plane which• Load balances• Grows• Shrinks

•This requires• Load estimation at controllers• Switch migration protocol

Naïve Switch MigrationSLAVEMASTER MASTERSLAVE

Role

Cha

nge

to

Mas

ter

Problem With Naïve Switch Migration

Packet-In

MASTER MASTERSLAVE SLAVE

Packet-OutRo

le C

hang

e to

Mas

ter

Packet-Out from Slave is dropped

Migration Protocol Requirements• Safety: Exactly 1 controller processes every message from the switch

• Liveness: For each switch, at least 1 controller is active at all times

• Openflow compliant

Flow-Add

Flow-DeleteFl

ow-R

emov

ed

4-Phase Switch Migration ProtocolMASTER SLAVE

Flow-Removed

EQUAL

Role

Chan

ge to

Mas

ter

SLAVE MASTER

Role

Chan

ge to

Equ

al

Barrier Request

Barrier Reply

Phase 1: Change from Slave to EqualPhase 2: Insert and remove dummy flowPhase 3: Flush in-

flight messagePhase 4: Change

from Equal to Master

A Mininet Testbed

Problem: Cannot generate sufficient traffic for a large distributed control plane

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veth Pair

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veth Pair

Emulation Host

A Multi-Host Mininet TestbedO

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Emulation Host

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GRE Tunnel`

GRE Tunn

el

GRE Tunnel

Emulation Host

Emulation Host

Evaluation

Evaluation

Next Step: ElastiCon

Physical Network Infrastructure

Core Controller Module

Application 1 Application 2

Core Controller Module

Application 1 Application 2

Distributed Data Store (e.g., Hazelcast)

Node 1

Load Measurements

Load Balance

Scale UpScale Down

Load Adaptation Decisions

Distributed SDN Control Plane

Node 2

Actions:• Migrate switch• Remove controller• Add controller

THANK YOU