[PPT] - The Controller Placement Problem Brandon Heller Rob Sherwood, Nick PowerPoint Presentation

SLIDE 1

The Controller Placement Problem

Brandon Heller Rob Sherwood, Nick McKeown HotSDN 2012 Helsinki, Finland contact: brandonh@stanford.edu

SLIDE 2

“Software Defined Networking (SDN) refactors the relationship between network devices and the software that controls them.” SDN is not alone.

from HotSDN 2012 CFP:

Control Software Network Devices

(decoupled from)

SDN, MPLS PCE, BGP RR, 4D, RCP, …

Each architecture faces a design choice in the WAN that fully distributed networks don’t have…

SLIDE 3

[Internet2 OS3E]

The Controller Placement Problem

(1) How many controllers? (2) Where should they go?

SLIDE 4

Who Cares?

Controller App Developers/Operato rs Platform Developers/Operato rs

Network Operators

load balancers, firewalls, NATs FlowVisor, ONIX, RouteFlow GENI, Internet2, ISPs

SLIDE 5

Optimal placement depends on goals

fault tolerance, load balancing, latency, …

SLIDE 6

WAN topologies brute-force metric computation

ptimal

controller placements

 

Latency “Methodology”

[www.topologyzoo.org]

SLIDE 7

Response Time

x

Link Failure

Time In Switch * 2 + Propagation * 2 + Time in Controller Event Response Time =

Control Packet New Flow Switch Controller A Controller B

Shortest paths only No Controller Coordination

x

Propagation Delay Only

SLIDE 8

Placement Examples

Chicago Kansas City

SLIDE 9

Topics

Is one location enough?
What is a good placement?
How do extra controllers reduce latency?
Are random placements good?
How to efficiently choose placements?
Tradeoffs between metrics?
How to combine metrics?

See paper for grayed-out topics.

SLIDE 10

Rest of this talk:

Is one location enough?
What is a good placement?
How do extra controllers reduce latency?
Are random placements good?
How to efficiently choose placements?
Tradeoffs between metrics?
How to combine metrics?

See paper for grayed-out topics.

SLIDE 11

Is one location enough? [for latency!]

SLIDE 12

Delay Comparison

Name Delay 1.0x 1.5x 2.0x Through the switch (measured last year) 10 ms 27% 22% 18% Optical ring protection in SONET, Wireless handover in WiMAX 50 ms 82% 60% 33% IP-level restoration 200 ms 100% 91% 89%

Round-trip Latency Target Safety Margin

SLIDE 13

Delay Comparison

Name Delay 1.0x 1.5x 2.0x Through the switch (measured last year) 10 ms 27% 22% 18% Optical ring protection in SONET, Wireless handover in WiMAX 50 ms 82% 60% 33% IP-level restoration 200 ms 100% 91% 89%

Round-trip Latency Target Safety Margin

One controller location may be enough, for many (smaller) topologies

SLIDE 14

Opt worst-case latencies

A few locations are enough for most topologies

SLIDE 15

Wrapping Up

SLIDE 16

My takeaways

One: probably good enough for many networks
Few: probably good enough for most
Placement likely to be dictated by other concerns

– e.g. load balancing, fault tolerance

SLIDE 17

What’s Next

Fault Tolerance
State Distribution
Controller Selection

SLIDE 18

Thanks!

Code at github.com/brandonheller/cpp.git

SLIDE 19

Backup Slides

SLIDE 20

Latency reduction w/more controllers

 Mostly proportional reduction

1/2 with 2x? 1/3 with 3x?

SLIDE 21

Optimal-latency placements

metric: corresponding Facility Location problem

Average-case latency: minimum k-median
Worst-case latency: minimum k-center
Nodes within a latency bound: maximum

cover

SLIDE 22

Networks are not alone

Other domains have graphs to

ptimize for latency:

Fire/police/hospital locations Amazon warehouses Netflix/Content servers  Facility location problems

SLIDE 23

Software Defined Network (SDN)

Global Network View

Network Virtualization

Packet Forwarding Packet Forwarding Packet Forwarding Packet Forwarding Packet Forwarding

Network OS

Abstract Network View

Control Programs

f View

( )

Control Programs

f View

( )

Control Programs

f View