OpenFlow and SDNs

7/31/2019 OpenFlow and SDNs

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Extreme Networks White Paper

2012 Extreme Networks, Inc. All r ights reserved.

Make Your Network Mobile

Abstract

OpenFlow is a new protocol designed to control ow

tables in Ethernet switches. OpenFlow is implementedon an Ethernet switch controller, using an internal ow-

table and a standardized interace to add and remove

ow entries. OpenFlow enables Sotware Dened

Networks (SDNs) which utilize abstractions in an efort

to simpliy networks or designers and operators.

The Open Network Foundation (ONF) has ormed

to accelerate and dene the use o SDNs. Extreme

Networks is an ONF Member and is participating in the

uture denition o OpenFlow and is actively involved

in interoperability testing in OpenFlow labs. This white

paper provides an overview o OpenFlow, SDNs and

Extreme Networks participation and involvement in the

direction o the OpenFlow standard.

OpenFlow and SDNs


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Extreme Networks White Paper: OpenFlow and SDNs

2012 Extreme Networks, Inc. All r ights reserved.

Executive Overview

OpenFlow is a new protocol implemented on

an Ethernet switch that allows its orwarding

plane to be managed by an external OpenFlow

controller. An OpenFlow controller can managea distributed set o network switches as a single

virtual switch. As most OpenFlow controllers

expose an API to applications, the controller

and applications together behave as a unifed

Network OS, allowing a network operator to

implement a Sotware Defned Network (SDN).

OpenFlow Overview

The OpenFlow protocol emerged rom the Clean Slate

research program at Stanord University. The objective

was to enable researchers to experiment with new

networking protocols and applications. Instead o

porting each new protocol/application to switches,

each brand with its own proprietary OS, the researchers

need only port an OpenFlow protocol client, exposing

the switchs orwarding plane. The experimental control

component could then be implemented on a standard

PC running a Unix OS (such as Linux).

This approach proved popular, and OpenFlow was

adopted as a core component by university researchers

participating in NSF GENI- and EU OPHELIA-unded

research projects. OpenFlow protocol denition was

opened to a group o interested researchers and

networking vendors meeting periodically at Stanord,

and via e-mail lists. OpenFlow version 1.0.0 was

published in December 2009, and version 1.1 was

published in February 2011. Multiple vendors, including

Extreme Networks, have implemented OpenFlow

1.0 prototypes. Some o these prototypes were

demonstrated at the Interop OpenFlow Interoperability

Lab, in May 2011.

OpenFlow exposes a switchs orwarding plane as a

set o Ethernet ports, ow tables, counters, queues,

and capabilities. A ow table entry consists o a set o

L2/L3/L4 match conditions, which may be variously

wildcarded or masked. Associated with each ow table

rule is a set o one or more actions, including Forwarding

(to a physical or virtual port, to the controller, or

ooded), Enqueueing, and Packet Modication. Added

in OpenFlow 1.1 are support or multiple cascaded

ow tables and MPLS label-related actions. By deault,

packets arriving at an OpenFlow-managed port which

do not match a ow entry are encapsulated and sent

to the controller, which as a result may send a ow

installation command to the switch and return the

packet back to the switch or orwarding.

The wide generality o the OpenFlow ow match

conditions allows a controller to manage orwarding

at L2, L3, and/or L4 layers, either in isolation, or

in combination. This enables a SDN with multiple

virtualized network topologies. As a simple example, a

controller can congure orwarding or UDP trafc on a

special restricted topology, with guaranteed bandwidth

allocated to dedicated queues used exclusively or

UDP trafc.

Industry Direction

In March 2011, the Open Networking Foundation (ONF)

was ormed to advance the adoption o SDNs. ONF

will manage uture evolution and specication o the

OpenFlow protocol, and may also dene standard

APIs to the OpenFlow controller, to allow or portableSDN applications. The board members are Deutsche

Telekom, Verizon, Google, Facebook, Microsot, NTT

Communications, and Yahoo. ONF currently has 54

additional members, including Extreme Networks. See

http://www.opennetworkingoundation.org/

or more inormation.

ONF published the OpenFlow 1.2 specication in

December 2011. It also published the rst version o

the OpenFlow Conguration protocol, OF-Cong 1.0,

in January 2012. ONF working groups are currently

working on new revisions o each specication, as wellas dening the requirements or hybrid OpenFlow

switches, and dening the long-term structure and

evolution o the OpenFlow protocol.


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Extreme Networks White Paper: OpenFlow and SDNs

2012 Extreme Networks, Inc. All rights reserved. Extreme Networks, the Extreme Networks logo, are either registered trademarks or trademarks o

Extreme Networks, Inc. in the United States and/or other countries. All other names and marks are the property o their respective owners. Specifcationsare subject to change without notice. 1795_02 04/12

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Multiple vendors have implemented prototypes o

OpenFlow 1.0, and a ew have released generally

available implementations. It is unclear whether

OpenFlow 1.1 will be widely implemented; it is likely that

most vendors will wait to reresh their implementations

to OpenFlow 1.3 or later versions.

The commercial landscape or SDNs includes notonly switch vendors, but also controller vendors. The

original controllers (Stanord, NOX, Beacon, SNAC) were

developed by researchers and released as open source.

NEC has announced a commercial controller, and two

startup companies (Big Switch, Nicira), that spun out

o the Stanord research team, are building commercial

OpenFlow controllers, and have recently received

venture capital unding.

Initial SDN applications which have attracted interest

in the campus, enterprise, and data center markets

include multi-path support (to avoid the capacity loss

and instability caused by STP and its ailures), simpliedadministration o add/move changes (via managing

the network as a single virtual switch), VM mobility

and multi-tenancy (or hosting/cloud providers). SDN

applications or the WAN including transport path

provisioning and routing.

Extreme Networks Opportunities

Extreme Networks initiated development o OpenFlow

support in ExtremeXOS based in part on requests rom

various university customers involved in GENI- and

OPHELIA-unded research projects. In the subsequent

year demand or OpenFlow rom university customers

has expanded beyond the research lab into the

production campus network. Extreme Networks is

working with a major university customer to trial SDN

applications within its campus network.

Extreme Networks is also exploring opportunities with

partners to deploy SDN applications in the enterprise

campus and datacenter network environments. An

SDN can serve as a platorm to deploy a variety o

intelligent network services in a scalable way, because

the network switches are centrally managed by the

OpenFlow controller. O particular value are the networkvirtualization capabilities enabled. It becomes easier

to deploy and dynamically manage security isolation

between classes o users in university, enterprise

campus or hospital networks, by isolating each class

o user to their own virtual network topology. Unlike

Ethernet VLANs, this isolation can also be enabled at

the L3 and/or L4 layers. In a datacenter network, the

network virtualization capabilities enabled by OpenFlow

can simpliy the provisioning o services or individual

tenants, and can enable scalable VM migration across

a large datacenter network or between physical

datacenter sites.

Extreme Networks Involvement

Extreme Networks participated in the OpenFlow

interoperability Lab at Interop 2011. Extreme Networks

has also joined the ONF, and is participating in the uture

denition o the OpenFlow protocol. Current plans or

Extreme Networks OpenFlow implementation include

support as part o the ExtremeXOS network operating

system, across a variety o switching products.

Documents

OpenFlow and SDNs