OpenFlow and SDNS - Extreme Networks

Extreme Networks White Paper
OpenFlow and SDNs
Abstract
OpenFlow is a new protocol designed to control flow
tables in Ethernet switches. OpenFlow is implemented
on an Ethernet switch controller, using an internal flowtable
and a standardized interface to add and remove
flow entries. OpenFlow enables Software Defined
Networks (SDNs) which utilize abstractions in an effort
to simplify networks for designers and operators.
The Open Network Foundation (ONF) has formed
to accelerate and define the use of SDNs. Extreme
Networks is an ONF Member and is participating in the
future definition of OpenFlow and is actively involved
in interoperability testing in OpenFlow labs. This white
paper provides an overview of OpenFlow, SDNs and
Extreme Networks participation and involvement in the
direction of the OpenFlow standard.
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© 2012 Extreme Networks, Inc. All rights reserved.

Extreme Networks White Paper: OpenFlow and SDNs
Executive Overview
OpenFlow is a new protocol implemented on
an Ethernet switch that allows its forwarding
plane to be managed by an external OpenFlow
controller. An OpenFlow controller can manage
a distributed set of network switches as a single
virtual switch. As most OpenFlow controllers
expose an API to applications, the controller
and applications together behave as a unified
Network OS, allowing a network operator to
implement a Software Defined Network (SDN).
OpenFlow Overview
The OpenFlow protocol emerged from the Clean Slate
research program at Stanford University. The objective
was to enable researchers to experiment with new
networking protocols and applications. Instead of
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 switch’s forwarding 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-funded
research projects. OpenFlow protocol definition was
opened to a group of interested researchers and
networking vendors meeting periodically at Stanford,
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 of these prototypes were
demonstrated at the Interop OpenFlow Interoperability
Lab, in May 2011.
OpenFlow exposes a switch’s forwarding plane as a
set of Ethernet ports, flow tables, counters, queues,
and capabilities. A flow table entry consists of a set of
L2/L3/L4 match conditions, which may be variously
wildcarded or masked. Associated with each flow table
rule is a set of one or more actions, including Forwarding
(to a physical or virtual port, to the controller, or
flooded), Enqueueing, and Packet Modification. Added
in OpenFlow 1.1 are support for multiple cascaded
flow tables and MPLS label-related actions. By default,
packets arriving at an OpenFlow-managed port which
do not match a flow entry are encapsulated and sent
to the controller, which as a result may send a flow
installation command to the switch and return the
packet back to the switch for forwarding.
The wide generality of the OpenFlow flow match
conditions allows a controller to manage forwarding
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 configure forwarding for UDP traffic on a
special restricted topology, with guaranteed bandwidth
allocated to dedicated queues used exclusively for
UDP traffic.
Industry Direction
In March 2011, the Open Networking Foundation (ONF)
was formed to advance the adoption of SDNs. ONF
will manage future evolution and specification of the
OpenFlow protocol, and may also define standard
APIs to the OpenFlow controller, to allow for portable
SDN applications. The board members are Deutsche
Telekom, Verizon, Google, Facebook, Microsoft, NTT
Communications, and Yahoo. ONF currently has 54
additional members, including Extreme Networks. See
http://www.opennetworkingfoundation.org/
for more information.
ONF published the OpenFlow 1.2 specification in
December 2011. It also published the first version of
the OpenFlow Configuration protocol, OF-Config 1.0,
in January 2012. ONF working groups are currently
working on new revisions of each specification, as well
as defining the requirements for hybrid OpenFlow
switches, and defining the long-term structure and
evolution of the OpenFlow protocol.
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© 2012 Extreme Networks, Inc. All rights reserved.

Extreme Networks White Paper: OpenFlow and SDNs
Multiple vendors have implemented prototypes of
OpenFlow 1.0, and a few 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 refresh their implementations
to OpenFlow 1.3 or later versions.
The commercial landscape for SDNs includes not
only switch vendors, but also controller vendors. The
original controllers (Stanford, 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
of the Stanford research team, are building commercial
OpenFlow controllers, and have recently received
venture capital funding.
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 failures), simplified
administration of add/move changes (via managing
the network as a single virtual switch), VM mobility
and multi-tenancy (for hosting/cloud providers). SDN
applications for the WAN including transport path
provisioning and routing.
Extreme Networks Opportunities
Extreme Networks initiated development of OpenFlow
support in ExtremeXOS® based in part on requests from
various university customers involved in GENI- and
OPHELIA-funded research projects. In the subsequent
year demand for OpenFlow from 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 platform to deploy a variety of
intelligent network services in a scalable way, because
the network switches are centrally managed by the
OpenFlow controller. Of particular value are the network
virtualization capabilities enabled. It becomes easier
to deploy and dynamically manage security isolation
between classes of users in university, enterprise
campus or hospital networks, by isolating each class
of 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 simplify the provisioning of services for 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 future
definition of the OpenFlow protocol. Current plans for
Extreme Networks OpenFlow implementation include
support as part of the ExtremeXOS network operating
system, across a variety of switching products.
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© 2012 Extreme Networks, Inc. All rights reserved. Extreme Networks, the Extreme Networks logo, are either registered trademarks or trademarks of
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are subject to change without notice. 1795_02 04/12