OpenFlow Reference Release v0.1.5 <http://openflowswitch.org>
What is OpenFlow?
-----------------
OpenFlow is a flow-based switch specification designed to enable
researchers to run experiments in live networks. OpenFlow is based on a
simple Ethernet flow switch that exposes a standardized interface for
adding and removing flow entries.
An OpenFlow Switch consists of three parts: (1) A Flow Table in which
each flow entry is associated with an action telling the switch how to
process the flow, (2) A Secure Channel connecting the switch to a remote
process (a controller), allowing commands and packets to be sent between
the controller and the switch, and (3) An OpenFlow Protocol
implementation, providing an open and standard way for a controller to
talk to the switch.
An OpenFlow Switch can thus serve as a simple datapath element that
forwards packets between ports according to flow actions defined by
the controller using OpenFlow commands. Example actions are:
- Forward this flow's packets to the given port(s)
- Drop this flow's packets
- Encapsulate and forward this flow's packets to the controller.
The OpenFlow Switch is defined in detail in the OpenFlow Switch
Specification [2].
What's here?
------------
This software is a reference implementation of an OpenFlow Switch kernel
module for the Linux operating system, a secure channel implementation,
and an example controller that performs switching with MAC learning.
The rest of this file contains the following sections:
- Description of the directory hierarchy
- Platform support
- Quickstart build and install instructions
- Shortcomings
- References
Directory Hierarchy
-------------------
Source:
datapath/ Linux kernel module implementing an OpenFlow Flow Table
that incoming packets are checked against. The
kernel module uses netlink (a socket protocol for
user-kernel communication, described in RFC 3549) to
pass OpenFlow messages with the secure channel to be
relayed to the controller.
secchan/ A Secure Channel that connects to a kernel datapath
via netlink and a remote controller via TCP,
relaying OpenFlow packets received on one end to the
other. (The current implementation does not
support SSL, but this will be added in future releases.)
controller/ A simple controller that connects to a datapath via
a Secure Channel, commanding the datapath to act as
a regular MAC learning switch.
utilities/ Contains the sorce for "dpctl", a command-line utility
for controlling the OpenFlow datapath kernel module.
With it, you can add physical ports to the datapath,
add flows, monitor received packets, and query the
datapath state.
include/ Header files common to the datapath, secure channel,
and controller components.
lib/ Implementation files common to the datapath, secure
channel, and controller components.
third-party/ Contains third-party software that may be useful for
debugging. Currently, it only contains a patch to
allow tcpdump to parse OpenFlow messages.
Documentation:
README Text file describing this OpenFlow implementation,
aka this document.
INSTALLATION Detailed configure, build, and installation
instructions
man/ Man pages describing how to administer datapath,
secure channel, and controller.
Platform support
----------------
The datapath kernel module supports Linux 2.6.15 and above, however,
testing has focused on Linux 2.6.23. Support for Linux 2.4.20 and
above is also in place, although testing has focused on Linux 2.6.
Components have been built and tested on Debian and Ubuntu.
If you are able to build/run the code on platforms not mentioned
here, or have problems with supported system, please report your
experiences to:
<info@openflowswitch.org>
GCC is required for compilation.
Building and Installing (Quick Start)
-------------------------------------
Building the datapath module requires that the source for the
currently running Linux kernel be installed on the machine and
been configured.
The following instructions assume the Linux 2.6 source is located in
/usr/src/linux-2.6.23 and Linux 2.4 in /usr/src/linux-2.4.35
1. ./configure the package, passing the location of one or more
kernel source trees on the command line:
For example, if compiling for Linux 2.6:
% ./configure --with-l26=/usr/src/linux-2.6.23
Or compiling for Linux 2.4:
% ./configure --with-l24=/usr/src/linux-2.4.35
2. Run make:
% make
The following binaries should be built.
Datapath kernel module:
./datapath/linux-2.6/openflow_mod.ko (If compiling for Linux 2.6)
./datapath/linux-2.4/openflow_mod.o (If compiling for Linux 2.4)
Secure channel executable:
./secchan/secchan
Controller executable:
./controller/controller
dpctl utility:
./utility/dpctl
3. Optionally you can "make install" to install binaries and the
man pages (/usr/local/ is the default prefix). If you just want
access to the man pages without installing, set your MANPATH to
include the openflow/ source root.
4. Insert the datapath kernel module into the running Linux instance.
(Linux 2.6)
% insmod datapath/linux-2.6/openflow_mod.ko
(Linux 2.4)
% insmod datapath/linux-2.4/openflow_mod.o
5. Create datapaths by running dpctl on the Linux host (see man
dpctl(8)). Start the controller on a remote host with
controller (see man controller(8)). Start the Secure Channel
on the datapath host to connect the datapath to the controller
with secchan(see man secchan(8)).
For more detailed installation instructions, refer to [3].
Bugs/Shortcomings
-----------------
- The current flowtable does not support all statistics messages
mentioned in the Type 0 OpenFlow spec
- The secure channel and sample controller don't support SSL
- The flowtable does not support the "normal processing" action
- Configure/build system does not support separate build directory for
the datapath. ./configure must be run from the source root.
- dpctl dump-flows may freeze when large numbers of flows are in the
flow table. This has no affect on the datapath
References
----------
[1] OpenFlow: Enabling Innovation in College Networks. Whitepaper.
<http://openflowswitch.org/alpha/openflow-wp-v0.1.pdf>
[2] OpenFlow Switch Specification.
<http://openflowswitch.org/alpha/openflow-spec-v0.2.pdf>
[3] Installation Instructions: INSTALL
Contact
-------
e-mail: info@openflowswitch.org
www: http://openflowswitch.org/alpha/