A presentation on software defined networks and an overview of openflow protocol.

1. Software Defined Networks
and Open flow Protocol
Mahesh M
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2. Introduction to SDN
 An innovative approach to network architecture that provides the ability to
create a whole new class of functionality
 Experimental
 Separates the data plane and the control plane of nodes
 Nodes will only be forwarding the information
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3. Why SDN?
 Network – Core element of an organization’s technology service
 Current Scenario
 Several discrete network devices require manual configuration and
management
 These devices will be closed, proprietary units that limit innovation
 Hence extensibility close to zero
 Need for a New network?
 Change in traffic patterns
 The “consumerisation of IT”
 Rise of cloud services
 Big Data => requirement of more bandwidth
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4. Transition to SDN…
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Features Features
Operating System
Specialized
packet
forwarding
hardware
Features Features
Operating System
Specialized
packet
forwarding
hardware
Features Features
Operating System
Specialized
packet
forwarding
hardware

5. Transition to SDN…
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packet forwarding
Features Features
Network Operating System
Control Plane
Data Plane
Open Flow Protocol
packet forwarding
packet forwarding

6. What is SDN?
 A flexible network architecture
 Control plane and Data plane – core components of a network switch
 Current devices have both control and data plane residing on the
physical switch
 SDN - Control plane separated from the data plane and placed on a
server
 Software application – provides direction to data plane
 Interaction between controller and data plane – using Open Flow protocol
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7. Open Flow Protocol
 TCP based
 Maintained by the open networking foundation
 Provides numerous functions and commands for
 Communication of data
 Status and management of the devices
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8. Open Flow Protocol
 Basic idea – use of flow tables as in Ethernet switches
 Flow Tables – vendor specific
 OFP : provides an open protocol to program the flow table in different switches
and routers
 In a OFP : data path consists of flow table
 An action will be associated with a flow entry
 Set of actions supported by the open flow is extensible
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9. The Open Flow Switch  Consists of at least 3 parts
 A flow table – an action associated with each
flow entry
 A secure channel – connects the switch to a
remote control process(controller)
 Open Flow Protocol – Open and standard way
for a controller to communicate with a switch
 Types
 Dedicated OF switches
 Open Flow Enabled switches
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10. OFP – How it works?
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Controller
Node 4
Node 2
Node 3
Flow
Table
If matchfield : forward message to node 4
If matchfield : change header and forward to node 2

11. Flow Table
 Consists of flow entries
 Each flow entry has
 Match fields
 Counters – update the number of matching packets
 Set of instructions to apply to matching packets
 Matching starts from 1st flow table and may continue to other flow tables
 Matching done in priority order – first match is used
 If no match – may continue to next flow table or may be forwarded to the
controller via OFP or packet can be dropped – depends on the switch configuration
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12. 11/27/2015Software Defined Networks and Open Flow Protocol
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Flowchart detailing packet flow through an Open
Flow switch

13. Instructions
 Each flow entry include set of instructions that are executed when a packet
matches the entry
 Supported instructions
 Apply-Actions action
 Clear-Action
 Write-Action actions
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14. Open Flow Channel
 Connects each open flow switch to the controller
 Usually encrypted using TLS, but may be run directly over TCP
PROTOCOL OVERVIEW
 Support 3 messages
 Controller to switch
 Asynchronous
 symmetric
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15. Controller to Switch
 Initiated by the controller
 Message types
 Features : Controller may request for the features of the switch – expects a features reply with
available capabilities of the switch
 Configuration : controller set/query conffig parameters
 Modify State : manages state on the switches – mainly to add/delete/modify flow entries
 Read State : to collect sttistics from the switch
 Packet-out : used to send packets out of a specied port on the switch, and to forward packets
received via Packet-in messages
 Barrier : to ensure message dependencies have been met or to receive notications for
completed operations
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16. Asynchronous
 Switches send these to indicate packet arrival, switch state change or error
 Message types:
 Packet In : For all packets that do not have a matching row entry, a packet-in event may
be sent to the controller
 Flow removed
 Port status
 Error
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17. Synchronous
 sent without solicitation, in either direction
 Hello: Hello messages are exchanged between the switch and controller upon connection
startup
 Echo : used to measure the latency or bandwidth of a controller-switch connection, as
well as verify its liveness
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18. Open Flow Channel Connection setup
 Switch must be able to connect to a known IP via a user specified port
 If IP is known – switch initiates a TLS or TCP connection to the controller
 After connection is established each side should send a OFTP_Hello message with
the version number
 If version supported connection proceeds
 Else – reply OFPT_Error with
 with a type field of OFPET_HELLO_FAILED,
 a code field of OFPHFC_COMPATIBLE, and
 optionally an ASCII string explaining the situation in data,
And terminate the connection
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19. Connection Interruption
 Switch may lose connection due to
 Echo request timeout
 TLS session timeout
 Or other disconnections
 Switch should contact one or more backup controllers – not specified in the
protocol
 Two modes
 Fail Secure – packets and messages destined to current controller is dropped
 Fail standalone – Switch act as a legacy Ethernet switch or router – processes all the
packets by itself
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20. Encryption and Message Handling
 Encryption
 Communication through TLS connection
 TLS initiated by switch during the startup
 Controller and switch mutually authenticate using certificates
 Controller Certificate
 Switch Certificate
 Message Handling
 OFP provide reliable message delivery and processing
 Does not provide automatic acknowledgements
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21. Benefits of Open flow SDN
 Centralized control of multi-vendor environments
 Reduced complexity through automation
 Higher rate of innovation
 Increased network reliability and security
 More granular network control
 Better user experience
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22. Summary
 Current networks - less extensible
 Solution - Software Defined Networking and Open Flow protocol
 SDN – Emerging technology
 Separates data and control planes
 Makes the network control centralized
 Network devices are only packet forwarding objects
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23. References
 OpenFlow Switch Specication, Version 1.1.0 Implemented (Wire Protocol 0x02 ),
February 28, 2011 – The Open Networking Foundation
 Software-Defined Networking: The New Norm for Networks, ONF White Paper, April 13,
2012
 Zanna, P.; Hosseini, S.; Radcliffe, P.; O'Neill, B., "The challenges of deploying a software
defined network," in Telecommunication Networks and Applications Conference
(ATNAC), 2014 Australasian , vol., no., pp.111-116, 26-28 Nov. 2014
doi: 10.1109/ATNAC.2014.7020883
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7020883&isnumber=7
020854
 Jian-Quan Wang; Haijing Fu; Chang Cao, "Software defined networking for telecom
operators: Architecture and applications," in Communications and Networking in China
(CHINACOM), 2013 8th International ICST Conference on , vol., no., pp.828-833, 14-16
Aug. 2013
doi: 10.1109/ChinaCom.2013.6694710
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6694710&isnumber=6
694549
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