The document provides an overview of software-defined networking (SDN) fundamentals, including: - In traditional networks, the control plane and data plane are logically coupled within each network device, whereas SDN separates these planes and centralizes the control plane in an SDN controller. - The SDN controller holds the entire network description as a graph and can perform optimization calculations. It programs flow entries into forwarding devices using the OpenFlow protocol. - OpenFlow defines a standard interface that gives access to the forwarding plane of network switches or routers. It separates the data and control planes and allows the control logic to be implemented separately in the SDN controller.

1. Software-Defined Networking
Fundamentals
Instructor: Azhar H Khuwaja
SDN Apps
Controller
azharhkhuwaja@gmail.com 1

2. Traditional: Logically Coupled Network Devices
2

3. CSED702Y: Software Defined Networking
Traditional Network Node (Router Example)
• Traditional network node (e.g. Router) is partitioned into three
logical planes.
 Management-Plane  Configuration, Policy, Commissioning,
Billing …
 Control-Plane  Make route decisions
 Data-Plane  Forwarding / Transport / Infrastructure
Adjacent Router Router
Management/Policy Plane
Configuration / CLI / GUI
Static RoutesControl Plane
OSPF
Neighbor
Table
Link State
Database
IP Routing
Table
Forwarding Table
Data PlaneData Plane
Control Plane
OSPF
Adjacent Router
Data Plane
Control Plane
OSPF
Routing
Switching
Router / Switch
3

4. Software-Defined Networking
Application
Plane
Control Plane
Data Plane
4

5. CSED702Y: Software Defined Networking
SDN Concept
• SDN physically separates Control & Data Planes (not logically).
SDN Controller
Load
Balancing
Traffic
Engineering
IDS
Forwarding
Device
Forwarding
Device
Forwarding
Device
Forwarding
Device
………..
• SDN merges the
Management-Plane
into a single
centralized Control-
Plane. (also uses
apps for
management)
• An SDN-Controller
holds the entire
network description
as Graph on which
optimization
calculations can be
performed.
5

6. Analogy with Computers
6

7. SDN Structure
7

8. 8
SDN in Data Center
Cost
200,000 servers
Fanout of 20 = 10,000 switches
$5k vendor switch = $50M
$1k commodity switch = $10M
Savings in 10 data centers = $400M
Control
More flexible control
Tailor network for services
Quickly improve and innovate
8

9. Hierarchal Controllers
What is the difference between Network Operating System and SDN Controller? 9

10. East / West Network Expansion
10

11. Using Cluster
11

12. Open-Source SDN Controllers
Open-Source SDN Controllers are also called as Open SDN.
• OpenDaylight
• Floodlight
• POX
• ONOS
• Ryu
• NOX
• Beacon
• FlowER
• NodeFlow
• ONIE
• OpenMUL
& others …….
12

13. Commercial SDN Controllers
Some of the famous SDN Controllers offered by vendors are;
• NEC ProgrammableFlow Controller released … 2013
• HP VAN SDN Controller (SDN Controller with several internal apps)
• Brocade SDN Controller (current version 2.3.0 based on OpenDaylight)
• Pica8 (offers variety of SDN products & solutions)
• Inocybe (offers OpenDaylight based SDN Controller)
• Cisco Application Policy Infrastructure Controller
• BigSwitch
• Nauge Networks Virtualize Services Controller
• VMware NSX Controller
& others ….
13

14. CSED702Y: Software Defined Networking
What is OpenFlow?
• A communication protocol that gives access to the Forwarding-Plane of the network
switch or router.
• Features
 OpenFlow is similar to an x86 instruction set for the network.
 Separation of Control-Plane & Data-Plane
o The data path of an OpenFlow switch consists of a Flow Table & an action
associated with each flow entry.
o The control path consists of a controller which programs flow entry in the flow
table.
 OpenFlow is based on an Ethernet switch with an internal flow table & a
standardized interface to add & remove flow entries.
 Managed & developed by ONF (Open Networking Foundation) since its version 1.2
14

15. How OpenFlow Works?
Controller
PC
OpenFlow Switch
OpenFlow Switch OpenFlow Switch
Mr. X's Code
Decision?
OpenFlow Protocol
Mr. X's Rule Mr. X's Rule
Mr. X's Rule
OpenFlow offloads control intelligence to a remote software!
Match L1: Tunnel ID, Switch Port
L2: MAC Addr, VLAN ID,
Ether Type
L3: IPv4/IPv6 fields, ARP
L4: TCP, UDP
Action • Output to zero or more
ports
• Encapsulate
• Header rewriting
• Send to controller
15

16. CSED702Y: Software Defined Networking
OpenFlow Switch
General Purpose PC / Server
OpenFlow
Protocol
Data Path, H/W
Control Path OpenFlow
Controller
(Server Software)
App App App
Ethernet Switch
16

17. OpenFlow Switch
OpenFlow Agent is also called as OpenFlow Client / OpenFlow Channel. 17

18. OpenFlow Vendor Switches
Some of the famous OpenFlow Switches offered by vendors are;
• NEC released OpenFlow 1.3 Switch… 2013
• HP released OpenFlow 1.3 Data Center Switch … 2013
• Centec Network released Open SDN Switch with OpenFlow1.3 support (implemented
on Open vSwitch) … 2013
• Brocade OpenFlow 1.3 Switch … 2014 (MLX & CLX Series)
• BigSwitch
• Ericsson
• Nicira
& others
• Are you aware of any Open-Source OpenFlow Switch?
• What is meant by HYBRID OpenFlow Switch?
• Do you know that some vendors also promote Open-Source products & even
develop it?
18

19. CSED702Y: Software Defined Networking
Packet Forwarding
Two types of Packet Forwarding offered by OpenFlow.
• Reactive Flow Insertion
 When a non-matched packet reaches to OpenFlow switch, it is sent to the
controller, based on the info in packet header, an appropriate flow will be inserted.
 Always need to query the path from controller during packet arrival  Slow
 Can reflect the current traffic status
• Proactive Flow Insertion
 Flow can be inserted proactively by the controller to switches before packet arrives
 No need to communicate during packet arrival  Fast packet forwarding
 Cannot reflect the current traffic status
What is the difference between Operational & Configuration Flows? 19

20. Proactive vs. Reactive Forwarding
• Reactive: Seeks Controller guidance every time a packet arrives
• Proactive: Forwarding rules are stored in Switch before packet arrival
20

21. CSED702Y: Software Defined Networking
Packet Forwarding
OpenFlow
Controller
Host1 Host2Switch1 (Reactive) Switch2 (Proactive)
acquire
route
insert
flow
SRC DST ACT … SRC DST ACT …
h1 h2 p2
21 21
h1 h2 p2
21

22. CSED702Y: Software Defined Networking
Message Structure
• OpenFlow control messages rely on TCP protocol
• Controllers listen on TCP port 6633/6653 to setup connection with switch
 6633/6653 became the official IANA port since 18th July 2013
• OpenFlow Message Structure includes following fields:
 Version: Indicates the version of OpenFlow which this message belongs
 Type: Indicates what type of message is present and how to interpret the payload
(version dependent)
 Message Length: Indicates where this message will be end, starting from the first
byte of header
 Transaction ID (xid): A unique value used to match requests to response
Bit Offset 0 ~ 7 8 ~ 15 16 ~ 23 24 ~ 31
0 ~ 31 Version Type Message Length
32 ~ 63 Transaction ID
64 ~ ? Payload
OpenFlow Message Structure
22

23. CSED702Y: Software Defined Networking
OpenFlow Protocol Messages
• OpenFlow protocol supports three message types;
 Controller to Switch
Initiated by the controller & used to directly manage or inspect the state of the switch.
Specify, modify or delete flow definitions
Request information on switch capabilities
Retrieve information like counters from the switch
Send a packet back to a switch for processing after a new flow is created
 Asynchronous
Initiated by the switch & used to update the controller of network events & changes to
the switch state.
Send the controller a packet that does not match an existing flow
Inform the controller that a flow has been removed because its time to live parameter
or inactivity timer has expired
Inform the controller of a change in port status or that an error occurred on the switch
23

24. CSED702Y: Software Defined Networking
OpenFlow Protocol Messages
 Symmetric
Initiated by either the switch or the controller & sent without solicitation.
Hello messages exchanged between controller & switch on startup
Echo messages used to determine the latency of the controller-to-switch connection &
to verify that the controller-to-switch connection is still operative
24

25. CSED702Y: Software Defined Networking
Protocol Messages
Category Message Type Description
Meta Info.
Configuration
Hello (SM) C  S
following a TCP handshake, the controller sends its version number to the
switch.
Hello (SM) S  C the switch replies with its supported version number.
Features Request (CSM) C  S the controller asks to see which ports are available.
Set Config (CSM) C  S in this case, the controller asks the switch to send flow expirations.
Features Reply (CSM) S  C
the switch replies with a list of ports, port speeds, and supported tables
and actions.
Port Status (AM) S  C
enables the switch to inform that controller of changes to port speeds or
connectivity..
Flow Processing
Packet-In (AM) S  C
a packet was received and it didn't match any entry in the switch's flow
table, causing the packet to be sent to the controller.
Packet-Out (CSM) C  S Instructs a switch to send a packet out to one or more switch ports.
Flow-Mod (CSM) C  S instructs a switch to add a particular flow to its flow table.
Flow-Expired (CSM) S  C a flow timed out after a period of inactivity.
C: OpenFlow Controller
S: OpenFlow Switch
AM: Asynchronous Message CSM: Control/Switch Message
SM: Symmetric Message
25

26. CSED702Y: Software Defined Networking
Connection Setup
26

27. CSED702Y: Software Defined Networking
Topology Discovery
• Purpose is to construct an entire network view.
• Method is to use the Link Layer Discovery Protocol (LLDP)
LLDP
PACKET_OUT
with LLDP
PACKET_OUT
with LLDP
PACKET_IN
with LLDP
OpenFlow Controller
IDX SRC DST SRC PORT DST PORT
153 sw. A sw. B p2 p1
… … … … …
357 sw. B sw. A P1 p2
p1
p2 p1
p2
27

28. CSED702Y: Software Defined Networking
Flow Table
Actions(Instructions)
1. Forward packet to port(s)
2. Encapsulate and forward to controller
3. Drop packet
4. Send to normal processing pipeline
5. Modify Fields
6. Etc.
Switch
Port
MAC
src
MAC
dst
Ether
type
VLAN
ID
VLAN
Priority
MPLS
Label
MPLS
traffic
class
Src
IP
Dst
IP
Protocol
No. ToS
Src
TCP/UDP
port
Dst
TCP/UD
P port
Meta
data
L2L1
L3
L4
Flow Entry Match Field Counters
Action
(Instruction)
n … … …
1
Priority Timeout
Flow Table
Match Fields of OpenFlow
Cookie
Match Field= L1~L4 header information
28

29. CSED702Y: Software Defined Networking
Flow Table
• Wild card (*) means “does not matter” – not important field
29

30. CSED702Y: Software Defined Networking
Pipeline Processing
• Useful to manage complicated processing
 For example, Table 1 for VLAN processing, Table 2 for Multicast Group processing
Flow
Table 0
Instruction
/Action
Flow
Table n
Instruction
/Action
Ingress Processing
…Packet In Group
Table
Flow
Table e
Instruction
/Action
Flow
Table e+m
Instruction/Ac
tion
Egress Processing
… Packet Out
30

31. CSED702Y: Software Defined Networking
Group Table
Table 0
Instruction/
Action
Table 1
Instruction/
Action
Table n
Instruction/
Action
……
Action
Bucket
Group Table
Match Field Counters Action
Group ID Counters Action BucketsGroup Type
Dst IP= 224.2.3.9
Flow Table
Group Table
Group 100
100 all Port1 : output
Port3 : output
Port5 : output
………
• A Group Table consists of
group entries.
• The ability for a flow entry to
point to a group enables
OpenFlow to represent
additional methods of
forwarding.
• There are four group types.
• A switch is supposed to
support two compulsory group
types (other two group types
are optional to support).
31

32. CSED702Y: Software Defined Networking
Type of Group Table
Multicast
Group Type=All Group ID Group Type Counter Action Buckets
100 All 999 Port2, Port3, Port4
Group Table
Switch
Port
MAC
src
MAC dst Ether
Type
VLAN
ID
Src IP Dst IP Proto
No.
TCP S
Port
TCP D
Port
Action
* * 00:FF:.. * * * * * * * Port 6
Port 1 * * 0800 * 224… 224… 4 4566 6633
Group
100
Flow Table
2
3
4
1
32

33. CSED702Y: Software Defined Networking
Meter Table
• A meter table consists of meter entries which define per-flow meters.
• Meter Table enable OpenFlow to implement QoS operations including rate-limiting,
DiffServ etc.
• A meter measures the rate of packets assigned to it & enables controlling the rate of
those packets.
• Meters are attached directly to flow entries.
Meter ID Band Type Rate Counter Argument
100
Drop (Remark
DSCP)
1000 kbps 1000 xxx
Meter Table
Switch
Port
MAC
src
MAC dst Ether
Type
Src IP Dst IP Proto
No.
TCP S
Port
TCP D
Port
Inst.
Meter
Action
Port 1 * * * 1.2.2 * * * * N/A Port 7
Port 1 00:FF… * 0800 1.2.3 11.1… * * *
Meter
100
Port 2
Flow Table
33

34. Questions?
34