Topology and Flow Management in
Multi-Controller OpenFlow Networks
Dr. Te-Lung Liu
Research Fellow
NCHC, NARLabs
Multi-Controller OpenFlow Networks
• OpenFlow differs from traditional networks by separating
Control and Data Path
– Openflow controller has global view of the network for
software-controlled routing decisions
– Routing protocols that periodically exchange information
among network devices are no longer needed
– Routing decisions are fast and accurate (no convergence time
and hop-by-hop decisions)
• However, only single controller scenario is available
currently
– For large-scale network or inter-DC environment, single
controller poses performance problem
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Multi-Controller OpenFlow Networks
• Multi-controller scenario would be a proper solution for
large-scale OpenFlow networks
– But OpenFlow lacks of inter-controller communication mechanisms
– Controllers decide routes in its own domain separately
• Inter-controller flow could be made by connecting partial
flows provisioned by controllers of each domain
– Lack of global view for inter-controller flows
– Difficult to support QoS or SLA functions across controllers
• Inter-domain topology auto-discovery is required for multicontroller management
– We modify the LLDP and BDDP so that both NOX and Floodlight can
discover each other
• Moreover, we can trace realtime host-to-host flows with
global information
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TWAREN OpenFlow Testbed in 2010
NOX
NCHC
OpenFlow
Switch
OpenFlow
Network
@KUAS
iGENI
Capsulator
TWAREN
L3
Network
Capsulator
Capsulator
OpenFlow
Network
@NCKU
NCKU and KUAS are pilot universities that connected with the Testbed
The OpenFlow Testbed is extended to iGENI@iCAIR
Capsulator (Ethernet-in-IP tunnel) is used to emulate pure L2 network for OpenFlow
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TWAREN OpenFlow Testbed now
NCTU
NCU
NIU
OpenFlow
Switch
OpenFlow
Switch
Capsulator
NARLabs/NCHC
OpenFlow
Switch
OpenFlow
Switch
TWAREN
VPLS
NCKU
KUAS
OpenFlow
Switch
OpenFlow
Switch
NTUST
OpenFlow
Switch
OpenFlow
Switch
Capsulator
CHT-TL
OpenFlow
Switch
SURFnet
Capsulator
NTUST, NCU, NIU, NCTU and CHT-TL joined the Testbed.
For TWAREN connectors (NCTU, NCKU, KUAS and NCU), a dedicated VPLS
VLAN is allocated for better transmission performance.
Extended International connections with JGN-X and SURFnet
OpenFlow
Switch
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VLAN Setup for OpenFlow
NCU
OF-SW
iCAIR-Chicago
NCU-7609V
Vlan 560
CHI-15454
NCTU
OF-SW
KUAS
Vlan 555
(Q-in-Q)
Vlan 1555
OF-SW
KUAS
Router
Vlan 2782
OF-SW
Vlan 563
NCTU-7609V
TWAREN
VPLS VPN
TWAREN
Vlan
2782
International
Lightpath
NSYSU-7609V
Vlan 548
(Q-in-Q)
NCKU
Vlan 2782
Vlan 1548
TN-15454
OF-SW
NCKU-7609P NCKU-7609V
Capsulator
NTUST
Vlan 2782
CHT-TL
Trunk
Trunk
TN-7609V
TN-7609P
OF-SW
NARL/NCHC
OF-SW
OF-SW
Capsulator
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iGENI - Taiwan Integrated Research Network
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Inter-Domain Topology Discovery (I)


OpenFlow Controller just only knows its directly connected
switches.
ENVI is a useful GUI tool to show OpenFlow topology under
single controller.
OFA
OFB
OFC
OFD
Controller1
Controller2
Topology of Domain1
Topology of Domain2
Domain
UI
OFA
OFB
OFC
OFD
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Inter-Domain Topology Discovery (II)


We add additional contents in LLDP (Link Layer Discovery
Protocol) packet to let Controllers have its neighbors’
connectivity details.
ENVI is also modified to show the whole topology.
OFA
OFB
OFC
Controller1
OFD
Controller2
Domain
UI
Topology of Domain1 & 2
OFA
OFB
OFC
OFD
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Inter-Domain ENVI Flow Viewer(IEFV)
ENVI
The function of I.E.F.V are as follows:
1.It can display Flow, Flow number, and Flow information.
2.It can support multi-connection to communication with all NOXs.
3.It can get all topology information to display Inter-domain nodes.
4.It cans how IP address of NOX controlling this node
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Our modification
＊Our modifications are marked
in red color.
CL A
CL B
4. Reply new topology
information (includung
other inter-domain NOXes)
NOX1
3. Request topology
information from NOX
input by user
1. CLA send flow
NOX2
CL B(client)
OF
s/w 2
2. Set new topology and
client position
OF S/W1
CL A(client)
OF
s/w 1
5. Request topology
information from next
NOX
7. Merge all topology messages
and show it
I.E.F.V
2. Set new topology and
client position
OF S/W2
OF
s/w 1
OF
s/w 2
CL A
CL B
6. Reply new topology
information
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Sample Topology
Flow1
Flow2
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Results
The digits indicate the number
of flows over the link
NOX2
Domain
NOX1
Domain
NOX3
Domain
When mouse moves over
the link, this panel shows
the flow information over
this link.
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SC13 Demo
NTUST
CHT-TL
SurfNet
iCAIR
NCU
North Part
NARLabs/NCHC
NIU
NCTU
NARLabs/NCHC
JGNX
NCKU
South Part
North Part Topology
SurfNet
NTUST
iCAIR
CHT-TL
NARLabs/NCHC
South Part Topology
NIU
NCU
NCTU
JGNX
NCKU
NARLabs/NCHC
The flow information
will be shown here
When
clicking
these flows
The Host-to-host
path of selected
flow is highlighted
Conclusion
• For large-scale OpenFlow networks and
collaborations among different research institutes or
countries, multi-controller scenario is well-suited
• Our modifications to NOX/ENVI could discover
network topology automatically and provide realtime flow observation over mutli-controller
networks.
• We will continue to explore Inter-domain
management and other functions (e.g. IPv6) to
support the testbed maintenance
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SDN Developing Trends
Industry Trends…
App
App
App
Windows
Windows
Windows
(OS)
(OS)
(OS)
Linux
Linux
Linux
App
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Mac
Mac
Mac
OS
OS
OS
Virtualization layer
x86
(Computer)
Computer Industry
Controller11
NOX
Controller
(Network OS)
Controller
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Network
OS
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Virtualization or “Slicing”
OpenFlow
Network Industry
Slide from Nick McKeown@Stanford
From:”Shougaku Ninensei” Magazine
Issue on Jan. 1979
Thank You !
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