Transcript Presentation - Roberto Bifulco

POSITION PAPER
Reactive Logic in Software-Defined Networking:
Accounting for the Limitations of the Switches
Roberto Bifulco, Maurizio Dusi
[email protected]
NEC Laboratories Europe
Equations
OpenFlow = SDN
SDN != OpenFlow
…but today we speak of
SDN using OpenFlow as
concrete example
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OpenFlow operations: reactive logic
Controller
flow_mod
L3_SCR: 10.2.54.1
L3_DST: 112.45.54.176
L4_SRC: 5433
L4_DST: 80
…
packet_in
L3_SCR: 10.2.54.1
L3_DST: 112.45.54.176
L4_SRC: 5433
L4_DST: 80
Forwarding
Element
L3_SRC
L3_DST
L4_SRC
L4_DST
Any
112/8
Any
Any
…
Action
Fwd-to: 2
3
1
2
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OpenFlow operations: reactive logic
Controller
flow_mod
L3_SCR: 10.2.54.1
L3_DST: 112.45.54.176
L4_SRC: 5433
L4_DST: 80
…
packet_in
L3_SCR: 10.2.54.1
L3_DST: 112.45.54.176
L4_SRC: 5433
L4_DST: 80
Forwarding
Element
L3_SRC
L3_DST
L4_SRC
L4_DST
Any
112/8
Any
Any
…
Action
Fwd-to: 2
3
1
2
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OpenFlow network
▌ The abstraction process hides the switches details
▌ But not all the switches are the same
 Current controller’s view is different from reality
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OpenFlow network
▌ The abstraction process hides the switches details
▌ But not all the switches are the same
 Current controller’s view is different from reality
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Flow Table Update Rate
▌ Current controllers ignore this bit of information
▌ Switches have very different performance*
1 order of magnitude
2 orders of magnitude
Data taken from:
-Danny Yuxing Huang, Kenneth Yocum, and Alex C. Snoeren. 2013. High-fidelity switch models for software-defined network emulation. In Proceedings of the second ACM SIGCOMM
workshop on Hot topics in software defined networking (HotSDN '13). ACM, New York, NY, USA, 43-48. DOI=10.1145/2491185.2491188 http://doi.acm.org/10.1145/2491185.2491188
-Andrew R. Curtis, Jeffrey C. Mogul, Jean Tourrilhes, Praveen Yalagandula, Puneet Sharma, and Sujata Banerjee. 2011. DevoFlow: scaling flow management for high-performance networks.
In Proceedings of the ACM SIGCOMM 2011 conference (SIGCOMM '11). ACM, New York, NY, USA, 254-265. DOI=10.1145/2018436.2018466 http://doi.acm.org/10.1145/2018436.2018466
-
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A practical example
10 +30/100
10 + 30/50
10 + 30/100
30
15/15
15/15
60
10 + 60/100
50/50
10 +50 + 15/100
10 missing
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10 + 50/ 60
Maximum number of flows
▌ Shortest path: 50
▌ Actual network’s physical limit: 100
50
100 and
100
100switches’
Taking
into account
limitations
differences can improve the network
performance and/or reduce the switch
resources requirements
100
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50
100
Why a reactive logic reacts?
▌ Packet_ins and flow_mods are generated in response to network
events
 Dependent on network traffic
▌ Network traffic is usually taken into account to drive data plane
optimizations
 What about the impact on control plane?
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Understanding switch requirements
▌ Switch simulator
 Based on the reactive OpenFlow model
 Flow entry definition is configurable
 Input:
• traffic trace
 Output:
• number of packet_in, flow_mod per second
• number of flow entries in the flow table per second
▌ Simplified controller model:
 Only packet_in and flow_mod interactions
 The same flow entry definition is applied for all the incoming flows
• E.g., flow entry is defined by the destination IP address/32 and idle timeout
is 10 seconds.
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Results on a real packet trace*
▌ Flow definition based on the destination IP address
 E.g., ACL-like network application
▌ Varying idle timeout value
This flow definition cannot
be used with current
switches technology
*MAWI Working Group Traffic Archive – Trace from Apr 4th 2013. http://mawi.wide.ad.jp/mawi/samplepoint-F/2013/201304041400.html.
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Results on a real packet trace*
2 orders of magnitude
*MAWI Working Group Traffic Archive – Trace from Apr 4th 2013. http://mawi.wide.ad.jp/mawi/samplepoint-F/2013/201304041400.html.
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How to handle the control plane load?
▌ If the control plane takes into account:
 switches’ limitations (E.g., max number of flow_mods per second)
 switches’ load (E.g., current number of handled flow_mods per
second)
▌ Then, we envision the following Solutions:
 Enhanced routing/control algorithms
 Switch enhancements
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How to handle the control plane load?
▌ If the control plane takes into account:
 switches’ limitations (E.g., max number of flow_mods per second)
 switches’ load (E.g., current number of handled flow_mods per
second)
▌ Then, we envision the following Solutions:
 Enhanced routing/control algorithms
 Switch enhancements
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Example: Hybrid switch design
▌ Software switch:
 Fast in handling control messages
 Slow in handling packet forwarding
▌ Hardware switch:
 Slow in handling control messages
 Fast in handling packet forwarding
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Software
Hardware
Summary…
▌ OpenFlow abstractions hide important switches’ properties
 E.g., the switches performance in handling control messages;
▌ Exploiting this information can help in improving the network
performance and can enable new applications.
 It enables a more reactive control logic;
▌ Understanding control plane workloads for different applications
and different networks is critical for reactive control plane design
 What is causing switches overloading and when/for how long?
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…and future work
▌ Measuring control plane workloads in real scenarios
 Preliminary work already published*
 Assessing reactive logic effects on the network flows performance
▌ Combining switching technologies to overcome current technology
limitations
 Smart combination of software and hardware
 Exploiting traffic properties to enhance SDN switches performance
▌ Improving/Rethinking SDN abstractions
*Reactive Logic in Software-Defined Networking: Measuring Flow-Table Requirements
M. Dusi, R. Bifulco (NEC), F. Gringoli (University of Brescia), F. Schneider (NEC)
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