2. Problems
Recently, it is difficult to make real-world impact on network
innovation.
Due to:
Enormous base of equipment
Cisco’s annual sale in 2015 is $49.16 Billion
Many kinds of protocols
Total number of RFCs > 7,400
Reluctance to experiment with production traffic
Thus, there is almost no practical way to experiment with new network
protocols in realistic network environment.
3. Solution:
SDN(Software Defined Networking)
GENI: A researcher will be allocated a slice of resources
across the WHOLE network
However, plans for nationwide like GENI are ambitious, costly, and they
take years to be deployed.
PC with several network interfaces and Operating System
But PC’s performance is less than satisfying, comparing to wiring closet:
PC College Wiring Closet
Packet processing rate 1Gb/s 100Gb/s
Number of ports ~10 ~100
4. Solution: OpenFlow
Enabling researchers to run experimental protocols in the
campus networks we use every day.
Which means:
Take less time to deploy(compare to large scale SDNs like GENI)
Acceptable cost
In short, realistic.
5. OpenFlow: Goals
High performance/cost ratio
Capable of supporting a broad range of research
Isolation of production traffic and experimental traffic
Consistent with vendors’ need for closed platforms
6. OpenFlow switch: meets all 4 goals
An OpenFlow switch consists of at
least three parts:
1. A Flow Table, used to instruct the
switch how to process the flow.
2. A Secure Channel, used to connect the
switch to a remote control process(called
Controller) using
3. The OpenFlow Protocol, which
provides an open and standard way for a
controller to communicate with a switch.
7. OpenFlow: concept explained
OpenFlow decouples
data plane & control
plane inside the switch,
and allows control
plane to exist outside of
the switch. This
external control plane
is controller.
Youtube Explanation
8. OpenFlow: What is flow?
Flow is broadly defined, for example:
A TCP connection
All packets with the same VLAN tag
All packets from the same switch port
Etc…
In general, you can define flow by yourself.
9. OpenFlow: Flow Table of OpenFlow switch
An entry in the Flow Table contains three fields:
1. A packet header that defines the flow.
2. The action, which defines how the packets should be processed.
3. Statistics, which keep track of the number of packets and bytes for
each flow.
10. OpenFlow: Actions on Flows by
OpenFlow switches
1. Forward this flow’s packets to a given port.
This action allows packets to be routed.
2. Encapsulate and forward this flow’s packets to a controller.
This action allows controller to decide whether the flow should be added to the Flow
Table.
3. Drop this flow’s packets.
This action can be used for security reasons, etc.
4. Optional: Forward this flow’s packets through the switch’s
normal processing pipeline.
This action allows experimental traffic to be isolated from production traffic.
Alternatively, isolation can be achieved through defining separate sets of VLANs.
We can also treat OpenFlow as generalization of VLAN!
11. OpenFlow: Upgrade to current devices
Flow Table will re-use existing hardware, such as
TCAMs(ternary content-addressable memory) used in modern
switches and routers.
Secure Channel and OpenFlow Protocol will be supported
through devices’ operating system ugrade.
12. OpenFlow Example: New Data Center
(from OpenFlow.org)
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
13. OpenFlow: Summary
OpenFlow is a pragmatic compromise that allows researchers
to run experiments on heterogeneous switches and routers.
14. OpenFlow: Discussion
How about reliability of OpenFlow?
Controller: Single point of failure
How about scalability of OpenFlow?
Flow table: How many flows can it handle?
How secure is OpenFlow?
Attacks are possible
