Software Defined Networking (SDN) is a new paradigm that facilitates network management and control. In our work, we explore the use of SDN for the control of network traffic on end-hosts. In particular, we use an OpenFlow software switch (OVS) to load balance application traffic across the multiple available network interfaces. A typical example is the simultaneous use of Wifi and 4G interfaces on a mobile device. In order to achieve optimal load balancing, it is critical to know the capacity of the last-hop links associated with the different interfaces. In this paper, we explore and adapt active packet probing mechanisms to the scenario of SDN-based endhost traffic control, in order to estimate the link capacity. In particular, we investigate the use of Variable Packet Size (VPS) probing, and demonstrate its viability via experiments.

1. Link Capacity Estimation in
SDN-based End-hosts
Anees Al-Najjar, Farzaneh Pakzad ,Siamak Layeghy,
and Marius Portmann
School of ITEE, The University of Queensland
Brisbane, Australia
Presented by Anees Al-Najjar
The 10th International Conference on Signal Processing and
Communication Systems, ICSPCS'2016
December 21st, 2016, The Gold Coast, Queensland, Australia

2. Paper Outline
1. Motivation
2. Background
3. Key Challenge
4. Methodology
5. Results
6. Conclusion
1

3. Motivation
 End-Hosts have multiple network interfaces
Goal:
Efficiently control the traffic in multi-interface end-hosts
(e.g. smartphones with WiFi, and 4G interfaces)
2

4. Proposed Solution
 Software Defined Networking (SDN) on the end-host
3

5. Background
What is Software Defined Networking
(SDN)?
Control Plane
Net. Device
Data Plane
Traditional Network SDN
SDN Switch Controller
SDN: it is a new paradigm in networking[1].
SDN Switch Controller
Benefits:
 Facilitate network management
 Enhance Network Efficiency
 Improve network programmability
 Empower innovation
 Reduce cost
4

6. Background
SDN Architecture
5

7.  Key idea:
Use unified interface (e.g. OpenFlow) to control
network traffic on end hosts.
SDN-based traffic control on
end-hosts
 Research Hypothesis
Using SDN-based network traffic control on end-hosts can increase network efficiency,
performance.
6

8. Load balancing
Use Case
(SDN based End-Host)
Server
GW Router
GW Router
Applications
OpenFlow Switch
SDN Controller
veth0
eth1
eth0
veth1
System Architecture
Applications
SDN Controller
veth0
eth1
eth0
OpenFlow Switch
Client
Simple Network interface load balancing[2]
In order to make optimal load balancing decisions, we need to know
the characteristics of the different links, in particular the link capacity.
8

9. Key Challenge
Measuring link parameters from end-host via
SDN, using only the OpenFlow interface.
Example of link parameters:
• Delay (transmission, propagation, jitter)
• Current flow
• Link capacity
9

10. Link Capacity Measurement
Traditional approaches [3]
1. Packet Pair/Train probing
2. Trains of Packet Pairs
3. Self-Loading Periodic Streams (SLoPS)
4. Variable Packet Size (VPS) probing [4]
Require control on both
ends of the link
Only requires control over one end
of the link.
It can be implemented via SDN
Based End-Host
10

11. How does VPS work?
 𝐶 =
𝑃𝐾𝑇 𝑠𝑖𝑧𝑒
𝑇𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑠𝑖𝑜𝑛 𝑇𝑖𝑚𝑒
 Transmission Time = RTT/2
 Assuming there is no significant queuing delay
 Assuming we can ignore processing and propagation delay
 VPS sends groups of probe packets (ICMP) with different packet size to
measure RTT
 Assumption: Packet with minimum RTT value for each packet size
has experienced no or only minor queuing delay
11

12. 1. Send n packets (ICMP packets) with different sizes x
2. Find the Minimum RTT for each packet size :
RTTx = 𝑚𝑖𝑛𝑖=1…𝑛(RTTi)
3. Calculate linear Regression based upon step 2:
4. Estimate the Capacity based upon the slope (𝛽):
∁= 2 ∗ (
1
𝛽
)
How does VPS work? (cont’d):
Y RTTx
X PKT size
α y-intercept
y = 𝛽x + α
12

13. Our Contribution:
Adapting VPS to SDN (VPS-SDN)
VPS probing has not been implemented in SDN
VPS-SDN
SDN controller
 Crafts the probing packets
 Computes the time difference (RTT) of the probing packets
13

14. Key Features of VPS-SDN
Only requires control over one side of connection
Is generic, works with all link types (e.g. WiFi, xG)
14

15. 10Mbps
Testbed
1. Two directly-connected PCs via
Ethernet
2. Link capacity is limited to 10Mbps.
3. Five Packet sizes
(64B, 128B, 256B, 512B, 1024B)
4. 20 ICMP packets per size
5. Probing packet delay 100ms
6. Total experiment time is 25s
7. No background Traffic
Results
Basic Capacity Scenario (No background traffic)
∁= 2 ∗
1
𝛽
 2 ∗ (
1
𝟎.𝟎𝟎𝟎𝟎𝟎𝟏𝟕𝟎𝟎𝟐𝟖𝟓
) =1176273 Byte  9.4
Mbps
Estimated Capacity:
15

16. Results
With varying background traffic
Backlog Queue on the client 16

17. Results
VPS-SDN with probe traffic prioritisation
Backlog Queue on the client
17

18. Conclusion
 Presented VPS-SDN, an adaption of Variable Packet Size
probing to SDN
 Implemented on end-host (client) only, without support from
network infrastructure
 Demonstrated good performance, even in case of high levels of
background traffic, due to probe traffic prioritisation
 Future work:
 Further evaluation of VPS-SDN on other links (WiFi, 4G, etc.)
 Integration of VPS-SDN for end-host based traffic load balancing [2]
18

19. References
[1] Software-defined networking: The new norm for networks. Available:
https://www.opennetworking.org/images/stories/downloads/sdn-resources/white-
papers/wp-sdn-newnorm.pdf
[2] A. Al-Najjar, S. Layeghy, and M. Portmann, “Pushing sdn to the endhost,
network load balancing using openflow,” in 2016 IEEE International Conference
on
Pervasive Computing and Communication Workshops (PerCom Workshops),
IEEE, 2016, pp. 1–6
[3] R. Prasad, C. Dovrolis, M. Murray, and K. Claffy, "Bandwidth estimation:
metrics, measurement techniques, and tools," IEEE network, vol. 17, pp. 27-35,
2003
[4] V. Jacobson, “Pathchar: A Tool to Infer Characteristics of Internet Paths,”
ftp://ftp.ee.lbl.gov/pathchar/, Apr. 1997.

21. Questions ?