IEEE Network - March / April 2017 - page 60

IEEE Network • March/April 2017
58
0890-8044/17/$25.00 © 2017 IEEE
A
bstract
Software-defined networking separates the
control and forwarding planes of a network
to make it more programmable and applica-
tion-aware. As one of the initial implementations
of SDN, OpenFlow abstracts a forwarding device
as a flow table and realizes flow processing by
applying the “match-and-act” principle. Howev-
er, the protocol-dependent nature of OpenFlow
still limits the programmability of the forwarding
plane. Hence, in this article, we discuss how to
leverage protocol-oblivious forwarding (POF)
to further enhance the network programmabil-
ity such that the forwarding plane becomes
protocol-independent and can be dynamically
reprogrammed to support new protocol stacks
seamlessly. We first review the development of
OpenFlow and explain the motivations for intro-
ducing POF. Then we explain the working prin-
ciple of POF, discuss our efforts on realizing the
POF development ecosystem, and show our
implementation of POF-based source routing as
a novel use case. Finally, we elaborate on the first
WAN-based POF network testbed that includes
POF switches located in two cities in China.
I
ntroduction
Over the past decade, the Internet's rapid devel-
opment has pushed the scales of end users, net-
working applications, and network elements to
grow exponentially. Meanwhile, due to the com-
petitive tussle among different stakeholders, the
network architecture has become more and more
complicated, brought to “ossification.” Conse-
quently, the introduction of new protocols and
services can be slowed down and even impeded.
In response to these issues, software-defined net-
working (SDN) has emerged as a new paradigm
to change how the Internet operates [1]. Specif-
ically, SDN separates the control and forwarding
planes of a network, and leverages centralized
network control and management (NC&M) to
make it more programmable, flexible and applica-
tion-aware. Therefore, new networking protocols
and services can easily be developed with the for-
warding plane abstraction provided by the control
plane.
As one of the initial implementations of SDN,
OpenFlow [2] provides a powerful tool set for
network operators to program and manage their
networks adaptively [3]. However, its protocol-de-
pendent nature still limits the programmability
of the forwarding plane. Specifically, OpenFlow
defines the matching fields in flow tables accord-
ing to existing network protocols (e.g., Ethernet
and IP). Therefore, OpenFlow switches need to
understand the protocol headers to parse pack-
ets and perform flow matching, which may cause
serious compatibility issues when new protocols
try to add or remove header fields. Hence, it is
desirable that the network programmability can
be further enhanced such that the forwarding
plane is protocol-independent and can be dynam-
ically reprogrammed to support new protocol
stacks seamlessly. Following this idea, recent stud-
ies have proposed a few new SDN technologies,
such as protocol-oblivious forwarding (POF) [4]
and programming protocol-independent packet
processors (P4) [5]. The basic idea behind POF
and P4 are similar, as they both try to decouple
network protocols from packet forwarding and
make the forwarding plane reconfigurable, pro-
grammable, and future-proof.
More specifically, POF introduces a proto-
col-independent instruction set, which allows a
network operator to define the protocol stack
and packet processing procedure in a much more
flexible manner than that in the current Open-
Flow specifications, while P4 designs a high-level
language to program an SDN switch more flexi-
bly for protocol innovations. As POF defines the
southbound interface that can be treated as a
promising enhanced version of OpenFlow, we
consider it in this work and try to demonstrate
that network innovations can easily be realized
with it.
This article discusses how to enhance the pro-
grammability of forwarding plane in SDN with
POF. We first review the development of Open-
Flow and explain the motivations for introduc-
ing POF. Then we discuss our efforts on realizing
the POF development ecosystem, and show our
implementation of POF-based source routing as a
novel use case. Our work to build the first WAN-
based POF network testbed, which includes POF
switches located in two cities in China, is also pre-
sented. Finally, we summarize the article.
R
eview
of
O
pen
F
low
Since its inception, OpenFlow has used a proto-
col-dependent forwarding plane. Specifically, the
evolution of OpenFlow specification takes a reac-
tive approach instead of a proactive one, that is,
all the matching fields and actions are defined
based on existing protocols. This means that we
have to update the matching fields and corre-
sponding actions constantly as it becomes more
Protocol Oblivious Forwarding: Software-Defined Networking with Enhanced
Programmability
Shengru Li, Daoyun Hu, Wenjian Fang, Shoujiang Ma, Cen Chen, Huibai Huang, and Zuqing Zhu
The authors are with the
University of Science and
Technology of China.
ACCEPTED FROM OPEN CALL
Digital Object Identifier:
10.1109/MNET.2017.1600030NM
1...,50,51,52,53,54,55,56,57,58,59 61,62,63,64,65,66,67,68,69,70,...100
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