It is a classic outcome of academic project on integrating SDN with Optical Network

1. 1
Abstract—Network traffic has rapid trend of growth that almost
doubles every 15-20 months. Other points of concern are cloud-
based services and mobility networks which are main cause of
unpredictability of ever increasing and dynamic traffic patterns.
On the other side the present manually configured and static
transport optical networks are woefully insufficient. Software
Defined Network enables many application-driven,
programmatic controls for packet forwarding. As we all are
aware that not all services are packet based and very rarely
network is designed with packet switches directly connecting
fibers that employs SONET/SDH circuit switching elements;
which OpenFlow does not support. This paper reviews recent
developments in Optical Transport to enable programmatic
control of optical elements.
Index Terms—OpenFlow, Packet-Optical Transport Network,
SDON.
I. INTRODUCTION
ost prominent and new Internet driven
applications are more or less cloud-
based and require an optical network
infrastructure with high capacity. For traversing
multiple network domains between remote data
centers and its users, an end-to-end high capacity
connectivity is needed. Network operators face the
challenge of delivering the application traffic in
context with the network operation while travelling
through the heterogeneous networks. Every
application sort requires its own particular system
administrations to fulfill its one of a kind
transmission capacity, quality of administration
(QoS) and dynamicity necessities. The present
specialized and operational complexities and also
CAPEX and OPEX contemplation's restrict the
capacity of system administrators to setup and
arrange committed optical system for every
application sort in an adaptable way.
Software Defined Networking (SDN), flexi
WDM grid and many more emerging optical
transport technologies is enabler of aforementioned
issues. Programmability of network functions
comes from SDN and flexi protocols also by
separating the data plane and the control plane.
These planes are vertically integrated in many
networking equipments [1]. Centrally located
component of SDN technology architecture is a
controller hosting the operating system of the
network. It extracts the hidden transport and packet
switching technology while building and displaying
a sensible guide of the whole system to
administrations or control applications programmed
on top of it. The SDN innovation permits system
administrators to control and monitor logical map of
the system and make various existing system cuts
(virtual systems) in an innovation and convention
agnostic way. Moreover, the detachment of control
plane and information plane upheld by an
intelligently unified control plane makes it a
suitable contender for a coordinated control plane
supporting different area and numerous transport
innovations.
Figure 1: SDN Architecture
Image Courtesy: [1]
OpenFlow (OF) is completely open and vendor
agnostic protocol which acts as a catalyst to
separate the control plane from data plane and
hence is treated as a suitable middle box for
Software Defined Optical Network
Ronak Vyas 100986764
ELG 5103 Optical Communications Systems Term Paper
E-mail: ronakvyas@cmail.carleton.ca
M

2. 2
realizing SDN. The fundamental functionality relies
on flow switching with potential to execute
software governed routing, applications within OF
controller and an external data path. For an optical
network running flow controller uses the protocol to
directly and safely manage forwarding plane of
network elements like switches.
OpenFlow gives a system control structure with a
typical equipment deliberation [2]. Utilizing these
asset deliberations, the concentrated controller can
arrange the condition of the switches. In spite of the
fact that the current OF convention is started from
the parcel exchanging (i.e. Ethernet), the OF based
SDN control system and augmentations OF
conventions can be considered as a sensible brought
together control plane answer for combination of
parcel and optical circuit exchanged systems.
Today, a new wave of innovation and technology
has been induced to optical systems in recent years.
A standout amongst the most encouraging
advances, giving adaptability in the inflexible
optical system is Adaptable Grid DWDM
technique. It permits allotment of a discretionary
and suitable range, as depicted in G.694.1 [3] and
adjustment configuration to an optical way as
indicated by application data transfer capacity and
QoS prerequisites considering optical physical layer
qualities, for example, weaknesses.
II. SDN OVERVIEW
The Software Defined Networking field has
brought in many features including that of agile and
cost-effective networks. If we study the architecture
carefully, we see three distinct layers being the
building block in application development; they are
accessible with the help of open APIs.
In preliminary traditional Networks, the control
plane and the information plane dwell in the same
equipment. This implies the controller – the product
that settles on the choices about how bundles are
directed through the equipment – is on the same
equipment that is really moving the parcels around.
Advanced interchanges components exist to arrange
the nearby control programming so that the system
goes about as a brought together system, however
neighborhood basic leadership is still controlled by
the neighborhood controller.
The three layers can be briefed as follows:
The Application Layer: Comprising of Cloud
orchestration, business and other SDN applications
which uses the communication services from SDN.
The interface between the Central layer and
application layer can be traversed by the
Northbound API.
The Central Layer alias the Control Layer: It is
brain working on centralizing the control
functionality that will govern the network packet
forwarding using the open interface.
The Infrastructure Layer: Comprises of several
network elements (NE) which more or less focus on
packet switching as well as forwarding.
Based on the above architecture, three key
attributes governing the network architecture are
Service Abstraction, Flexible Programming and
Logically Centralized intelligence
Service Abstraction: In a SDN system, the
business and cloud applications that expend SDN
administrations are preoccupied from the
fundamental system advancements. System gadgets
are likewise preoccupied from the SDN Control
Layer to guarantee transportability and future-
sealing of interests in system benefits, the system
programming occupant in the Control Layer.
Flexible Programming: SDN systems are
fundamentally tied with software and its usefulness,
which might be given by merchants or the system
administrators independently. Such
programmability empowers system setup to be
robotized, impacted by fast appropriation of the
cloud. By giving open APIs to applications to
connect with the system, SDN systems can
accomplish remarkable advancement what's more,
separation.
Logically Centralized Intelligence: From the
SDN design, system control is handed out from
forwarding plane utilizing an institutionalized
southbound interface: OpenFlow. By unifying
system insight, basic leadership is encouraged in
view of a worldwide (or area) perspective of the
system, instead of today's systems, which are based
on a self-sufficient framework view where hubs

3. 3
don't know about the general condition of the
system.
III. OPTICAL NETWORKS
The Optical networks could be defined as a type
of communication that makes use of the signals
which are encoded into light in order to transit
information from distinguished nodes in a
telecommunications network [4]. This type of
network works in the constrained scope of a
network specific to local-area (LAN) or sometimes
over a wide-range network (WAN), they can
traverse distance ranging from metropolitan regions
to as far as international or transoceanic distances. It
is a type of optical correspondence that depends on
optical enhancers, lasers or LEDs and wave division
multiplexing (WDM) to transmit vast amounts of
information, by large crosswise configuration over
fiber-optic links. Since it is fit for accomplishing
greatly high data transfer capacity, it is an
empowering innovation throughout today's Web
world and the correspondence organizes that
transmit most by far of all human and machine-to-
machine data.
Figure 2: Optical Network: Components
The above schematic represents optical network
components.
 OLS: Optical Line System (Centrally
located)
 OXC: Optical Cross-Connect
 PXC: Transparent Optical Cross-Connect
 Service Delivery Platform: Router, ATM,
SONET ADM
 DWDM: Dense Wavelength Division
Multiplexing
 OLS Client: Any device using OLS plug-in
to transport data.
Opaque SDH/SONET are those device who
provide extensive algorithms to detect fault or for
the notification and the recovery. But overall, the
configuration and management of present day
optical networks rely on significant human
intervention. That impacts the time consumed to
boost the revenue generating services as well as are
error prone and inefficient [5]. There are physical
tremors like fiber cuts, node failure, amplifier gain
control and many more. In order to make it reliable
the optical network started providing protection or
back up nodes, OLI synchronization and enhanced
discovery of link characteristics in general for
optical networks.
Even after the above measures were brought into
action the transport networks are still under
pressure. Huge rise in the bandwidth capacity is
growing but apparently no end in sight. Different
trend are noted in the traffic patterns which are
drifting since the indulgence of cloud services. We
haven’t perfectly transitioned to mega sized data
centers but on the other hand are facing the drastic
increase in video, image and other data usage.
In the meantime, gadget versatility and a "Web of
things" have changed where and how transfer speed
is being devoured. Self-serve, on-interest
framework, and applications in light of virtualized
process and capacity, have changed client desires of
the WAN. Usage is alterable, and the system needs
backbone to that amount of dynamism.
Conventional L2/L3 VPN administrations could
give the fundamental adaptability, but however lack
to provide the level of determinism or control that is
necessary for network to get going. High crest to-
normal and/or transient data transfer capacity
requests between specific areas needs transport
benefits that are turned up, auto adjusted, and torn
down in close constant.
Current transport systems lack to address these
client’s ever increasing requests, as they are for the
most part static and worked independently from the
customer layers and applications they serve.
Conventional transport administrations can take
weeks or months to turn up and should be
contracted for times of months or years—an
impression of the arranging and provisioning
exertion right now persevered. On account of the
long procedure to turn up new administrations,
numerous clients scratch off requests before they

4. 4
get to be operational.
IV. SERVICE CHARACTERISTICS: OPTICAL NETWORKS
Traditional Optical Network circuit or a packet
switch makes use of control structure with
centralized Network Management System (NMS)
which is flexible with modifications via additional
application interface plug-in or configurations of
application-driven resources. Flexibility of network
is determined from its physical architectural
limitations. Element Management Systems (EMS)
has been governing the age old optical network
which considerably needs Network Engineers to sit
and design the circuits and simultaneously drive the
configurations of several network elements. A few
executions of optical systems have developed to
bolster a dynamic control plane disseminated to
network components to assist the circuit outline
prepare and enhance provisioning times [7].
In order to be able to understand SDN control
paradigm in the optical networks to support several
switching and transport technologies we would need
a overview of its application specific requirements
and also service characteristics that can take
advantage in terms of bandwidth, resiliency,
connectivity from SDN control. These qualities are
must for the network to work smooth and so the
following two applications would be highlighted
were SDN paradigm can be brought into use.
 Setting up and computing the connection
path.
 Transport Virtual Private Network (tVPN).
Several applications need assurance in terms of
meeting the performance goals. As a case, an
application may require an association with ensured
transfer speed, an upper bound on restricted
deferral, low packet drops, and system security and
protection. This association might be a stream on a
bundle system, for example, a name exchanged way
(LSP) on a MPLS system, a circuit on a period
division multiplexed (TDM) system, for example,
Ethernet mapped into an optical transport system
(OTN) or synchronous optical system (SONET)
circuit, or an optical wavelength administration. The
application may likewise have time-variation
necessities, for example, high transmission capacity
request amid the day and lower data transfer
capacity prerequisites around evening time that will
require the system to powerfully adjust the
administration it accommodates the application. The
general objective is a joint enhancement of use
execution and system asset usage to boost system
adaptation and system productivity, and minimize
administration costs.
For example, without the presence of dynamic
resource allocation and considering a worst-case
usage of application the dedicated resources must
be allocated to respective application that leads to
less used resources [8]. Dynamic distribution of
assets could permit unused assets doled out to an
application or a support of be reallocated to
different applications or administrations. At long
last, certain operational situations or applications
may demand constant observation of associations
for running applications and dedicatedly executing
those applications in order to achieve the end goal
and make a move when administration targets are
not met. Various other applications at the transport
layer are system cutting whereby ways are set up
with requirements on data transfer capacity, deferral
and jitter and devoted to a customer to frame a
transport virtual private network (tVPN).
Figure 3: SDN enabled API in Network Architecture

5. 5
System slicing can happen at various layers in the
system pecking order. For example, wavelengths
might be set up and devoted to a customer. Later
TDM circuits of the customer could then be
confined to be set up over committed wavelengths
promised to the customers. Whether a optical
network adapts a SDN paradigm, a complete
distributed control plane embedded in network
components, or else a mixture relies on mix of
distinct services supported by network as well as
their requirements while taking into consideration
the trade-off between underlining paradigms.
V. OPTICAL NETWORK ARCHITECTURE
Software that are characterized for organizing
standards can be connected to a wide range of
optical transport system designs, yet the
fundamental system attributes will decide the
usage's suitability to different applications. In this
area, some key system advancements and structures
that are material to the SDN control worldview are
exhibited. The majority of the designs considered
here give an exchanging capacity that permits the
system to be reconfigured or reconstructed in view
of use layer activity requests and execution
prerequisites. Exchanging can be upheld in both the
electrical and optical areas [9]. Electrical
exchanging can be at the edge granularity for
bundle administrations, or at the time space level
for TDM circuits with ensured data transfer
capacities. TDM is for the most part characterized
by the OTN optical data unit (ODUx) principles (or
synchronous optical system guidelines) with an
inflexible data transmission progressive system, and
gives settled and ensured transmission capacity for
customer ports independent of whether movement is
available or not. The transmission that is based on
packets is the kind of approach that gives more
adaptability and better transmission capacity
granularity than with TDM. Singular parcels, rather
than altered time openings, are exchanged, and
factual varieties in data transfer capacity can be
utilized to build system use.
To make network element work in accordance
while assuring that bandwidth and some other
latency related issues are taken care; requires an
appropriate packets sequencing and scheduling
algorithm. Optical structures can be built to switch
optical fibers or ports that may contain different
channels over a wide range (> 5 THz approx.
transmission capacity) or to give wavelength
specific exchanging altered or adaptable cuts of
range. Transmission can be affected from the
transients in optical switching and also not all the
transmission paths performance be guaranteed
based on the impairments in optical fiber. A generic
switched network is needed with multiple
functionality like time slot, packet or fiber based
switch. One such architecture can be illustrated as
follows;
Figure 4: Generalized Packet/TDM/Fiber switching
A reconfigurable add/drop multiplexer
(ROADM) is typically based on wavelength
switching, and as the name suggests it can add,
drop, and even express wavelengths via node [10].
There are different add/drop structures
conceivable, from the least difficult motion-less
multiplexer to a structure that can include or drop
wavelengths without confinements on shading,
entrance/departure heading, or shading reuse from
various bearings. This is alluded to as a dreary,
directionless, and contention-less (CDC) add/drop
structure [13].
Even when there is no modification in ROADM
and amplifying hardware, we can improvise the
provisioning time by optimizing the power control

6. 6
Figure 5: ROADM with CDC based Network
algorithm as well as by establishing engineering
norms for tolerances which ultimately improvises
faster adjustment and provisioning [10].
VI. CENTRALIZED AND DISTRIBUTED CONTROL
COMPARISON
Ultimate aim of SDN is to ensure application
execution and satisfy asset needs while amplifying
system proficiency, as already examined. SDN
control systems and controllable system qualities
rely on upon the hidden system innovation. In a
network we can have a connection-oriented or a
connectionless packet service. For example, IP
routing; a connectionless packet administration can
make use of connection-oriented service but not the
other way round. As in case of connection-oriented
service, GMPLS can give transport administrations
to applications or connectionless systems. A LSP
between two endpoints may have limitations on
insurance, deferral, and data transfer capacity to
fulfill the necessities of administrations running
over it. For this situation, it gets to be judicious to
choose a way that fulfils those imperatives, set up
the way on the system, and screen it. Those
activities could be performed by the system
components in the way in an appropriated control
plane environment, or by means of a unified SDN
controller. The inclination for some methodology
could be operational in nature or all the more on a
very basic level reliant on specialized and cost
exchange offs.
Whereas if take distributed control plane,
connection setup, other attributes in terms of
connection setup (bandwidth, protection measures
and quality of service attributes say) are made
available for one of the end-points [6]. On the other
hand if there are different autonomous endpoints in
the system setting up associations in the meantime,
it is conceivable that the system may not be used in
the most ideal way. A few connections might be
more stacked than others. Join usage may likewise
be divided such that no single connection might
have the capacity to fulfill another request despite
the fact that the system is underutilized. There are
likewise situations where the administration can't be
fulfilled by a system component since it or the
system does not have the fundamental abilities to
learn or disperse pertinent topology data. Case in
point, a conveyed control plane experiences issues
in keeping up differing qualities between
progressively registered ways crosswise over
system components since the calculation of every
way is a free process. A unified controller could
address these issues on the off chance that it has the
right abilities.
In case of such application a SDN controller
should be aware with overlay network topology,
bandwidth and some other attributes like delay, and
also the dependencies among several links; say the
shared risk link group. Many topological data can
be collected and stored in form of database or as
information adapted from the network making use
of network link failures, link additions or many
such events. Delay analysis can be part of either the
database or topology information as well. For an
SDN controller, that makes use of topological data,
can now register a way on a system that could fulfill
circuit, connection or wavelength related
limitations. Also, it can better all around upgrade
the situation of associations (or circuits) on the
system as the calculation is done midway for all
rather than being conveyed where each association
(or circuit) is set up freely. In this manner,
connections could be all the more proficiently used,
prompting system cost diminishments. SDN
controller is capable enough to compute diverse
paths irrespective of them sharing the similar end

7. 7
points [13]. Hence, a centralized control which has
global knowledge of network resources and
application requirements can overcome the
shortcomings of distributed control plane.
A SDN controller equips a system with two APIs,
one for applications to demand assets from the
system and the other to bridge directly to the system
components or to an EMS that controls the system.
While brought together controllers accommodate
worldwide system advancement and coordination
among associations, they might be slower to
respond to network changes (e.g., node breakdown)
as compared to distributed control plane. This can
come from an ideal opportunity to spread the
change from the system to the SDN controller and
from the reaction time at the SDN controller, which
is possibly handling occasions or demands relating
to numerous system components, dissimilar to a
control plane processor devoted per system
component.
Figure 6: Current Optical Network
Notable fact is such that the reliability, network
events responses and scale are the driving force for
deploying multiple geographically placed CPUs
which leads to formation of a unanimous, smart and
responsive SDN control cluster. Coordination inside
of the group gets to be essential to keep up choice
centralization and profit from brought together
control. Thus, control crosswise over operational or
legitimate space limits controlled by means of
individual SDN controllers will require
correspondence among the controllers to build up
administrations that cross these areas. It is likely
that these SDN controllers will have a place with
various sellers; in this manner, between SDN
controller interoperability is likewise required [14].
These are difficulties that don't emerge in a
compelled and homogeneous environment, for
example, server farms worked by one cloud
administration supplier, yet are prone to emerge in
bigger or interconnected systems from various
administration suppliers and/or merchants.
Figure 7: Future Optical Network
While brought together SDN control can address
the coordination of utilization necessities with the
system, huge systems will in any case need to
depend on a distributed control plane to give quick
response to network issues. Compared to others,
this embedded control plane is more adaptable, and
influences adult and solid advancements that were
created to supplant early incorporated control
approaches [16]. Connectionless IP systems are a
decent illustration of genuinely disseminated
control. In particular, the centralized SDN control
approach can brings us full circle however it does
not resolve the greater part of the fundamental

8. 8
impediments of unified control. Consequently, to
actualize extensive adaptable systems that are
coupled to the application layer, it gets to be vital
that SDN-based incorporated control and
disseminated inserted control exist together on the
same system. The blend of distributed and as well
as centralized control requires cautious outline since
capacities are conveyed in view of handling
prerequisites, and a few more information
synchronization is mandatory in between the SDN
controller and the embedded control processors.
VII. SOFTWARE DEFINED OPTICAL NETWORKS
Overall till now we have seen some of service
characteristics of optical networks and also pointed
out a discussion on centralized v/s a distributed
control giving a overview of SDN. Now let us
discuss the software defined optical network.
Optical transport network has several unique
advantages when compared to IP network.
Transport network offers bigger limit. 100 Gb/s per
channel WDM framework is being conveyed
comprehensively, superchannels with 400 Gb/s or 1
Tb/s information rate have additionally been
exhibited in the field [20]. Single fiber transmission
limit has surpassed 100 Tb/s [18 -20], and can be
considerably higher through spatial division
multiplexing [20]. Also, optical circuit exchanging
can switch at much bigger granularity contrasted
with electronic bundle switch, and is more
adaptable. Also, optical circuit switch expends a
great deal less power than electronic bundle switch.
Moreover, numerous optical sign operations, for
example, joining and separating, are totally
uninvolved. Unexpectedly, the energy devoured by
packet systems is ever increasing because of the
expanding volume of traffic flow. Subsequently,
adding optical transport system to SDN will give
the system administrators with advantage of
increased scalability and capacity of network and on
the other hand reducing the power consumption.
SDN can likewise provide numerous advantages
to the optical system, particularly the adaptability.
The open interface and the partition of control and
physical equipment permit the administrators to
have more adaptability in equipment choice, shorter
time to actualize new innovations and items, more
effective and solid programmed control, and
enhanced usage of system assets. Blended line rate
framework, adaptable lattice WDM framework,
outsider wavelengths, and wavelength on-interest
can be better upheld. Analysts can directly try to
assess new advances with ease, prompting speedier
and handier developments. Ultimately this would
benefit in reduction of OPEX and CAPEX [19].
Moreover the packet exchanged SDN advances
created for IP system can't be specifically
exchanged to and executed in circuit-switched
optical transport system, in light of the fact that
these two systems have huge contrasts. For
instance, optical transport organize as of now has
brought together control however numerous system
reconfiguration errands still require manual
operation, the activity in optical system is more
static, also the switching granularity is more coarser
and rigid, and the exchanging pace gets slower by
requests of extent.
Hence, even before we march towards our
ultimate aim of completely converged cross-layer
packet-circuit hybrid SDN, an imperative step is to
firstly enhance the optical transport system by
presenting SDN-like component and adaptability.
Such optical transport system is alluded to as
software defined optical network (SDON). It has
comparable components as SDN, for example, the
system controller and the physical
transmission/exchanging framework will be
isolated; these two planes will be associated by a
typical open interface; most system control and
administration insight will live in a brought together
controller; and the physical equipment will offer
abnormal state of adaptability to bolster diverse
system requests and conditions.
It contains three principle components. The most
reduced component is the physical equipment,
including transmitter, collector, exchanging hub,
amplifiers. They are flexible with software
programming ready to perform adaptable
operations, for example, reconfigurable colorless,
contentionless (CDC) and directionless, flexible
modulation format for transmission, flexible
bandwidth switching and many more [14].
Customization and optimization of SDON is
established with the help of above mentioned
hardware components. The top component is a
smart and adaptable controller that uses the

9. 9
adaptability of physical equipment to deal with the
system and to perform Openflow based packet
optimization and customization. Diverse application
driven software can be utilized to accomplish
distinctive capacities, for example, resource
protection, restoration and as well as allocation, and
achieves energy optimization. Other than the
applications, the system controller additionally
incorporates system hypervisor, OS, debugger and
process controller-manager.
Figure 8: SDON Schematic
The above elements are connected to hardware
through interface which can be OpenFlow with
extended circuit switching capability in transport
network.
VIII. TRANSPORT NETWORK WITH OPENFLOW
Through automation and logically centralized
intelligence, OpenFlow-based Transport SDN
simplifies operators’ complex, rigid, and multi-
vendor environments and enables the introduction
of new transport network services to better
monetize the network. Until recently, the OpenFlow
standard focused on the packet-oriented Layers 2
and 3. Transport SDN extends OpenFlow to support
Layer 0 (photonic) and Layer 1 (SONET/SDH,
OTN) networks, allowing the same support for
logically centralized control and independent
software and hardware development.
Fundamentally, extensions are added to OpenFlow
to program switch ports and fabrics that operate on
fibers, wavelengths, and timeslots as well as packet
headers, while retaining the same simple model of
match and action tables across these multiple layers.
OpenFlow is rapidly prototyped to cater some
requirements addressed by the transport network
and hence the OpenFlow is extended to provide
support for link/path protection, performance
monitoring and several other critical maintenance,
administration and operations capabilities.
Finally, an important architectural improvisation
inducted is through successful introduction of
transport network virtualization giving flexibility in
portioning the physical transport network of
operator into several virtual networks and study
their optical characteristics.
IX. CONCLUSION
The drastic changes in cloud networking, optical
communication results in bandwidth peaks in order
to cater ever increasing enterprise needs. OpenFlow
based transport SDN would not only enable the
carriers to offer bandwidth as per demand but also
services to dynamically resize network connectivity
and enhance the utilization of network resources.
Optical transport SDN will speed up the streamline
operations and automation would logically
centralize the control, obviously better than the
manual order entry. Network operators would start
getting flexibility in developing their own service
models where different services are instantiated
based on connection routing algorithm. Conjunction
of photonic, packet and circuit transport resources
would enable multi layer path optimization
increasing efficiency of overall network. It will
boost multi-vendor networking while reducing the
operational and capital expenditures simultaneously
increasing the operations agility and revenue
opportunities.
ACKNOWLEDGMENT
I would like to thank Professor Dr. Trevor Hall for
his insight and approval on the project topic also for
arranging some important sessions from industrial
mentors on current trends and drift of technology.

10. 10
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