INTRODUCTION TO SOFTWARE

DEFINED NETWORKING

PRASANNA A
Traditional Networking
• Networking has always been very traditional. We have specific network devices like
routers, switches, and firewalls that are used for specific tasks.
• A network device, for example, a router has different functions that it has to perform.
Think for a moment about some of the things that a router has to do in order to forward
an IP packet:
• It has to check the destination IP address in the routing table in order to figure out where
to forward the IP packet to.
• Routing protocols like OSPF, EIGRP or BGP are required to learn networks that are
installed in the routing table.
• It has to use ARP to figure out the destination MAC address of the next hop or
destination and change the destination MAC address in the Ethernet frame.
• The TTL (Time to Live) in the IP packet has to be decreased by 1 and the IP header
checksum has to be recalculated.
• The Ethernet frame checksum has to be recalculated.
Limitations of traditional
networking
Difficult to perform real world experiments on large scale production
networks.
•Research stagnation-huge costly equipment to be procured and networks to
be setup by each team for research
•Networks have remained the same for many years. Rate of innovation in
networks is slower as protocols are defined in isolation-lack of high level
abstraction.
Closed systemsHard to collaborate meaningfully due to lack of standard open
interfaces.
•Vendors starting to open-up but not meaningfully.
•Innovation is limited to vendor/vendor partners
•Huge barriers for new ideas in networking.
SDN

Software-defined networking
(SDN) is an architecture that
abstracts different,
distinguishable layers of a
network to make networks
agile and flexible. The goal of
SDN is to improve network
control by enabling enterprises
and service providers to
respond quickly to changing
business requirements.
• Data Plane: processing and delivery of packets Based on state in routers
and endpoints E.g., IP, TCP, Ethernet, etc.
• Control Plane: establishing the state in routers Determines how and
where packets are forwarded Routing, traffic engineering, firewall state.
• Separate control plane and data plane entities
• Have programmable data planes-maintain, control and program data
plane from a central entity i.e. control plane software called controller.
• An architecture to control not just a networking device but an entire
network.
NEED FOR SDN

• Facilitate innovation in network.

• Infrastructure layer: it is the foundation layer consists of both physical and virtual
network devices such as switches and routers. All the network devices will
implement OpenFlow protocol to implement traffic forwarding rules.
• Control layer: This layer consists of a centralized control plane that is decoupled
from the physical infrastructure to provide centralized global view to entire
network. The layer will use OpenFlow protocol to communicate with below layer
i.e. infrastructure layer.
• Application layer: it consists of network services, application and orchestration
tools that are used to interact with control layer. It provide an open interface to
communicate with other layers in the architecture.
OPENFLOW PROTOCOL
• OPENFLOW is an open API that provides a standard interface for programming
the data plane switches. It is a protocol for remotely controlling the forwarding
table of a switch or router and is one element of SDN.
• It is implemented on Ethernet switches to allow the forwarding plane i.e.
data plane to be managed by a controller present on control plain in SDN
architecture.
• OpenFlow based controllers will discover and maintain an inventory of all
the links in the network and then will create and store all possible paths in
entire network.
• OpenFlow protocol can instruct switches and routers to direct the traffic by
providing software-based access to flow tables that can be used to quickly
change the network layout and traffic flows as per users requirements.
OPENFLOW SWITCH AND
CONTROLLER
• An OpenFlow Switch contain one or more flow tables that implement packet
lookups and forwarding, and an OpenFlow channel to link to an external
controller.
• The switch interconnects with the controller and the controller directs the switch
using the OpenFlow protocol.
• The controller can delete, add or update flow entries in flow tables existing in
the switch, both reactively i.e. in response to packets or proactively, using the
OpenFlow protocol.
• Controller make this decision based on policies set by . administrator or
depending on the conditions of the network and the decision it makes is
forwarded to flow table entries of all the switches in the network.
CURRENT STATUS OF SDN
• Google built hardware and software based on the OpenFlow
protocol
• VMware purchased Nicira for $1.26 billion in 2012
• IBM, HP, NEC, Cisco and Juniper also are offering SDNS
that may incorporate Open Flow, but also have other elements
that are specific to that vendor and their gear.
CHALLENGES OF SDN
• Security
Security is both a benefit and a concern with SDN technology. The centralized SDN controller presents a
single point of failure and, if targeted by an attacker, can prove detrimental to the network.
• Unclear definition
Another challenge with SDN is the industry really has no established definition of software-defined
networking. Different vendors offer various approaches to SDN, ranging from hardware-centric models
and virtualization platforms to hyper-converged networking designs and controllerless methods.
• Market confusion
Some networking initiatives are often mistaken for SDN, including white box networking, network
disaggregation, network automation and programmable networking. While SDN can benefit and work with
these technologies and processes, it remains a separate technology.
• Slow adoption and costs
SDN technology emerged with a lot of hype around 2011 when it was introduced alongside the OpenFlow
protocol. Since then, adoption has been relatively slow, especially among enterprises that have smaller
networks and fewer resources. Many enterprises cite the cost of SDN deployment to be a deterring factor.
FUTURE SCOPE
• In future, networking will rely more on software to pick up the pace
the innovations in networks.
• SDN can transform today's static networks into more flexible,
programmable platforms to provide scalability to support large data
centers.
• It will also provide virtualization that is needed to support
automated, dynamic and secure cloud environment.Mostly
implementations of newly proposed systems, frameworks, or
applications