SDN Software Defined Networks

CS457 Fall 2014

SDN

�  The SDN lectures were based on proprietary slides generously made available to us by the authors of the SDN book by Goransson and Black. In respect for their copyright, the slides cannot be posted.

�  Students who did not attend the live lectures will have to view the video lectures to get an overview of SDN. SDN will be covered in the final exam.

�  Only a brief summary is given in these slides.

SDN Motivation

�  Despite the evolution of network, applications, and cloud computing, we are still using networking technologies defined in the 1990s.

�  These technologies are not efficient in many environments, especially large data centers.

�  Some of the problems include long convergence time and the inability to use blocked links due to spanning trees.

�  Other problems include the inability to expand beyond 4096 VLANs, overflowing switch MAC tables in large data centers, and inefficient traffic flow.

�  There is an opportunity to perform traffic engineering to prioritize large data migrations across data centers. See the article on Google’s Data Center on the CS457 web page.

SDN Definition

�  Separate data and control plane

�  Move control plane to a centralized point. Routing decisions are no longer performed across distributed systems.

�  Architecture: network operating system, a suite of network applications, communication between central controller and devices using OpenFlow API.

�  Other components include network virtualization, overlays and tunnels.

SDN Implementation

�  #1: OpenFlow and “pure SDN” �  Note: OpenFlow protocol was not discussed in class,

but the general idea was given.

�  #2: SDN by APIs �  Provide an API on top of existing switch configuration

mechanisms

�  Hybrid implementation; partial HW, partial SW

�  #3: SDN via OVERLAYS �  Completely virtualized networks �  Independent of equipment

SDN Use Cases

�  Data Center �  Needs for agility, resiliency, traffic engineering and

multi-tenancy

�  WAN/Backbone �  Optimal path calculation; failover; follow-the-sun,

bandwidth-on-demand

�  Campus �  Access control, BYOD (bring your own device)

�  Security

SDN Related Technologies

�  OpenStack �  Cloud Operating System for controlling large pools of

compute, storage, and networking resources in a datacenter.

�  Neutron �  Network as a Service �  Can take advantage of SDN

�  NFV (Network Functions Virtualization �  “devices on a stick” (e.g. “firewall on a stick”)

SDN Criticisms

�  Too much change, too risky, too expensive, etc.

�  Single Point of Failure �  Therefore need: Failover controller

�  Performance and Scalability �  Therefore need: Hierarchical set of controllers

�  Deep Packet Inspection �  Don’t have a scalable solution yet

�  Stateful Awareness �  Don’t have a solution yet