The OCSA exam tests your understanding of components in an SDN framework, your ability to articulate the fundamental workings of networking and the OpenFlow protocol, as well as your knowledge of vendors, solutions and projects available in the SDN landscape.
This is the third part in a series of posts that review the blueprint for the OCSA exam and provide descriptions and resources to help you achieve the certification. The posts are broken down by the sections detailed in the OCSA blueprint.
Domain 3: OpenFlow®
From the Blueprint:
Identify at a concept/definition level the OpenFlow® Protocol operations and list the packet types and contents.
- TCP level secure channel/communication/session establishment between controller/switch
- Message Types
- Basic Operation/Packet Matching
- Differences between OpenFlow® versions
- Proactive vs Reactive Flows
- Setting up a flow
- Policy Enforcement
- OpenFlow® Management and Configuration Protocol (OF-Config, OAM, OFDPA, OVSDB, etc.)
- Flow Table Entry Format
- Flow Timers
- Pipeline Processing
- Match Types
- Match Actions
Below are the study resources I followed when learning OpenFlow.
Read the OpenFlow Switch Specification
The OpenFlow Switch Specification document details almost everything required to understand in this section. It’s a critical source for your success in obtaining the OCSA Certification.
I cannot stress this enough — you need to read through this document! I go over some of the base concepts and theories in a previous post.
Read the OF-CONFIG 1.2 Documentation
The OF-CONFIG 1.2 document is relatively short and easy to read through. You probably won’t be asked any excruciating detail, but you need to understand that OpenFlow Config (OF-CONFIG) can be used between either the controller or some other management server, to make configuration changes on an OpenFlow-enabled switch.
The OpenFlow protocol will be used for instantiating flows, but OF-CONFIG could be used for instantiating interfaces like VXLAN, or for making system configuration changes such as port up/down. It’s based on NETCONF and uses XML data models, with defined models for YANG.
Build a lab
It’s very easy to get started on a small OpenFlow lab running entirely on your laptop. All you need is Mininet and a controller of your choice (e.g. OpenDaylight), and you’re in business. Alternatively, download the Floodlight VM by Big Switch Networks, which includes everything you need for a full education rig.
There are tons of great articles out there showing you how to set this up, such as Brian Linkletter’s blog.
If you’re looking for guided education, I recommend the GNS3 SDN & OpenFlow Course by David Bombal. There is a fee associated, but the content is solid in respect to OCSA.
Take a visit to ONF’s site and check out their list of approved training vendors.
Don’t forget to review my last blog post as well, which briefly covers some of these topics.
Continue on to Part 4 of this series which covers Domain 4 of the blueprint.