Routing – If routing protocol in physical routers in SDN network

This is a nice idea. We are using Floodlight for our SDN experiments. At the point in time we started, it was much more mature than the OpenDaylight software. As this has been more than a year ago, it might not be true anymore.

SDN offers you the following features that should be helpful to your use case:

• Link parameter measurements to find such paths:
  • Delay by using customly crafted probe packets and correlate timestamps
  • Loss can be done by sampling the port statistics
  • Bandwidth is still something we are working on
• As you are implementing reactive routing, you are most likely going to react on the packet_in event. In this case, you have two options:
  • Simple: use the transport protocol and port to deduce the app
  • Difficult: do some kind of deep-packet inspection to deduce the traffic type

First note that all of these technical terms are subject to distortion by Marketing, so sometimes you have to read between the lines.

The term switch refers to a layer-2 device, so it is forwarding on layer-2 info. On an Ethernet this would be the 48 bit MAC. With MPLS it would be the Label. The term router officially refers to a layer-3 device, so it is forwarding on layer-3 info (the 32/128 bit IPv[46] address, unless you have a very strange network). That's the primary difference between the terms.

How each device actually implements that forwarding is partly controlled by the protocols defined to exchange the relevant data, and the engineering choices made by the device designer, and is mostly opaque to the outside. So, to get more detail on how a particular product does it's thing, you need to get more detail from the manufacturer than the legal department wants them to divulge, so under NDA (Non-Disclosure Agreement). Unless the device you care about is just a general purpose computer running Free or Open Source Software, in which case, you look at the source.