With the availability of 25G and 50G switching silicon data center operators have been able to address the low latency high throughput needs of their applications in the local data center or between two fixed locations (i.e. a point-to-point connection). Outside the data center it is more challenging. The design of the Wide Area Network (WAN) consists of connections that are “nailed up” and traffic engineered. Routing protocols such as MPLS and RSVP are used to make and maintain the connections. The traffic is isolated within a particular Forwarding Equivalency Class (FEC) and is all treated the same within the class. The application does not have control. Think of traffic on a roadway where cars, trucks, and bicycles share the road. If the roadway between sites is predetermined, it is possible the car has the potential of being on the same path as the bicycle. If the car could choose it path it would avoid the path with the bicycle. If a less congested roadway existed the driver of the car would surely like to be on it.
Source Packet Routing in Networking (SPRING) is a relatively new method of routing where the source can determine the path a packet takes through the core network. It has robust traffic engineering capabilities and is designed with today’s dynamic applications in mind. Networks that are operating with RSVP-TE won’t be replaced overnight. There will be a need for some time to have RSVP-TE co-exist with SPRING as network and application engineers migrate programs to take advantage of SPRING’s traffic engineering capabilities. For an introduction to some of the challenges of adding SPRING to your network have a look at this blog written by one of our cloud architects. One way to ease the transition would be for a SPRING enabled device to communicate with a central controller, such as Juniper’s NorthStar, that is aware of both RSVP-TE and SPRING paths. The application could ask the controller for a specific path and the controller would be able to respond with a view of the actual traffic usage. The controller would know about both SPRING and RSVP-TE usage of specific paths. Using the roadway analogy again, the NorthStar controller acts as the traffic officer. It is aware of both roadways (RSVP-TE and SPRING) and receives traffic updates (telemetry). The traffic officer can advise the car the best path to choose based on what is actually going on the roadways. For more information about NorthStar and SPRING check out this short video.