Resource Reservation Protocol (RSVP) and Constraint-Based Routing (CBR) are advanced traffic engineering techniques used in computer networking to control network traffic flows and provide Quality of Service (QoS) guarantees for network applications.
RSVP is a signaling protocol that is used by network devices to request and reserve the necessary network resources to support a specific traffic flow. RSVP works by sending messages known as RSVP PATH and RSVP RESV messages to the devices along the path of a traffic flow. The RSVP PATH message is used to request the necessary network resources, while the RSVP RESV message is used to reserve the resources requested by the PATH message. These messages propagate through the network to all devices that are along the path of the traffic flow. The devices that receive the RSVP PATH message reserve the necessary network resources and respond with a RSVP RESV message indicating that the resources have been successfully reserved.
CBR is a routing technique that ensures that the traffic flows along a particular path of the network that meets certain constraints or requirements. CBR works by using a path computation algorithm that computes a path for each traffic flow that satisfies the constraints specified by the QoS requirements of the application. These constraints can include things like bandwidth requirements, delay requirements, or jitter requirements. Once the path computation algorithm has computed the path for the traffic flow, the network devices use the RSVP protocol to reserve the necessary resources for that path.
Here’s an example of how RSVP and CBR could be used together to provide QoS guarantees for a video streaming application. Let’s say that a user is streaming a high-definition video on their computer. The video stream requires a minimum bandwidth of 10 Mbps and must be delivered with less than 100 ms of delay. The network administrator has configured the network to use CBR to calculate the optimal path for the video stream based on the QoS requirements. The CBR algorithm calculates a path that satisfies the requirements, and the network devices use the RSVP protocol to reserve the necessary resources to support the video stream. As a result, the video stream is delivered to the user with the required bandwidth and delay guarantees, providing a high-quality viewing experience. If the network resources become congested, the RSVP protocol can dynamically adjust the resource reservation to ensure that the QoS requirements for the video stream are still satisfied.