An RSVP enabled router receives an RSVP reservation message for a new RSVP path. The router is unable to accommodate the reservation request.
Which action does the router take?
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A. B. C. D.D
RSVP (Resource Reservation Protocol) is a signaling protocol used to reserve network resources for specific flows in IP networks. It allows a sender to request specific QoS (Quality of Service) guarantees from the network for its data flow. RSVP works by sending messages between the sender and the receiver, and between routers along the path of the data flow.
When an RSVP enabled router receives an RSVP reservation message for a new RSVP path, it first checks whether it has enough resources to accommodate the reservation request. If the router has enough resources, it sends a Resv message back to the sender to confirm the reservation. If the router does not have enough resources, it takes one of the following actions:
A. The router sends a ResvErr (Reservation Error) message to the upstream router. The upstream router is the router that sent the original PATH message, and it is responsible for propagating the reservation request towards the sender. The ResvErr message informs the upstream router that the downstream router is unable to accommodate the reservation request due to lack of resources.
B. The router sends a ResvErr message to the downstream router. The downstream router is the router that sent the original RESV message, and it is responsible for propagating the reservation request towards the receiver. The ResvErr message informs the downstream router that the router is unable to accommodate the reservation request.
C. The router sends a ResvTear (Reservation Teardown) message to the upstream router. The ResvTear message is used to tear down an existing reservation request. If the router is unable to accommodate the reservation request, it may send a ResvTear message to tear down the reservation request and free up resources.
D. The router sends a ResvTear message to the downstream router. Similar to option C, the ResvTear message is used to tear down an existing reservation request. If the router is unable to accommodate the reservation request, it may send a ResvTear message to tear down the reservation request and free up resources.
In summary, when an RSVP enabled router is unable to accommodate an RSVP reservation request, it may send a ResvErr message to inform the upstream or downstream router, or it may send a ResvTear message to tear down the existing reservation request. The specific action taken depends on the network topology and the RSVP implementation.