Juniper Networks Certified Internet Specialist (JNCIS) Exam: RSVP Messages for Establishing New LSPs

Juniper Networks Certified Internet Specialist (JNCIS) Exam: RSVP Messages

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Question

Which two RSVP messages are used to establish a new LSP? (Choose two.)

Answers

Explanations

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A. B. C. D.

AC

RSVP path messages are sent downstream from the ingress router to the egress router. RSVP Resv messages are then sent upstream from the egress router to the ingress router. The path messages contain information about resources needed, and the Resv messages reserve these resources.

The Resource Reservation Protocol (RSVP) is a signaling protocol that enables the setup and maintenance of Quality of Service (QoS) paths through a network. RSVP messages are used to signal the creation and modification of Label Switched Paths (LSPs) in Multiprotocol Label Switching (MPLS) networks.

To establish a new LSP using RSVP, two types of RSVP messages are exchanged between the sender and receiver nodes:

  1. Path Message (A): The Path message is sent by the sender node to the receiver node to establish a new LSP. The Path message carries information about the requested QoS, such as bandwidth, delay, jitter, and packet loss. The Path message also includes a list of hops, which identifies the intermediate nodes that the LSP must traverse. Each intermediate node along the path receives the Path message and records the QoS requirements for the LSP.

  2. Resv Message (C): The Resv message is sent by the receiver node to the sender node to reserve resources along the LSP. The Resv message contains the same QoS information as the Path message and a list of the hops that the LSP must traverse. Each intermediate node along the path receives the Resv message and reserves resources for the LSP. When the Resv message reaches the sender node, the LSP is established, and the sender can start sending traffic along the LSP.

Therefore, the correct answers to the question are A (Path) and C (Resv). The Path message is used to request the establishment of a new LSP, and the Resv message is used to reserve resources along the LSP. The PathConfirm and ResvConfirm messages are not used to establish a new LSP; instead, they are used to confirm the establishment of an existing LSP or to modify its QoS parameters.