Resource Reservation Protocol (RSVP)
An Introduction
Prof. David Bernstein
James Madison University
Computer Science Department
bernstdh@jmu.edu
Overview
Objective:
Provide a guaranteed quality of service (QoS) between a
sender and receiver on a connectionless network
Properties:
Uses end-to-end reservations
Is robust (to failures in routers and links)
Is receiver-initiated
Works with simplex data flow to a multicast group
PATH Messages
What:
The sender periodically sends the specification of the
transmitted traffic (TSpec) to the multicast group
Why:
The network and reciver are made aware of the TSpec
The network is made aware of the path taken
(which can change over time)
RESV Messages
Contents:
Delay requirements
Bandwidth requirements
A filter that describes the senders that can use this reservation
(e.g., in a videoconference multiple senders can share a
reservation)
Filter Styles:
Wildcard - any sender (to this receiver)
Fixed - one specific sender
Dynamic - multiple explicit senders (which can be modified
over time)
Establishing a Reservation
Receiver:
Periodically sends RESV messages up the multicast tree to
reserve resources
Routers:
Merge requests from different receivers (e.g., a request for
a 200ms delay and a request for a 100ms delay can be merged
into a single request for a 100ms delay)
Determine if the reservation can be fulfilled
Forward RESV messages to the source
"Soft" State Information
Defined:
State information is lost when a timer expires
Sender and receiver periodically refresh the state
(using PATH and RESV messages)