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Resource Reservation Protocol (RSVP)
An Introduction


Prof. David Bernstein
James Madison University

Computer Science Department
bernstdh@jmu.edu

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Overview
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  • 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
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  • 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
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  • 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
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  • 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
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  • Defined:
    • State information is lost when a timer expires
    • Sender and receiver periodically refresh the state (using PATH and RESV messages)
  • Advantages:
    • No need to clean up after failures
    • Signalling messages needn't be reliable
    • Robust (i.e., recovers from failures)
Teardown Messages
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  • Purpose:
    • Explicitly delete state information
  • Types:
    • PathTear
    • ResvTear
There's Always More to Learn
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