RSVP: A New Resource Reservation Protocol

Zhang et al. (Xerox PARC/USC)

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Content Summary

RSVP is a modular reservation protocol that sits on top of existing routing and transport protocols (e.g. TCP). Its unique contributions include separation of packet filtering from reservation; maintenance of soft (easily reconstructible after disruption) state at intermediate switching nodes that helps avoid redundant reservation; and periodic refresh of path information along a reservation path which if timed out results in freeing of orphaned resources. (This last feature is supposed to use adaptive timeout, NYI.) The authors suggest that path maintenance is essentially an inverse routing table and this service could therefore be provided by the underlying routing service.

As a reservation protocol, RSVP provides a reservation mechanism but makes no policy decisions; in particular, it does not schedule packets or select routes, asking for only a single accept/reject decision from each intermediate switch. One open issue is whether the interface for doing this admits the use of sophisticated reservation scheduling such as the scheme proposed by Ferrari et al.

Main points

Relevance to Multimedia

Modularity and simplicity are two of the characteristics that have made layered Internet protocols (SMTP, FTP, etc.) successful, and may make RSVP a popular "substrate" for work on reservation scheduling.


4 out of 5: A little verbose and atrociously formatted, but the work is well-circumscribed, based on sound design goals, and satisfies a well-defined set of needs common to many reservation protocols with a simple design.
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