Illustrated TCP/IP Illustrated TCP/IP
by Matthew G. Naugle
Wiley Computer Publishing, John Wiley & Sons, Inc.
ISBN: 0471196568   Pub Date: 11/01/98  

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Chapter 335
Merging Flowspecs

One last statement should be made here, a point that should have come up as a question about multiple reservations being made and the availability of resources to handles such requests. Given the state of today’s routers, wouldn’t we simply run out of resources within a short amount of time? The question is hard to answer and depends on the manufacturer of the router. Some routers are high performance, possess multiple processors (some of them on the I/O card), and have lots of memory, high-speed interfaces, and so on.

Merging Flowspecs

•  RSVP will accommodate transparent operations through non-RSVP-capable devices or clouds.
•  One Pass With Advertising (OPWA) is an RSVP enhancement that may be used to predict end-to-end QoS.
•  RSVP will merge reservations as they travel upstream to optimize network resources.
•  RSVP uses “styles” to define specific options desired by the application.

Some router vendors do not support this. Therefore, it is hard to tell how this control protocol (RSVP) is going to work on routers.

There are some efficiencies in the RSVP protocol itself. One of them is called merging flowspecs. Multiple reservation requests from different next hops for the same session and with the same filter spec will have only one reservation on that interface. Contained in the Resv message forwarded to a previous hop is the “largest” of the flowspecs requested by the next hops to which the data flow will be sent. In other words, flowspecs can be cumulative or merged.


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