RSVP is a idea that doesn't cut the mustard in the real world. There are several show-stopper problems with RSVP.
1) somewhat like multicast, anyone using RSVP is vulnerable to others mis-using or mis-configuring RSVP. ISPs several AS's away can really screw up things for other ISPs. Because of this, it is unwise to deploy it because it requires too much trust in other ISPs.
That isn't a fault of RSVP, the protocol. Rather, it's a fault of insufficient authorization for a requested flow.
That relegates RSVP to the enterprise Lan, where it usually isn't needed. Remember, RSVP is only useful if you have a congestion problem and need to choose which packets to discard. If you have no congestion problem, then you have no need of RSVP.
Enterprises have WANs (ATM, FR, MPLS) which do have congestion problems. Even within a LAN it's possible to have congestion problems (PC backups, database replication).
> However, having a congestion problem also opens
the question of the nature of the congestion and what is the best way to deal that problem. I was involved in a study done by Genuity and Cisco in which the congestion problem was found to most often involve the tail circuit--the link between the customer and the ISP. The best solution for this problem was found to be low latency queuing, not RSVP.
2) Unlike multicast, every hop end-to-end must use RSVP for it to be useful.
RSVP only needs to be enabled on the links that might become congested, such as an enterprise's WAN links. It usually doesn't need to be enabled on a non-bandwidth-constrained LAN.
-d
> An RSVP tunnel is useless. >
3) RSVP doesn't detect certain kinds of problems that are important. For example, a mid-span failure is not visible to RSVP.
While RSVP is important research, it is not a widely deployable technology.
What I-D's are you encountering that depend on RSVP?
--Dean
On Tue, 10 Aug 2004, Fleischman, Eric wrote:
I am aware of some use of RSVP in labs but I am not aware of any use of RSVP in production networks (i.e., real life networks people connect to the Internet with). Simultaneously, I am encountering I-Ds and other work planning to use RSVP. This possible disconnect concerns me. Therefore, I would appreciate being educated by anybody using RSVP in production settings. Would you please let me know how many devices, what applications, and how successful these deployments (if any) are? Thank you.
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