Re: Question about use of RSVP in Production Networks

[Dan Wing <[e-mail]>]

Dean Anderson wrote:
> 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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> 
> 
> 
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