Linux-kernel mailing list archive 1999-23,: Re: XTP: A better TCP than TCP

# Re: XTP: A better TCP than TCP

Matthew Wilcox (Matthew.Wilcox@genedata.com)
Tue, 8 Jun 1999 17:52:35 +0200

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On Thu, Jun 03, 1999 at 04:37:03PM -0400, Greg Lindahl wrote:
> > As I understand it, the idea behind not requiring flow-control in IL
> > was that the higher level protocols would take care of this; in 9P
> > (which is the main user of IL), there's a reply to each request, so if
> > the server is replying slowly, the client will slow down to compensate.
>
> NFS and CORBA don't have such a feature. And even if you *think* you
> have such a feature, you may be surprised. In the example I gave (with
> Legion and MPI), the server was simply being overrun with requests,
> even though it replied to every one.

Actually, NFS v3 does - it returns the error NFS_JUKEBOX. Admittedly,
this is to handle HSM situations, not flow control. NFS is not specified
over IL in any case, so one could write a specification which described
how flow control was to be performed. I don't see how NFS/IL is any
worse than NFS/UDP, clients must implement their own flow control (or
not at all) for this case too.

> Likewise, IL attempts to do a good job at being adaptive over a
> WAN. But it's hard to believe that it's as good at it as TCP.

It's hard to know without any benchmarks. I don't have any, do you?

    --
    Matthew Wilcox <willy@bofh.ai>
    "Windows and MacOS are products, contrived by engineers in the service of
    specific companies. Unix, by contrast, is not so much a product as it is a
    painstakingly compiled oral history of the hacker subculture." - N Stephenson

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