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Date:      Tue, 15 Dec 1998 18:49:13 +0100 (CET)
From:      Johan Granlund <johan@granlund.nu>
To:        Poul-Henning Kamp <phk@critter.freebsd.dk>
Cc:        "Jonathan M. Bresler" <jmb@FreeBSD.ORG>, julian@whistle.com, lars@akerlings.t.se, current@FreeBSD.ORG, isdn@FreeBSD.ORG
Subject:   Re: if_sppp is BROKEN!!! 
Message-ID:  <Pine.BSF.4.05.9812151823070.11916-100000@phoenix.granlund.nu>
In-Reply-To: <6841.913677780@critter.freebsd.dk>

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On Tue, 15 Dec 1998, Poul-Henning Kamp wrote:

> In message <199812142307.PAA27390@hub.freebsd.org>, "Jonathan M. Bresler" write
> s:
> >> Date: Mon, 14 Dec 1998 22:12:29 +0100 (CET)
> >> From: Johan Granlund <johan@granlund.nu>
> >> 
> >> This is really interesting!
> >> One of the concepts i liked in SYSV (ducking for cover) was streams and
> >> its ability to chain together modules to process a datastream.
> >> If it's coupled with kld to dynamically load/unload modules i think
> >> you have something _very_ good.
> >> 
> >> That network thing. Can a module route a package thru different modules
> >> based on contents and state?
> >
> >  the idea of streams is wonderful, the realization is costly.  each
> >  layer added (or module pushed) slows down processing and hurts
> >  throughput.  ritchie developed streams for serial, if i remember
> >  correctly.  streams was then applied to networks.  there is an RFC
> >  about layering being bad for networking and the relative performance
> >  of NIT vs BPF prove the case.
> 
> But with that said, there is still something to be said for modular
> and well defined interfaces.  But streams ?  No.  They were great
> for async protocols, but they fail badly for packet stuff.

Lets get something clear. I was not talking about migrating our networking
to SYSV style streams. If someone was talking about converting our
networking code to streams i would probably scream. Multiple layers cause
more latency, nothing new there at all!

What i was thinking about was something more like lowbandwidth / high
processing protocols. If the endpoint is a serial port, network interface
or the network protocol stack (for tunneling) should't be a issue if
it's used right.

PPP seems as a contender there and it would get
streams used. If it's not used then it's rotts.

/Johan

> 
> --
> Poul-Henning Kamp             FreeBSD coreteam member
> phk@FreeBSD.ORG               "Real hackers run -current on their laptop."
> "ttyv0" -- What UNIX calls a $20K state-of-the-art, 3D, hi-res color terminal
> 
> 


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