Subject: Re: Slow start question ...

From: "Howard Berkey" <[email-masked]>
Date: Mon, 22 May 2000 13:08:57 PDT

Seems like a moot point anyway, since in the case of sending to someone 
on the same LAN segment as yourself (i.e. not routed), slow start will 
be exited quickly if the amount of data being transferred on the 
connection exceeds a couple mtu's in size.

Howard

>> If the peer to which a TCP connection has been established is on a 
"direct connected" network (i.e. the route doesn't point to a gateway), 
why exactly is slow start required? Linux and NetBSD seem to do slow 
start for this case while FreeBSD doesn't seem to (I haven't picked 
through the source to verify this though). Since slow start is meant to 
"probe the available network bandwidth" of a route (involving routers), 
it seems to me that I really shouldn't have to use slow start for the 
case mentioned above. 
>
>Your definition of direct connected includes things like ATM networks, 
slow
>dialup links, and even IPIP tunnels across the internet.
>
>Are you telling me you dont want slow start on these ?
>
>The fundamental flaw in your argument is to assume the routers are at 
IP level.
>There are resource issues both on all networks including your own 
buffering
>on modems, switches, bridges and other devices below the IP layer. The
>slow start procedure makes us behave well to them as well.
>
>Alan
>
>

---

From: Alan Cox <[email-masked]>
Date: Tue, 23 May 2000 14:26:07 +0100 (BST)

> connection exceeds a couple mtu's in size.

The difference is in that tiny time period starting up if there is congestion
we don't swamp the lan. But yes the only reason to disable slow start is
benchmarketing. For real world use it should be lost in the noise