I've included two referenced E-mails below...
Can we expand a bit on this? There are really two different topics
buried in here:
1. What is/who has the problem with certain MTU and certain net sites?
2. How do you change MTU in Win95? and when you get it changed, how
do you know on a PM?
I'll expand below:
1. I have seen definite problems with an MTU of 1500 going to certain Web
sites... the hang David Bodet describes below happens. His mail implies
that he has had the problem with values less than 576 as well. Apparently
there is some kind of problem somewhere here. It may be the PM or it may
be something else in the path (since it seems to be "destination" site
dependant)... Is this an indication that some piece of hardware in the
path isn't handling fragmentation correctly? If so, is it worth pursuing
to find out what piece?
2. A customer tried everything known to man trying to get Win95 to change
its MTU. I checked via the "if" command on the PM to see if he would get
connected at a smaller MTU.. it *always* shows 1500. HOWEVER - if you
trace the network, the packet sizes to/from his machine are always tracking
with what he sets it to be on Win95 (I don't know the mechanism he's using
to change it, but can find out). Why doesn't the PM know about the smaller
packet sizes?
(Sorry this is a bit late. You can "CC: dtscott@scott.net" if you like,
otherwise I'll read any replies tonight, since I subscribe to the digest.).
Later!
Derric
> > From: (David L. Bodet)
> > Date: Sun, 17 Sep 95 14:29:18 EDT
> > Subject: Web Browser problems
> >
> > Has anyone noticed a problem with dialin accounts accessing
> > certain web sites? In our system, we have noticed that
> > several web sites, including www.home.msn.com and
> > www.pcworld.com, connect but hang, i.e. constant wait. After
> > several experiments, I found that setting the MTU on the
> > dialin software to 576 or greater cures the problem. The
> > browsers that have had this problem are Win95 with Netscape
> > and Explorer, Win3.11 with Netscape Navigator Personal
> > Edition, and OS/2 Warp with WebExplorer.
> >
> > Our setup is one Livingston PM2E-20s at two different sites
> > using Radius 1.16 with the .ppp extension patch. Adding the
> > Framed-MTU= in the users file makes no effect.
> > The Portmasters are running ComOS 3.1.3c2. I also tried
> > ComOS 3.1.2.
> >
> > Using Win95, the show s?? on the Portmaster says the
> > connection is running an MTU of 1500. Only patching the
> > netTrans Registry file in Win95, to specify the MTU, fixes
> > the problem.
> >
> > Is this a Portmaster problem or somewhere else??
> >
>
> From: "Brian 'MegaZone' Bikowicz" <megazone>
> Date: Sun, 17 Sep 1995 15:49:23 -0700 (PDT)
> Subject: Re: Web Browser problems
...
> PPP default MTU is 1500, the only one I know had a problem (not just with PMs)
> was Trumpet 2.0b, which 1006 work on. (Remember if you change MTU to change
> RWIN and MSS.)
>
> >Framed-MTU= in the users file makes no effect.
>
> The connection will use the lower MTU, if the client asks for a lower MTU
> the PM will use that for the actual connection, even if the port is set for
> a higher value.
>
> I'm using Trumpet 2.1f with EWAN 1.04 for telnet and Navigator 1.2 beta 5
> for WWW (also have NCSA Mosaic 2.00 final beta that I play with some times).
> I'm still tweaking 2.1f, so I have some connection problems now and then,
> but under 2.0b things seemed to be ok. And under 2.1f I was able to grab
> those pages without a hitch.
>
> - -MZ
-- Derric Scott Scott Network Services, Inc. P. O. Box 361353 derric@scott.net (205)987-5889 Birmingham, AL 35236