From: Bob Chahal (bob.chahal@xxxxxxxxxxxx)
Date: Tue Aug 28 2001 - 18:51:27 GMT-3
Ok, that makes sense because the explorer "pre-negotiates" the frame size.
The MTU discovery is done between TCP DLSW+ peers but the netbios or SNA
frame size has already been negoatiated by the initial explorers. I'm going
to have to give this another read but you're right I've heard that Cisco
like to have the LF set when DLSW+ peers have connected ethernet and token
ring segments.
Still not absolutely sure about this though.
Bob
----- Original Message -----
From: "Jerry Toomey" <jetoomey@yahoo.com>
To: "Bob Chahal" <bob.chahal@ntlworld.com>; "Zeng Puyang"
<zbridge98@yahoo.com>; <ccielab@groupstudy.com>
Sent: Tuesday, August 28, 2001 7:00 PM
Subject: Re: dlsw lf question
> Bob,
> In a Cisco ASET lab it was explained to me that LF is part of the explorer
> negotiation and that by setting LF properly, the packets are sent
> correctly without having to chop them up. Why? Because the sending
> workstation gets an explorer reply that says to keep the packet size down
> to 1500 bytes.
>
> I heard that if you don't do the "LF 1500" then they mark you down because
> it is sloppy, not because it doesn't work.
>
> Please correct me if I'm wrong.
>
> Jerry
>
> --- Bob Chahal <bob.chahal@ntlworld.com> wrote:
> > I don't understand how if the LF is smaller that the MTU, then TCP will
> > fragment. Surely when the LF is greater than the MTU then TCP
> > fragments???
> >
> > ----- Original Message -----
> > From: "Zeng Puyang" <zbridge98@yahoo.com>
> > To: <ccielab@groupstudy.com>
> > Sent: Tuesday, August 28, 2001 5:22 AM
> > Subject: dlsw lf question
> >
> >
> > > Hi, group:
> > >
> > > ring1-------R1<---dlsw--->R2----ethernet
> > >
> > > I always see (lf 1500) in the dlsw remote-peer command from cisco's
> > example and ccie power session. But when read the design guide of the
> > dlsw,
> > I think it's not neccesary, at least for the TCP encapsulation. Could
> > anyone
> > make this clear for me?
> > >
> > > The following is from the design guide:
> > http://www.cisco.com/warp/public/cc/pd/ibsw/ibdlsw/prodlit/dlsw4_rg.htm
> > >
> > > In general, when using TCP encapsulation, you probably will not need
> > to
> > change the largest frame size because TCP
> > > fragments the frame size according to the MTU. For example, if the LF
> > is
> > smaller than the MTU, then TCP will fragment each packet and send them
> > in
> > sections across the WAN. If the LF is larger than the MTU, then
> > individual
> > packets will be placed into the TCP/IP frame.
> > >
> > >
> > > Regards
> > >
> > > Zeng Puyang
> > >
> > > |:"f
> > > |g-J +~7&!"\"fv7,1+a6Zy
> > > _rj(}J&
> > > **Please read:http://www.groupstudy.com/list/posting.html
> > **Please read:http://www.groupstudy.com/list/posting.html
> =====
> Jerry Toomey of http://www.wansend.com can be reached at 949-439-4685
>
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