(Message mtu:10) Date: 01 Dec 1997 15:37:38 MST From: "Darwin K. Gensel" Newsgroups: comp.dcom.sys.cisco Subject: Re: Cannot reach sites with MTU<1500 Approved: news@news.colorado.edu X-Return-Path: dhesi@rahul.net X-Nojunk-Status: OK 0 Organization: University of Colorado at Boulder Sender: daemon@lace.colorado.edu Distribution: world References: <3.0.32.19971201084456.009703c0@lint.cisco.com> Nntp-Posting-Host: lace.colorado.edu Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" X-Sender: dgensel@diablo.cisco.com X-Mailer: QUALCOMM Windows Eudora Pro Version 3.0.2 (32) In-Reply-To: <199712011755.JAA13847@bubbuh.cisco.com> X-Note1: message-id generated by recnews X-Note2: mail msgid was <3.0.2.32.19971201135212.007d33d0@diablo.cisco.com> Xref: samba.rahul.net comp.dcom.sys.cisco:41046 I experienced the MTU>1500 at a location using Token Ring with Windows 95 workstations. What the problem appears to be is in the Microsoft Win/95 and NT code that negotiates the mtu and has the no fragmentation bit set. A number of WEB servers are on FDDI rings and support a large frame size. When the remote stations negotiated the connection they requested a 4K MTU and the server responded back with an OK. When the server sends a packet larger than 1500 bytes it never gets thru. Solution at the site was to set the token ring stations to the 1500 byte MTU size. Microsoft has notes on how to set different bits in the registry but my client chose the easy way out. Did not want to have a custom registry. At 10:43 AM 12/1/97 -0500, Quan Nguyen wrote: >On Mon, 1 Dec 1997, Wade Williams wrote: > >> At 02:55 PM 12/1/97 +1200, Franck Martin wrote: >> >I had this strange problem with a very few sites on the net: >> > >> >www.hotmail.com >> >www.compaq.com >> >www.ausaid.gov.au >> ... >> >> I've seen this behavior before. In our case, it was happening with the >> Novell technical support web site. We could reach the first page of the >> Novell site fine, but when we wanted to go to the tech support area (served >> by a different server), we couldn't reach it. >> ... > >To add to the tales of MTU size, we have seen problems in the opposite >direction i.e. with Token-ring attached PCs using default MTU size > 1500. >Those PCs are able to access almost everywhere except... >altavista.digital.com, www.adobe.com and www.mcafee.com (the PCs are >connected to 2502 routers). PCs running OS/2 don't have that problem, >Win95 and NT have that problem. The solution again is to change the MTU >size on those PCs to 1500. > >When we put a sniffer in front of the PC we see that the first part of the >home page was missing. Couldn't tell who ate it. > > >Quan, > >-----Quan Nguyen, RISQ Network Operations Center/Centre d'Operation----- > McGill UNIVERSITY > -o Voice (514)398-3709 Computing Center (Burnside Hall) > ()/// FAX (514)398-6876 805 Sherbrooke St West, Rm 222 >\ quan@CC.McGill.CA Montreal, Quebec H3A 2K6 > > > > > > > > +----------------------+---------------------------+-----------------------+ + || || + Darwin K. Gensel + + + || || + Cisco Systems, Inc. + + + || || + dgensel@cisco.com + Pager: 1-800-365-4578 + + |||| |||| + + + +..:||||||:..:||||||:..+ 1250 Pittsford-Victor Rd + Ph: (716) 249-1806 + + Cisco Systems + Rochester, NY 14534 + Fax:(716) 249-1899 + +----------------------+---------------------------+-----------------------+ + ** The Network Works, No Excuses ** + +--------------------------------------------------------------------------+