Date: Thu, 18 Apr 1996 07:59:58 -0700 To: Mick Seaman From: seifert@netcom.netcom.com (Rich Seifert) Subject: Re: [JR Rivers: Re: [Mark Sankey/US/3Com: gigabit enet and vlan]] Cc: jrrivers@cisco.com, P8021@nic.hep.net At 6:22 PM 4/16/96, Mick Seaman wrote: >> Is 802.1 going to ask 802.3 to extend the Ethernet MTU for tagged frames?? >> Mark referred to the "frame length problem" in his second bullet. > >Yes. We have already had such discussions in the context of defining limits for Length and Type field designations, and are anticipating just such a request. Please note: The current draft of 802.3x (Full Duplex/Flow Control Supplement) clarifies the Length/Type field distinction. We have declared that Length/Type field values numerically greater than or equal to 0x0600 (decimal 1536) are considered Type fields. (The existing 802.3 says nothing about Type field values.) "Currently", we have designated Length/Type field values that are numerically less than or equal to 0x05DC (decimal 1500) to be considered Length fields. Values between these (i.e., 0x05DD through 0x05FF) are currently "undefined", but the clear intent was that we were reserving this range for possible expansion of the MTU for VLAN tagging. We just couldn't put that into the specification at this time. -- Rich Seifert Networks and Communications Consulting seifert@netcom.com 21885 Bear Creek Way (408) 395-5700 Los Gatos, CA 95030 (408) 395-1966 FAX "... specialists in Local Area Networks and Data Communications systems"