From owner-freebsd-net Fri Aug 4 7:46:53 2000 Delivered-To: freebsd-net@freebsd.org Received: from khavrinen.lcs.mit.edu (khavrinen.lcs.mit.edu [18.24.4.193]) by hub.freebsd.org (Postfix) with ESMTP id 5314437BB61 for ; Fri, 4 Aug 2000 07:46:49 -0700 (PDT) (envelope-from wollman@khavrinen.lcs.mit.edu) Received: (from wollman@localhost) by khavrinen.lcs.mit.edu (8.9.3/8.9.3) id KAA27928; Fri, 4 Aug 2000 10:46:38 -0400 (EDT) (envelope-from wollman) Date: Fri, 4 Aug 2000 10:46:38 -0400 (EDT) From: Garrett Wollman Message-Id: <200008041446.KAA27928@khavrinen.lcs.mit.edu> To: Bob Van Valzah Cc: freebsd-net@FreeBSD.ORG Subject: Re: VLAN MTU? 1500? 1504? Why? In-Reply-To: <398AB99C.9D5938B9@WhiteBarn.Com> References: <398A3549.902A31F5@WhiteBarn.Com> <200008040434.AAA41523@whizzo.transsys.com> <398AB99C.9D5938B9@WhiteBarn.Com> Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org < said: > Is there any existing mechanism for "negotiation" of MTU between the > physical layer and virtual layer? Yes. In FreeBSD's implementation, the network interface driver indicates its ability to handle 802.1p-enacapsulated frames (as used in 802.1Q) by advertising a header length of 18 rather than the standard (no encapsulation) 14 octets. (The current implementation does not, however, have a mechanism for rejecting 1518-byte *unencapsulated* packets, as should officially be done. I don't think this is a serious problem.) -GAWollman -- Garrett A. Wollman | O Siem / We are all family / O Siem / We're all the same wollman@lcs.mit.edu | O Siem / The fires of freedom Opinions not those of| Dance in the burning flame MIT, LCS, CRS, or NSA| - Susan Aglukark and Chad Irschick To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message