[29307] in North American Network Operators' Group
Re: MAE-EAST Moving? from Tysons corner to reston VA.
daemon@ATHENA.MIT.EDU (Steven M. Bellovin)
Fri Jun 16 18:06:59 2000
From: "Steven M. Bellovin" <smb@research.att.com>
To: trall@almaden.ibm.com
Cc: nanog@merit.edu
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Date: Fri, 16 Jun 2000 18:04:42 -0400
Message-Id: <20000616220442.C0E7735DC2@smb.research.att.com>
Errors-To: owner-nanog-outgoing@merit.edu
In message <87256900.00780D04.00@d53mta03h.boulder.ibm.com>, trall@almaden.ibm.
com writes:
>
>
>
>On 06/16/2000 at 11:10:55 AST, John Fraizer <nanog@EnterZone.Net> wrote:
>> If I'm not mistaken, 9000bytes is the max.
>
>I don't understand how ethernets, at the MAC layer, can support frames
>greater than 1500 bytes. Looking at the MAC frame format, we have:
>
>ethernet DIX V2 DA(16 bits), SA(16 bits), type (16 bits), data
>IEEE 802.3 DA(16 bits), SA(16 bits), length (16 bits), LPDU (802.2)
>
>The traditional way to distinguish between the 2 formats depends on the
>length value (in 802.3) being no greater than 1500, and on the type value
>(in DIX) being greater than 0x05dc (1500 decimal).
>
>Assuming you're still going to allow both formats on the same lan, how does
>it work if the length is greater than 1500?
See http://search.ietf.org/internet-drafts/draft-kaplan-isis-ext-eth-02.txt
for one proposal.
--Steve Bellovin
