[29349] in North American Network Operators' Group
Re: Jumbo Frames (was Re: MAE-EAST Moving? from Tysons corner toreston
daemon@ATHENA.MIT.EDU (William Allen Simpson)
Mon Jun 19 12:13:18 2000
Message-ID: <394E45CA.B60502DD@greendragon.com>
Date: Mon, 19 Jun 2000 12:09:56 -0400
From: William Allen Simpson <wsimpson@greendragon.com>
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Which is one of the reasons that we specified 1600 as the frame size
for most line disciplines, such as PPP over Frame Relay, etc., since
circa 1992....
PPP itself is 1500, matching ethernet, in the vain hope that folks
would remember to distinguish "packet" data size from "frame" size.
Also, I'd like to note that jumbograms render the TCP checksum nearly
useless. It's only an effective 7 bits of strength, which one might
describe as "minimally" useful.
michael.dillon@gtsip.net wrote:
>
> When 1500 byte frames from the customer's LAN enter the customer's
router and enter some form of IP tunnel, then a core fabric which
supports larger than 1500 byte frames will not cause fragmentation.
It's not necessary to do the full jumbo size frames. I suspect that
supporting two levels of encapsulation will be enough in 99.9% of the
cases. For the sake of argument, what would be the downside of using a
2000 byte MTU as the minimum MTU in your core?
>
WSimpson@UMich.edu
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