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Re: Jumbo Frames (was Re: MAE-EAST Moving? from Tysons corner toreston VA. )
From: William Allen Simpson <wsimpson () greendragon com>
Date: Mon, 19 Jun 2000 12:09:56 -0400


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
    Key fingerprint =  17 40 5E 67 15 6F 31 26  DD 0D B9 9B 6A 15 2C 32




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