From owner-freebsd-net  Fri Nov 10 21:10:25 2000
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From: "Wilbert de Graaf" <wilbertdg@hetnet.nl>
To: "wu haijun" <haggai.wu@huawei.com>
Cc: <freebsd-net@freebsd.org>
References: <001f01c04afb$9b6e07a0$1b22690a@huawei.com.cn>
Subject: Re: A question for PPPoE 's MTU:
Date: Fri, 10 Nov 2000 21:06:38 -0800
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Hi Wu,

I remember this problem when we implemented an IP aggregator behind our
terminal servers. We configured our servers to respond with packet telling
the client to start over again and use smaller, not fragmented, ip packets.
This definitely improved performance. I think this is rfc879 (The TCP
Maximum Segment Size) related.
I don't remember how we did it but I believe just setting the MTU on that
interface to 1492 in your case, and set don't fragment.

- Wilbert


----- Original Message -----
From: wu haijun
To: freebsd-net@freebsd.org
Sent: Friday, November 10, 2000 1:50 AM
Subject: A question for PPPoE 's MTU:


Hi:

The MTU of PPPoE is 1492 Bytes. But if the PPPoE Server receives IP  packets
from the WAN and the packets's will be always 1514 Bytes,so the Server must
fragment the Packets to fit in the PPPoE packets ,and this will degrade the
performance of the Server.
Why not suggest that PPPoE header didn't be included in the MTU
calculation,just like VLAN encapsulation?

Regards

Wu Haijun
Huawei Tech. Corp. LTD  in CHINA
Senior Firmware Engineer



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