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jumbo frame mtu setting

0

Once If I set jumbo frame on a specific interface like:

ifconfig eth0 mtu 9000

what will be the minimum and maximum packet size ?

Say for example, if I send a 1 byte packet, whether padding happens till 64 byte frame size(minimum required) will be done (OR) some other minimum size ?

Also, If I set packet size as 100, what will be the frame size ? Is it 1500 (OR) 9000 ? How the padding happens in this case ?

OS: linux 2.6.32 Thanks.

asked 07 Jan '14, 04:37

saro's gravatar image

saro
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One Answer:

3

Minimum frame size is always 64 bytes, so if you send 1 byte you'll be padded up to 64 bytes. If you send 100 bytes the frame size is still 100 bytes. Maximum is only the size a frame cannot exceed. It doesn't mean that all frames need to be that big.

I'm not sure if you use the terms "packet size" and "frame size" as it is meant. "Packet Size" would be the IP part of the frame, while frame is the whole data including ethernet headers and FCS being sent. So if you send an IP "packet" of 100 bytes you'll end up with 118 bytes "frame" size (14 bytes ethernet header and 4 bytes FCS).

answered 07 Jan '14, 04:56

Jasper's gravatar image

Jasper ♦♦
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accept rate: 18%

And the MTU is "the IP part of the frame", so the maximum IP packet size, with an MTU of 9000, is 9000, but a 9000-byte IP packet would be 9018 bytes "on the wire", with a 14-byte header and a 4-byte FCS).

(07 Jan '14, 19:25) Guy Harris ♦♦