Subject: Carry IP Packet in Ethernet Frame in IEEE 802.3 LLC Encapsulation Format

From: David Wang <[email-masked]>
Date: Thu, 30 Mar 2000 11:46:53 -0600

Dear Friends,

I never see or heard any product use 802.3 LLC frame format to carry IP
packet. But I am not sure I am correct. Does anyone knows that some product
does use the LLC frame to carry IP packets and why?

There are 2 type of Ethernet frames:
Ethernet Version 2 Frame: 

	| destination | source | type | data | fcs|

IEEE 802.3 LLC frame:

	| destination | source | length | LLC | org code | type | data |
fcs|

The key difference is the 2 bytes behind the source MAC address. Using
Ethernet Version 2 Frame, the type field value will large than the maximum
Ethernet frame length 1518. For frames carrying IP packet the type field
value is 0x0800. The interface device driver will check this field and
realize that this frame carries IP packet. It will send the packet to the IP
module for father processing.

Thanks
David

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From: [email-masked]
Date: Thu, 30 Mar 2000 22:06:20 +0200

> does use the LLC frame to carry IP packets and why?

Older HP-UX (300 & 400 series) systems could do this.

Steinar Haug, Nethelp consulting, [email-masked]