Ethernet Version II does not have a length field, as you say, although IEEE
802.3 does. But Ethernet Version II still supports variable frame sizes. It
just makes the NIC work a little harder. The NIC listens until clocked bits
have stopped coming in and then it knows it's at the end of the frame. It
could count the bits and still pass this info to the next layer up, but I
don't think it does. The length field in IEEE 802.3 is an enhancement. The
NIC can use the information for itself and it can easily pass the info to
the next layer up.
Priscilla
At 07:59 PM 5/25/01, [EMAIL PROTECTED] wrote:
>Dear Members List,
>
>I've just started the track for CCNA and, following all the repeated advices
>posted in this list, I started studing for Internetworking with TCP/IP, by
>Douglas Comer.
>
>The ethernet frame format stablishes as necessary information for the frame
>as DA, SA, Type, Data Area(variable from 46 to 1500 bytes) and a trailer FCS
>4 bytes.
>
>I don't see how can we have different frame sizes correctly received, since
>there is no information about the specific lenght for every single frame,
>taking in account the asynchrounous nature of this communication.
>
>I thought that the layer 3 would pad till the MTU was reached, but I saw a
>trace on an ethernet network and I could see different frame sizes.
>
>Thanks in advance,
>
>Douglas Baltazar de Queiroz - Field Enginner
>
>---
>UOL: o melhor da Internet.
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________________________
Priscilla Oppenheimer
http://www.priscilla.com
Message Posted at:
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