ethernet packet preamble

My beginner level understanding tells me that yes, there will always be a preamble as stated in the 802.3 specs.

The preamble is always the first part of the transmission on the wire, even in FDX mode.

Not sure what you mean by long distance communication, my simple explanation is that the preamble is "NIC to NICs" or seen in a single collision domain.

So account for the preamle in the LAN segments, if your calculating BW across the WAN I would say it is not to be considered.

Kentster

However, aren't there "frame packing" considerations when passing large numbers of very small frames at 1GE and above? i.e. the preamble precedes each transmission, but there may be more than one frame per preamble?

When posting homework (and/or network certification) questions, you should at least go to the trouble of paraphrasing the question!

It is a good question, though.

For 10 megabit ethernet the preamble is used to sync. the PLL in the receiver. For ethernets with continuous signalling, there is no need to sync. the PLL for each frame, and so no need for preamble.

-- glen