[e2e] Ethernet Encapsulation

[Dennis Rockwell]

On 7 Nov, Greg Minshall wrote:

> the link layer hardware knows when packets on the wire start and stop using 
> framing (manchester encoding or whatever).  it delivers this information to 
> the link layer software (device driver), which then provides it to IP.

This is all true, but also TCP and UDP packets are
self-describing; that is, there is a header field which
contains the data length of the packet.  So, if the length
supplied by the link layer is is too short, the packet
should be discarded.  If it is longer, the excess data is
simply ignored.

Dennis Rockwell                 dennis at bbn.com
BBN Technologies
A Verizon Company               +1-617-873-5745
Cambridge, MA                   +1-617-873-6091 (Fax)