philipp@LARRY.MCRCIM.MCGILL.EDU (Philip A. Prindeville) (06/13/88)
FRAME - lowest level of bits/bytes. One speaks of Ethernet Frames, etc A FRAME has ONE data link header (e.g. Ethernet header). FRAGMENT - the thing that IP spits out to the data link driver. Each FRAGMENT has ONE IP header. A FRAGMENT may be split into multiple FRAMES by the lower layers. Not quite. A DATAGRAM becomes fragmented (in FRAGMENTS, of course) so that each will fit into a FRAME. The whole purpose of the MTU and fragmentation is to avoid lower level fragmentation and reassembly. The only exception to this is X.25 where you have complete-packet-sequences (but since X.25 is reliable, and in order, this doesn't present a problem). Under LAN technologies (ARCNET, PRONET, Ethernet, Token Ring, etc) 1 FRAGMENT == 1 FRAME. [ ... ] DATAGRAM - this is also the 'larger' thing that IP tries to send. A DATAGRAM USUALLY has a one to one relationship with a SEGMENT It may be broken up (fragmented) into a number of FRAGMENTS by IP before being sent through the data link. Yes. -Philip