Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!pasteur!ucbvax!CLASH.CISCO.COM!cire
From: cire@CLASH.CISCO.COM
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Convert /etc/hosts to RR format pgm anyone?
Message-ID: <8806110829.AA10728@ucbvax.Berkeley.EDU>
Date: 9 Jun 88 19:29:01 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 64

>> Date:         Thu, 09 Jun 88 09:33:04 EDT
>> From: Frank Kastenholz <KASTEN@MITVMA.MIT.EDU>
>> Subject:      Re: Convert /etc/hosts to RR format pgm anyone?
>> To: der Mouse <mcgill-vision!mouse@bloom-beacon.mit.edu>
>> Cc: tcp-ip@sri-nic.arpa
>> 

Good start!    I've added some corrections to the heirarchy.
It strikes me that this kind of info would be reasonable in an intro
of some kind to IP.

>> This sounds to me like there is some confusion over the meaning of
>> some of the terms used (which, to the best of my limited knowledge,
>> have never been fully codified - perhaps an addendum to the Assigned
>> Numbers RFC is in order - "Assigned Abbreviations and Terms and Their
>> Meanings").
>> 

I'd recommend Douglas Comer's book 'Internetworking with TCP/IP, Principals,
Protocols, and Architecture' or Andrew Tanenbaum's book 'Computer Networks'.
Both include a glossary at the back with very succinct definitions of most
everything you mention below.

>> As I understand things the "hierarchy" of terms in use in the Internet
>> protocols (among others) are:
>> 

Here is perhaps a better set of definitions:  (some of these are essentially
pulled from Comer's book).

FRAME - The unit of information encapsulated for transmission on physical
	media or network.
	
FRAGMENT - a unit that the IP layer breaks a DATAGRAM into if necessary
	   for transmission across networks that can not handle the size
	   of the entire DATAGRAM.   A FRAGMENT has essentially the same
	   IP header as the original DATAGRAM.

DATAGRAM - The basic unit of information dealt with by the IP layer.  This
	   is what is sent across the TCP/IP Internet.  It may be broken
	   into FRAGMENTS if a network can not handle the DATAGRAM's size.

SEGMENT - the basic unit that TCP deals with.  A segment consists of a block
	  of bytes that arrive or are sent at one time.  These bytes make up
	  part of stream of bytes.  Information in the segment identifies
	  where in the stream these bytes exist.  A segment will be
	  passed to the IP layer as one or more DATAGRAMS for transmission
	  by that layer.

PACKET - the basic unit of information sent across a packet-switching network.
	 It's exact meaning is dependent upon the context.

BUFFER - an implementation detail that is used for passing blocks of information
	 including DATAGRAMS to the layers for processing.

-c
cire|eric

Eric B. Decker
cisco Systems
Menlo Park, California

email:	cire@cisco.com
uSnail: 1360 Willow Rd.,  Menlo Park, CA  94025
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