Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!helps!uudell!Kepler!mjhammel From: mjhammel@Kepler.dell.com (Michael J. Hammel) Newsgroups: comp.dcom.lans Subject: Re: Ethernet Vs. IEEE 802.3 ?????????? Message-ID: <13213@uudell.dell.com> Date: 14 Dec 90 20:58:17 GMT References: <3443@lectroid.sw.stratus.com> <1990Dec5.145439.9133@cs.utk.edu> Sender: news@uudell.dell.com Reply-To: mjhammel@Kepler.dell.com (Michael J. Hammel) Organization: Dell Computer Corp. Lines: 55 In article <3443@lectroid.sw.stratus.com>, fmbutt@mrbt.sw.stratus.com (Farooq Butt) writes: > Is IEEE 802.3 the very same thing as the "Ethernet" standard ? In what > ways are the two different ? I know that 802.3 is usually implemented > at a hardware level, what about "Ethernet" ? Which one is older ? Version 2.0 of Ethernet was published in November 1982. The first edition of 802.3 was published in early 1985. > Does using one seriously preclude you from connecting with machines > using the other flavor ? Finally which is "better" ;-) ? They can coexist on the same wire but unless your physical interface is sophisticated enough to recongize both types at least some of the data will not get through. Which is better is probably a religous question. ;-) They are not the same, but they are somewhat similar. The Ethernet frame format looks like this: 8 octet preamble 6 octet destination address 6 octet source address 2 octet type 46-1500 octets of data 4 octet CRC The 802.3 frame format looks like this: 7 octet preamble 1 octet start frame delimiter 2 or 6 octet destination address 2 or 6 octet source address 2 octet length 46-1500 octets data and pad (in 10BASE5 definition) 4 octet CRC The preamble and SFD of 802.3 are basically the same as the preamble of ethernet. The 10BASE5 version of 802.3 specifies use of 6 octet addresses so these are the same as ethernet. The type field of ethernet is, I've been told, always less than some number and the length field of 802.3 is always greater than that number. This *might* be a way to tell the two frame types apart, but don't count on it. Both formats require frame sizes between 64-1518 octets total (excluding preamble). In ethernet the client layer must guarantee this size. In 802.3 the 802.2 LLC can hand off invalid size frames to the 802.3 MAC layer and the MAC layer will compensate (at least it will if the LLC provides a frame thats too short; I'm not sure what will happen if its too long). I got all this info from an article by Gary Kessler in the July 1987 issue of LAN Magazine. Its a very good article if you'd like to read more about the specific differences in the two formats. Michael J. Hammel | mjhammel@{Kepler|socrates}.dell.com Dell Computer Corp. | {73377.3467|76424.3024}@compuserve.com #include | zzham@ttuvm1.bitnet | uunet!uudell!feynman!mjhammel #define CUTESAYING "Your cute quote here"