Messages in this thread | | | From | (H. Peter Anvin) | Subject | Re: IEEE 802 and Ethernet Packet Encapsulations | Date | 20 Aug 1999 21:18:34 GMT |
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Followup to: <37BDBC6E.47221FE5@sso.sytexinc.com> By author: "Keith J. Jones" <kjones@sso.sytexinc.com> In newsgroup: linux.dev.kernel > > Could anyone shed some light on the issue of the IEEE 802.* and the > Ethernet encapsulation in linux? I can only find support for the > Ethernet encapsulation in the kernel source. Is 802.* still being used? > Does linux support it? Where is 802 being used at? >
Sounds like you've learned the rather bogus Novell terminology for Ethernet packet formats. There are basically four in use:
IEEE 802.2 without SNAP (available on all IEEE 802 networks) IEEE 802.2 with SNAP (available on all IEEE 802 networks) Ethernet II ("DIX") Novell "raw IEEE 802.3" (nonstandard!!! - IPX only)
All these frames can coexist on the wire; in the case of the "raw IEEE 802.3" frame this so happened by pure dumb luck, but nevertheless...
Some protocols are tied to a frame type, for example, TCP/IP is *always* used with Ethernet II frames, and Ethertalk (DDC, Appletalk over Ethernet) is always in SNAP frames.
On IEEE 802 networks that are not Ethernet and doesn't have the Ethernet 1514-byte packet size limit (e.g. IEEE 802.5 Token Ring) DIX frames are unrepresentable; on these networks DIX-using protocols are encapsulated in a specific kind of SNAP frame.
IPX, in particular, can be transmitted over either of these frames, just to make it confusing; furthermore, most systems treat the different frame types as different logical networks. I believe Novell recommend configuring using SNAP frames, whereas Ethernet II is popular where interoperability with TCP/IP is important. Linux can talk IPX over either of these kinds of frames (in fact simultaneously); the ipx_interface or ifconfig command is used to configure the appropriate network numbers and frame types.
-hpa -- <hpa@transmeta.com> at work, <hpa@zytor.com> in private!
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