jwabik@shamash.UUCP (Jeff Wabik) (04/21/88)
Does anyone know which version of tcp-ip is implemented in the standard
Sun OS (Sun UNIX 3.x) ? 802.2? 802.2/snap? 802.3?
Thanks in advance ..
-Jeff
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Jeff A. Wabik UUCP: {rosevax,umn-cs,meccts,ems}!shamash!jwabik
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Live long and program.hedrick@athos.rutgers.edu (Charles Hedrick) (04/23/88)
In article <6140@shamash.UUCP> jwabik@shamash.UUCP (Jeff Wabik) writes: > Does anyone know which version of tcp-ip is implemented in the standard > Sun OS (Sun UNIX 3.x) ? 802.2? 802.2/snap? 802.3? The wording of this question is not perhaps as precise as it might be. TCP/IP as a protocol suite covers OSI layers 3 and above. The 802 things you cite are at layers 2 and below. So whether or not of 802.2 is used, with or without SNAP's, is not really a matter of the version of TCP/IP. The way IP works is that there is a standard for how to run it on each particular type of network medium. This is referred to as an "encapsulation", since normally what happens is that the IP packets get encapsulated in a packet appropriate to the medium. So whether 802.2 is used is a question of the particular encapsulation used, not the version of IP used. There is an official IP encapsulation for 802-type networks. It is defined by RFC 1042. It supports 802.2 LLC and SNAP over 802.3, .4, and .5 networks. However this is a new RFC, defined primarily for the benefit of IBM token ring and similar new 802 technologies. In fact the "traditional" TCP/IP medium is Ethernet, as opposed to 802.3, and this is what Sun supports. Of course there's very little difference between Ethernet and 802.3. The main one is that what Ethernet calls a type field, 802.3 calls a length field. The IP encapsulation for Ethernet uses the type field to identify the packets as IP packets. This encapsulation has a bare minimum of overhead. The Ethernet headers are put immediately in front of the IP headers. So you've just got Ethernet addresses and a type code identifying the packet as IP. No LLC or SNAP type stuff is used. (There is also a different Ethernet type code used for a secondary protocol called ARP. This protocol is used to map from IP address to Ethernet address. This protocol is officially considered part of the Ethernet encapsulation specification.) Suns normally use this Ethernet encapsulation, not the newer 802-style encapsulation. Of course the defined Ethernet types are large enough that they do not form legal 802.3 packet lengths, so in fact there's no reason that a single cable can't carry both types of protocol. Indeed in theory one could have two separate (and non-communicating) TCP/IP networks on the same cable, one using the traditional Ethernet encapsulation, and the other using the new 802-style encapsulation. However so far I haven't seen 802-style encapsulations used on Ethernet or 802.3, except by HP (who designed a different encapsulation that apparently only HP and cisco implemented) and cisco (who implement all three encapsulations: Ethernet, the HP version, and the new 802.3 standard). In general the TCP/IP community is really using Ethernet version 2, not IEEE, except to the extent that IEEE happens to be compatible with Ethernet. This may change over time, as other 802 networks become more common. At the moment the same is true of DECnet, XNS, and other network protocols that we see on our cables.
melohn@SUN.COM (Bill Melohn) (04/23/88)
In article <6140@shamash.UUCP> jwabik@shamash.UUCP (Jeff Wabik) writes: > Does anyone know which version of tcp-ip is implemented in the standard > Sun OS (Sun UNIX 3.x) ? 802.2? 802.2/snap? 802.3? Charles's observations are correct; the standard SunOS kernel provides support for TCP/IP over Ethernet/802.3. Sun does offer TCP/IP using snap over 802.2 (as defined in RFC1042) layered on either 802.3 or 802.4 using the Sunlink OSI product, which also comes with TP4/CLNS.