IEEE 802 networks may be used as IP networks of any class (A, B, or C). These systems use two Link Service Access Point (LSAP) fields of the LLC header in much the same way the ARPANET uses the "link" field. Further, there is an extension of the LLC header called the Sub-Network Access Protocol (SNAP).
IP datagrams are sent on IEEE 802 networks encapsulated within the 802.2 LLC and SNAP data link layers, and the 802.3, 802.4, or 802.5 physical networks layers. The SNAP is used with an Organization Code indicating that the following 16 bits specify the EtherType code (as listed in Assigned Numbers ).
Normally, all communication is performed using 802.2 type 1 communication. Consenting systems on the same IEEE 802 network may use 802.2 type 2 communication after verifying that it is supported by both nodes. This is accomplished using the 802.2 XID mechanism. However, type 1 communication is the recommended method at this time and must be supported by all implementations. The rest of this specification assumes the use of type 1 communication.
The IEEE 802 networks may have 16-bit or 48-bit physical addresses. This specification allows the use of either size of address within a given IEEE 802 network.
Note that the 802.3 standard specifies a transmission rate of from 1 to 20 megabit/second, the 802.4 standard specifies 1, 5, and 10 megabit/second, and the 802.5 standard specifies 1 and 4 megabit/second. The typical transmission rates used are 10 megabit/second for 802.3, 10 megabit/second for 802.4, and 4 megabit/second for 802.5. However, this specification for the transmission of IP Datagrams does not depend on the transmission rate.