Ethernet II uses one bit to indicate multicast addresses, 802.3 uses two
bits. On 802.3, the first bit is similar to the multicast bit in that it
indicates whether the address is for an individual or for a group, and the
second bit indicates whether the address is locally or universally
assigned. The second bit is rarely used on Ethernet (CSMA/CD) networks.

In Novell's 802.3 Raw format, the Data field begins with IPX header
information. The first two bytes in this header (for this format) are
always hexadecimal FF FF. These two bytes help confirm that an 802.3 Raw
packet contains encapsulated IPX information, but they correspond to IPX's
Checksum field. Because this static information interferes with use of the
IPX Checksum field, 802.3 Raw packets will not be able to use the security
features, such as packet signing, planned for the IPX format. Packets
incorporating 802.2 link information are free to use the IPX Checksum
feature. Note that IEEE does not recognize Novell's 802.3 Raw format; it
recognizes only 802.3 packets encoded with 802.2 and 802.2 SNAP headers.

100BaseT is the IEEE specification for the 100-Mbps Ethernet implementation
over unshielded twisted-pair (UTP) and shielded twisted-pair (STP) cabling.
The Media Access Control (MAC) layer is compatible with the IEEE 802.3 MAC
layer.
100VG-AnyLAN is an IEEE specification for 100-Mbps Token Ring and Ethernet
implementations over 4-pair UTP. The MAC layer is not compatible with the
IEEE 802.3 MAC layer. 100VG-AnyLAN was developed by Hewlett-Packard (HP) to
support newer time-sensitive applications, such as multimedia. A version of
HP's implementation is standardized in the IEEE 802.12 specification.

================================================================
802.2 and SNAP Ethernet packet types
================================================================
802.2 Logical Link Control (LLC) header:
- 1-byte Destination Service Access Point (DSAP) =K1
- 1-byte Source Service Access Point (SSAP) =K1
- 1-byte CNTRL
---------
  3 bytes

Some Service Access Point (SAP) codes:
    - 04h = IBM SNA             - 06h = TCP/IP          - 80h = 3Com
    - AAh = SNAP (see below)    - BCh = Banyan          - E0h = Novell
    - F0h = NetBIOS             - F4h = Lan Manager     - FEh - CLNS

SubNetwork Access Protocol (SNAP) header:
- 3-byte protocol ID or org code =K2 =0
- 2-byte Ether type
---------
  5 bytes

For SNAP, K1 value in 802.2 header = 170, and CNTRL value = 3
("Unnumbered Information").

Note that Ethernet SNAP allows only 1492 bytes for payload,
but Ethernet MaxTU is 1500 bytes.

encapsu-
lation/         Crynwr
framing Ether   packet
type    type    driver  Notes
------- -----   ------  --------------------------------------------------
802.3   len;    NO?     Obsolete. Novell "raw" or "Ethernet_802.3" format.
         <1518 xxx      Not for use with IP.

802.3   len;    NO?     802.2 header after MAC header. One source claims
with     <1518          this format can be used for IP by using SAP code
802.2                   06h; another says not. Novell "Ethernet_802.2"
                        format(?).

802.3   len;    yes?    802.2 and SNAP headers after MAC header. Can be
with     <1518          used for IP (see RFC-1042) and AppleTalk (Phase II).
SNAP                    Novell "Ethernet_SNAP" format(?)

Ether-  type;   yes     Also known as: DIX Ethernet, XEROX PARC Ethernet,
net II   >=1536         Traditional Ethernet. Can be used for IP (see
                        RFC-894), Novell, and AppleTalk (Phase I).

Hardware type code (used for ARP) is 1 for Ethernet, 6 for IEEE-802.

Ethernet broadcast address is all ones (FF:FF or FF:FF:FF:FF:FF:FF)
