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Figure 4.8. The SNAP and 802.3 (Novell RAW) frame
formats.
The 802.3 frame is a proprietary variation on the IEEE 802.3 packet. It is used
primarily by end-stations that are running Novell's IPX protocol (it can also be used
with NWlink). The Novell RAW frame uses the 802.3 MAC without the 802.2 LLC PDU.
Instead, it drops the IPX header and ULP data raw into the 802.3 data field. Because
the frame is proprietary, it is not compliant with other 802.3 implementations. In
terms of hardware support, 3COM and other NIC vendors market cards that can
support both frame formats. However, NIC's cards are only IEEE 802.3 compliant
and will not support Novell RAW 802.3 frames.
As stated earlier, the significant difference between DIX Ethernet and 802.3 is the
supported physical transmission medium and operating rates. To facilitate changes
to the operational characteristics and provide support for different transport
technologies, the IEEE 803.3 standard provides for separate interfaces between the
MAC and the PHY. Additionally, the PHY is segmented into different service-logical
interfaces, which differ as the transmission rate increases. One of the main
functions of the PHY is to provide data transmission signaling.
802.3 10Mbps (Classic Ethernet) Layer 1 (PHY)
Implementations
For 10Mbps operation, there are four logical PHY interfaces: