FDDI Management
Ethernet 802.3 (Ethernet Raw)
The Ethernet 802.3 frame format has an 802.3 MAC layer header (as do Ethernet 802.2 frames); however, it does not contain an 802.2 LLC header. Instead, Novell IPX is fixed within the packet as the network layer protocol. This frame type – also known as Raw
802.3– is the default frame type for Novell NetWare software before version 3.11. Since these frames do not carry the 802.2 header, they do not conform to the IEEE 802.3 specification. If you are using the Ethernet 802.3 Raw frame format, you should consider upgrading your Novell NetWare software to ensure interoperability with other communications protocols (unless your current network is not likely to be upgraded, and has no interoperability problems).
Note that IPX packets with checksums which provide data integrity (a feature of newer Novell NetWare releases) cannot be transmitted on Ethernet 802.3 networks. Note also that a single Ethernet can carry both Ethernet 802.3 and Ethernet 802.2 traffic simultaneously. The Novell software will treat the two frame types as two logical networks (and function as an IPX router between the two networks).
Ethernet SNAP
To allow for proprietary protocols, such as IBM’s SNA protocol, the Ethernet SNAP frame was created. This frame format extended the Ethernet 802.2 packet by improving the frame’s byte alignment, and by allowing further protocol identification than the one byte LSAP protocol identifier of Ethernet 802.2 frames (which is reserved for standard protocols). Ethernet SNAP packets have an LSAP protocol ID of hex AA, indicating that they contain a SNAP (Subnetwork Access Protocol) packet. A SNAP packet, encapsulated within the Ethernet 802.2 packet, has a five byte SNAP header which is simply a five byte protocol identifier. The first three bytes of the header indicate the Organizationally Unique Identifier (OUI) – or the authority assigning the protocol ID – and the last two bytes indicate the protocol according to that authority. Note that for most protocols, the OUI is
FDDI Frames
There are two legal FDDI data frame types:
FDDI 802.2
The FDDI 802.2 frame type has two headers: the FDDI header (which includes the Frame Control field that indicates the class of frame, length of the address field, and the type of FDDI frame), and the 802.2 header.
FDDI SNAP
The FDDI SNAP frame type has an FDDI header with a Frame Control field that provides FDDI framing information, and the 802.2 LLC header with FDDI Frame Control, a SNAP LSAP identifier, and a five byte protocol identifier.
There is no FDDI equivalent for Ethernet 802.3 Raw frames or Ethernet II frames. Enterasys’ Ethernet/FDDI bridges will automatically translate Ethernet II frames into
Configuring FDDI Frame Translation Settings |
