Ethernet Standards IEEE802.3 Data Link Layer contains two sub-layers:

Media Access Control (MAC) Logical Link Control (LLC)

Four generic Ethernet frame standards of IEEE 802.3 Ethernet 802.3 (Raw) (No LLC information, supports IPX/SPX only) Ethernet 802.2 (contains LLC header, supports IPX/SPX and FTAM) Ethernet II (no LLC header, uses Type instead of Length, supports

IPX/SPX, TCP/IP) Ethernet SNAP (with extended LLC capacities, support TCP/IP,

IPX/SPX, AppleTalk Phase 2)

Network Layer

Physical Layer

LLC Sub-Layer

MAC Sub-Layer

Ethernet Standards

Not all frame types can support all traffic variants. For example, NetWare IPX/SPX packets are usually transmitted by 802.3 (Raw) frames. In fact, the 802.3 (Raw) frame type can only support IPX/SPX traffic. When TCP traffic is generated, the Ethernet II frame is often used. Some desktop LAN analyzers will employ Sub-Network Access Protocol (SNAP) frames.

Ethernet/IEEE 802.3 Frame

Destinaddress FCS

Preamble (for synchronization) (01010…0111)

Type (Ethernet II, TCP/IP - 0800H, IPX - 8138H)Length (IEEE 802.3)If the value > 0x05-DC (decimal 1500), then Ethernet II

Logical Link Control data

6 46 - 1500 octets 4

IEEE 802.2 LLC standard for access to higher layers.PAD may be added to ensureenough length for CollisionDetection (CD)

6 27

Sourceaddress

Frame CheckSequence

Logical Link Control Sub-layer

Destinaddress FCS

Sourceaddress

Type

Destination Service Access Point (DSAP) 1 octet

Source Service Access Point (SSAP) 1 octet

Control Field 1 octet

LLC header

DataPAD

IEEE 802.2

More Ethernet Information

http://www.techfest.com/networking/lan/ethernet.htmhttp://www.networkmagazine.com/magazine/tutorial/hardware/9602tut.htmhttp://telecom.tbi.net/frmlan.html