Download Ethernet - Texas Tech University

Ethernet Standards
IEEE802.3
 Data Link Layer contains two sub-layers:
Media Access Control (MAC)
Logical Link Control (LLC)
Network Layer
LLC Sub-Layer
MAC Sub-Layer
Physical Layer
 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)
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
Destin
address
7
6
Source
address
6
Logical Link Control data
2
46 - 1500 octets
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
FCS
4
Frame Check
Sequence
IEEE 802.2 LLC standard
for access to higher layers.
PAD may be added to ensure
enough length for Collision
Detection (CD)
Logical Link Control Sublayer
LLC header
Destin
address
Source Type
address
Destination Service Access Point
(DSAP) 1 octet
Data
Source Service Access Point
(SSAP) 1 octet
P
A
D
FCS
Control Field 1 octet
IEEE 802.2
More Ethernet Information
http://www.techfest.com/networking/lan/ethernet.htm
http://www.networkmagazine.com/magazine/tutorial/hardware/9602tut.htm
http://telecom.tbi.net/frmlan.html