Ethernet Standards IEEE802.3

1
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
LLC Sub-Layer
MAC Sub-Layer
Physical Layer
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.

3
Ethernet/IEEE 802.3 Frame
Destin address
Logical Link Control data
Source address
FCS
4
6
46 - 1500 octets
6
2
7
Frame Check Sequence
Preamble (for synchronization) (010100111)
IEEE 802.2 LLC standard for access to higher
layers. PAD may be added to ensure enough length
for Collision Detection (CD)
Type (Ethernet II, TCP/IP - 0800H, IPX -
8138H) Length (IEEE 802.3) If the value gt 0x05-DC
(decimal 1500), then Ethernet II
4
Logical Link Control Sub-layer
LLC header
Destin address

Source address
P A D
Type
Data
FCS
Destination Service Access Point (DSAP) 1 octet
Source Service Access Point (SSAP) 1 octet
Control Field 1 octet
5
IEEE 802.2
6
More Ethernet Information
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