Local Area Networks

• 10BASE-2 (thin coaxial up to 185M), 10BASE-5 (thick coaxial up to 500M), 10BASE-T (twisted pair using hubs and switches).

• 100BASE-TX (CAT-5 twisted pair up to 100M), 100BASE-T4 (CAT-5 twisted pair, can use CAT-3 or 4, up to 100M), 100BASE-FX (fiber up to 2000M).

• 1000BASE-T (gigabit on CAT-5 twisted pair up to 100M), 1000BASE-SX (fiber using short wavelength lasers up to 550M), 1000BASE-LX (fiber using long wavelength lasers up to 3000M), 1000BASE-CX ( copper up to 25M, used in computer rooms).

Carrier Sense Multiple Access with Collision Detection (CSMA/CD) is the network access method used with Ethernet. CSMA listens to the network to see if it is free to use, and then starts sending data. CD detects whether any other hosts start sending. If activity is detected , a collision has occurred and both hosts back off a random amount of time before trying again.

• Ethernet Frames are the basic unit of transfer, consisting of

  • Preamble ” An 8-byte synchronization field.

  • Destination Ethernet address

  • Source Ethernet address

  • Type ” could be IP, ARP, RARP or IPv6.

  • Data ” The actual data to be transmitted.

  • CRC ” A checksum to verify integrity.

• The maximum transfer unit (MTU) for Ethernet is 1500 bytes.

• Use ifconfig “a to display interface status and netstat “i to display statistics.

• Troubleshoot Ethernet interfaces with ifconfig , ping , netstat and snoop .

• Use ndd to view or set network parameters.