Networking basics: LAN
   
    TCP/IP is the protocol used in the Internet and 
    dominates the internet and transport layers
   
    The subnet layer -- the Local Area Network (LAN), 
    however, uses the OSI standards, predominantly based 
    on Ethernet technologies. 
   
    Each device in a subnet has a special number (MAC 
    address) and this number is hardwired in the device: 
    Network Interface Card (NIC), hub, etc. 
  Network traffic and devices
   
    Most of the traffic in networks happens at the 
    LAN, subnet layer, with users sharing data, using 
    applications available in the LAN, etc. 
   
    The main devices at the subnet layer are cabling, 
    Network Interface Card (NIC) , hubs and switches. 
   
    The NICs are placed in a PC or other device (e.g. a 
    network printer) and is linked to a subnet using 
    (generally) Ethernet cat 5 (category 5) cable. 
   
    Of course, the cable needs to be connected to a 
    subnet device which links the PCs, printers, etc. 
    These devices are either a hub or a switch. 
 LAN with single Hub
 LAN with multiple Hubs
  Hubs and Switches
   
   The difference between a hub and a switch is simple: 
   when the hub receives a message for a device, it 
   sends the message to all devices (broadcasts), and it 
   is up to the device to check and see if the message is 
   for it or not, if it is it should get it. 
   
   A switch receives a message to a device and delivers 
   the message directly to that device; it does not 
   broadcast.
   
    Hubs were cheaper than switches, and were used in 
   most subnets, but increasingly switches are getting 
   cheaper and switches are becoming the  device of 
   choice in the subnet.