Overview of simple LANs
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.
How switches work
Networking basics: internet
 A subnet communicates with another subnet through
an internet (lower case i, not the big Internet) -- a
local connection among LANs
 Any station (PC, etc) communicates with another
station simply by giving the internet address of the
other station.
 This internet address (IP number) is assigned
permanently or dynamically to each device in the
internet (it is not hardwired like the MAC address).
Internet Routers