network adapter or a network interface card that provides the physical access
to a network or the Internet.
The network adapter or interface has a unique identifier called the media
access control (MAC) address assigned by the manufacturer. There are
variations of user devices and personal computers typically used on a network,
such as “thin clients” (essentially a PC without any local storage) and network
“appliances” (devices geared to a specific application, such as Internet access
and email).
Network Switches
Network switches are the “traffic cops” of the network, connecting Ethernet
network segments. The switch allows each device that is connected to have
dedicated bandwidth to the switch without any potential for “collisions”
of data packets. When devices on the network (users and servers) transmit
information over the network, the switch determines the origin of the message
or data packet, its destination and the best path or route to get the message to
its destination.
Most switches will handle multiple variations of Ethernet, with transmission
speeds of 10/100/1000 Mbps. Large, more sophisticated switches may have
10 Gbps ports. Network ports for other types of networks such as Fibre Chan-
nel or asynchronous transfer mode (ATM) may also be available. Typical
switches will provide for ports in multiples of eight: 8-ports, 16-ports, 24-ports,
48-ports, and so on.
Network switches may operate at one or multiple open system interconnec-
tion (OSI) layers: physical layer, data link layer, network layer or transport
layer.
Layer 1
Network hubs deal strictly with Layer 1, the physical layer. Hubs simply
repeat or broadcast out traffic to all other ports. Hubs do not manage
any traffic and therefore “packet collisions” can result and affect throughput.
In some cases it is advantageous to broadcast traffic to other ports, but more
sophisticated switches can do something similar with port mirroring.
Layer 2
The network equipment that manages Layer 2 connectivity is referred to as
bridges. Bridges provide only one path between any two points using a “spanning
tree protocol” to learn the network topology and then find the best path. The
bridge then forwards the frame or packet using one of the following methods:
124 Smart Building Systems for Architects, Owners, and Builders