Recall from Chapter 3, "Local-Area Networking Introduction," that local-area network, or LAN, segments are shared-media networks in which each user and device shares the network bandwidth with others on the same segment. Microsegmentation of the LAN through switches limits the number of users per segment, ultimately dividing the LAN so that there is a single user per-dedicated LAN segment. LAN switches can create microsegments because each switch port provides a dedicated 10-Mbps, 100-Mbps Ethernet, or Gigabit Ethernet segment to each user or network device, such as a file server or network printer.
LAN segments are connected to each other by networking devices that enable communication between these LANs while blocking other types of traffic. Switches monitor traffic between these segments and build address tables enabling them to forward frames to specific LAN ports. Switches also can provide nonblocking service, enabling multiple LAN conversations (traffic between two ports) to occur simultaneously.
Switch technology is the solution for most LAN traffic for the following reasons:
Unlike hubs, which do not permit more than one data stream to pass through the hub, switches enable multiple data streams to pass simultaneously through the switch, resulting in more conversations occurring between hosts on the network.
Switches support increased speed and bandwidth requirements of emerging technologies, which means that when you are looking at those new gadgets for your users, such as desktop videoconferencing, it is your switch that will enable the implementation of this technology.
Switches deliver dedicated bandwidth to users because users don't like to share bandwidth. If a user has to share bandwidth with another user, that means the network connection isn't as fast as it could be, and how many times a day do you want to answer the phone and hear "The network is slow again." (I'm guessing, not many times.)
Switches provide for a quality of service (QoS) capability that you can configure in your network. QoS is a defined performance level in a communications system, such as a data or voice network. To ensure that real-time voice and video are delivered without blips or static, such as with IPTV (IP television), for instance, a guarantee of bandwidth across the local-and wide-area network is required; QoS guarantees this bandwidth. Applications such as voice over IP (VoIP) rely on QoS for timely, clean delivery of voice traffic across the data network.