In some legacy networks, workstations or other devices may still be connected as into a LAN segment using hubs. All incoming and outgoing traffic is propagated throughout the entire hub, often resulting in a collision when two or more devices attempt to send data at the same time. For each collision, the original information will need to be resent, reducing performance.
Operationally, this can lead to up to 100% of 5000-byte packets being lost when sending traffic off network and 31%-60% packet loss within a single subnet. It should be noted that common applications (e.g. email, FTP, WWW) on LANs produce packets close to 1500 bytes in size, and that packet loss rates >1% render applications such as video conferencing unusable.
To prevent collisions from traveling to every workstation in the entire network, bridges or switches should be installed. These devices will not forward collisions, but will permit broadcasts to all users and multicasts to specific groups to pass through.
When only a single system is connected to a single switch port, each collision domain is made up of only one system, and full-duplex communication also becomes possible.
– Main.AnnRHarding - 18 Jul 2005