Hubs

Provide full bandwidth to each client, unlike BUS networks where the bandwidth is shared. Often include buffering of packets and filtering, so that unwanted packets (or packets which contain errors) are discarded. In standard ethernet, all stations are connected to the same network segment in bus configuration. Traffic on the bus is controlled using the CSMA protocol and all stations share the available bandwidth.

Hubs dedicate the entire bandwidth to each port (workstation). The workstations attach to the hub using UTP. The hub provides a number of ports, which are logically combined using a single backplane, which often runs at a much higher data rate than that of the ports. Ports can also be buffered, to allow packets to be held in case the hub or port is busy. As each workstation has their own port, they do not contend with other workstations for access, having the entire bandwidth available for their exclusive use.

The ports on a hub all appear as one single ethernet segment. In addition, hubs can be stacked or cascaded (using master /slave configurations) together, to add more ports per segment. As hubs do not count as repeaters, this is a better option for adding more workstations than the use of a repeater.

Hub options also include SNMP (Simple Network Management Protocol) agent. This allows the use of network management software to remotely administer and configure the hub. Detailed statics related to port usage and bandwidth is often available, allowing informed decisions to be made concerning the state of the network.

Routers

Packets are only passed to the network segment they are destined for. They work similar to bridges and switches in that they filter out unnecessary network traffic and remove it from network segments. Routers generally work at the protocol level. Routers were devised in order to separate networks logically. For instance, a TCP/IP router can segment the network based on IP subnets. Filtering at this level ( on IP addresses) will take longer than that of a bridge or switch which only looks at the MAC layer.

Most routers can also perform bridging functions. A major feature of routers, because they can filter packets at a protocol level, is to act as a firewall. This is essentially a barrier, which prevents unwanted packets either entering or leaving the network.

Typically, an organization which connects to the Internet will install a router as the main gateway link between their network and the outside world. By configuring the router with access lists (which define what protocols and what hosts have access ) this enforces security by restricted (or allowing) access to either internal or external hosts.

For example, an internal WWW server can be allowed IP access from external networks, but other company servers which contain sensitive data can be protected, so that external hosts outside the company are prevented access.