Network Infrastructure Devices

        Network Infrastructure Devices 

Hub

Hubs were the common network infrastructure devices used for LAN connectivity but switches are rapidly replacing hubs. Hubs function as the central connection point for LANs. Hubs are designed to work with Twisted pair cabling and normally use RJ45 jack to connect the devices. Network devices (Servers, Workstations, Printers, Scanners etc) are attached to the hub by individual network cables. Hubs usually come in different shapes and different numbers of ports.

When a hub receives a packet of data (an Ethernet frame) at one of its ports from a network device, it transmits (repeats) the packet to all of its ports to all of the other network devices.  If two network devices on the same network try to send packets at the same time a collision is said to occur.

 Bridges and Switchs

A bridge is a network device that operates at the Data Link layer (Layer 2) of OSI model. There are many different types of bridges and include Transparent bridges, Encapsulation bridges, Source-route bridges. Source-route bridges are for Token Ring network. Bridges allow segmenting a Local Network into multiple segments, thus reducing the network traffic. A bridge performs the segmenting function by examining the Data Link Layer (Layer 2) data packet (Ethernet Frame) and forwarding the packet to other physical segments only if necessary. Both swiches and bridges function using Data Link Layer (Layer 2) addressing system, also known as MAC addresses.

Bridge can connect only a few Networks, LANs or Hosts. A Bridge has comparatively less ports than a Switch. A Switch has usually 24 ports or 48 ports. Brides and Switches are considered to operate at Data Link Layer (Layer 2) of OSI model.

Router

A router is another network infrastructure device that directs packets through the network based on information from Network Layer (Layer 3) of OSI model. A router uses a combination of hardware and software to "route" data from its source to its destination. A router can be configured to route data packets from different network protocols, like TCP/IP, IPX/SPX, and AppleTalk.

Routers segment large networks into logical segments called subnets. The division of the network is based on the Layer 3 addressing system, like IP addresses. If the Network Layer (Layer 3) Data packet (IP Datagram) is addressed to another device on the local subnet, the packet does not cross the router and create a traffic congestion problem in another network. If data is addressed to a computer outside the subnet, the router forwards the data to the addressed network. Thus routing of network data helps conserve network bandwidth.