Introduction to Network Hardware CAS Theory day Introduction to Network Hardware

Introduction People sometimes think of a network as a single, local cabling systems that enables any device on the network to communicate directly with any other device on the same network. An Internetwork consists of multiple independent networks that are connected and can share resources. These independent networks can dissimilar in physical type or topology i.e. Bus, Ring, Peer to peer & Client server etc. There are a number of connectivity devices and transfer mechanisms that are used, these are: Hubs & Switches Wireless access points Bridges Servers Repeaters Firewalls Routers Gateways

Hubs & Switches Hubs Hubs come in a variety of sizes, speeds and ports (nuber of connections). They provide a central attachment point for network cabling.      Hubs come in two different types: Passive Active

Hubs Cont….. Passive Hubs Passive hubs do not contain any electronic components and do not process the data signal in any way. The only purpose of passive hubs is to combine the signals from several network cable segments. Because the hub does not amplify the signal (Like a repeater) the distance between a computer and the hub can be no more than half of the maximum distance the cable can reach before signal loss. As you might guess, the limited functionality of passive hubs makes them inexpensive and easy to configure, but offers very little in return

Hubs Cont….. Active Hubs Active hubs incorporate electronic components that can amplify and clean up the electronic signals that flow between devices on the network. This process of cleaning up the signal is called signal regeneration. Signal regeneration has the following benefits: The network is more robust (less sensitive to errors) Distances between devices can be increased These advantages outweigh the fact that active hubs cost more than passive hubs.

Switches Switches look similar to hubs but function quite differently. Modern switching technology is an easy, quick and cost-effective way to improve network performance. Implementing a switch lowers the amount of bandwidth that devices on the network must share. In a standard Ethernet network using a hub, all of the users on the network share the available bandwidth. This type of network can cause slowdowns, collisions and serious bottlenecks. In a switched network, each user on the network receives the full amount of available bandwidth. If a network is starting to suffer from slowdowns, maybe it is time to consider installing a switch.

Switches Switches come in a variety of different sizes, for home use or business below is a sample of CISCO large business switches

Or for smaller business users Switches Or for smaller business users

Managed Switches Managed switches allow network administrators access through a web browser to view traffic through the ports and to balance the load Problems can be viewed remotely from the network office without the need to visit the switch location

Managed Switches This is the web browser interface for a HP procurve managed switch

Hubs V’s Switches Below is a basic diagram of how a hub-based network handles a single request.  In this example, Computer "A" is sending a request to Computer "C."  As the request travels across the network, it is 'broadcast" to all of the devices on the network, in this case computer "B" and the Printer.  Since computer "B" and the printer recognize that the request is not for them, the packet is rejected, while Computer "C" recognizes the request and accepts it.

Hubs V’s Switches In the diagram above, computer A is sending a command to computer C, while computer B is sending a print job to the printer.  Both requests pass through the switch, reaching their destination at the same time. 

Hubs V’s Switches A "switch" has one distinct advantage over a hub which can have a tremendous effect on how well a network performs.  While a hub can only "broadcast" a request for all devices to hear, a switch has the added ability to direct the request to the intended device.  A switch can analyse a packet, determining who to direct the request to by scanning the packet for the MAC address of the desired recipient.  Once the switch determines the destination machine, the packet is sent directly to the port that machine is connected to, while leaving the other ports on the switch free for other traffic.

Bridges Bridges are devices that are used to restrict heavy traffic on a large network by subdividing it into two smaller networks, thus reducing traffic on both sides of the bridge. Reducing the traffic in this way results in better network performance. All Ethernet packets, on each side of the network, are monitored by the bridge. Only packets destined for the other side of the bridge are forwarded. The MAC addresses determine whether a package should be forwarded to its destined node on the other side of the bridge or whether it should be left on the current side of the bridge.

Bridges Bridges learn the topology or physical layout of the network by checking the source MAC address of each packet seen on its ports. When the bridge sees a source MAC address for the first time, it records which side of the bridge it came from and stores that information for future use. Eventually, by monitoring traffic, the bridge learns the location of all the nodes with reference to the ports of the bridge.

Bridges Cont…. If Node 123 sent a message to C3C, Port 'A' would then forward it for transmission to Port 'B' and on to node C3C. If the next message from Node 123 was destined for Node ABC, Port 'A' would NOT forward it to the other side of the bridge, thus leaving port B free for its own local traffic. Bridges normally only connect sub-networks of the same type. Heterogeneous bridges can link sub-networks of different types.

Repeaters Strong Signal Weak Signal Repeater Repeaters are hardware devices added to a network, which extend the transmission power of a LAN over greater distances. They are called dumb devices, which means they do nothing to change the data. They merely send an exact copy of what they received from one LAN to another. They have no intelligence of their own. They simply receive, amplify, and retransmit data, one bit at a time.

Repeaters A repeater is used to connect two similar LAN networks, for example Ethernet to Ethernet. The nodes still believe themselves to be on a single LAN. Therefore, in the case of Ethernet, the nodes are in the same collision domain. At home you may have a wireless repeater to extend your wireless signal

Wireless repeater

Routers Business class router Wireless router for home use

Routers Routers are devices generally used to connect networks to the outside world via the Internet. Routers operate at an higher level than switches or bridges they use IP addresses to send and receive data

Routers are sometimes referred to as gateways

Wireless access points These come in a variety of different types from basic to more advanced. With single or multiple antenna to increase signal strength.

Network Servers Servers are larger powerful computers that provide network services to networked computers. There are many types such as:- File servers which store data Application servers which distribute computer programs such as Microsoft office Web servers hosts web pages. A proxy server Acts as an intermediary between a client and a server, accepting incoming traffic from the client and sending it to the server. Also filters incoming and outgoing data.

Servers Stand alone small business server Enterprise servers in a data centre

Firewall A firewalls job is to prevent unauthorised access to the network. Hackers target unprotected systems and can gain access to corporate data. Firewalls can prevent this by blocking network ports. A firewall can be either software installed on a proxy server or a separate device

Firewall