Devices on the Network
Michael Gustafson
NTC/405
10/8/2012
JOHN-HUNG HO

Devices on the Network
There have been many advances in the world of networking and there are a multitude of devices which are a part of any particular network. I will go over the following network devices: Network interface card (NIC), modems, network hubs, switches, routers, gateways, and repeaters. Also the difference between channels and circuits and the difference between circuit switching and packet switching will be addressed as well as the concept of Ohm’s law and its importance to circuit trouble shooting. A NIC or network interface card is a device which lets a piece of equipment interface with a network. A NIC is a card encoded with a special 48 bit unique number known as a MAC address which helps the network recognize the user so that it can access the network, a NIC supports a transfer up to 1000+ mbps. A transceiver is embedded in the NIC that can transfer media from the network to the NIC. A wireless NIC or WNIC is essentially the same as a wired NIC in that it too has a 48 bit address although the connection is through radio waves transmitted electronically from the NIC’s antennae. The connection is started electronically through antennae and transferred over radio waves then back into an electronic signal in the device. A modem is a piece of equipment used to connect a user’s computer to a network. The modem is essentially a converter in that it can convert analog cables to digitals ones and vice versa. The analog signals come from a telephone wire that is inserted in the modem and the digital signals are what the computer sends out, the signals need to be converted because a digital to digital connection is not possible with a modem. There are generally three types of modems, dial-up, DSL, and cable. Dial-up internet connections where the user’s computer is connected to the internet through an ordinary telephone network (Jones, 2009). When the user is connected the voice is tied up and the telephone cannot be used, the transfer rate of these modems is at a maximum of 56 kbps. A DSL is similar in that it uses a phone line although it can support voice and data at the same time. The DSL modem has a filter in it which separates voice and data. A cable modem provides internet connections through a broadband cable television network. These modems contain additional hardware to separate the network data from television signals (Panes, 2007). A hub is a connection point for various hubs which is used to pass data from different computer devices on a star network. A hub contains multiple ports so that the nodes can be connected, usually by UTP although hubs can also use fiber optic. When a data packet is transmitted to the hub it is copied then sent on to the other devices. The data is directed for one particular node and has certain protocols for the device to accept it, all other devices discard the data. There is also a jam signal that is produced to only allow certain data to be accepted from the hub. There are three types of hubs, passive, active, and intelligent. A passive hub is generally for smaller networks and simply passes the data on from the source and does not process any type of data. An active hub can regenerate a signal before transmission in order to increase signal strength. These hubs are used in networks where the cable length is long. The intelligent hubs which are also known as managed hubs provide processing functions that manage the flow of data through the network as well as all the features in an active and passive hub. Hubs and switches are similar in that they both use ports and transfer the data from node to node. The big difference between a hub and a switch is performance. A switch on a network can send a packet specifically to the required port instead of sending it to all, therefore there are almost not collisions on a switch and it is more efficient. A bridge is a type of switch which can extend a network although it splits networks in two to increase performance. In a bridge even though the different nodes are connect, a node on one side of the network cannot send to a node on the other side.
A router is a network devices which is capable of adjoining other networks together. It consists of an operating system, RAM, flash memory, and microprocessors. The router follows specially designed routing protocols. It connects other networks by these protocols and routes the data with a special destination on each packet. A router is similar to a switch although it is even more efficient and used for a multitude of connections, it contains routing table which stores information about all the possible routes. A router is generally used in larger networks and WAN’s and MAN’s. A gateway is a device similar to a router that is used interconnect networks with a different set of protocols and data formats (Garrett, 2008). This differentiates it from a router which can connect networks with similar protocols only. Gateways are used to translate protocols and data formats between different operating systems, different emails, and different networks using the same type of protocols. The gate way can be implemented as hardware or software although mostly these days a gateway is implemented through software installed in a router and this way eliminates the need for separate hardware. Each gateway on a large network like a WAN will be assigned separate addresses by the service provider. Besides the gateway providing access to everyone on the network it can also act as a firewall, preventing unauthorized access to parts of the network or the entire network.
The lowering of a signals strength is known as attenuation. The loss happens gradually because of the absorption of signal by the material of the medium, also the longer the medium or wire such as UTP the more attenuation. A signal with higher frequency will have lower attenuation than a signal with lower frequency. A repeater is a device which has the ability to regenerate an analog or digital signal that has been weakened or distorted due to its length or lack of frequency in the medium. These mediums can be, copper wire, fiber optics, or wireless connections. The repeater will even connect other networks as long as the protocols are the same.

References
Garrett, L. (2008, May). Switches and Routers; and the efficiency of the networks. Generating speed, 1(1), 2-5.
Jones, R. (2009, March). Network system analysis. Network devices, 12(1), 10-13.
Panes, A. (January, 2007). Network technologies. Network control, 2(2), 45-60.