Author: Neftaly Malatjie

Network configuration is the process of setting a network’s controls, flow and operation to support the network communication of an organization and/or network owner. This broad term incorporates multiple configuration and setup processes on network hardware, software and other supporting devices and components.

In a networked environment, such as a company, typically there are many computers connected together using a router or a switch (for more information, see router or switch in the definitions section). In larger companies, there may be several different routers distributed in buildings and plant locations. A router allows any LAN-side computer communicate with computers and devices outside the LAN (local area network). Routers send data packets from one place to another place on a network. Routers use network addresses to route packets to the correct destination. For example, in a TCP/IP network, the IP (internet protocol) address of the network interface is used to direct router destinations. Because routers help computers inside the LAN “talk” with computers outside of the LAN. The security of a company’s LAN may be compromised by gaps of open ports in the router. Security measures may have been instituted to compensate for these vulnerabilities. Consult your network administrator to learn about the security measures taken to protect your network. VPN, or virtual private network, is one such security measure to protect the intelligence of the LAN. A computer outside the LAN must have an address or key known by the VPN to allow access to the LAN. Many companies use a VPN to connect two different LANs, thus allowing the transfer of data between the two networks.

Accessing the Wide Area Network (WAN) Figure  shows LAN IP addresses using a common IP address, 10.2.100.x (192.168.x.x is another common address). Most devices are shipped with these addresses as its default. It is recommended to use these addresses for LANs.

Network Address Translation (NAT) Using the initial IP address, then converting it to a valid WAN IP address is how the network address translation works in theory. Once the IP address is changed, it is up to the network interface device (such as a router, gateway, switch, etc.) to keep track of which computers are talking on which ports. For example, if two local devices (PC1 and PC2 in Figure 3) both wanted to talk via port 1031, then the network interface device would have to change one of the port requests to the next available port, 1032.

Ports

In general, a network port is an endpoint to a logical connection. The port number identifies what type of port it is. For example, port 80 is used for HTTP traffic. When you type an address into the address bar of a web browser, your computer goes to find an IP address for the url you are requesting (http:// www.telex.com). To obtain this address, the computer contacts a DNS server (Domain Name Server). Once the IP address is found, it tries to connect to the http port of the network device (port 80). See Table 1 for a list of the more well-known Port numbers. Each network device can be set up to respond or not respond to the various ports. The function of responding or “hosting a service” is called “serving”.

If a second work station on the LAN wants to communicate to the same server, and happens to use the same source port number, then the LAN Modem will translate the source port number as well as the source IP address. In Table 2, a second LAN computer wants to access.

Amazingly, all the address translation that occurs takes place automatically in order to make web browsing and other functions easier. This is also a way for large web hosting services to speed up the network by having different devices perform different functions.

Ping a Computer

Pinging a computer on the network makes sure it is able to be “seen” and receive messages on the network. Note: You can also ping your RVON-8 card to verify that it is responding over the network by putting the cards IP address in place of the computer IP address. To ping a computer on the network, do the following,

1. From the Start Menu, open a Command Prompt screen.
2. 

3. . At the prompt, type the IP Address of the computer you wish to ping. (for example, 10.2.100.130) 3. Press Enter.

4. 

5. Note: If the computer you are pinging is not responding to the ping, you will receive a time out message in the command prompt screen.

   Possible Pitfall with Routers, Gateways, and Switches Anytime computers communicate through routers, gateways, and switches, they may be allowed or denied the connection. Network interface devices can be configured to block specific outgoing requests, as well as incoming requests, based on the IP address and/or port. This is one of the security mechanisms of a router. This also happens when broadcast messages are sent and received. To view the path an IP address takes to retrieve information, you can execute a tracert from the Command Prompt screen.

   To run tracert, do the following:

   1. From the Start Menu, open a Command Prompt screen.
   2. At the prompt, type tracert and type the url or IP address you want to trace.
   3. Press Enter

A Local Area Networks connects computers together to exchange data. Apart from the computers, and other devices like printers and faxes, a LAN has to have six essential components to function. The components used to establish a local area network (LAN) have a variety of functions. The common unifying theme among them is that they facilitate communication between two or more computers. LAN components are configurable in a variety of ways, but a LAN always requires the same basic components.

1. Network Cards

At the most basic level, a network card is a component that allows the computer to communicate across a network. This component is frequently built into the motherboard of today’s computers, but it can also be a separate card for use in a PCI slot, or part of an external unit that connects to the computer via a USB port. Network cards are further categorized according to whether they operate on wired or wireless networks. However, some cards do support both wireless and wired networking.

2. Network Cables

Network cables are the physical lines used to carry information between computers in a wired LAN. The cables are labelled by their category and are commonly referred to as CatX–where X is the category number–cable. The most commonly used type in 2010 is Cat5, although other categories with different properties do exist.

3. Network Hubs

A network hub acts as a centralized point for data transmission to computers in a LAN. When data from one computer reaches the hub it is broadcast to every computer in the network regardless of where the data is intended to go. Network bandwidth on LANs using a network hub is shared, which means that four computers on a hub will each get one-quarter the total bandwidth available on the hub.

4. Network Switches

An alternative to the network hub is the network switch. Switches represent a newer networking technology that assigns each computer in the network a specific MAC address. This allows LANs using a network switch to route information to individual computers. Because network switches do not broadcast to every computer on the network, they can simultaneously allot their full bandwidth to each computer.

5. Routers

Unlike switches and hubs, network routers are used to connect networks to one another, rather than connecting computers in a single network. Routers can connect groups of computers that are separated by a wall or by an ocean. They are most commonly found in the home, where they facilitate the connection of home computers to the Internet; however, they can be used to connect networks of any kind. Most modern network routers are actually combination units that contain a router and a network switch, in addition to a handful of other networking-related tools such as a DHCP server and a firewall.

6. Server

A local area network (LAN) server is a program (and by implication usually the computer it runs in) that “serves” the resources (files, storage, application programs, printers, and other devices) for a number of attached workstations. A LAN server can also be housed in a computer that has other servers such as a proxy server.

7. Workstation

A workstation is a computer intended for individual use that is faster and more capable than a personal computer. It’s intended for business or professional use (rather than home or recreational use). Workstations and applications designed for them are used by small engineering companies, architects, graphic designers, and any organization, department, or individual that requires a faster microprocessor, a large amount of random access memory (RAM), and special features such as high-speed graphics adapters. Historically, the workstation developed technologically about the same time and for the same audience as the UNIX operating system, which is often used as the workstation operating system. Among the most successful makers of this kind of workstation are Sun Microsystems, Hewlett-Packard, DEC, and IBM.

8. Repeaters

In digital communication systems, a repeater is a device that receives a digital signal on an electromagnetic or optical transmission medium and regenerates the signal along the next leg of the medium. In electromagnetic media, repeaters overcome the attenuation caused by free-space electromagnetic-field divergence or cable loss. A series of repeaters make possible the extension of a signal over a distance.

Repeaters remove the unwanted noise in an incoming signal. Unlike an analog signal, the original digital signal, even if weak or distorted, can be clearly perceived and restored. With analog transmission, signals are strengthened with amplifiers which unfortunately also amplify noise as well as information.

9. Terminator

A device attached to the end-points of a bus network or daisy-chain. The purpose of the terminator is to absorb signals so that they do not reflect back down the line. Ethernet networks require a terminator at both ends of the bus, and SCSI chains require a single terminator at the end of the chain.

The Token-Passing Protocol relies on a control signal called the token. A token is a 24-bit packet that circulates throughout the network from NIC to NIC in an orderly fashion. If a workstation wants to transmit a message, first it must seize the token. At that point, the workstation has complete control over the communications channel. The existence of only one token eliminates the possibility of signal collisions. This means that only one station can speak at a time.

 Logical Ring Physical Star topology for Token-Passing Standard.

 It is sure that any break in the ring at any point will interrupt communications for all machines. To solve this problem, IBM developed a modified ring topology, which they called the logical ring physical star. The central point of the physical star configuration is Token Ring hub called the multi-station access unit (MSAU, pronounced as masow).

Workstations and servers attached to the MSAU through special STP adapter cables. IBM converted stars into a logical ring by connecting all MSAU hubs together through special ring-in (RI) and ring-out (RO) ports.

The frame format specified by IEEE 802.3 standard contains following fields

1. Preamble: It is seven bytes (56 bits) that provides bit synchronization. It consists of alternating Os and 1s. The purpose is to provide alert and timing pulse.
2. Start Frame Delimiter (SFD): It is one byte field with unique pattern: 10 10 1011. It marks the beginning of frame.
3. Destination Address (DA): It is six byte field that contains physical address of packet’s destination.
4. Source Address (SA): It is also a six byte field and contains the physical address of source or last device to forward the packet (most recent router to receiver).
5. Length: This two byte field specifies the length or number of bytes in data field.
6. Data: It can be of 46 to 1500 bytes, depending upon the type of frame and the length of theinformation field.
7. Frame Check Sequence (FCS): This for byte field contains CRC for error detection.

CSMA/CD Procedure:

Fig. Shows a flow chart for the CSMA/CD protocol.

To reduce the impact of collisions on the network performance, Ethernet uses an algorithm called CSMA with Collision Detection (CSMA / CD): CSMA/CD is a protocol in which the station senses the carrier or channel before transmitting frame just as in persistent and non-persistent CSMA. If the channel is busy, the station waits. it listens at the same time on communication media to ensure that there is no collision with a packet sent by another station. In a collision, the issuer immediately cancel the sending of the package. This allows to limit the duration of collisions: we do not waste time to send a packet complete if it detects a collision. After a collision, the transmitter waits again silence and again, he continued his hold for a random number; but this time the random number is nearly double the previous one: it is this called back-off (that is to say, the “decline”) exponential. In fact, the window collision is simply doubled (unless it has already reached a maximum). From a packet is transmitted successfully, the window will return to its original size.

Again, this is what we do naturally in a meeting room if many people speak exactly the same time, they are realizing account immediately (as they listen at the same time they speak), and they interrupt without completing their sentence. After a while, one of them speaks again. If a new collision occurs, the two are interrupted again and tend to wait a little longer before speaking again.

The entire scheme of CSMA/CD is depicted in the fig.