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Networking
The function of a network is to share resources between computers. In order for this to happen the computers must be able to "talk" to each other which is accomplished with the use of protocols which are essentially a set of "rules" that govern communication over a network. Computers must be configured with a common protocol in order to be able to communicate. Below are some of the most common protocols:
- IPX/SPX - The fastest routable protocol and is used on Novell Netware networks.
- TCP/IP - TCP/IP is the most largely used protocol as it is the foundation for communication over the internet.
- NETBEUI - The NetBios Extended User Interface is a non-routable protocol that establishes connections between computers with the use of NetBIOS.
- HTTP - Stands for Hypertext Transfer Protocol and is the set of rules for exchanging files and multimedia on the internet. HTTPS denotes that it is a secure connection.
- SMTP - Stands for Simple Mail Transfer Protocol and is used to reliably send mail over the Internet.
- POP3 - This is the Post Office Protocol and is used for the receiving of email.
Protocols such as TCP/IP can be configured in the network properties window shown below.
Most networks are governed by a network operating system (NOS) such as NT or Windows 2000 Server. The servers are responsible for providing and denying access to resources with the use of shares, rights and permissions for the various users. In order for a resource to be accessed across a network, it must be shared first. There are a couple of different ways to create shares in Windows. From a command prompt the NET SHARE command can be issued in the following format - NET SHARE \\computername\directory - this format is known as the Universal Naming Convention (UNC format). Shares can also be created by right clicking on a resource and selecting sharing in My Computer or Windows Explorer. Once a drive is shared permissions can be set to control access to its contents. Users that have access to the shared resource can "Map a Drive" to it so that it appears as a local drive in my computer. When mapping the drive make sure that the "Reconnect at logon" option is checked, otherwise the mapped drive will disappear when the computer is rebooted. The computer that the drive is mapped to, must be powered on and connected to the network for this to work. In order to connect to a share, the network must be set up correctly and the user must have appropriate permissions to access the share.
Computers are given unique names to help identify them on the network. In Windows 9x the computer name can be up to 15 characters long and cannot use spaces. In Windows 2000 and XP, the name can be up to 63 characters and should only contain letters, numbers and hyphens.
Name Servers
Name servers such as WINS and DNS are used to make finding resources on large network easier without having to memorize IP addresses. They provide a more "friendly" way of locating things.
WINS is used to register NetBIOS names and resolve them to IP addesses for both local and remote hosts. If a WINS server is configured, then name resolution requests are sent directly to it and in turn the WINS server will send the IP address to the requesting client.
The internet used to use a hosts file to resolve IP addresses to host names or domain names. The internet grew to the point where the administration and the traffic needed to maintain this file became unbearable and DNS was born. The way DNS works is very similar to calling information. You call them with a name, they check their database and give you the phone number. Nameservers are distributed into tiers called domains.
TCP/IP Utilities
- Telnet - Provides a virtual terminal or remote login across the network. The remote server must be running a Telnet service for clients to connect.
- Tracert - By sending out ICMP packets, it determines the path taken by a data packet to reach it’s destination and can help determine at what point a network connection is now longer active.
- WINIPCFG - Displays current TCP/IP configurations on the local workstation for Windows 9x computers.
- IPCONFIG - IPCONFIG displays the TCP/IP configuration on the Windows NT computers. The /all switch will display more in depth configuration information. The /release and /renew options can be used to update DHCP settings.
- FTP - Used for transferring data across a network from a server to a client.
- PING - Uses ICMP to verify a connection to a remote host by sending echo requests and "listening" for replies.
- FTP - Stands for File Transfer Protocol and is a method of transferring files between 2 machines.
- NSLOOKUP - This utility is used to enter a host name and find out the corresponding IP address and is often used for troubleshooting DNS problems. Reverse lookups can also be performed.
Internet:
The internet is essentially many networks connected together. Users then connect to the internet using either dial-up networking or newer digital technologies. In either case, these services are provided by an Internet Service Provider(ISP). The ISP also will assign your computer a unique IP address and provide email and Newsgroup services.
- Root Level Domains - The top of the tree.
- Top Level Domains - These are divided into different categories. Com, net, mil, edu, org and gov are the most common.
- Second Level Domains - These domains make up the rest of networks as all sub-domains are categorized under this heading. So if you visit Intel's site, you are visiting the sub-domain intel.com. Within intel.com many other sub-domains may also exist.
- Hosts - Hosts are the final level in the hierarchy as they are the individual computers that occupy or comprise a domain and are where the web pages are located.
IP addresses are resolved to domain names using DNS as previously discussed.
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