TCP/IP, or Transmission Control Protocol / Internet Protocol, is a protocol suite, and is split into layers, like most modern network protocols. Every layer builds upon the layer below it, adding new functionality. The lowest level protocol is concerned purely with the business of sending and receiving raw data using specific network hardware. At the top are protocols designed specifically for tasks like transferring files or delivering email. In between are levels concerned with areas such as routing and reliability. The advantage of the layered protocol stack is that if you create a new network application or new type of hardware, you only need to create a protocol for that application or that hardware: the entire protocol suite does not need to be rewritten..

TCP/IP is a protocol of four layers: the link layer (IEE 802.x; PPP; SLIP), network layer (IP), transport layer (TCP; UDP) and application layer (FTP; SMTP; SNMP). Each layer obviously requires a more in-depth analysis and explanation, but this knowledge is essential to progress as a networking professional. A number of quality textbooks are available which would greatly complement a more formal certification, such as a SkillsTrain distance-learning course.

A Proxy is a central machine on the network that allows other machines in that network to use a shared Internet connection. Proxy servers are intermediate servers that accept requests from clients and forward them to other proxy servers, a source server, or service the request from their own cache. The proxy is also called ’server’ or ‘gateway’. Proxy allows users on a network to browse the Web, send files over FTP, and work with E-mail and other Internet services.

A Firewall Proxy provides Internet access to other computers on the network but is mostly deployed to provide safety or security. It controls the information going in and out the network. Firewalls are often used to keep the network safe and free of intruders and viruses. Firewall proxy servers filter, cache, log, and control requests coming from a client. A firewall proxy is one that is used for restricting connections from a proxy to the outside world or to the source server inside of the LAN. This differs from a conventional firewall, in the respect that a conventional firewall restricts outside connections.

To put it simply, proxies are gateway applications used to route Internet and web access from within a firewall. Proxy servers work by opening a socket on the server and allowing the connection to pass through. There is often only one computer in a company with a direct Internet connection. Other computers access the Internet through this computer, which functions as a gateway.

A conventional network consists of file servers and workstations. File Servers manage shared data and resources - files, programs and printers. The workstations are used to access and share these resources. To facilitate a workstation’s access to network resources, it needs software installed that allows the workstation’s operating system to access network resources. This is known as a network client.

Microsoft and Novell have their own client software, so a mixed Novell and Microsoft network must have both network clients installed on the workstation. For someone new to network clients, I would recommend the Microsoft Client This tends to be a little less complicated than the Novell Client due to the relatively small number of Directory Services in Microsoft networks.

Client software can be used to support a variety of network functions: e.g. logging in to the network, printing, allocating drive letters to network folders, sending messages, enabling software to be distributed from a server to the workstation and sending messages to other clients on the network.