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General Technical Advice


CDI Group aim to provide accurate technical advice and support to both clients and visitors to our site. We will cover a wide range of topics relating to both existing and emerging IP network technologies.



Ethernet – The physical communication technology underlying the Internet, Ethernet was created by Robert Metcalfe and David Boggs in 1973.

When first widely deployed in the 1980s, Ethernet supported a maximum theoretical data rate of 10 megabits per second (Mbps). Later, Fast Ethernet standards increased this maximum data rate to 100 Mbps. Today, Gigabit Ethernet technology further extends peak performance up to 1000 Mbps.

TCP/IP – In May, 1974, the Institute of Electrical and Electronic Engineers (IEEE) published a paper titled “A Protocol for Packet Network Interconnection.” The paper’s authors – Vinton Cerf and Robert Kahn – described a protocol called TCP that incorporated both connection-oriented and datagram services. This protocol later became known as TCP/IP.. 

Topology in Network Design


Think of a topology as a network’s virtual shape or structure. This shape does not necessarily correspond to the actual physical layout of the devices on the network. For example, the computers on a home LAN may be arranged in a circle in a family room, but it would be highly unlikely to find a ring topology there. Network topologies are categorised into the following basic types:

• bus

• ring

• star

• tree

• mesh

More complex networks can be built as hybrids of two or more of the above basic topologies..

Network Protocols



A network protocol defines rules and conventions for communication between network devices. Protocols for computer networking all generally use packet switching techniques to send and receive messages in the form of packets. Network protocols include mechanisms for devices to identify and make connections with each other, as well as formatting rules that specify how data is packaged into messages sent and received.

Some protocols also support message acknowledgement and data compression designed for reliable and high performance network communication. Hundreds of different computer network protocols have been developed, each designed for specific purposes and environments. 

Network Switch



A network switch is a small hardware device that joins multiple computers together within one local area network (LAN). Technically, network switches operate at layer two (Data Link Layer) of the OSI model. Network switches appear nearly identical to network hubs, but a switch generally contains more intelligence (and a slightly higher price tag) than a hub. 

Unlike hubs, network switches are capable of inspecting data packets as they are received, determining the source and destination device of each packet, and forwarding them appropriately. By delivering messages only to the connected device intended, a network switch conserves network bandwidth and offers generally better performance than a hub. 

Network Router


Routers are physical devices that join multiple wired or wireless networks together. Technically, a wired or wireless router is a Layer 3 gateway, meaning that the wired/wireless router connects networks (as gateways do), and that the router operates at the network layer of the OSI model.

Network Firewall


A network firewall protects a computer network from unauthorized access. Network firewalls may be hardware devices, software programs, or a combination of the two. Network firewalls guard an internal computer network (home, school, business intranet) against malicious access from the outside. Network firewalls may also be configured to limit access to the outside from internal users.

Network Address


A network address serves as a unique identifier for a computer on a network. When set up correctly, computers can determine the addresses of other computers on the network and use these addresses to send messages to each other. One of the best known forms of network addressing is the Internet Protocol (IP) address. 

IP addresses consist of four bytes (32 bits) that uniquely identify all computers on the public Internet. Another popular form of address is the Media Access Control (MAC) address. MAC addresses are six bytes (48 bits) that manufacturers of network adapters burn into their products to uniquely identify them.

Network Categories


One way to categorise the different types of computer network designs is by their scope or scale. For historical reasons, the networking industry refers to nearly every type of design as some kind of area network. Common examples of area network types are:

• LAN – Local Area Network

• WLAN – Wireless Local Area Network

• WAN – Wide Area Network

• MAN – Metropolitan Area Network

• SAN – Storage Area Network, System Area Network, Server Area Network, or sometimes Small Area Network

• CAN – Campus Area Network, Controller Area Network, or sometimes Cluster Area Network

• PAN – Personal Area Network

• DAN – Desk Area Network

LAN and WAN were the original categories of area networks, while the others have gradually emerged over many years of technology evolution. Note that these network types are a separate concept from network topologies such as bus, ring and star.