Since its earliest development in the 1970s through to today, networking has become increasingly integral in our daily lives. If you stop and imagine what life was like before you had streaming television, a smartphone, a laptop, a personal computer, or the Internet, you’ll soon realize how much we rely on these technologies. While a career in networking requires much training and knowledge, a rudimentary understanding of networking can be achieved by understanding some basic terminology. This list is a high-level overview of the top networking terms you should know before pursuing a networking career
Few concepts in technology have eluded the understanding of so many people as much as “The Internet.” For most of the population of the modern world, the Internet is an enigma. For those of us that study networking, we understand that it is a complex amalgam of proprietary and open technology standards, signaling technologies and infrastructure. There is no one organization that owns the Internet. The physical infrastructure is owned and managed by a handful of large telecommunications companies. But the data that resides on the Internet and the way we access it, known as the World Wide Web, is owned by us all, in some form, either through paying taxes to the government or through our support of the private sector by signing up for services provided by these telecommunication companies.
At its foundation, “the Internet” is simply a web of network nodes connected to other network nodes all around the world. “Inter” means between and “net” stands for “Network.” So, the Internet is a network between networks, connecting all networks together for the purposes of communication and sharing information. From its creation in 1969 to today, the individuals and organizations that maintain and develop technologies for the Internet are passionate about the free and open use of the Internet. The distributed nature of the Internet is what makes it so robust. Because it is owned by many different organizations simultaneously, the Internet continues to function even if individual elements go offline.
Initially in the early days of the Internet – originally known as ARPANET (Advanced Research Projects Agency Network) – there were many competing networking standards. But by the early 1980s, a clear leader emerged. The world began to adopt as its standard communication protocol the suite of protocols known as TCP/IP. Transmission Control Protocol/Internet Protocol is a layered suite of protocols that provides functions related to addressing, routing, session management, data formatting and more. It has become the de facto standard for all Internet communication. While competing standards do still exist, in order to use the Internet, one must support TCP/IP.
TCP/IP and all of its related protocols are currently managed by the Internet Engineering Task Force, or the IETF. Each element of TCP/IP is described in a document called a Request for Comment, or RFC. These RFCs number in the thousands and are available for free online by visiting ietf.org. Any further detail on TCP/IP is too much for a list like this. Whole courses and careers are made by studying TCP/IP. But it is one protocol suite of which you should not be ignorant.
Around the same time that the IETF was standardizing TCP/IP, another organization was tackling the challenge of local communication within a private network. Like with the Internet, initially, there were many competing standards relating to local private communication between devices. Throughout the 1970s, Ethernet, a product of Xerox, slowly began to become a frontrunner in the race toward standardization. By 1980, the Institute for Electronics and Electrical Engineers (IEEE) selected Ethernet as its primary standard for local communication. These standards became known as the 802 standards, named after the year (1980) and the month (February) that this protocol was standardized. Today, over 90% of the world’s private networks use Ethernet and it has spread to becoming a metropolitan area network to connect cities together at very high speeds. Ethernet has always remained on the cutting edge of network speeds. Standards exist within Ethernet to support connection speeds in excess of 400 Gbps. We are just waiting on the hardware to catch up.
Ethernet is characterized by how it labels the various endpoints and on how it gives access to the network. First of all, an Ethernet address is a 48-bit hexadecimal value called a MAC address. These addresses are assigned by the manufacturer when the network node is created. Secondly, Ethernet utilizes a unique “first-come, first served” approach to access control, allowing each endpoint to handle its own access based on how busy the network is. With modern upgrades to this approach, Ethernet has continued to prove its superiority over other protocols by maintaining very fast connection speeds and efficient error handling.
While it is managed by a completely different organization, Ethernet was specifically designed to operate well with TCP/IP. Certain protocols help to map the MAC Address of Ethernet to the IP address of TCP/IP, making these two protocols the most widely used technologies in the world.
In your study of networking, it’s critical to understand the layered nature of this technology. By having separate but related layers, new protocols can be written and old protocols can be either eliminated or modified without having to completely rework the entire suite. You simply fit the protocols into their associated layers and the other layers can remain untouched.
One of the most popular ways to understand this layered approach to networking is the OSI Model. It was developed by an organization called the International Organization for Standardization (aka ISO) and remains one of the most widely taught models in networking training. At its essence, these seven layers show how data is packaged to be sent across a data cable and how it is unpackaged at the end. Having been developed back in the 1980’s, modern networking protocols don’t fit perfectly into its seven layers, but generally speaking, you can see how all of the networking technologies we use today relate to one or more layers of the OSI model. In the figure below is a brief summary of the seven layers and their primary functions within networking.
|Layer 7: Application||Provides a set of rules on how an application can communicate with the network, including how it requests and sends data and how it handles errors. There are thousands of protocols that can be found at this layer including web, e-mail, phone, file transfer, remote access and more.|
|Layer 6: Presentation||Provides a standardized formatting for data so it can be shared more easily with other systems. It also can perform file compression and encryption as needed. Examples of protocols at this layer are XML, JPG, and PDF.|
|Layer 5: Session||Provides structure to the application session, including the initialization, maintenance, and teardown of each session. A common protocol found here is SIP, the session protocol that supports VOIP.|
|Layer 4: Transport||Provides flow control, error management, encryption, and end-point session identification through port numbers. The two most common protocols at this layer are TCP and UDP.|
|Layer 3: Network||Provides logical addressing, routing, and error management features. Common protocols include IP, ARP, IGMP, ICMP, OSPF, and EIGRP.|
|Layer 2 Data Link||Provides a logical interface between the logical network protocol suite above and physical network below. This is the layer that processes MAC Addresses and contains hardware like switches and wireless access points.|
|Layer 1: Physical||Provide local and physical network connections. This can include copper cables, fiber optic cables and various wireless frequencies. Common hardware elements include hubs, repeaters, cabling and wireless frequencies.|
A deeper understanding of the OSI model is required if you hope to be a networking expert. However, you can begin to recognize how this model affects IT by hearing how people use the terminology. For example, you might hear of someone installing a Layer 3 switch. They mean a switch that functions at the same layer as a router. Or you might hear of an Application Layer firewall. This is a firewall that can make block and allow decisions based on Application layer data headers.
To better understand networking, you must understand the IP address. Now this article won’t be going into a ton of technical detail, but at the very least, let’s break down what the IP address is and what it does. Firstly, the IP address is a binary number, like a MAC Address but shorter. It’s also not permanently assigned by the manufacture but often changes by location. This binary address has two versions. Version 4 is a 32-bit address (written in 4 decimal digits grouped into 8-bit chunks, called octets). An example is 10.13.177.230. The only limit to the IPv4 address is the size of the address itself. 32 bits of binary digits only allows for approximately 4.239 billion individual addresses. IPv6 exponentially increased the number of available addresses by using a 128-bit address. This means there are over 340,000,000,000,000,000,000,000,000,000,000,000,000,000 possible address to choose from. That’s 340 undecillion (3.4 x 10^38).
With IPv4, the address can be broken up into two parts. The first section is called the Network ID. All network nodes in a particular location and on the same network will have the same network ID. The rest of the address is the unique identifier for the host. The subnet mask (IPv4) and the network prefix (IPv6) help to split the IP address into the two parts. Depending on how big your network is, you can split up the network space into different sized networks with a specific number of hosts.
The Internet is a vast and diverse network with millions of nodes. There are innumerable paths connecting those nodes together in a massive mesh network. Even the larger internal networks of corporations can be a complex infrastructure. Routing can be compared to the roads and highways of a large country. Routing is the technology that acts as a kind of GPS for these complex networks.
Routing, which occurs at the third layer of the OSI model, involves the use of devices called routers. A router is a networking device that maintains a list of all relevant networks and uses its processor to find the shortest path to the destination of choice and figure out the next hop in order to reach that destination. The beauty of routing is that each router recalculates the best route to the destination. So, if something goes wrong with a particular path, the router that discovered the failure can choose the next best path and route around it, not unlike your GPS identifying that a road is closed due to a car accident and finding you a new path around.
This list of relevant networks is called a route table. There are two ways to maintain a route table. Static route tables are maintained manually by administrators. This is a very cumbersome way of maintaining a routed network and will result in slow recovery from failures and an increased risk of user error. Dynamic route tables are automatically maintained by routing protocols. There are a variety of routing protocols standardized for TCP/IP routing, some for internal networks and some for the Internet itself. They each use different metrics and addressing, but all of them succeed in the primary function of finding the best path from point A to point B.
Due to where the data is located in the packet, routing does require higher amount of processing power than other data transfer methods, but it is more advanced and can move data across vast distances and to almost any other connected network in the world.
Switching is similar to routing but operates at a much simpler level. Switching operates at the second layer of the OSI model and is focused solely on the direct connections of the switch. Switching takes data coming in on one interface and quickly calculates through which outbound interface to send it. How this is calculated depends on the protocol. Ethernet uses MAC Addresses. Frame Relay uses Data Link Connection Identifiers (DLCI). Fibre Channel uses World Wide Names (WWN). Because the data needed to make switching decisions is the very first header on the packet, switching requires very little processing power as compared to routers and is much faster.
There are two basic types of switching. The original switching is called circuit-based switching. Each segment between source and destination is established at the connection. The connection is an exclusive connection where full bandwidth is available to the two endpoints and the entire path is not shared with any other connection. This is the kind of switching is used by phone lines and modems.
The newer type of switching is called packet-based switching. Rather than the entire connection choosing a single path, each data packet gets to choose its path based on network conditions. This allows the network segments to maximize their resources by allowing any data packet from any source to use any network segment. Technologies that use this kind of switching are Ethernet, Frame Relay and Asynchronous Transfer Mode (ATM), among others.
I could write an entire dictionary of important networking terms. But for the purposes of this article, these terms represent the fabric of networking technologies. All other networking protocols, systems and technologies are built on the foundation of these core elements.