A computer network (also referred to as a "data network" or simply a "network") consists of a set of devices connected together in order to exchange data between themselves. These devices create a network using their respective network interfaces. Some devices may use a single network interface; others may connect via multiple interfaces.
The type of interface(s) a device uses to connect to a network depends on the physical medium. A wireless interface connects to a network over the air using a standard such as IEEE 802.11 (known colloquially as WiFi). Various types of wired mediums are in use today, the most common of which follows the IEEE 802.3 standard (Ethernet). Most devices with a wired network interface will have at least one Ethernet interface.
A device connected to a computer network is typically called a node. Based on the function of a node within the network, we can classify it as one of 2 types of devices:
Hosts are devices that either store data to serve to other hosts or request data from other hosts when necessary—for example, a laptop or a web server.
The previous post provided an overview of computer networks and described how data is encapsulated in multiple layers of headers
in order to correctly identify its source (application, device and interface) as well as its destination (application, device and interface).
In this post, we will discuss the role played by network devices such as switches, routers and firewalls in transfering data from its source
to its intended destination over a network.
Let's start by revisiting the HTTP request from the previous post. The request, encapsulated in TCP, IP and Ethernet headers looks like the following:
Data Link (MAC)70:F4.7D:A5.BC:4FEC:70:2C:5D:AF:F2Layer 2 Network (IP)10.0.0.9110.0.0.10Layer 3 Transport (TCP)1080180Layer 4 GET / HTTP/1.1
One way of categorizing network devices is by using the layer at which the device primarily operates.
In order for online networking courses to be effective, they must be delivered on a platform that is purpose-built for the subject matter. Furthermore, in order to provide a truly comprehensive learning experience, an e-learning platform must be able to reproduce some of the most effective features of a hands-on, instructor-led classroom learning experience.
Keeping this in mind, we created an e-learning platform explicitly-designed to deliver effective computer networking training. In particular, it features the following:
What is the best way to master computer networking? This question is asked often in online forums and may be of interest to someone seeking to embark on a career as a network engineer. In this post, we will address the question by sharing our insight on the topic.
When someone starts a journey to learn or master computer networking it is usually for one of the following reasons:
Enhance existing skills
Gain new skills in order to make a career change
Gain industry certifications for career progression
Simply out of interest or curiosity
Our end-goal influences our approach to learning in a particular field of study — and the approach has a direct impact on how effectively we learn.
Let's start with the "why" first. Why should we put in the effort to master subnetting? The answer is simple - it is essential to master subnetting if one wants to pursue a career in computer networking. Why are we writing a post on the topic? Our purpose is simply to demonstrate that subnetting is not as challenging a topic as it might sometimes seem.
The first step in simplifying everything related to subnetting is to identify the key outcomes we are aiming for:
Identify network boundaries (Network and Broadcast Addresses) from an IP Address and Subnet Mask
Break up a range of IP Addresses into a number of smaller ranges (subnets)
Summarize a number of contiguous subnets into a single network
A subnet mask table can be handy when we need to calculate to the size of subnets with different prefix lengths or subnet masks. The following table lists out CIDR subnet masks along with the decimal equivalents and includes the total number of addresses as well as the total number of host addresses for each subnet mask.
This list of networking related terms is updated on an ongoing basis. For any questions or comments on any of the terms listed here, please use the comments section at the bottom of the page.
802.1Q Encapsulation
IEEE 802.1Q is a standard that defines how traffic for multiple VLANs can be carried on a single physical ethernet link. This is accomplished by modifying the Ethernet header to include a VLAN ID tag.
To encapsulate an ethernet frame with a VLAN ID tag, a 32-bit field is added to the ethernet header before the EtherType field in the header.
The first 16 bits in the 32-bit field represent the Tag Protocol Identifier. This is set to hexadecimal 8100 (0x8100) to identify it as a VLAN tagged frame.
