A wide area network (WAN) is a network generally transmitted over the telecommunications network that interconnects long-distance networks. If it wasn't for the WANs, the Internet wouldn't exist, and the smaller LANs and Metropolitan Area Networks (MANs) wouldn't be interconnected. The telecommunications network was originally built for voice traffic but as the demand for packet ("data") traffic grows, the existing telecommunication was used to deliver data traffic over WANs.

A VLAN is a logical partition of a physical LAN into virtual segments. By dividing a physical LAN into virtual networks, network administrators can group devices together according to their traffic characteristics. Not all devices in the same LAN need to communicate with each other and by segmenting a physical network into logical groups, resources available within a VLAN can only be shared amongst devices contained within.

We've learned that SSID is the network name, and we use this name to know which wireless network we're connecting to. If you've established a connection previously, your computers and smart devices have saved the password in some location for later use. Next time you need a wireless connection, the device will automatically connect to the network it has connected to before. If you can't recall the WiFi password of your router, there are ways to find the password as they are stored in your Windows, macOS, and smartphones.

SSID is a short name for Service Set IDentifier, and it is referring to your WiFi network name. For network devices to find the WiFi networks, wireless routers and wireless access points generally broadcast their SSIDs to allow nearby devices to connect to it.

When you set up a gateway at home, you may opt to enable a bridge or pass-through mode. Depending on how you want to configure your network, you may configure the gateway to bridge over passthrough. So, what is the bridge mode, and what is the pass-through mode?

To provide Internet connectivity to homes, ISPs often provide a gateway device to their customers. By connecting a router to the gateway, users create their own local network. A gateway used to be a layer-2 device that extends WAN into an individual's home, but it now provides routing functionality built into the gateway so the term is loosely used.

A DMZ (Demilitarized Zone) is a network (or a node) used to connect internal resources to the untrusted outside world, usually the Internet. By creating a separate "danger" zone, internal resources are within the private network are not directly accessible from the outside world. In traditional corporate networks, the servers providing services to the outside world such as the webserver, email server, and DNS server are isolated inside the DMZ network so that the internal network is protected even if DMZ is compromised. With the explosive growth in cloud networks, the majority of public servers are relocated to cloud servers and there is less demand for DMZ than before. However, there are still some gateway servers providing access to the internal resources that are confined within the DMZ network.

A local area network (LAN) is a group of smart devices connected together to create a network within the same location. A home is a good example of LAN consisting of a few computers, tablets, smartphones and IoTs devices over the physical wires and through the Wi-Fi. A LAN can be as small as connecting 2 devices or as large as enerprise network interconnecting thousands of computers, servers and smart devices. A few other examples of LAN include offices, buildings, schools, and corporations.

Both TCP and UDP are protocols used to send data from one device to anoter within the TCP/IP network. When sending data, they are broken into smaller IP packets and sent over the TCP or UDP transport layer. Applications may choose to use either TCP or UDP to send data to the other end depending on whether the reliability or speed is more important. For reliable delivery, TCP is used while UDP is used for faster delivery. TCP/IP is comprised of 4 layers with each providing a specific protocol functions as shown below:

An Autonomous System (AS) is a large network that has a common routing policy used to serve a set of IP prefixes. An AS is assigned to a single organization and is connected to multiple ASes to route IP packets in a redundant manner. An AS is assigned a 16-bit or 32-bit number (ASN) by the IANA to Internet Service Providers (ISPs), governments, universities, and enterprises.