With all of today’s modern devices, some of the terminology can be quite confusing. Pretty much everyone has heard of the term router, but what does it actually mean? Is your router just a router or can it also be a switch, an access point and a gateway?
In the past, each term above usually referred to a single device that performed a single function. That is no longer the case today. Your ISP’s “modem” is probably a modem, router, switch, and access point all in one. You don’t necessarily want an all-in-one device, as I’ll explain later, although some ISPs push you that way.
In this article, I will try to explain the concept behind each of these terms without getting too technical. First I will talk about the difference between switches and hubs as both devices fall into the same category. Next, we’ll talk about routers and why they’re different from switches and hubs. Finally, we will talk about modems and other network terms such as access points and gateways.
Switches vs Hubs
A hub is an outdated device that you would never want to buy again these days. It looks like a switch, but works differently inside. You connect devices to a hub using an Ethernet cable and any signal sent from a device to the hub is simply repeated on all other ports connected to the hub.
Hubs are considered Layer 1 (physical) devices while switches are placed in Layer 2 (Data Link). This is where hubs and switches differ. The Data Link layer of the OSI model handles MAC addresses and switches look at MAC addresses when processing an incoming frame on a port.
A frame is a data type used to carry data on all network devices. Don’t worry about the technicalities, just know that it contains source and destination MAC addresses and source and destination IP addresses within the frame. The part of the frame that contains the source/destination IP addresses is called a packet.
Rather than blindly forwarding all the frames it receives on one port to all the other ports on the device, a switch creates a MAC address source table and then forwards the frame to the port with the correct MAC destination address. This significantly reduces the amount of traffic on the network because there is direct communication between the two devices instead of a one-to-all communication.
With hubs, the more devices you connect to the hub, the more collisions will occur on the network. Collision means when two computers or devices transmit data at the same time and the signals physically collide before reaching the destination. This happens a lot on hubs because all the traffic coming in on each port is iterated to all the other ports.
With switches, there are no collisions because only the two devices communicating are sending data back and forth. The bandwidth is not shared with other ports.
This is also why a hub is a half duplex device while a switch is a full duplex device. The more devices on a hub, the more bandwidth has to be shared and thus the network becomes slower. With switches, the bandwidth does not have to be shared and all ports work at full speed.
Router vs Modem
Routers operate on Layer 3 (Network) of the OSI model, which deals with IP addresses. While MAC addresses are used to move frames from one device to another directly connected device, IP addresses are used to route packets across the Internet.
A router is a device that connects networks together and directs the traffic between them. At home, this usually means that your router connects your internal local network to your ISP’s network. This can be done in various ways. A router can be connected to your modem at one end (ISP) and to a switch (local area network) at the other end. If you have a combo modem/router device, one end will connect to your ISP and the other end will be either a switch if you’re using Ethernet or just Wi-Fi, if the device supports it too.
Above is a typical router-only device (technically, it’s a wireless router above). The Internet port connects to your modem and the rest of the ports are switch ports. A router almost always has a built-in switch. A modem connects to your ISP over a telephone line (for DSL), cable connection, or fiber optic (ONT).
Above is a typical cable modem. It has a single coaxial port for the cable connection coming in from your ISP and a single Ethernet port that you can plug into your router’s Internet port. If possible, it is always best to have two different devices for your modem and router.
With a wireless router, you can easily share the wired connection with all the wireless devices you have. Most routers today are wireless routers that also include several wired ports.
Wireless Router vs. Wireless Access Point
Now let’s talk about wireless routers versus wireless access points. A wireless access point is a device that allows wireless devices to connect to an existing wired network by bridging the traffic between the two networks. The reason these two terms are so confusing is that a wireless router is basically a combined router and wireless access point.
However, a wireless access point cannot be a wireless router. A standalone wireless access point has an Ethernet cable that runs to the router and converts the wired signal into a wireless signal. It will not route packets from the local network to another network or the Internet like a typical router.
Wireless access points are usually used by businesses or in large public areas where many wireless stations are required, all connected together to form one network. Wireless routers usually also have built-in firewalls, while wireless APs do not.
Other network terms
One of the other common terms you will hear is Default Gateway. So what is the default gateway? It is basically the device that connects your local network to the outside world. Usually this is the last router on your local network.
On a home network, the default gateway is most likely your wireless router, because whenever you need to communicate with a device outside your network, the router is the device connected to your modem. Note that you do not need a default gateway to communicate with other devices on your local network. Default gateways are only used when communicating with external networks, ie the Internet.
Hopefully this will solve some of the mystery behind all these network conditions. It’s a simplistic overview, but enough to explain it to someone else. Enjoying!