When browsing the Internet, routers and servers need to navigate through paths and confirm that the signal is sent to the correct device. So, how to identify computers on a network?
We have to pinpoint a single online device from billions of them in the world to perform HTTP requests and responses. It’s not like people talking because the sender and the receiver are physically near, while it’s not on networks. So, we have to invent some identifiers to build the Internet.
Well, the credential which we’re most familiar with is IP addresses. It’s on the network layer, below the transport layer but above the link layer. The system uses 32 bits (4 bytes) that can have 4,294,967,296 values for devices worldwide. Also, using the “ping” command, either in CMD or in Terminal, we can be acknowledged for a website’s IP address. For example, one of google.com’s IP address is 126.96.36.199. In reality, the DNS turns the domain name into an IP address, and the rest of the connection relies on the IP!
However, if you assign a random address for all computers across the globe, it will be tenuous to maintain. So, developers invented a method called subnets. That means a certain number of bits remain the same for each computer’s IP address. For instance, a common subnet only has three bytes, and the remaining byte is up to the device. That leaves a maximum of 254 online gadgets (0 and 255 are used by default).
In contrast, there are private IP addresses that are only used behind a router. For instance, maybe thousands, if not millions of families are using 192.168.30.xxx, but the devices can’t mix up because these addresses only operate on the routers and the computers that are physically nearby.
MAC (Media Access Control) Address
Despite IP addresses containing unique information about your gadget, it’s also necessary to have another identifier: a MAC Address on the link layer. Why? If you take a look at the packets, you will see the source and destination IP unchanged, while the MAC address is always modifying itself as the data arrives at different routers and servers.
Then, how about the format? Each MAC address contains 12 hexadecimal digits, meaning that it is worth 6 bytes as a byte has 256 possible combinations. For example: FF-55-67-A1-B5-99.
But, how about the isolation in the transport layer? Well, we randomize ports for each browser window. Imagine that if a computer connects to different websites in an identical IP address, the servers might not know which tab should receive the message. Therefore, clients usually use port 49,152 to 65,535, which can neither be managed nor registered. However, we can also utilize port 1024 to 49,151, but someone can block access to the ports by registering them.
So, here’s a brief introduction to how to identify computers on a network. However, this article is not enough. Let’s learn more from the references below.
References and Credits
- Tim Fisher, (2020, June 12). Private IP Addresses: Everything You Need to Know – Lifewire. Retrieved December 7, 2020, from https://www.lifewire.com/what-is-a-private-ip-address-2625970
- (2020, January 13). Introduction of MAC Address in Computer Network – GeeksforGeeks. Retrieved December 7, 2020, from https://www.geeksforgeeks.org/introduction-of-mac-address-in-computer-network/
- Techquickie, (2016, November 15). What is a MAC Address? – YouTube. Retrieved December 7, 2020, from https://www.youtube.com/watch?v=UrG7RTWIJak
- (2010, February 17). What is a Network Port and why do I need one?. Retrieved December 7, 2020, from https://www.networkwebcams.co.uk/blog/2010/02/17/network-port-and-why-do-i-need-one/
- (2009.). Registered Port – an overview | ScienceDirect Topics. Retrieved December 7, 2020, from https://www.sciencedirect.com/topics/computer-science/registered-port