Ports, and Protocols
Ports – Programs connect using different ports. Ports are something like slots that programs can use to create or accept connections on that computer. There are 65,535 ports available on a computer with ports up to 1024 being the most commonly used. For example your web browser usually uses port 80 to download webpages, and your email program usually uses port 110 to download email.
Protocols – Protocols can be thought of as the "language" that a program speaks across the network. Different programs may need to transmit data differently than other types of traffic, and so they use different protocols.
The two main protocols used over the internet are:
- TCP – Makes sure that both sides are ready and waiting, and checks to make sure that each packet was downloaded correctly. If a packet gets corrupted during the transfer then it will ask for it again. This extra checking takes some time but is more reliable at transferring data
- UDP – Is much faster, but without the same kind of verification. Instead it just sends all the data as fast as it can, trusting the software at the other end to take care of the rest.
Other protocols include:
- RAW - Any IP (Internet Protocol) other than TCP or UDP is known as a RAW protocol. The RAW protocol allows programs to send and receive packets directly without relying on TCP or UDP. The RAW protocol is the default print protocol for most print devices. Diagnostic tools may also use the RAW protocol to access IP directly.
- ICMP – ICMP stands for Internet Control Message Protocol, and is a special type of RAW protocol used for sending small control messages between computers and reporting errors. Computers use ICMP to do things like sending one small packet to another computer to make sure that the other system is available and can be reached.