Determines message recipient and sender during communication using the electronic mail.

Protocol for WWW pages transfer. By default, TCP protocol and port 80 is used.

Secured version of HTTP protocol. Security is ensured by the encrypted protocol SSL.

By default, TCP protocol and port 443 is used.

Clients can work with their e-mail messages on a server using IMAP. Messages don't need to be downloaded to local computer.

By default, TCP protocol and port 143 is used.

Basic communication unit of network layer (i.e. independent of the communication medium). The IP protocol works on packet layer in TCP/IP.

Post Office Protocol enables users to download e-mail messages from a server to their own local disc.

By default, TCP protocol and port 110 is used.

A port is a 16-bit number (the allowed range being 1 through 65535) used by TCP and UDP protocols for identification of applications (services) on a particular computer. Several applications may run at once (e.g. WWW server, e-mail client, WWW client — browser, FTP client, etc.). Each application is uniquely determined by its port number. Ports 1 through 65535 are reserved for standard or system use (e.g 80 = WWW). Ports above 1024 (inclusive) may be used by any application (typically as a source port by a client or by a non-standard server application).

Format specification of transferred data and methods of their processing. Two computers must use the same protocols to be able to communicate.

Majority of network protocols is standardized, so they can be used for a communication between devices from different vendors. Set of protocols used in the Internet and known in general as TCP/IP can be used as an example.

An older method of Internet connection sharing. Client in a local network does not communicate directly with the target computer in the Internet but it passes its request to a proxy server. The proxy server will process the request and deliver the response.

Basic protocol used for e-mail delivery in the Internet. Sender and recipient are identified by an e-mail address.

By default, TCP protocol and port 25 is used.

In network terminology, application used in an network environment is called a service. In TCP/IP, the service is identified by a transport protocol and port (e.g. HTTP uses TCP protocol and port 80).

Protocol for secured and encrypted TCP connection. Originally, it was created to secure the transmission of WWW pages by the HTTP protocol (this protocol is called HTTPS). Today, almost all standard Internet services — SMTP, POP3, IMAP, LDAP, etc. — supports SSL.

Communicatin starts by the exchange of an encryption key, which is later used for a (symetrical) encryption of the real data.

Transport Layer Security. SSL successor, de facto SSL version 4.