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SMTP (Simple Mail Transfer Protocol) -
SMTP is used for sending and receiving e-mail. However, as it is ‘simple,’ it is limited in its ability to queue messages at the
receiving end, and is usually used with one of two other protocols, POP3 or IMAP. These other protocols allow the user to save
messages in a server mailbox and download them periodically from the server.
SMTP authentication is an extension of SMTP, whereby the client is required to log into the mail server before or during the
sending of email. It can be used to allow legitimate users to send email while denying the service to unauthorized users, such as
spammers.
Sockets -
Sockets are a method for communication between a client program and a server program over a network. A socket is defined as
‘the endpoint in a connection. Sockets are created and used with a set of programming requests or ‘function calls’ sometimes
called the sockets application programming interface (API).
SSL/TSL (Secure Socket Layer/Transport Layer Security)
These two protocols (SSL is succeeded by TSL) are cryptographic protocols that provide secure communication on a network. SSL
is commonly used over HTTP to form HTTPS, as used e.g. on the Internet for electronic financial transactions. SSL uses public key
certificates to verify the identity of the server.
Subnet/subnet mask -
A subnet is an identifiably separate part of an organization's network. Typically, a subnet may represent all the machines at one
geographic location, in one building, or on the same local area network (LAN). Having an organization's network divided into
subnets allows it to be connected to the Internet with a single shared network address.
The subnet mask is the part of the IP address that tells a network router how to find the subnet that the data packet should be
delivered to. Using a subnet mask saves the router having to handle the entire 32-bit IP address; it simply looks at the bits
selected by the mask.
Switch -
A switch is a network device that connects network segments together, and which selects a path for sending a unit of data to its
next destination. In general, a switch is a simpler and faster mechanism than a router, which requires knowledge about the
network and how to determine the route. Some switches include the router function. See also Router.
TCP (Transmission Control Protocol) -
TCP is used along with the Internet Protocol (IP) to transmit data as packets between computers over the network. While IP takes
care of the actual packet delivery, TCP keeps track of the individual packets that the communication (e.g. requested a web page
file) is divided into, and, when all packets have arrived at their destination, it reassembles them to re-form the complete file.
TCP is a connection-oriented protocol, which means that a connection is established between the two end-points and is
maintained until the data has been successfully exchanged between the communicating applications.
Telnet -
Telnet is a simple method with which to access another network device, e.g. a computer. The HTTP protocol and the FTP protocols
allow you to request specific files from remote computers, but do not allow you logon as a user of that computer. With Telnet,
you log on as a regular user with whatever privileges you may have been granted for specific applications and data residing on
that computer.
UDP (User Datagram Protocol) -
UDP is a communications protocol that offers limited service for exchanging data in a network that uses the Internet Protocol (IP).
UDP is an alternative to the Transmission Control Protocol (TCP). The advantage of UDP is that it is not required to deliver all data
and may drop network packets when there is e.g. network congestion. This is suitable for live video, as there is no point in
re-transmitting old information that will not be displayed anyway.
Unicast -
Communication between a single sender and a single receiver over a network. A new connection is established for each new user.
URL (Uniform Resource Locator) -
An "address" on the network.
Varifocal lens -
A varifocal lens provides a wide range of focal lengths, as opposed to a lens with a fixed focal length, which only provides one.
WAN (Wide-Area-Network) -
Similar to a LAN, but on a larger geographical scale.
W-LAN (Wireless LAN) -
A wireless LAN is a wireless local area network that uses radio waves as its carrier: where the network connections for end-users
