Broadband
Broadband comes from the words "broad bandwidth"
and is used to describe a high-capacity, two-way link between
an end user and access network suppliers capable of supporting
full-motion, interactive video applications.
In other words, Broadband refers to communications medium that
uses wide-bandwidth channels for sending and receiving large
amounts of data, video or voice information.
Port
As you know every computer or device on the Internet must have a unique number assigned to it called the IP address. This IP address is used to recognize your particular computer out of the millions of other computers connected to the Internet. When information is sent over the Internet to your computer how does your computer accept that information? It accepts that information by using TCP or UDP ports.
An easy way to understand ports is to imagine your IP address is a cable box and the ports are the different channels on that cable box. The cable company knows how to send cable to your cable box based upon a unique serial number associated with that box (IP Address), and then you receive the individual shows on different channels (Ports).
Ports work the same way. You have an IP address, and then many ports on that IP address. When I say many, I mean many. You can have a total of 65,535 TCP Ports and another 65,535 UDP ports. When a program on your computer sends or receives data over the Internet it sends that data to an ip address and a specific port on the remote computer, and receives the data on a usually random port on its own computer. If it uses the TCP protocol to send and receive the data then it will connect and bind itself to a TCP port. If it uses the UDP protocol to send and receive data, it will use a UDP port.
Baseband
Baseband is an adjective that describes signals and systems whose range of frequencies is measured from 0 to a maximum bandwidth or highest signal frequency; it is sometimes used as a noun for a band of frequencies starting at 0.
The low frequency would not reach the final destination without being distorted otherwise. These low frequency signals are called baseband signals and once they are changed to higher frequencies the name changes as well to radio frequency (RF) signals. Although, just because the signals are now called radio frequency signals it does not mean they must be in the frequency range reserved for radio transmissions.
A baseband signal has all the frequencies from 0 Hz to the highest frequency component with significant power. After the frequency it changed for transmission the higher frequency RF signal will have at least double what the baseband signal had initially. This simply means that the baseband signal is converted to the radio frequency in order to have twice the bandwidth. However, this bandwidth can also cause some transmission problems and undesirable results. So, the radio frequency signal is subjected to filtering in order to reduce the bandwidth effect before transmitting. Once the RF signal is received it is demodulated and de-multiplexed in order to achieve the original baseband signal.
There are several advantages of baseband in the communication arena, in practical communication, and in research including single pulse studies and ultra-high time precision studies.
Virtual circuit
A communications arrangement in which data from a source user may be passed to a destination user over various real circuit configurations during a single period of communication. Virtual circuits are generally set up on a per-call basis and are disconnected when the call is terminated; however, a permanent virtual circuit can be established as an option to provide a dedicated link between two facilities.
Virtual circuit communication resembles circuit switching, since
both are connection oriented, meaning that in both cases data is delivered
in correct order, and signaling overhead is required during a connection
establishment phase. However, circuit switching provides constant
bit rate and latency, while these may vary in a virtual circuit service
due to reasons such as:
varying packet queue lengths in the network nodes,
varying bit rate generated by the application,
varying load from other users sharing the same network resources by
means of statistical multiplexing, etc.
Many virtual circuit protocols, but not all, provide reliable communication service, by means of data retransmissions due to error detection and automatic repeat request (ARQ)