Protocols and Architecture
Before examining it in greater detail, we must first establish the
fundamental identity of a protocol. This word is a fairly common one in the English
language, with varying meanings, connotations and definitions when used in different
contexts. In its most common form, protocol refers to the set of rules, be it written or
unwritten, which determine how individuals in society act, the etiquette which enables us
to interact with each other without misunderstandings. The word protocol comes from the
Greek word protocollon, which was a leaf of paper glued to a manuscript volume,
describing its contents.
As in its most common form, protocols are also a set of rules governing behavior of
computers, like format, timing, sequence and error control of messages on a data network.
It may be oriented toward data transfer over an interface, between two logical units
directly connected or to an end-to-end basis between two users over a large and complex
Protocols exist in many forms and at several levels in a telecommunications connection,
among which are hardware protocols, protocols between end points in communicating programs
within the same computer or at different locations. A requirement is that both end points
must recognize and observe the protocols.
Taking this definition into the context of the computer world, in its simplest form,
protocols are special instructions found that enables computers to communicate with each
other. They provide a common language and a set o rules for computer communication, such
as over the Internet using TCP/IP.
For example, the Internet Protocol (IP) portion of TCP/IP allows datagrams, or portions of
messages, to take different routes through the Internet. These datagrams are later
assembled together into one message at the receiving end of the route. The IP sends and
receives messages at Internet address levels, whereas the Transmission protocol (TCP)
portion uses a set of rules to exchange other Internet points of the information packet
Other protocols enable communication among personal computers within an
organizations building, the most common being Ethernet.
Like most everything on Earth, protocols also come in different structures, which have
implications on speed and efficiency of the telecommunication network. A well-known
example is Kermit, which enables PCs to communicate with DEC minicomputers and IBM
mainframes. This is aptly a rather slow protocol.
Another significant protocol structure is that of the modemthe XModem and the
ZModem. The XModem enables PCs to send entire files like word or spreadsheet
documents one group of bits at a time, then waits until the recipient acknowledges data
received correctly before sending the next block of data. The ZModem is very much like the
XModemas reflected in their similar names. However, it is a newer and faster
protocol boasting the latest technology. This is so, because unlike the XModem, the
sending PC doesnt wait for acknowledgment before sending the next block of data.
Instead, it keeps sending data until the receiving end sends error messages. Then it
re-transmits starting from the group of bits that had errors.
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