Protocols and Architecture -
pages 1 & 2
(Located at http://library.advanced.org/27887/gather/fundamentals/protocols_and_architecture.shtml)
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
network.
Protocol
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.
Internet Protocol
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
level.
Other protocols enable communication among personal computers within an
organization’s 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.
The Modem
Another significant protocol structure is that of the modem—the XModem and the
ZModem. The XModem enables PC’s 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
XModem—as 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 doesn’t 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.
Architecture
Architecture in telecommunications is the framework for multiple networks. They tie unlike
protocols together into a compatible whole. By comparison, the term design connotes
thinking that has less scope than architecture. Architecture is design, but most designs
are not architecture. A single component or a new function has a design that has to fit
within the overall architecture. Architecture is a term applied to both the process and
the outcome of specifying the overall structure, logical components, and the logical
interrelationships of a computer. In addition, architecture also refers to operating
systems and networks. Architecture has been around for quite some time now, and was
actually a very good solution to a problem people had with incompatible devices.
By the mid-1970s, IBM sold its customers various computer devices, including printers,
computers, and terminals, which communicated with each other via a variety of incompatible
protocols. As such, IBM developed architecture to tie in all the other protocols,
providing the means for these devices to transmit to each other. This particular
architecture is called SNA and is specific to IBM.
Open Systems Interconnection
The Open Systems Interconnection (OSI) was developed by the International Standards
Organization (ISO) to allow multiple vendors to communicate with each other. This
architecture, as opposed to the SNA, is an open architecture. OSI laid the foundation for
the concept of open communications among various devices, and has had a deep influence on
communications despite the fact that it has not been widely implemented. OSI has a basic
concept of layering, where each of its seven layers can be changed and developed without
affecting any other layer. This layered architecture developed by the OSI has been the
basis for both Local Area Networks (LANs) and the Internet.
Layer 1 of the OSI was the most basic layer. It defines the
electrical
interface, or plugs, and types of media (e.g. copper, wireless, fiber
optics).
As such, it is more commonly remembered to as the physical layer.
Layer 2 on the other hand is known as the data link area,
as they provide
rules for error control and gaining access to the network. Due to this,
LANs, or networks within corporations, conform to this layer.
Layer 3 is called the network layer. This layer has more
complex rules
for addresses and also has a lot more error control than Layer 2. So, it is
generally the basis of a larger-scale communication, like between
different networks. The TCP/IP suite of protocol allows devices all over
the world to communicate with each other through a particular way. The
U.S. Department of Defense that developed the TCP/IP suite in the
1970s did not charge end-users for it in its basic format, and thus it
became simple to acquire. The availability of this standard, easily
accessible protocol, is actually one of the prime reasons for the spread
of the Internet.
In conclusion, protocols are similar to etiquette between alike computers. It spells out
the order in which computers take turns transmitting and how long computers should wait
before terminating a transmission. Protocols also handle error functions such as error
correction, error detection and file transmissions in a common manner so computes can
"talk" to each other. Architectures on the other hand are like the translating
devices which allows devices, and these protocols, to talk to each other effectively.