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.
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 level.
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.
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.