In an earlier chapter we discussed the topic of protocols, especially with respect to buses which often connect components from different, competing vendors. In the world of networks, standardized protocols are even more crucial for the multi-vendor nature of the hardware is given anymore now that most places are connected to at least some network, if not the Internet. The ability of different computers to talk to each other is called interoperability and has been somewhat slow in coming.
Just to reinforce the protocol concept, let's define it again. A protocol is nothing more than a set of agreements which specify software and hardware characteristics. International standards organizations promulgate these agreements which then take on the force of law such that a vendor that doesn't conform to the rules can't interoperate with other vendors.
In the world of networking, there are literally hundreds of protocols. Some deal with the physical aspects of how wires plug together, such as the RS-232C protocol that specifies the shape, size and number of pins in connectors. These connectors allow modems to plug into motherboards. Voltage levels and methods of bit encoding are part of the protocol (or standard as it is often called.)
Other protocols are at a higher conceptual level, such as the famous TCP/IP protocol suite (set of protocols that form one coherent system.) When the bits arrived through the hardware interface into the computer, they are stored in main memory so that the CPU can interpret them appropriately.
There are two parts to most protocols:
| static | what the packets look like, what kind of error checksum is used whether ASCII or EBCDIC is used and little or big-endian integers, etc. |
| dynamic | what the sequence of packets is, how fast do they arrive, how do streams of packets get synchronized? Who goes first? How is the stream terminated? How do packets get shuffled through gateways to their proper destination? |
All of this has to be spelled out in absolute unambiguous detail in order for communication to succeed.