1. Although it appears that information on the Internet is transferred in the same manner as it eventually is displayed·such as an entire document·it actually is broken into smaller data sets called packets. Each packet is preceded by the internet protocol (IP) address and is also assigned a sequence number. Packets are sent from the source to the destination computer, but may get routed along a different path. The IP addresses and sequence numbers ensure that the packets are properly reassembled at the other end. The result is an apparently seamless transfer of information that occurs within a few milliseconds and is transparent to the user.
2. The International Standards Organization (ISO) developed the seven-layer Open Systems Interconnection (OSI) data communications model in the early 1970s. It has since become the model used for most major data communications standards. The model breaks up information into seven stacked layers, the top of which is the most sophisticated applications layer and the bottom-most of which is the physical layer. Transmission Control Protocol/Internet Protocol (TCP/IP) is the way that users are able to communicate across different hardware platforms on various networks. As its name implies, TCP/IP is the requisite protocol for sending and receiving messages on the Internet. TCP/IP typically resides in the transport layer of the OSI model.
3. Different pieces of equipment work at different layers of the OSI model, so different security measures are appropriate at different OSI levels. Thus security requirements at the lowest (physical) level are different from requirements and strategies higher up in the model. Routers, for example, operate on the network level while bridges work at the data link level connecting routers and repeaters. At the data link layer, error-checking capabilities are introduced, and thus security requirements and strategies are different than at the lowest leve...