Although there are other types of networks and network protocol suites, the combination of TCP/IP and Ethernet represents the vast majority of network connectivity and use today. Chapter 12 presented a careful introduction to the basic concepts of networking, and introduced TCP/IP and Ethernet. In Chapter 13, we expand the discussion to clarify many areas of importance and interest in the implementation of TCP/IP and Ethernet networks. The goal in Chapter 12 was to help you to achieve a basic understanding of networking.
DOMAIN NAMES AND DNS SERVICES
As a user you know that domain names serve as user address identifiers for most of your network transactions. Domain names are used throughout the Internet, as well as on local area networks, intranets, and extranets. As we noted in Chapter 12, network navigation within the network itself relies on numeric IP addresses and physical addresses. The inventors of the Internet understood that the average user would have difficulty remembering the number groupings that are used as IP addresses, and created a hierarchical system of domain names as an alternative
Ethernet was originally based on a bus topology. Hub-based Ethernet provides a simple means of wiring a bussed Ethernet together, but the hub does not affect the operation logically. Any node may use the bus to send a message to another node any time the bus is not in use; there is no specific timing control on the bus. When a node has a message to send, it listens to see if the bus is in use. If not, it begins to send its packet. If the bus is already in use, the node waits until the bus is available. This is the ‘‘CSMA’’ part of CSMA/CD.
QUALITY OF SERVICE
Certain types of data are dependent on reliable end-to-end transport where packets arrive at the receiving host in order, with sufficient throughput, with minimum, or at least, consistent, delay, at precise, even time intervals, and with a low probability of errors and missing packet failures. These necessary qualities are particularly important for streaming audio and video applications, such as IPTV and VoIP, and for online gaming and virtual reality applications.
The domain name system translates, or resolves, user-friendly names into their corresponding IP addresses. The domain name addressing system is hierarchical, with a root, generic and country-code top-level domains, local domains, and, sometimes, subdomains. DHCP is a protocol that allows the dynamic assignment of IP addresses on a short-term lease basis.