Internet Environment

An internet is a logical collection of networks supported by gateways, routers, bridges, hosts, and various layers of protocols. An internet permits different physical networks to function as a single, large, virtual network, and permits dissimilar computers to communicate with each other, regardless of their physical connections. Processes within gateways, routers, and hosts originate and receive packet information. Protocols specify a set of rules and formats required to exchange these packets of information.

Protocols are used to accomplish different tasks in TCP/IP software. To understand TCP/IP, you should be familiar with the following terms and relationships.

A client is a computer or process that requests services on the network. A server is a computer or process that responds to a request for service from a client. A user accesses a service, which allows the use of data or some other resource.

A datagram is a basic unit of information, consisting of one or more data packets that are passed across an internet at the transport level.

A gateway is a functional unit that connects two computer networks of different network architectures. A router is a device that connects networks at the ISO Network Layer. A router is protocol-dependent and connects only networks operating the same protocol. Routers do more than transmit data; they also select the best transmission paths and optimum sizes for packets. A bridge is a router that connects two or more networks and forwards packets among them. The operations carried out by a bridge are done at the physical layer and are transparent to TCP/IP and TCP/IP routing.

A host is a computer, connected to a network, that provides an access point to that network. A host can be a client, a server, or a client and server simultaneously. In a communication network, computers are both the sources and destinations of the packets. The local host is the computer to which a user’s terminal is directly connected without the use of an internet. A foreign host is any machine on a network that can be interconnected. A remote host is any machine on a network that requires a physical link to interconnect with the network.

An internet address is a unique address identifying each node in an internet. Internet addresses are used to route packets through the network. Currently, there are two versions used for internet addressing: Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6). Mapping relates internet addresses to physical hardware addresses in the network. For example, in IPv4, the Address Resolution Protocol (ARP) is used to map internet addresses to Token-Ring or Ethernet physical hardware addresses. In IPv6, Internet Control Message Protocol Version 6 (ICMPv6) is used to map internet addresses to physical hardware addresses.

A network is the combination of two or more nodes and the connecting branches among them. A physical network is the hardware that makes up a network. A logical network is the abstract organization overlaid on one or more physical networks. An internet is an example of a logical network.

Packet refers to the unit or block of data of one transaction between a host and its network. A packet usually contains a network header, at least one high-level protocol header, and data blocks. Generally, the format of the data blocks does not affect how packets are handled. Packets are the exchange medium used at the internetwork layer to send and receive data through the network.

A port is an end point for communication between applications, generally referring to a logical connection. A port provides queues for sending and receiving data. Each port has a port number for identification. When the port number is combined with an internet address, a socket address results.

Protocol refers to a set of rules for achieving communication on a network.

Characteristics of the Internet

The characteristics of the Internet that are clearly of importance in cyberlibel proceedings are:

• its global nature
• interactivity
• its potential to shift the balance of power in the offline world
• accessibility
• anonymity
• its facilitation of republication
• the prominence of intermediaries
• its reliance on hyperlinks/hypertext
• its long-term impact — the use of permanent archives
• its multimedia character
• its temporal indeterminacy