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Practical TCP/IP and Ethernet Networking- P45: The transmitter encodes the information into a suitable form to be transmitted over the communications channel. The communications channel moves this signal as electromagnetic energy from the source to one or more destination receivers. The channel may convert this energy from one form to another, such as electrical to optical signals, whilst maintaining the integrity of the information so the recipient can understand the message sent by the transmitter | 202 Practical TCP IP and Ethernet Networking requires at least a set of 254 Class C IP addresses either permanently allocated to hosts or dynamically allocated via a DHCP server which could run on the same machine. The UNIX NT machine is set up with two network adapters i.e. as a multi-homed host. The first adapter is connected to the internal LAN the second to the Internet. This implies that the second adapter should have the necessary connectivity e.g. X.25 built-in. Each card will need its own permanent IP address and each card will be configured in such a way that the other card s IP address will be given as its default gateway. In this way each card will pass on a received message to the other card. 12.3.5 Connection via dedicated router The simplest way of connecting a network to the Internet is via a dedicated 2-port IP router also referred to as an Internet router . One port of the router will be for example an Ethernet port to be connected to the local area network. The other port could be an X.25 WAN port which will be connected to a public packet switching network. The X.25 link provides the connection to the ISP. As in the previous case a set of IP addresses is required and these are allocated either permanently or via a DHCP server. 13 The Internet for communications Objectives When you have completed study of this chapter you should be able to Briefly explain the speed bandwidth issues Briefly explain the various options for e-mail Briefly describe the use of voice over IP Indicate briefly how voice mail is performed using TCP IP Briefly indicate how video conferencing is performed using the Internet 13.1 Introduction The following chapter gives an overview of the current as of mid 2001 state-of-the-art in Internet communications. This particular area of technology is advancing so rapidly that the only way to keep track of developments is by regularly browsing the Internet. The list of products mentioned in this section is by no means complete but .
