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Lesson 1

Internet Networks Theory

You log on, you check your favorite sites, browse through their catalogs, and perhaps purchase something over the Internet. Just a few keystrokes, and all sorts of actions are performed. But how does it all work?
This module will discuss the network and internet-related requirements necessary for a website development team to meet client's business goals. After completing this module, you should be able to:
  1. Describe backbones and Network Access Points
  2. Identify the components and function of the URL
  3. Explain domain levels
  4. Describe the registration process
  5. Describe how protocols are used to send and receive information
  6. Explain the differences between TCP/IP and UDP protocols
  7. Explain how IP addresses are classified and what are remote and Web system protocols
In the next lesson, how NAPs and backbones fit into the Internet infrastructure will be discussed.

Limitations of IPv4

The current version of IP (known as version 4 or IPv4) has not changed substantially since Request for Comments (RFC) 791, which was published in 1981. IPv4 has proven to be robust, easily implemented, and interoperable. It has stood up to the test of scaling an internetwork to a global utility the size of today's Internet. This is a tribute to its initial design. However, the initial design of IPv4 did not anticipate the following:
  1. The recent exponential growth of the Internet and the impending exhaustion of the IPv4 address space Although the 32-bit address space of IPv4 allows for 4,294,967,296 addresses, previous and current allocation practices limit the number of public IPv4 addresses to a few hundred million. As a result, public IPv4 addresses have become relatively scarce, forcing many users and some organizations to use a NAT to map a small number of public IPv4 addresses to multiple private IPv4 addresses. Although NATs promote reuse of the private address space, they violate the fundamental design principle of the original Internet that all nodes have a unique, globally reachable address, thus preventing true end-to-end connectivity for all types of networking applications. Additionally, the rising prominence of Internet-connected devices and appliances ensures that the public IPv4 address space will eventually be depleted.
  2. The need for simpler configuration Most current IPv4 implementations must either be manually configured or use a stateful address configuration protocol such as Dynamic Host Configuration Protocol (DHCP). With more computers and devices using IP, there is a need for a simpler and more automatic configuration of addresses and routing configuration that does not rely on the administration of a DHCP infrastructure.
  3. The requirement for security at the Internet layer Private communication over a public medium such as the Internet requires cryptographic services that protect the data being sent from being viewed or modified in transit. Although a standard now exists for providing security for IPv4 packets (known as Internet Protocol security, or IPsec), this standard is optional for IPv4, and additional security solutions, some of which are proprietary, are prevalent.
  4. The need for better support for prioritized and real-time delivery of data Although standards for prioritized and real-time delivery of data.sometimes referred to as Quality of Service (QoS).exist for IPv4, real-time traffic support relies on the 8 bits of the historical IPv4 Type of Service (TOS) field and the identification of the payload, typically using a User Datagram Protocol (UDP) or Transmission Control Protocol (TCP) port. Unfortunately, the IPv4 TOS field has limited functionality and, over time, has been redefined and has different local interpretations. The current standards for IPv4 use the TOS field to indicate a Differentiated Services Code Point (DSCP), a value set by the originating node and used by intermediate routers for prioritized delivery and handling. Additionally, payload identification that uses a TCP or UDP port is not possible when the IPv4 packet payload is encrypted.

To address these and other concerns, the Internet Engineering Task Force (IETF) has developed a suite of protocols and standards known as IP version 6 (IPv6). This new version, previously called IP "The Next Generation (IPng)", incorporates the concepts of many proposed methods for updating the IPv4 protocol. IPv6 is designed to have minimal impact on upper-layer and lower-layer protocols and to avoid the random addition of new features.

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