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Chapter 4 TCP/IP Networking
The U.S. Defense Department's Advanced Research Projects Agency (DARPA) produced the designs and experimental networks that evolved into the public Internet. The TCP/IP network model that was developed is based on the OSI reference model. TCP/IP is now the predominant protocol suite used in networking.
4.1 History of TCP/IP
4.1.1 Origins and growth of TCP/IP Based on TCP/IP open standards, the Internet has been enormously successful.
In the early 1980s the Internet connected only a few hundred computers.
By the year 1997 the Internet connected more than 16 million computers, and it had doubled in size approximately every 10 months.
Today, corporations and individuals are increasingly dependent on the Internet to conduct business and the activities of daily life.
4.1.2 The TCP/IP network model The TCP/IP network model contains four layers, unlike the OSI model which contains seven layers.
What is the function of the Application layer?
What is the function of the Transport layer?
What are port numbers?
What is the function of the Internet layer?
What is the function of the Network Interface layer?
Worksheet 4.1.2 The TCP/IP Network Model
4.1.3 TCP/IP and network operating systems To carry the requests and responses between clients and servers, the NOS vendors designed their own special rules or protocols. Novell called its protocols IPX/SPX, Banyan called its protocols VINES, Apple produced AppleTalk, while IBM and Microsoft used NetBIOS. Each of these solutions was closed, or proprietary, meaning that it was owned and controlled by one company.
Why did that have to change?
4.2 IP Addressing
4.2.1 IPv4 addressing For any two systems to communicate, they must be able to identify and locate each other. In everyday life, names or numbers, like telephone numbers, are often used as unique identifiers. Similarly, each computer in a TCP/IP network must be given at least one unique identifier, or address. This address allows one computer to locate another on a network.
Can a device have an address?
Lab: Configuring Static TCP/IP settings in Linux
4.2.2 IPv4 addressing overview
TCP/IP is designed as an internetworking set of protocols. IP has the job of forwarding packets from the network on which they originate to the destination network. This addressing scheme, therefore, must include an identifier for both the source and destination networks.
How is IP addressing like the post office?
What is a hierarchical address?
Are duplicate addresses allowed?
How is an IP address stored in a computer?
What determines which portion of the address identifies the network and which portion identifies the host?
Worksheet 4.2.2 IPv4 Addressing Overview
4.2.3 Class A addresses
In a class A address the first number in the dotted decimal notation (octet) is the network portion. The format is Network.Host.Host.Host, or N.H.H.H.
For example, in the address 56.1.2.3, the first octet 56, identifies the network. The last three octets, 1.2.3, identify the host on that network. Address 56.1.2.4 identifies a different host, 1.2.4, on the same 56 network. The address 57.1.2.3 identifies host 1.2.3 on network 57.
The first octet in a class A address always falls between which two numbers?
4.2.4 Class B addresses
A class B IP address divides the network portion from the host portion between the second and third octet. The format is N.N.H.H. The address 165.5.6.7 represents network 165.5 and host 6.7.
The first octet in a class B address always falls between which two numbers?
4.2.5 Class C addresses
A class C IP address divides the network portion from the host portion between the third and fourth octet. The format is N.N.N.H. The address 192.8.9.10 represents network 192.8.9 and host 10.
The first octet in a class C address always falls between which two numbers?
4.2.6 Class D and E addresses
Class D and class E addresses are used for special purposes.
range. The corresponding default subnet mask will be 255.255.255.0, which is a class C subnet mask.
The online course provides an extensive example of a subnet mask.
Worksheet 4.2.8 Subnetting
4.3 Name Resolution
4.3.1 Overview of name resolution IP address numbers are necessary to identify points of connection to a network. IP address numbers are designed to make possible the efficient operation of networked devices. However, in their numerical form, IP addresses are difficult to remember and to manage. This is especially true when there is a need to change the IP addresses to adapt to changing network conditions. Although network devices use numerical addresses, names are easy to work with. The technique that allows names to represent network addresses is called name resolution. What is the advantage to using name resolution? What do networks use to associate names with addresses?
4.3.2 Hostnames and host tables On the network, each computer is given a unique name to identify it. This name is used to communicate with a particular computer. To reach another computer, the network needs to use the IP address of that computer. Host tables are lists that can be configured in each computer, associating the names of the computers in the network with the IP address host table. What are the disadvantages of using a host table?
4.3.3 The domain name system The use of host tables requires a lot of maintenance. In contrast, the Domain Name System (DNS) assigns this task to servers in the network. The work of translating names into addresses is accomplished by specialized servers within the network. Host computers are then relieved of keeping a listing of name-to-address mappings. This simplifies network maintenance and allows greater flexibility. How is DNS like directory assistance? What does .com refer to? What does .org refer to? What does .edu refer to?
4.3.4 Name services and the NOS In Network Operating Systems (NOSs), user programs can access network devices and services by name. Today, all NOSs use DNS to translate computer names into IP addresses. However, before the general use of TCP/IP and the Internet domain naming system by the makers of different NOSs, other naming techniques were used to identify systems and services.
In order to accommodate earlier naming schemes and the applications that use them, the NOS vendors have developed extensions to DNS that allow their own types of names to be associated with IP addresses. What is NetBIOS?
4.3.5 WINS The Windows Internet Naming Service (WINS) is not a built-in part of the Internet DNS name-to-address service. In order to resolve or map the NetBIOS names used by applications into IP addresses, Microsoft added WINS as an extension to DNS. WINS automates the process of translating NetBIOS names into IP addresses so packets can be properly delivered to devices or services. A WINS server associates NetBIOS names with IP addresses and automatically updates its database of name-to-address associations as systems enter and leave the network. Therefore, a WINS server does not require ongoing maintenance. Client systems, however, must be configured with the address of a WINS server that performs this translation.
4.4 TCP/IP Protocols
4.4.1 Overview of TCP/IP protocols A protocol is a set of messages exchanged between systems in a defined sequence to accomplish a specific networking task. The layout, or format, of the messages is strictly defined. The rules for the exchange of messages between systems are strictly specified in standards documents. TCP/IP is a "suite" or collection of different protocols, each suite performing a specialized task. In a well-functioning network, the individual protocols are coordinated so that, taken together, they deliver network services to application programs.
4.4.2 Address Resolution Protocol (ARP) The Address Resolution Protocol (ARP) starts when a system begins a conversation with another host on a Local Area Network (LAN). The first system knows that the second system is located somewhere on the network from the second system's IP address. However, the first system does not know the second system's exact location on the network, which is the second system’s Ethernet address. How does ARP work?
4.4.3 Internet Control Message Protocol (ICMP) A network requires tools for reporting errors that may arise, and network administrators need tools for discovering the reasons for errors. The Internet Control Message Protocol (ICMP) provides a set of error and control messages to help track and resolve network problems. What is an echo request? What is traceroute routine?
4.4.4 Transmission Control Protocol (TCP) Two programs may communicate with each other across a series of many interconnected networks. An e-mail application, for example, may send a message to a mail server in another city or country for the recipient to read.
Telnet uses the services of TCP for establishing a logical connection between the terminal and the remote computer.
4.4.10 SMTP Simple Mail Transfer Protocol (SMTP) is a protocol for sending e-mail messages between servers. Most e-mail systems that send mail over the Internet use SMTP to send messages from one server to another. The messages can then be retrieved with an e-mail client using either Post Office Protocol (POP) or Internet Message Access Protocol (IMAP). In addition, SMTP is generally used to send messages from a mail client to a mail server. This is why both the POP or IMAP server and the SMTP server must be configured in an e-mail application.
4.4.11 POP Post Office Protocol version 3 (POP3) is a common mail service protocol that is used by ISPs that provide Internet and e-mail service to home customers. POP3 permits a workstation to retrieve mail that the server is holding. After the mail is retrieved, it can be deleted from the server.
4.4.12 IMAP Internet Message Access Protocol (IMAP) is a newer e-mail protocol and more straightforward than POP3. IMAP is offered by many ISPs, and some of the ISPs are even discontinuing their POP3 support. IMAP is a method for accessing electronic mail or bulletin board messages that are kept on a mail server. IMAP is fully compatible with Multipurpose Internet Mail Extension (MIME) Internet messaging standards. IMAP allows message access and management from more than one computer. Also, the client software needs no knowledge about the file storage format of the server.
Chapter 4 Summary
This chapter discussed TCP/IP. Some of the important concepts to retain from this chapter include the following:
- A network system is called Closed when one company owns and controls it. In contrast, the TCP/IP protocol suite is an open system.
- The four layers that make up the TCP/IP model are the Application layer at the top, followed by the Transport layer, the Internet layer, and finally the Network Interface layer.
- Every IP address has two parts. One part identifies the network to which the system is connected, and a second part identifies that particular system on the network.
- Available IP addresses are placed into classes. The large addresses are defined as class A, medium as class B, and small as class C networks.
- Subnetting a network means to use the subnet mask to divide the network. Subnetting breaks a large or extremely large network up into smaller, more efficient, and manageable segments, or subnets.
- Networks use two basic techniques to associate names with addresses, host tables and the Domain Name Service (DNS).
- The major protocols that compose the TCP/IP Protocol Suite include the Address Resolution Protocol (ARP), Internet Control Message Protocol (ICMP), Transmission Control Protocol (TCP), User Datagram Protocol (UDP), Dynamic Host Configuration Protocol (DHCP), Hypertext Transport Protocol (HTTP), File Transfer Protocol (FTP), Telnet, Simple Mail Transfer Protocol (SMTP), Post Office Protocol version 3 (POP3), and Internet Message Access Protocol (IMAP).
An important network service is remote administration. Information to accomplish this and other network services is provided in the next chapter on Network Operating Systems (NOSs).
Chapter 4 Notes
