Data Networking Fundamentals Chapter 7

Objectives In this chapter, you will learn to: Discuss basic networking concepts, including the elements common to all client-server networks Provide examples of multiple network services Describe the differences between LANs, MANs, and WANs Understand the functions of each layer of the OSI model Describe the purpose of protocols and list several types of protocols Recognize the core protocols and addressing scheme for the TCP/IP suite

Terminology Standalone workstation - a workstation that is not connected to a network, but relies on its own hard disk for data storage and applications. Client - a workstation connected to a network. A person whose workstation is part of a network may also be called a client, or that person may be known more informally as a user. Servers - store shared data and programs on their hard disks. They can also perform management functions, such as determining which users have access to certain programs. Client-server - a network that uses a server to enable clients to share data, data storage space, and devices.

Terminology

Requirements for Connectivity

Requirements for Communications Node - any device (for example, a server, client, or printer) that can receive a transmission over a network. To receive data, each node must have a unique address, or identifying number. Protocol - a rule that governs how the parts of a network communicate.

Servers Server - A computer on the network that manages shared resources. Redundancy - the practice of using more than one component to guard against outages (or failures). Network operating system (NOS) - software that can manage not only data, but also users, groups, security, and applications on the network.

How Networks are Used The main purpose for using networks is to share programs, data, and devices, such as printers or fax machines, all of which are known as resources. Network services can be categorized as follows: File services Print services Communication services Mail services Internet services Management services

LANS, MANS, and WANS Local area network (LAN) - a network of computers and other devices that is confined to a relatively small space, such as one building or even one office. Connectivity device - when multiple networks or multiple parts of one network need to communicate with each other, this device is used to exchange data between them. Hub - retransmits a digital signal to all its connected devices.

LANS, MANS, and WANS Metropolitan area network (MAN) - a network that connects clients and servers in multiple buildings in a region. Wide area network (WAN) - a network that connects two or more geographically distinct LANs

LANS, MANS, and WANS

The Internet The Internet is a unique WAN not only because of its size, but also because of its diversity. It may transmit confidential information between two offices within the same organization, or it may transmit public records to anyone who requests them. To connect users from around the globe, the Internet relies on a hierarchical structure of connection points, just as the PSTN relies on a hierarchy of central offices. An Internet Service Provider (ISP) is a company that operates a network and provides consumers with a link to the Internet.

The Internet

The OSI Model

Physical Layer Protocols at this layer generate and detect voltage (or in the case of fiber optic transmission, pulses of light) so as to transmit and receive signals carrying data. The Physical layer sets the data transmission rate and monitors data error rates, though it does not provide error correction services. Physical network problems, such as a severed wire, affect the Physical layer.

Data Link Layer Controls communications between the Network layer and the Physical layer. Frame - a structured package for moving data that includes not only the raw data, or "payload," but also the sender’s and receiver’s network addresses, and error checking and control information.

Data Link Layer

Network Layer Translates network addresses into their physical counterparts and decide how to route data from the sender to the receiver. Network layer addresses,which reside at the Network layer of the OSI model, follow a hierarchical addressing scheme and can be assigned through operating system software.

Transport Layer Primarily responsible for ensuring that data is transferred from point A to point B reliably, in the correct sequence, and without errors. Transport protocols also handle flow control, or the method of gauging the appropriate rate of transmission based on how fast the recipient can accept data. Segmentation - the process of decreasing the size of the data units when moving data from a network segment that can handle larger data units to a network segment that can handle only smaller data units.

Session Layer Session - a connection for data exchange between two parties. The Session layer’s functions include: Establishing and keeping alive the communications link for the duration of the session Synchronizing the dialog between the two nodes Determining whether communications have been cut off, and, if so, figuring out where to restart transmission

Presentation Layer Serves as a translator between the application and the network. At the Presentation layer, data becomes formatted in a schema that the network can understand; this format varies with the type of network used. Encryption - the use of a mathematical routine to scramble data so that it can only be read by reversing the formula.

Application Layer Provides interfaces to the software that enable programs to use network services. Application program interface (API) - a routine (a set of instructions) that allows a program to interact with the operating system.

Applying the OSI Model

TCP/IP Compared to the OSI Model The TCP/IP model includes the following: Application layer - provides authentication and compression services, and is roughly equivalent to the Application, Presentation, and Session layers of the OSI model. Transport layer - roughly corresponds to the Transport layer of the OSI model. Network layer - equivalent to the Network layer of the OSI model. Link layer - roughly equivalent to the Data Link and Physical layers of the OSI model.

TCP/IP Compared to the OSI Model

Internet Protocol Belongs to the Network layer of the OSI model and to the Internet layer of the TCP/IP model. It provides information about how and where data should be delivered. Datagram - the IP portion of a data frame, acts as an envelope for data and contains information necessary for routers to transfer data between subnets. IP is an unreliable, connectionless protocol, which means that it does not guarantee delivery of data.

Internet Protocol

Transmission Control Protocol (TCP)

The TCP/IP Application Layer Protocols Dynamic Host Configuration Protocol (DHCP) - an automated means of assigning a unique Network layer (or IP) address to every device on a network. File Transfer Protocol (FTP) - an Application layer protocol used to send and receive files between hosts. Hypertext Transfer Protocol (HTTP) - the Application layer protocol that enables Web browsers to issue requests to Web servers and interpret the response.

The TCP/IP Application Layer Protocols Simple Mail Transfer Protocol (SMTP) - the protocol responsible for moving messages from one mail server to another over the Internet and other TCP/IP-based networks. Telnet - a terminal emulation protocol used to log on to remote hosts using the TCP/IP protocol suite.

Addressing in TCP/IP

To view your current IP information on a Windows 2000 or Windows XP workstation connected to a network: Click Start, then click Run. The Run dialog box opens. In the Open text box, type cmd, then click OK. The Command Prompt window opens. At the DOS prompt, type ipconfig /all.Your workstation’s IP address information is displayed Type exit, then press Enter to close the Command Prompt window.

Addressing in TCP/IP

Summary Workstations on a network typically share data, programs, and devices through a central computer called a server. A network that uses a server to enable clients to share data, data storage space, and devices, is known as a client-server network. The main purpose for using networks is to share programs, data, and devices, such as printers or fax machines.