Responsibilities of the Network Administrator

As a network administrator, your tasks generally will fall into four areas:

• Designing and planning the network
• Setting up the network
• Maintaining the network
• Expanding the network

Each task area corresponds to a phase in the continuing life cycle of a network. You may be responsible for all the phases, or you may ultimately specialize in a particular area, for example, network maintenance.

Designing the Network

The first phase in the life cycle of a network involves creating its design, a task not usually performed by new network administrators. Designing a network involves making decisions about the type of network that best suits the needs of your organization. In larger sites this task is performed by a senior network architect: an experienced network administrator familiar with both network software and hardware.

Chapter 3, "Planning Your Network," describes the factors involved in network design.

Setting Up the Network

After the new network is designed, the second phase of network administration begins, which involves setting up and configuring the network. This consists of installing the hardware that makes up the physical part of the network, and configuring the files and/or databases, hosts, routers, and network configuration servers.

The tasks involved in this phase are a major responsibility for network administrators. You should expect to perform these tasks unless your organization is very large, with an adequate network structure already in place.

Chapter 4, "Configuring TCP/IP on the Network," contains instructions for the tasks involved in this phase of the network life cycle.

Maintaining the Network

The third phase of network administration consists of ongoing tasks that will typically comprise the bulk of your responsibilities. They might include:

• Adding new host machines to the network
• Network security
• Administering network services, such as NFS, name services, and electronic mail

• Troubleshooting network problems

Chapter 4 explains how to set up new hosts on an existing network. Chapter 6, "Troubleshooting TCP/IP," contains hints for solving network problems. For information on network services, you can refer to the documents NFS Administration Guide, Name Services Administration Guide, NIS+ Transition Guide, and User Accounts, Printers, and Mail Administration. For security-related tasks, refer to Security, Performance, and Accounting Administration.

Expanding the Network

The longer a network is in place and functioning properly, the more your organization will want to expand its features and services. Initially, you can increase network population by adding new hosts and expand network services by providing additional shared software. But eventually, a single network will expand to the point where it can no longer operate efficiently. That is when it must enter the fourth phase of the network administration cycle: expansion.

Several options are available for expanding your network:

• Setting up a new network and connecting it to the existing network via a machine functioning as a router, thus creating an internetwork.
• Configuring machines in users' homes or in remote office sites and enabling these machines to connect over telephone lines to your network.
• Connecting your network to the global Internet, thus enabling users on your network to retrieve information from other systems throughout the world.
• Configuring UUCP communications, enabling users to exchange files and electronic mail with remotely located machines.

Chapter 5, "Configuring Routers," contains procedures for setting up an internetwork. Part 2, "Expanding Your Network with PPP," explains how to set up nomadic computers. Part 3, "Administering UUCP Communications," explains how to use UUCP to exchange information between your machine and other UUCP systems.

What a Network Is

Computer networks now proliferate throughout the world. More and more organizations set up networks of computers within their buildings. More and more individuals are establishing communications with public networks

featuring special interest bulletin boards. Newspapers, radio, and television programs feature stories about the "information highway" and the global reach of giant networks.

Because of its subject matter, this book uses numerous networking terms, many of which may be familiar to you. The following section explains these terms and tries to answer some basic networking questions from a Solaris and--perhaps more importantly--from a TCP/IP perspective.

What TCP/IP Is

A network communications protocol is a set of formal rules that describe how software and hardware should interact within a network. For the network to function properly, the information being sent must be delivered to the intended destination in an intelligible form. Because different types of networking software and hardware need to interact to perform the network function, designers developed the concept of the communications protocol.

The Solaris operating system includes the software needed for network operations for your organization. This networking software implements the communications protocol "suite" collectively referred to as TCP/IP. TCP/IP is recognized as a standard by major international standards organizations and is used throughout the world. Because it is a set of standards, TCP/IP runs on many different types of computers, making it easy for you to set up a heterogeneous network running the Solaris operating system.

TCP/IP provides services to many different types of computers, operating systems, and networks. Types of networks range from local area networks, such as Ethernet, FDDI, and Token Ring, to wide area networks, such as X.25 and ATM.

You can use TCP/IP to construct a network out of a number of local area networks. You can also use TCP/IP to construct a wide area network using virtually any point-to-point digital circuit.

TCP/IP and its aggregate protocols are fully described in Chapter 2, "TCP/IP Protocol Suite."

Types of Hardware That Make Up a Solaris Network

The term local area network (LAN) refers to a single network of computers limited to a moderate geographical range, such as the floor of a building or two adjacent buildings. A local area network has both hardware and software components. From a hardware perspective, a basic Solaris LAN consists of two or more computers attached to some form of local area network media.

Local Area Network Media

The cabling or wiring used for computer networks is referred to as network media. Figure 1-1 shows four computers connected to the Ethernet. In the Solaris LAN environment, Ethernet is the most commonly used local area network media. Other types of local area network media used in a Solaris LAN might include FDDI or Token Ring.

Figure 1-1

Computers and Their Connectors

Computers on a TCP/IP network have two different types of connectors that you use for connecting them to network media, the serial port and the ports on the network interface.

Serial Ports Each computer has at least two serial ports, the connectors that enable you to plug a printer or modem into the computer. The serial ports may be attached to the CPU board, or you may have to purchase them. You use these ports when attaching a modem to the system to establish a PPP or UUCP connection. PPP and UUCP actually provide wide area network services, since they use telephone lines as their network media.

Network Interfaces The hardware in a computer that enables you to connect it to a network is known as a network interface. Many computers come with a pre-installed network interface; others may require you to purchase the network interface separately.

Each LAN media type has its own associated network interface. For example, if you want to use Ethernet as your network media, you must have an Ethernet interface installed in each host to be part of the network. The connectors on the board to which you attach the Ethernet cable are referred to as Ethernet ports. If you plan to use FDDI, each prospective host must have an FDDI network interface, and so on.

This document refers to the default network interface on a host as the primary network interface.

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Note - Installing network hardware is outside the scope of this guide. Refer to Peripherals Administration for instructions for configuring serial ports and manuals accompanying network media for installation instructions.

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How Network Software Transfers Information

Setting up network software is an involved task. Therefore, it helps to understand how the network software you are about to set up will transfer information.

Figure 1-2 shows the basic elements involved in network communication.

Figure 1-2

In this figure, a computer sends a packet over the network media to another computer attached to the same media.

How Information is Transferred: the Packet

The basic unit of information to be transferred over the network is generically referred to as a packet. A packet is organized much like a conventional letter.

Each packet has a header, which corresponds to the envelope. The header contains the addresses of the recipient and the sender, plus information on how to handle the packet as it travels through each layer of the protocol suite.

The message part of the packet corresponds to the letter itself. Packets can only contain a finite number of bytes of data, depending on the network media in use. Therefore, typical communications such as email messages are sometimes split into packet fragments.

Who Sends and Receives Information: the Host

If you are an experienced Solaris user, you are no doubt familiar with the term "host," a word often used as a synonym for "computer" or "machine." From a TCP/IP perspective, only two types of entities exist on a network: routers and hosts.

A router is a machine that forwards packets from one network to another. To do this, the router must have at least two network interfaces. A machine with only one network interface cannot forward packets, and therefore is considered a host. Most of the machines you set up on a network will be hosts.

When a host initiates communication, it is called a sending host, or, simply, the sender. For example, a host initiates communications when its user types rlogin or sends an email message to another user. The host that is the target of the communication is called the receiving host, or recipient. For example, the remote host specified as the argument to rlogin is the recipient of the request to log in.

Each host has three characteristics that help identify it to its peers on the network. These characteristics include its:

• Host name
• Internet address, or IP address, the form used in this book
• Hardware address

Host Name The host name is the name of the local machine, combined with the name of your organization. Many organizations let users choose the host names for their machines. Programs such as sendmail and rlogin use host names to specify remote machines on a network. The guide User Accounts, Printers, and Mail Administration contains more information about host names.

The host name of the machine also becomes the name of the primary network interface. This concept becomes important when you set up the network databases or configure routers.

When setting up a network, you will have to obtain the host names of all machines to be involved. You will use this information when setting up network databases, as described in Chapter 4, "Configuring TCP/IP on the Network."

IP Address The IP address is one of the two addresses each machine has on a TCP/IP network that identifies the machine to its peers on the network. This address also gives peer hosts a notion of where a particular host is located on the network. If you have installed Solaris on a machine on a network, you may recall specifying the IP address during the installation process. IP addressing is a significant aspect of TCP/IP and is explained fully in "Designing Your IP Addressing Scheme" on page 31.

Hardware Address Each host on a network has a hardware address, which also identifies it to its peers. This address is physically assigned to the machine's CPU or network interface by the manufacturer. Each hardware address is unique.

This book uses the term Ethernet address to correspond to the hardware address. Because Ethernet is the most commonly used network media on Solaris-based networks, the text assumes that the hardware address of your Solaris host is an Ethernet address. If you are using other network media, such as FDDI, refer to the documentation that came with your media for hardware addressing information.

Reaching Beyond the Local Area Network--the Wide Area Network

As your network continues to function successfully, users may need to access information available from other companies, institutes of higher learning, and other organizations not on your LAN. To obtain this information, they may need to communicate over a wide area network (WAN), a network that covers a potentially vast geographic area and uses network media such as leased data/telephone lines, X.25, and ISDN services.

A prime example of a WAN is the Internet, the global public network that is the successor to the WANs for which TCP/IP was originally developed. Other examples of WANs are enterprise networks, linking the separate offices of a single corporation into one network spanning an entire country, or perhaps an entire continent. It is entirely possible for your organization to construct its own WAN.

As network administrator, you may have to provide access to WANs to the users on your local net. Within the TCP/IP and UNIX community, the most commonly used public network has been the Internet. Information about directly connecting to the Internet is outside the scope of this book. You can find many helpful books on this subject in a computer bookstore.