ion

UNIT 1 INTRODUCTION TO NETWORK Introduction to Network

Administration
ADMINISTRATION
Structure Page Nos.

1.0 Introduction 5
1.1 Objectives 5
1.2 Roles and Responsibilities of Network Administrator 6
1.3 Linux and TCP/IP Internetworking Concepts 6
1.4 Using Network Clients 10
1.5 Understanding System Initialization 11
1.6 User Remote Administration Services and Tools 16
1.7 Summary 17
1.8 Answers to Check Your Progress 18
1.9 Further Readings 19

1.0 INTRODUCTION
Computer network is a telecommunications network that connects a collection of
computers to allow communication and data exchange between systems, software
applications, and users. The computers that are involved in the network that originate,
route and terminate the data are called nodes. The interconnection of computers is
accomplished with a combination of cable or wireless media and networking
hardware. Two devices are said to be networked when a process in one device is able
to exchange information with a process in another device. Networks may be classified
by various characteristics, such as the media used to transmit signals, the
communications protocols used to organize network traffic, network scale, network
topology and organizational scope. The best-known computer network is the Internet.

Communication protocols define the rules and data formats for exchanging
information in a computer network. Well-known communications protocols include
Ethernet, a hardware and link layer standard that is widely used for local area
networks, and the Internet protocol suite (TCP/IP), which defines a set of protocols
for communication between multiple networks, for host-to-host data transfer, and for
application-specific data transmission formats. Protocols provide the basis for
network programming.

1.1 OBJECTIVES
After going through this unit, you will be able to:
• know the roles and responsibilities of a Network Administrator;
• know about network client and its purpose;
• understand LINUX system initialization; and
• understand remote system administration and available tools.

5
Network Administration
With Linux 1.2 ROLES AND RESPONSIBILITIES OF Introd

NETWORK ADMINISTRATOR
A Network Administrator is an individual, who is responsible for configuring,
commissioning and maintenance of network infrastructure and services. It also
includes the computer hardware and software systems that make up a data network. In
an organization, Network Administrator generally don’t typically get involved
directly with users, instead focus upon configuring, monitoring and maintenance of
network components within organization’s LAN/WAN infrastructure. Depending on
the organization and its size, the Network Administrator may also involve in design
and deployment of computer networks.

Roles of a Network Administrator

The roles of a Network Administrator include activities and tasks to be performed
such as configuring, commissioning and maintenance of various network devices-
routers, switches, VPN gateways, security devices-Firewall and IDS/IPS , creation of
De Militarized Zones (DMZ) , IP addresses allocation & management. It also
includes configuring and commissioning of various network services/protocols-
DHCP, DNS, FTP, HTTP, NFS, etc.

Apart from roles, the Network Administrator is also responsible to

• Ensure data network connectivity
• Network monitoring and management
• Testing the network for breaches, if any
• Keeping an eye out for needed updates
• Update Access Control Lists (ACLs) time to time to regulate network traffic
• Security controls enforcement
• Preparing and implementation of security policy and standards

1.3 LINUX AND TCP/IP INTERNETWORKING

CONCEPTS
Linux is a Unix-like computer operating system assembled under the model of free
and open source software development and distribution. Linux was originally
developed as a free operating system for Intel x86-based personal computers. It is a
leading operating system and supports different computer hardware platforms like
other operating systems. Linux also runs on embedded systems (a devices where the
operating system is typically built into the firmware and highly tailored to the system)
such as mobile phones, tablet computers, network routers, building automation
controls, televisions, video game consoles and. The Android system, which is in
wide use on mobile devices is built on the Linux kernel.

Typically Linux is packaged in a format known as a Linux distribution for desktop

and server use. Some popular mainstream Linux distributions include Debian (and its
derivatives such as Ubuntu and Linux Mint), Red Hat Enterprise Linux (and its
derivatives such as Fedora) , and openSUSE (and its commercial derivative SUSE
Linux Enterprise Server).

Linux is the most popular network operating system (NOS) runs on a server and
enables the server to manage data, users, groups, security, applications, and other
networking functions. It runs based on a client/server architecture in which a server
6 enables multiple clients to share resources. Linux allows shared file and printer access
ion among multiple computers in a network, typically a local area network (LAN), a Introduction to Network
private network or to other networks. Linux well supports to configure and Administration
commissioning of various network servers and services such as proxy servers,
Domain name systems, Mail servers, Web servers, etc that are to be accessed through
internet.

Internetworking with TCP/IP

Internetworking is the practice of connecting a computer network with other networks
through the use of network gateways that provide a common method of routing data
packets between the networks. The most notable example of internetworking is the
Internet, which a network of networks based on many underlying hardware
technologies, but unified by an internetworking protocol standard, referred to as the
Internet Protocol Suite and known as TCP/IP.

TCP/IP ( Transmission Control Protocol (TCP) and the Internet Protocol (IP)) is a
networking model and provides end-to-end connectivity specifying how data should
be formatted, addressed, transmitted, routed and received at the destination. It has
four abstraction layers which are used to sort all related protocols according to the
scope of networking involved.

The Figure 1 shows different networks connected to internet.

Figure 1: Different networks connected to Internet

How TCP/IP Works

TCP/IP for IP version 4 (IPv4) is a networking protocol suite that uses to
communicate over the internet with other computers. It interacts with naming services
like Domain Name System (DNS) and security technologies, such as IPsec for secure
transfer of IP packets between computers.

Linux provides extensive support for the Transmission Control Protocol/Internet

Protocol (TCP/IP) suite, as both a protocol and a set of services for connectivity and
management of IP internetworks. Knowledge of the basic concepts of TCP/IP is an
absolute requirement for the proper understanding of the configuration, deployment,
and troubleshooting of IP-based Linux server.

7
Network Administration TCP/IP Protocol Architecture Introd
With Linux
TCP/IP protocols map to a four-layer conceptual model. The four layers are
Application, Transport, Internet, and Network Interface. Each layer corresponds to
one or more layers of the seven-layer Open Systems Interconnection (OSI) model.

Figure 2 shows the TCP/IP protocol architecture.

Figure 2: TCP/IP Protocol Architecture

Network Interface Layer

The Network Interface layer also called the Network Access layer that handles
placing TCP/IP packets on the network medium and receiving TCP/IP packets off the
network medium. TCP/IP was designed to be independent of the network access
method, frame format, and medium. In this fashion, TCP/IP can be used to connect
differing network types and these include local area network (LAN) media such as
Ethernet and Token Ring and also WAN technologies such as X.25 and Frame Relay.
The network interface layer encompasses the data link and physical layers of the OSI
model.

Internet Layer
The Internet layer handles addressing, packaging, and routing functions. The core
protocols of the Internet layer are IP, ARP, ICMP, and IGMP.

• The Internet Protocol (IP) is a routing protocol that handles IP addressing,

routing, and the fragmentation and reassembly of packets.
• The Address Resolution Protocol (ARP) handles resolution of an Internet layer
address to a Network Interface layer address, such as a hardware address.
• The Internet Control Message Protocol (ICMP) handles providing diagnostic
functions and reporting errors due to the unsuccessful delivery of IP packets.
• The Internet Group Management Protocol (IGMP) handles management of IP
multicast group membership.
The Internet layer is similar to the Network layer of the OSI model.

8
ion Transport Layer Introduction to Network
Administration
The Transport layer handles and provides session and datagram communication
services to Application layer. The core protocols of the Transport layer are
Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).

• TCP provides a one-to-one, connection-oriented, reliable communications

service. TCP handles the establishment of a TCP connection, the sequencing and
acknowledgment of packets sent, and the recovery of packets lost during
transmission.
• UDP provides a one-to-one or one-to-many, connectionless, unreliable
communications service. UDP is used when the amount of data to be transmitted
is small (such as data that fits into a single packet), when you do not want the
overhead of establishing a TCP connection, or when the applications or upper
layer protocols provide reliable delivery.
The TCP/IP Transport layer is similar to the Transport layer of OSI model.

Application Layer
The application layer provides services for an application program to ensure that
effective communication with another application program in a network is possible.
The application layer is not the application itself that is doing the communication, but
with various application layer protocols.

The most widely known Application layer protocols are those used for the exchange
of user information:

• The Hypertext Transfer Protocol (HTTP) is used to transfer files that make up the
Web pages of the World Wide Web.
• The File Transfer Protocol (FTP) is used for interactive file transfer.
• The Simple Mail Transfer Protocol (SMTP) is used for the transfer of mail
messages and attachments.
• Telnet, a terminal emulation protocol, is used for logging on remotely to network
hosts.
Additionally, the following Application layer protocols help facilitate the use and
management of TCP/IP networks:

• The Domain Name System (DNS) is used to resolve a host name to an IP address.
• The Routing Information Protocol (RIP) is a routing protocol that routers use to
exchange routing information on an IP internetwork.
• The Simple Network Management Protocol (SNMP) is used between a network
management console and network devices (routers, bridges, intelligent hubs) to
collect and exchange network management information.

The TCP/IP Application layer encompasses the responsibilities of the Session,

Presentation, and Application layers of OSI model.

How Data Transmitted

Figure 3 shows, how data transmitted from source computer to destination
computer.

9
Network Administration
Introd
With Linux Network Topology

Data Flow

Figure 3: Data transmission between two Hosts

1.4 USING NETWORK CLIENTS

A client is a piece of computer hardware or software or both or a computer program
that sends a service request to a server/computer program or accesses a service made
available by a server/computer program. A network client is a client that can interact
with servers/computer program through network/internet. The term client was first
applied to devices that were not capable of running their own stand-alone programs,
but could interact with remote computers via a network.

For example, web browsers are clients that connect to web servers and retrieve web
pages for display. Email clients retrieve email from mail servers. Online chat uses a
variety of clients, which vary depending on the chat protocol being used. Multiplayer
video games or online video games may run as a client on each computer. The term
"client" may also be applied to computers or devices that run the client software or
users that use the client software. Similarly, the devices such as laptops, notebooks,
palmtops, tablet PCs, smart phones, and other such devices also called network
clients through which services requests can be sent or services can be retrieved
to/from servers that are providing services. Figure 4 shows network clients that are
being used in a cloud computing model.

10
ion
Introduction to Network
Administration

Figure 4: Network clients in a Cloud computing model

1.5 UNDERSTANDING SYSTEM

INITIALIZATION
Here system means the combination of the computer hardware and the software
(generally it the operating system installed on the computer hardware). Linux system
( the computer installed with Linux operating system) initialization means how
system gets stared after power is on. The Linux startup process is the process of
Linux-operating system initialization. It is in many ways similar to the BSD and other
Unix style boot processes, from which it derives.

In Linux, the flow of control during a boot is from BIOS (Basic Input/output System),
to boot loader, to kernel. The kernel then starts the scheduler and runs the first
program Init (which is mostly responsible to run startup scripts for each runlevel), at
which point the kernel goes idle unless called externally.

init (short for initialization) is a program for Unix-based computer operating systems
that spawns all other processes. It runs as a daemon and typically has PID 1. The boot
loader starts the kernel and the kernel starts init. If some one has to delete init
without a replacement, the system would encounter a kernel panic on the next reboot.

Overall system initialization process

i) The BIOS performs hardware-platform specific startup tasks

ii) Once the hardware is recognized and started correctly, the BIOS loads and
executes the partition boot code from the designated boot device, which contains
phase 1 of a Linux boot loader. Phase 1 loads phase 2 (the bulk of the boot loader
code). Some loaders may use an intermediate phase (known as phase 1.5) to
achieve this since modern large disks may not be fully readable without further
code.

11
Network Administration iii) The boot loader often presents the user with a menu of possible boot options. It Introd
With Linux
then loads the operating system, which decompresses into memory, and sets up
system functions such as essential hardware and memory paging, before calling
‘start_kernel()’.
‘start_kernel()’ then performs the majority of system setup (interrupts, the rest of
memory management, device initialization, drivers, etc.) before spawning
separately, the idle process and scheduler, and the Init process (which is executed
in user space).
iv) The Init process executes scripts as needed that set up all non-operating system
services and structures in order to allow a user environment to be created, and
then presents the user with a login screen.
The standard sequence for initializing a Linux system is as follows:
• Power on the System
• Initializing the BIOS
• Bootloader
• Kernel initialization
• Starting from "init"

Initializing the BIOS

• The BIOS (Basic Input/Output System) is the interface between the hardware and
software at a very basic level, it provides all the basic instructions used by the
operating system.
• The BIOS begins by executing an auto-ignition test (POST), and then it searches
for devices.
• After the POST, a boot device is selected from a list that is configurable in the
BIOS.
• The BIOS reads and executes the first physical sector of the boot media selected
on the system, which is usually contained in the first 512 bytes of hard disk.
Bootloader
The bootloader is usually contained in the first sector of the disk and then read and
executed by the BIOS. The storage space that reads the BIOS is not sufficient to
contain all the bootloader, but just a part sufficient enough to start the rest of the
bootloader, which is usually contained in a configuration file stored elsewhere on the
disc. Hence the start is done in two steps:

• Launch via BIOS

• Launch a file under boot
The bootloader is designed to load and run the system kernel. The standard
bootloader is GRUB but can also shift to LILO.

Kernel initialization
The kernel in Linux handles all operating system processes, such as memory
management, task scheduling, I/O, interprocess communication, and overall system
control. This is loaded in two stages - in the first stage the kernel is loaded into
memory and decompressed, and a few fundamental functions such as basic memory
management are set up. Control is then switched to the main kernel start process.
Once the kernel is fully operational, it looks for an init process to run, which sets up
a user space and the processes needed for a user environment and ultimate login. The
kernel itself is then allowed to go idle, subject to calls from other processes.
12
ion
Introduction to Network
Administration
The kernel initialization includes:

• The detection and initialization of devices. It means any device drivers compiled
into the kernel are called and try to locate their corresponding devices.
• Mounting the root file system in read-only mode
• Loading the initial process "init"

The kernel initialization is very rapid and therefore it is very difficult to follow
visually. One can read system generated log file to check what happened during
kernel initialization. Generally log file can be stored under /var/log/dmesg

Initialize "init"
Init (initialization) is the father of all processes. Its primary role is to create processes
from a script stored in the file /etc/inittab. This file usually has entries which cause
init to spawn gettys on each line that users can log in. It also controls autonomous
processes required by any particular system.

• "init" is the main process, it will always have a PID value: 1.

• "init" reads its configuration from the /etc/inittab file, that contains the settings
for the system at every level of execution.

Run Levels
A run level is a software configuration of the system which allows only a selected
group of processes to exist. The processes spawned by init for each of these run levels
are defined in the /etc/inittab file.

"init" defines the following run levels:

• Level 0: Stop (not to be attributed to the initdefault)
• Level 1, S: single user mode (only the root user can log). Typically used for
maintenance.
• Level 2: Multi-user mode without NFS network
• Level 3: full mode for multiple users including network
• Level 4: User Configurable duplicate but the level 3 by default.
• Level 5: X11 (including network)
• Level 6: Restart

Runlevel (System V)
The ability to change runlevel offers easy interaction with administrators; this allows
to switch between different levels of startup.

Scripts services are in /etc/rc.d/init.d. Each runlevel correspond to a /etc/rc.d/rcX.d

directory, where X is the runlevel.

System Shutdown
On shutdown, Init is called to close down all user space functionality in a controlled
manner, again via scripted directions, following which Init terminates and the Kernel
executes its own shutdown.

13
Network Administration To stop the system, use commands like: Introd
With Linux
#Shutdown -h now
#halt
#poweroff
#init 0

Check Your Progress 1

1. Write the main responsibilities of a Network Administrator.
…………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
2. What are the various run levels of Linux system?
…………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………

1.6 USER REMOTE ADMINISTRATION

SERVICES AND TOOLS
Remote administration is an approach being followed to control either a computer
system or a network or an application or all three from a remote location. A remote
location may refer to a computer in the next room or one on the other side of the
world. Generally, remote administration is essentially adopted when it is difficult or
impractical to a person to be physically present and do administration on a system’s
terminal.

Requirements to perform Remote Administration

Network connectivity is essentially needed to perform remote administration. The
network could be either Local Area Network (LAN) connectivity or internet
connectivity depending on remote location. It means, any computer with an internet
connection or on a LAN can be remotely administered.

For non-malicious administration, the user must install or enable remote

administration software/tool on the host system then the user/client can access the
host system from another computer using the remote tool.

Common Services for which remote administration is used

Generally, remote administration is needed for user management, file system
management, software installation/configuration, network management- Network
Security/Firewalls, VPN, Infrastructure Design, Network File Servers, Auto-
mounting etc. and kernel optimization/ recompilation.

14
ion The following are some of the tasks/ services for which remote administration need Introduction to Network
to be done: Administration

General
Controlling one's own computer from a remote location (e.g. to access the software
on a personal computer from an internet café).

ICT Infrastructure Management

Remote administration essentially needed to administer the ICT infrastructure such as
the servers, the routing and switching components, the security devices and other
such related.

Shutdown
• Shutting down or rebooting a computer over a network

Accessing Peripherals
• Using a network device, like printer
• Retrieving streaming data, much like a CCTV system

Modifying
• Editing another computer's registry settings
• Modifying system services
• Installing software on another machine
• Modifying logical groups

Viewing
• Remotely assisting others
• Supervising computer or internet usage
• Access to a remote system's "Computer Management" snap-in

Hacking
Computers infected with malware such as Trojans sometimes open back doors into
computer systems which allow malicious users to hack into and control the computer.
Such users may then add, delete, modify or execute files on the computer to their own
ends.

Remote Desktop Solutions for Linux

Most people who are used to a Unix-style environment know that a machine can be
reached over the network at the shell level using utilities like telnet or ssh. And some
people realize that X Windows output can be redirected back to the client
workstation. But many people don’t realize that it is easy to use an entire desktop
over the network. The following are some of proprietary and open source applications
that can be used to achieve this.

SSH (Secure Shell)

Secure Shell (SSH) is a proprietary cryptographic network tool for secure data
communication between two networked computers that connects, via a secure
channel over an insecure network, a server and a client (running SSH server and SSH
client programs, respectively). The protocol specification distinguishes between two
major versions that are referred to as SSH-1 and SSH-2. 15
Network Administration The best-known application of the tool is for access to shell accounts on Unix-like Introd
With Linux
operating systems-GNU/Linux, OpenBSD, FreeBSD, but it can also be used in a
similar fashion for accounts on Windows.

SSH is generally used to log into a remote machine and execute commands. It also
supports tunneling, forwarding TCP ports and X11 connections, it can transfer files
using the associated SSH file transfer (SFTP) or secure copy (SCP) protocols. SSH
uses the client-server model.

SSH is important in cloud computing to solve connectivity problems, avoiding the

security issues of exposing a cloud-based virtual machine directly on the Internet. An
SSH tunnel can provide a secure path over the Internet, through a firewall to a virtual
machine

OpenSSH (OpenBSD Secure Shell)

OpenSSH is a tool providing encrypted communication sessions over a computer
network using the SSH protocol. It was created as an open source alternative to the
proprietary Secure Shell software suite offered by SSH Communications Security.

Telnet
Telnet is used to connect a remote computer over network. It provides a bidirectional
interactive text-oriented communication facility using a virtual terminal connection
on internet or local area networks. Telnet provides a command-line interface on a
remote host. Most network equipment and operating systems with a TCP/IP stack
support a Telnet service for remote configuration (including systems based on
Windows NT). Telnet is used to establish a connection to Transmission Control
Protocol (TCP) on port number 23, where a Telnet server application (telnetd) is
listening.

Experts in computer security, recommend that the use of Telnet for remote logins
should be discontinued under all normal circumstances, for the following reasons:

• Telnet, by default, does not encrypt any data sent over the connection (including
passwords), and so it is often practical to eavesdrop on the communications and
use the password later for malicious purposes; anybody who has access to a
router, switch, hub or gateway located on the network between the two hosts
where Telnet is being used can intercept the packets passing by and obtain login,
password and whatever else is typed with a packet analyzer.

• Most implementations of Telnet have no authentication that would ensure

communication is carried out between the two desired hosts and not intercepted
in the middle.

• Several vulnerabilities have been discovered over the years in commonly used
Telnet daemons.

rlogin
rlogin is an utility for Unix-like computer operating systems that allows users to log
in on another host remotely through network, communicating through TCP port 513.

rlogin has several serious security problem- all information, including passwords is
transmitted in unencrypted mode. rlogin is vulnerable to interception. Due to serious
security problems, rlogin was rarely used across distrusted networks (like the public
internet) and even in closed networks.

16
ion rsh Introduction to Network
Administration
The remote shell (rsh) can connect a remote host across a computer network. The
remote system to which rsh connects runs the rsh daemon (rshd). The daemon
typically uses the well-known Transmission Control Protocol (TCP) port number 514.
In security point of view, it is not recommended.

PuTTY
PuTTY is a free and open source terminal emulator application which can act as a
client for the SSH, Telnet, rlogin, and raw TCP computing protocols and as a serial
console client. The name "PuTTY" has no definitive meaning, though "tty" is the
name for a terminal in the Unix tradition, usually held to be short for Teletype.
PuTTY was originally written for Microsoft Windows, but it has been ported to
various other operating systems as well

VNC (Virtual Network Computing)

VNC is a remote display system which allows the user to view the desktop of a
remote machine anywhere on the internet. It can also be directed through SSH for
security

Install VNC server on a computer (server) and install client on local PC. Setup is
extremely easy and server is very stable. On client side, set the resolution and connect
to IP of VNC server.

One can download VNC software from the following URLs:

http://www.realvnc.com/download.html
http://www.tightvnc.com/download.html
http://www.uvnc.com/

FreeNX allows to access desktop from another computer over the internet. One can
use this to login graphically to a desktop from a remote location. One example of its
use would be to have a FreeNX server set up on home computer, and graphically
logging in to the home computer from work computer, using a FreeNX client. One
can download FreeNX software from the following URLs:

https://help.ubuntu.com/community/FreeNX
http://ubuntuforums.org/showthread.php?t=97277&highlight=freenx
http://freenx.berlios.de/ (FreeNX homepage)

Wireless Remote Administration

Remote administration software has recently started to appear on wireless devices
such as the BlackBerry, Pocket PC, and Palm devices, as well as some mobile
phones.

Generally these solutions do not provide the full remote access seen on software such
as VNC or Terminal Services, but do allow administrators to perform a variety of
tasks, such as rebooting computers, resetting passwords, and viewing system event
logs, thus reducing or even eliminating the need for system administrators to carry a
laptop or be within reach of the office.

AetherPal and Netop are some of the tools used for full wireless remote access and
administration on Smartphone devices.

17
Network Administration Disadvantages of Remote Administration Introd
With Linux
Remote administration has many disadvantages too apart from its advantages. The
first and foremost disadvantage is the security. Generally, certain ports to be open at
Server level to do remote administration. Due to open ports, the hackers/attackers
takes advantage to compromise the system. It is advised that remote administration to
be used only in emergency or essential situations only to do administration remotely.
In normal situations, it is ideal to block the ports to avoid remote administration.

Check Your Progress 2

1. Why remote administration is needed? Explain.

……………………………………………………………………………………..

……………………………………………………………………………………..

……………………………………………………………………………………..

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2. List the different network clients.

……………………………………………………………………………………..

……………………………………………………………………………………..

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3. What are the different remote administration tools?

……………………………………………………………………………………..

……………………………………………………………………………………..

……………………………………………………………………………………..

……………………………………………………………………………………..

……………………………………………………………………………………..

1.7 SUMMARY
In this unit, different roles and responsibilities of a network administrator are clearly
explained The TCP/IP and its role in data transmission from source to destination is
made clear. System initialization process and importance of remote administration
also covered.

1.8 ANSWERS TO CHECK YOUR PROGRESS

Check Your Progress 1

1) Network Administrator is responsible to

18 • Ensure data network connectivity

ion • Network monitoring and management Introduction to Network
Administration
• Testing the network for breaches, if any
• Keeping an eye out for needed updates
• Update Access Control Lists (ACLs) time to time to regulate network traffic
• Security controls enforcement
• Preparing and implementation of security policy and standards

2) The following are various run levels of a Linux system

Level 0: Stop (not to be attributed to the initdefault)

Level 1, S: single user mode (only the root user can log). Typically used for maintenance.
Level 2: Multi-user mode without NFS network
Level 3: full mode for multiple users including network
Level 4: User Configurable duplicate but the level 3 by default.
Level 5: X11 (including network)
Level 6: Restart
Check Your Progress 2

1) The need for remote administration is for

• User management
• ICT Infrastructure management
• Problem Diagnosis and Troubleshooting
• File system management
• Software installation/configuration
• Network Management- Network Security/Firewalls, VPN, Infrastructure
Design, Network File Servers, Auto-mounting etc.

2) The different network clients are

Computers, Notebooks, Palmtops, Tablet PCs, Smart phones and other such related.

3) The following are different remote administration tools

SSH, Telnet, rsh, rlogin, openSSH, VNC, etc

1.9 FURTHER READINGS

1. Computer Networks by Andrew S Tanenbaum , Fifth Edition
2. SA2, Redhat System Administration I & II, Student Workbook
3. Cisco Certified Network Associate Study Guide, Seventh Edition by Todd
Lammle
4. Redhat Enterprise Linux System Administration
5. http://en.wikipedia.org/wiki/Internetworking
6. http://en.wikipedia.org/wiki/Remote_administration
19