the waiting list and printed last. The printing
wait time can sometimes be long, depending on the size of the
print jobs at the head of the queue. A network print service
will provide system administrators with the necessary tools to
manage the large number of print jobs being routed throughout
the network. This includes the ability to prioritize, pause,
and even delete print jobs that are waiting to be printed.
File sharing
The ability to share files over a
network is an important network service. There are many file
sharing protocols and applications in use today. Within a
corporate or home network, files are typically shared using
Windows File Sharing or the Network File Sharing (NFS)
protocol. In such environments, an end user may not even know
if a given file is on a local hard disk or on a remote server.
Windows File Sharing and NFS allow users to easily move,
create, and delete files in remote directories. File
Transfer Protocol (FTP)
Many organizations make files
available to remote employees, to customers, and to the general
public using FTP. FTP services are made available to the public
in conjunction with web services. For example, a user may
browse a website, read about a software update on a web page,
and then download the update using FTP. Smaller companies may
use a single server to provide FTP and HTTP services, while
larger companies may choose to use dedicated FTP servers.
Although FTP clients must logon, many FTP servers are
configured to allow anonymous access. When users access a
server anonymously, they do not need to have a user account on
the system. The FTP protocol also allows users to upload,
rename, and delete files, so administrators must be careful to
configure an FTP server to control levels of access. FTP is a
session-oriented protocol. Clients must open an application
layer session with the server, authenticate, and then perform
an action, such as download or upload. If the client session is
inactive for a certain length of time, the server disconnects
the client. This inactive length of time is called an idle
timeout. The length of an FTP idle timeout varies depending on
the software. Web services
The World Wide Web is now
the most visible network service. In less than a decade, the
World Wide Web has become a global network of information,
commerce, education, and entertainment. Millions of companies,
organizations, and individuals maintain websites on the
Internet. Websites are collections of web pages stored on a
server or group of servers. The World Wide Web is based on a
client/server model. Clients attempt to establish TCP sessions
with web servers. Once a session is established, a client can
request data from the server. HTTP typically governs client
requests and server transfers. Web client software includes GUI
web browsers, such as Netscape Navigator and Internet
Explorer. Web pages are hosted on computers running web service
software. The two most common web server software packages are
Microsoft Internet Information Services (IIS) and Apache Web
Server. Microsoft IIS runs on a Windows platform and Apache Web
Server runs on UNIX and Linux platforms. A Web service software
package is available for virtually all operating systems
currently in production. Domain Name System (DNS)
The Domain Name System (DNS) protocol translates an Internet
name, such as www.cisco.com, into an IP address. Many
applications rely on the directory services provided by DNS to
do this work. Web browsers, e-mail programs, and file transfer
programs all use the names of remote systems. The DNS protocol
allows these clients to make requests to DNS servers in the
network for the translation of names to IP addresses.
Applications can then use the addresses to send their messages.
Without this directory lookup service, the Internet would be
almost impossible to use. Dynamic Host Configuration
Protocol (DHCP)
The purpose of Dynamic Host
Configuration Protocol (DHCP) is to enable individual computers
on an IP network to learn their TCP/IP configurations from the
DHCP server or servers. DHCP servers have no information about
the individual computers until information is requested. The
overall purpose of this is to reduce the work necessary to
administer a large IP network. The most significant piece of
information distributed in this manner is the IP address that
identifies the host on the network. DHCP also allows for
recovery and the ability to automatically renew network IP
addresses through a leasing mechanism. This mechanism allocates
an IP address for a specific time period, releases it, and then
assigns a new IP address. DHCP allows all this to be done by a
DHCP server which saves the system administrator considerable
amount of time.
Content 6.2 Network Management
6.2.1 Introduction to network management As a network
evolves and grows, it becomes a more critical and indispensable
resource to the organization. As more network resources are
available to users, the network becomes more complex, and
maintaining the network becomes more complicated. Loss of
network resources and poor performance are results of increased
complexity and are not acceptable to the users. The network
administrator must actively manage the network, diagnose
problems, prevent situations from occurring, and provide the
best performance of the network for the users. At some point,
networks become too large to manage without automated network
management tools. Network Management includes: -
Monitoring network availability
- Improved automation
- Monitoring response time
- Security
features
- Traffic rerouting
- Restoration
capability
- User registration
The driving
forces behind network management are shown in Figure and
explained below: - Controlling corporate assets
– If network resources are not effectively controlled, they
will not provide the results that management requires.
- Controlling complexity – With massive growth in the
number of network components, users, interfaces, protocols, and
vendors, loss of control of the network and its resources
threatens management.
- Improved service – Users
expect the same or improved service as the network grows and
the resources become more distributed.
- Balancing
various needs – Users must be provided with various
applications at a given level of support, with specific
requirements in the areas of performance, availability, and
security.
- Reducing downtime – Ensure high
availability of resources by proper redundant design.
- Controlling costs – Monitor and control resource
utilization so that user needs can be satisfied at a reasonable
cost.
Some basic network management terms are
introduced in Figure . Interactive Media Activity Drag
and Drop: Network Management Terminology When the student has
completed this activity, the student will be able to identify
the terminology used in Network Management.
Content
6.2 Network Management 6.2.2 OSI and network
management model The International Standards Organization (ISO)
created a committee to produce a model for network management,
under the direction of the OSI group. This model has four
parts: - Organization
- Information
- Communication
- Functional
This is a
view of network management from the top-down, divided into four
submodels and recognized by the OSI standard. The Organization
model describes the components of network management such as a
manager, agent, and so on, and their relationships. The
arrangement of these components leads to different types of
architecture, which will be discussed later. The Information
model is concerned with structure and storage of network
management information. This information is stored in a
database, called a management information base (MIB). The ISO
defined the structure of management information (SMI) to define
the syntax and semantics of management information stored in
the MIB. MIBs and SMI will be covered in more depth later. The