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Chapter 3

Internet Protocols

X Window

Designed for client-server operations,

X Window

defines a protocol for writ-

ing client/server applications based on a graphical user interface (GUI). The
idea is to allow a program, called a client, to run on one computer and have
it display a program called a window server on another computer.

Simple Network Management Protocol (SNMP)

Simple Network Management Protocol (SNMP)

collects and manipulates

this valuable network information. It gathers data by polling the devices on
the network from a management station at fixed or random intervals, requir-
ing them to disclose certain information. When all is well, SNMP receives
something called a

baseline

--a report delimiting the operational traits of

a healthy network. This protocol can also stand as a watchdog over the
network, quickly notifying managers of any sudden turn of events. These net-
work watchdogs are called

agents

, and when aberrations occur, agents send an

alert called a

trap

to the management station.

Domain Name Service (DNS)

Domain Name Service (DNS)

resolves host names, specifically Internet

names, like

www.routersim.com

. You don't have to use DNS; you can just

type in the

IP address

of any device you want to communicate with. An IP

address identifies hosts on a network and the Internet as well. However,
DNS was designed to make our lives easier. Think about this: What would
happen if you wanted to move your web page to a different service provider?
The IP address would change and no one would know what the new one
was. DNS allows you to use a domain name to specify an IP address. You
can change the IP address as often as you want, and no one will know the
difference.

DNS is used to resolve a

fully qualified domain name (FQDN)

--for

example,

www.lammle.com

todd.lammle.com

. An FQDN is a hierarchy

that can logically locate a system based on its domain identifier.

If you want to resolve the name "todd," you either must type in the

FQDN of

todd.lammle.com

or have a device like a PC or router add the suf-

fix for you. For example, on a Cisco router, you can use the command

domain-name

lammle.com

to append each request with the

lammle.com

domain. If you don't do that, you'll have to type in the FQDN to get DNS
to resolve the name.

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