LAN Refresher - Home

raggedsquadNetworking and Communications

Oct 30, 2013 (4 years and 13 days ago)

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Table of Contents

1.

Educational Objectives


2.

LAN Hardware


3.

LAN Software


1.

Packet Switched Network


2.

Host Addresses and Names


4.

Protocols


5.

Clients and Servers


1.

A Few Well Known Services


2.

A Few Well Known Clients


6.

Lab Experiment


7.

Acknowledgements


8.

References



Educational Objectives

1.

Understand the role of network interface cards (NIC), hubs, and routers.

2.

Understand what an IP address is.

3.

Setup a peer
-
to
-
peer network of two PCs

4.

Setup a LAN of several
PCs as clients and servers.

5.

Refresh the needed details from TCP and IP.


LAN Refresher

The Internet is comprised of thousands of regional networks scattered throughout the
globe.


The Web refers to a body of information
-

an abstract space of knowledge,

while
the Internet refers to the physical side of the global network, a giant mass of cables and
computers.


The WWW uses the Internet to transmit hypermedia documents between
computer users internationally.



A LAN (Local Area Network) is a network of comp
uters within a relatively small
geographic area, such as an office building





A WAN (wide area network) is a geographically dispersed telecommunications
network. A wide area network may be privately owned or rented, but the term
usually connotes the inclus
ion of public (shared user) networks. A connection
made through a telephone modem falls into this category.



An intermediate form of network in
terms of geography is a metropolitan area
network (MAN).

LAN Hardware

There are many ways of setting up a LAN.
The ruling king of such technologies is
Ethernet for the hardware layer, and TCP/IP for software layer.


The 10 megabits/sec
(Mb/s) is now (1999) considered obsolete.


The 100 Mb/s is current, and 1000 Mb/s
(Gigabit Ethernet) is becoming common.

Network To
pology

refers to how the computers are connected.


In the Star Topology, all
the computers are connected to a common point.


It is fault
-
tolerant, and is easy to add
new clients and easy


for management and monitoring of network performance.


The Bus
Topol
ogy is a straight line with a tap for each computer.


It is simple, easy to add new
computers by inserting a T
-
connector, but problems are hard to isolate and the network
slows down during periods of heavy use.



Network Interface Cards
: Professional works
tations have built
-
in network hardware.


In
PCs, NICs are hardware boards that you insert into empty slots in the PC.


Today (1999),
a good PCI
-
based card for 10 or 100 megabits/sec (Mb/s) sells for about $15.


A typical
card will have two connectors at th
e back:


a telephone
-
jack like RJ45, and an RCA
-
like
BNC connector.

Through this physical connection,


the data


bits go


from the computer
to the cable and back again when receiving.

Each NIC is identified by a unique 6
-
byte number called its Ethernet ad
dress that is
stored, at manufacture time, in a ROM on the card.


This number is also called a MAC
(media access control) address.






The RJ45 Twisted Pair Cable
, whose connector is shown at right, is made from
insulated strands of wire twisted together

inside a sheath that may or may not be shielded.
Unshielded Twisted Pair (UTP) is the most commonly used cable for small LANs. It is
often referred to as 10BaseT because the most popular size of this cable can carry 10
Mb/s. It comes in different categori
es that carry between 4 Mb/s and 100 Mb/s of data to
about 300 feet before the signal strength suffers.

If you connecting only two computers, you do not need any hubs.


You use one RJ45
cross over cable
that has two of their signal wires transposed between

the connectors as
described below.


cross over cable connections:

Pin Name

End1 Pin

End2 Pin

Pin Name

TX+

1

3

RX+

TX
-

2

6

RX
-

RX+

3

1

TX+

RX
-

6

2

TX
-

(You may also connect 4
-
4, 5
-
5, 7
-
7, 8
-
8.)


This cable can be used to cascade hubs, or for
connectin
g two Ethernet stations back
-
to
-
back without a hub. It works with both 10Base
-
T and 100Base
-
TX.

To connect more than two computers, you need


network hubs or switches.


All the PCs
connect to the hub.


An inexpensive starter network kit for home


sells for

$50 (in 1999)
and includes two NICs and a hub that has 5 RJ45 ports.

The Thin Coaxial Cable

looks similar to a TV
cable but its impedance rating and other
characteristics are different. It has a core of solid
or braided copper wire surrounded by insulati
on,
braided metal shielding, and an outer cover.
These cables can carry a signal about 600 feet
before the signal starts to suffer from loss of
strength.

The thin coaxial cable


does not need hubs.


It
uses the bus topology.


Imagine it as a long
unbroken
line of cable terminated with 50
-
ohm resistors at either end, and with a T
-
connector for each computer.



Hubs and Switches

If more than two devices are to be networked, a
hub

is the central device into which all
networks cables are connected. Hubs typical
ly connect from 4
-
24 devices and can be
"stacked" or "cascaded" together for more capacity.



A hub is a place of convergence
where data arrives from one or more directions and is forwarded out in one or more other
directions.


An arriving packet is sent o
ut to all the connections.


Repeaters

repeat an Ethernet transmission (frame) on other ports. Repeaters operate at
the electrical level; they don't have any intelligence.


Switch

is a term for a multi
-
port bridge.


A
bridge

is a small computer with at leas
t two
network interfaces. It receives Ethernet frames, figures out which interface the
destination is on, and sends it appropriately (or not at all, if the destination and source
interface are the same). If the bridge doesn't know which interface the desti
nation is on, it
sends the frame out on all of them (except the source interface).


A switch analyzes the
packet and sends an arriving packet to only the destination NIC, and not to all the
connections that are made on the switch.

Routers, Gateways

Typical
ly, a packet may travel through a number of network points with routers before
arriving at its destination. A router is a hardware device or, in some cases, software in a
computer, that determines the next network point to which a packet should be forwarde
d
toward its destination. The router is connected to at least two networks and decides which
way to send each information packet based on

its current understanding of the state of the networks it is connected to. A router is
located at any juncture of netw
orks or gateway, including each Internet point
-
of
-
presence.
A router is often included as part of a network switch.

A
gateway

is a computer that lies at the intersection of two networks, and routes traffic
correctly between them, while keeping traffic inte
rnal to the two networks separated.

Switch

Used to segment networks into smaller connected subnets. Networks can easily overload:
switching them into separate subnets can enhance performance easily and inexpensively
while preserving existing investments.



Modems

Modem stands for MOdulator/DEModulator. A modem converts (modulates) digital
signals generated by the computer into analog signals which can be transmitted over a
telephone line and transforms (demodulates) incoming analog signals into their digita
l
equivalents. The specific techniques used to encode the digital bits into analog signals are
called modulation protocols. This encoding process puts the transmission into a mode
that is compatible with the various transmission media used by the telephone

company,
such as copper wire, microwave, satellite, and fiber optics. Most new modems can send
and receive data at 57.6 kbps (kilo bits per second) and faxes at 14.4 kbps.


ISDN
(Integrated Services Digital Network) modems use digital telephone lines to a
chieve a
transmission speed of 128 kbps.

LAN Software

LAN software consists of layers of software that is an integral part of an operating system,
and various clients and servers.


There is an ISO defined stack of seven layers, but in a
practical setting o
f Windows and Unix OSs, we will briefly describe the Ethernet NIC
device driver layer, the IP layer, and the TCP + UDP + ICMP layers.

Host Addresses and Names

Internet has a rigid and word
-
wide enforced addressing scheme that every computer on
the network
understands. Each NIC is rigidly identifed by a MAC address and an IP
address.


Each NIC is identified by a unique 6
-
byte number called its Ethernet or MAC
address that is stored, at manufacture time, in a ROM on the card. An IP address is a 4
-
byte number


that uniquely identifies a specific computer connected to the Internet.


The
four bytes are written as four numbers, separated by periods, as in 130.108.1.20.


In


this
form each byte is converted to a decimal number (0
-
255) dropping any leading zero's
un
less the number is zero and written with each byte separated by a `.' character.

Groups of these numbers are assigned by a world
-
wide authority.


For example, all
computers at WSU have IP addresses of the form 130.108.*.* and 130.108.1.20 is the
address of

a specific server at WSU. When you connect to an ISP,


your computer has an
IP address (the same one all the time or a different address each time you
connect).


Isolated LANs, such as the on that we will use in this course, or one that you
can setup at h
ome,
should

have IP addresses in the group of 192.168.*.*.

All addresses within a network have the same prefix. The portion of the address that is
common amongst all addresses within the network is called the `network portion' of


the
address. The remainin
g digits are called the `host portion'. The number of bits that are
shared by all addresses within a network is called the
netmask.


For example, consider the
following:
















-----------------


---------------
















Host Address







19
2.168.110.23
















Network Mask







255.255.255.0
















Network Portion




192.168.110.
















Host portion


















.23
















-----------------


---------------
















Network Address




192.168.110.0
















Broadcast Address


192.168.110.255
















-----------------


---------------

The
broadcast address

is a special address that every host on the


network listens to in
addition to its own unique address. If every host on the network is
meant to receive a a
packet, you send the packet to the broadcast address.

For administrative reasons, certain groups of addresses were formed into networks and
these networks were grouped into what are called
network classes
. These classes provide
a numbe
r of standard size networks that could be allocated. The ranges allocated are:


----------------------------------------------------------


| Network | Netmask







| Network Addresses












|


| Class



|















|






























|


----------------------------------------------------------


|




A




| 255.0.0.0





| 0.0.0.0




-

127.255.255.255 |


|




B




| 255.255.0.0



| 128.0.0.0


-

191.255.255.255 |


|




C




| 255.255.255.0 | 192.0.0.0


-

223.255.255.255 |


|Multicast|
240.0.0.0





| 224.0.0.0


-

239.255.255.255 |


----------------------------------------------------------



Internet domain names
are the next level of Internet addressing, just as the street name
is followed by the city and state.


IP addresses are


hard

to remember, so we use


names.
All hosts registered on the Internet must have names that reflect them domains under
which they are registered. Such names are called Fully Qualified Domain Names
(FQDNs).



The domain name identifies all the computers in a
group. Domain names
create a single identity for a set of locally connected computers used by a company or an
institution. So while there may be 38 servers at a given organization, each with its own IP
address, they all share a common domain name, such as
wright.edu
. In a name such as
gamma.cs.wright.edu


the "edu" shows that this host is sponsored by an education related
organization. The top
-
level domain is wright.edu, and the second level domain is
cs.wright.edu, and gamma is the name of the host machine
.

Packet Switched Network

A packet is the unit of data that is routed between an origin and a destination on the
network. When any file (e
-
mail message, HTML file, GIF file, URL request, and so
forth) is sent from one machine to another on the net, the Tra
nsmission Control Protocol
(TCP) layer of TCP/IP divides the file into "chunks" of an efficient size for routing. Each
of these packets is separately numbered and includes the Internet address of the
destination. The individual packets for a given file may

travel different routes through the
net. When they have all arrived, they are reassembled into the original file (by the TCP
software layer at the receiving end).

Ethernet is just a "party" line. When packets are sent out on the Ethernet, every host on
th
e Ethernet sees them. To make sure the packets get to the right place, the Ethernet
designers wanted to make sure that each address is different. For this reason 48 bits are
allocated for the Ethernet address, and a built in Ethernet address on the Etherne
t
controller. The Ethernet packets have a 14
-
octet header, this includes address "to" and
"from."

Protocols

A protocol is the set of rules that a telecommunication connection uses when the two end
points send signals back and forth. Protocols exist at seve
ral levels in a
telecommunication connection. There are hardware telephone protocols. There are
protocols between the end points in communicating programs within the same computer
or at different locations, etc. Both end points must recognize and observe t
he
protocol.


Protocols are implemented as software in the network operating system.

Transports are


the enabling network components that let clients talk to the server and
that let one network talk with another network of a different brand. NetBEUI stands

for
Network Basic End User Interface. It supports small LANs and it is fast and simple.

On the Internet, there are the TCP/IP protocols, consisting of: TCP (Transmission Control
Protocol), which uses a set of rules to exchange messages with other Internet

points at the
information packet level. IP (Internet Protocol), which uses a set of rules to send and
receive messages at the Internet address level.


These were developed to be routable and
can accommodate large networks.


TCP/IP is a general term relati
ng to the whole family
of Internet protocols. The protocols in this family are IP, TCP, UDP, ICMP, ARP. The
most accurate name for the set of protocols we are describing is the "Internet protocol
suite". TCP and IP are two of the protocols in this suite. E
ven NFS, which uses UDP and
not TCP, is often considered part of this suite. TCP (Transmission Control Protocol) is a
method (protocol) used along with the Internet Protocol (IP) to send data in the form of
message units between computers over the Internet
. While IP takes care of handling the
actual delivery of the data, TCP takes care of keeping track of the individual units of data
(called packets) that a message is divided into for efficient routing through the Internet.
The figure below is of a basic TC
P/IP network node.


-----------------------------------


| Network Application |


| |


| ...
\

| / ..
\

| / ... |


|
-------

-------

|


|

| TCP | | UDP | |


|
-------

-------

|


|
\

/ | % Key %


|
-------

---------

| ~~~~~~~


| | ARP | | IP | | UDP Use
r Diagram
Protocol


|
-------

------
*
--

| TCP Transfer Control
Protocol


|
\

| | IP Internet Protocol


|
\

| | ENET Ethernet


|
-----------
--

| ARP Address Resolution


| | ENET | | Protocol


|
-------
@
-----

| O Transceiver


| | | @ Ethernet Address


--------------

|
------------------

* IP address


|

========================O==============================================
===


^


|


Ethernet Cable




We recommend the

TCP/IP Refresher

in the References for further details.

Clients and Servers

All network computing is based on the idea of clients and servers.


Occasionally, a so
-
calle
d client may become a server for a brief transient period, and vice
-
versa, but
generally speaking servers are programs listening for requests from clients, and work on
the requests after some authentication.

The "Windows PC World"

The meaning of clients an
d servers is some what narrow in the world of PCs running
Windows because not all variants of Windows provide "services."



In a peer
-
to
-
peer network, a group of PCs are hooked together, with each PC, having
equal status in the network. All the PCs can sha
re files, send each other messages, and
share a printer or two.


You can setup one of the computers as a server.


The other PCs
are then known as client computers.


The server stores the applications, files, and e
-
mail
messages. This server delivers applic
ations such as database, word processors, as well as
data and e
-
mail.


It also acts as the center for sharing printers, doing backup,
etc.


Windows 9x by itself, without additional software, cannot be a server.


Windows NT
Server, a higher priced version o
f NT, comes with all required software to setup as a
server to Windows 9x and Windows NT Workstation clients.

The "Unix World"

Computers running Unix are typically configured as servers even when they are
otherwise puny machines.

A Few Well Known Services

Domain Name Service

The domain name service is expected to run on selected server machines at port
53.


These selected server machines are called the ``name servers'' which are authoritative
for the names of a particular domain. All other machines describe

how they resolve
names in a file; on Unix, it is /etc/resolv.conf.


Typically, a client machine has a table of
host names and their IP addresses in a file called hosts.


If a host name is not found in this
file, the client machine requests the name server
s listed in resolv.conf.

For every domain, such as wright.edu, there is only one primary name server and any
number of secondary name servers. The primary name server is the most authoritative
name server for that domain. The secondary name servers get the
ir information about a
domain from the primary name server. The DNS stores such information as name
-
to
-
IP
-
address mappings, name servers for subdomains, mail exchangers for hosts and domains,
gateway pointers and host information.

Network File System

NFS p
ermits multiple systems to share a file system. An NFS server ``exports'' a file
system to certain client machines with certain permission regarding read / write as
described in the file /etc/exports.

Network Information System

The Network Information Sys
tem (NIS) allows the sharing of a single password system
by a large number of users who may wish to login on any one of a number of systems.



A Few Well Known Clients

Telnet

Telnet is the name of a client program and an underlying TCP/IP protocol for acc
essing
remote computers.

FTP

FTP (File Transfer Protocol)


is an application protocol that uses the Internet's TCP/IP
protocols.

Ping

Ping is a standard network client that sends a packet to the target machine you named,
and waits for a response.


So you
verify that a particular Internet address exists and alive
through a ping.


Ping can also be used with a host that is operating to see how long it
takes to get a response back. Using ping, you can learn the dot
-
decimal number form of
the IP address from th
e symbolic domain name.

paladin% /usr/sbin/ping
-
s www.mit.edu

PING DANDELION
-
PATCH.MIT.EDU: 56 data bytes

64 bytes from DANDELION
-
PATCH.MIT.EDU (18.181.0.31): icmp_seq=0.
time=118. ms

64 bytes from DANDELION
-
PATCH.MIT.EDU (18.181.0.31): icmp_seq=1.
time=5
4. ms

64 bytes from DANDELION
-
PATCH.MIT.EDU (18.181.0.31): icmp_seq=2.
time=46. ms

64 bytes from DANDELION
-
PATCH.MIT.EDU (18.181.0.31): icmp_seq=3.
time=118. ms

64 bytes from DANDELION
-
PATCH.MIT.EDU (18.181.0.31): icmp_seq=4.
time=84. ms

64 bytes from DAND
ELION
-
PATCH.MIT.EDU (18.181.0.31): icmp_seq=5.
time=80. ms

64 bytes from DANDELION
-
PATCH.MIT.EDU (18.181.0.31): icmp_seq=6.
time=280. ms

64 bytes from DANDELION
-
PATCH.MIT.EDU (18.181.0.31): icmp_seq=7.
time=57. ms

64 bytes from DANDELION
-
PATCH.MIT.EDU (18.
181.0.31): icmp_seq=8.
time=95. ms

64 bytes from DANDELION
-
PATCH.MIT.EDU (18.181.0.31): icmp_seq=9.
time=63. ms

^C

----
DANDELION
-
PATCH.MIT.EDU PING Statistics
----

10 packets transmitted, 10 packets received, 0% packet loss

round
-
trip (ms) min/avg/max = 46
/99/280

Traceroute

Traceroute (some times also spelled as tracert) is a client that records the path (route)
through the net between your computer and a specified destination computer. It also
calculates and displays the amount of time each hop took. Trace
route is a handy tool both
for understanding where problems are in the Internet network and for getting a detailed
sense of the Internet itself. Another utility, ping, is often used prior to using traceroute to
see whether a host is present on the network.



Here is an example that traces the route
taken from Paladin to Yahoo.com.

paladin% traceroute www.yahoo.com

traceroute to www.yahoo.com (204.71.200.67), 30 hops max, 40 byte
packets


1


130.108.128.4 (130.108.128.4)


1.755 ms


0.831 ms


0.859 ms


2


ser
ver
-
fw (130.108.128.65)


0.799 ms


0.862 ms


0.702 ms


3


130.108.1.2 (130.108.1.2)


2.458 ms


3.233 ms


2.265 ms


4


dlp2
-
sl3
-
2.dayton.oar.net (199.18.109.125)


133.789 ms


190.015
ms


223.619

ms


5


tlp3
-
atm1
-
0.toledo.oar.net (199.18.202.53)


34.568 ms


10.086
ms


85.328 ms


6


atm9
-
0
-
0
-
153.br1.CHI1.globalcenter.net (204.246.198.73)


62.788
ms


43.312 m

s


42.406 ms


7


pos4
-
1
-
155M.cr1.CHI1.globalcenter.net (206.132.118.85)


43.675
ms


43.714 ms



83.308 ms


8


www2.yahoo.com (204.71.200.67)


82.251 ms


8
8.184 ms


83.306 ms

rsh, rexec, ...


Remote shell


is one of an entire family of remote commands patterned after the normal
local commands.


For example, rcp is similar to cp, the UNIX "who is logged in"
command, who, becomes rwho. These commands are colle
ctively referred to as the "r"
series commands or the "r*" (r star) commands.


The r* commands are designed for
interaction between trusted hosts. Little consideration is given to security, but they
provide a convenient user environment.

To allow anyone f
rom a host H to remote login into host A, you add H to
/etc/hosts.equiv

file on the machine A.



This needs super user privileges.


A user can
permit himself to rlogin to A from H without a password as follows. For example, to
allow pmateti who is currentl
y logged on
gamma.cs.wright.edu

to rlogin without
having to supply a password on machine A, pmateti


would add one line of text
``
gamma.cs.wright.edu pmateti
'' to his
~/.rhosts

file on the machine A.



Note that
the .rhosts feature is needed only between m
achines that do not share file systems via
NFS.


Lab Experiment

Our goal in this lab is to learn the hardware and software setup of peer
-
to
-
peer
networking of two PCs, and a LAN of several PCs running Linux.

Pre Lab

Do the following prior to your schedule
d lab.


Turn in your work as you enter the lab.

1.

Which of the following are valid IP addresses?

1.

192.268.1.37

2.

253.128.129.0

3.

130.108.2.10

2.

Re
-
read the Unix related parts of the lab handout on
Web, E
-
Mail, and Unix
.

3.

Login to
paladin

or
discover

and read the man page on the command
"
talk
".


In a couple of lines describe what this program is useful for.On
paladin

or
discover

run the command
traceroute www.cnn.com

after y
ou started
script
. Attach the printout of the results obtained from the
traceroute
.

Precautions

1.

Make sure that you aren't full of static electricity
--
it can zap and ruin components.
Touch the metal case of the PC, every once in a while, to discharge stati
c.

2.

Never turn the power off, or press the Reset button without shutting the system
down properly. If you do, in all likelihood, the hard disk content is trashed.
Several files are cached in RAM that need to be written out to the hard disk before
the syste
m shuts down.
Proper shut down

of the system is initiated by pressing
the Control
-
Alt
-
Delete keys simultaneously.

3.

In the following, whenever we ask you to add or remove a hardware component,
make sure that you shut the machine down properly, turn the powe
r switch (on the
front panel) off, and also unplug the power chord from the back of the case. You
can leave the monitor turned ON through out.

4.

Remember to align the ribbon cable's red
-
edge with pin 1 on both the floppy and
hard disk connectors.

Collect t
he PCs, etc

1.

Collect two complete PCs: Choose one HP PC, and one AT&T PC. The AT&T
PCs have 16 MB of RAM. Verify that the HP you chose has 12 MB (three
SIMMS) installed. Collect two monitors,


two keyboards, and four AC power
cords. We do not need mice.


Th
e NICs should already be installed.

2.

Collect two hard disks loaded with Linux. The HP PC should use the
HP/Quantum hard disk, and the AT&T should use the Seagate hard disk, even
though it does not really matter.

3.

Collect one Ethernet 10B2 (a.k.a thin) cabl
e of short (less than 10 ft) length.

Booting from Linux Hard Disk

1.

For each of the two PCs follow the steps below.


(It is possible that the PC is
nearly fully assembled from a previous lab.)

2.

Discharge any static electricity built up on you by touching th
e metal case of the
PC box. Make sure the power switch on the front panel is off, and the power cable
is disconnected.

3.

Verify that the HP PC has 12 MB (three SIMMs), and the AT&T has 16 MB (one
SIMM).

4.

Connect the floppy disk, hard disk, and keyboard. Mak
e sure to attach the power
connectors


to the hard and floppy disk drives. Mouse is not needed.

5.

Make sure there is no floppy disk in the drive.

6.

Connect the CRT monitor video cable to the SVGA connector on the PC box.
Turn the power on the CRT.

7.

Connect t
he PC power cable to the power supply, and turn the power on the PC
box.

8.

Wait until the PC completes the boot process, and the Login prompt
appears.


Watch the messages as they get spit out. Verify that both PCs boot into
Linux without errors. If the erro
rs are due to changes in hard disk or memory size,
enter BIOS setup and correct the configuration. If the errors are from Linux, and
no login: prompt appears, seek help.

9.

Login as
root
, with no password (i.e., type just a Return).

10.

Type the command:
fortun
e
.


Q1:
Record the Chinese fortune cookie message
you received.

Peer to Peer Networking

1.

It is ok to leave both machines powered on when connecting the Ethernet cable.

2.

Prepare a thin Ethernet cable as follows. Attach two BNC T
-
connectors at both
ends of t
he thin cable.


Terminate the other end of the T with a terminator. The
vertical part of the T should now be free at both ends of the cable.

3.

Connect the free ends of the cable to the PCs.

4.

At this point, the two PCs are networked.

5.

The AT
-
1500BT+ Ethernet

card has LEDs in the back.


Q2:
Record the lighting
conditions (lit steadily, blinking, unlit) of the LEDs.


Make a note of the stamped
legend on the bracket.


If neither of the two PCs, has this card, write instead the
make and model of the NICs in the t
wo PCs.

Configuring the Network Parameters of the PC

1.

Invoke the command
netconfig

on both PCs, and answer its questions. Host
Name:


Choose a name yo like. Are you using only looback?


No.


IP address: as
shown on the hard disk. Netmask: 255.255.255.0.


G
ateway: Replace the last
dot.number of IP address with a 1 (one).


Name server: none.

2.

Type the command:
ifconfig
.


The name of the command stands for "network
InterFace CONFIGuration."


Verify that the IP address etc. match what you had
given.

3.

Try at lea
st the following commands:
ping, traceroute, telnet, ftp
, and
talk
.
Q3
:


What was the response time given by the ping?



What other Unix commands
did you try?

LAN of Several PCs

1.

The goal of this section is to connect all the 12 PCs of the six groups into
one
LAN.

2.

Do not turn your PCs off.

3.

Remove one terminator from the thin cable.


Attach another length of cable from
your PC to the PC of the next group in your row.



4.

After this step, for two groups, there should be three lengths of cable connecting
four
PCs and there are exactly two terminators at the first PC and at the fourth
PC.



5.

To connect the two rows of PCs on work tables across the room, use one long
length of thin cable.


After this step, for six groups, there should be eleven lengths
of cable co
nnecting twelve PCs and there are exactly two terminators at the first
PC and at the fourth PC.

6.

Try the following commands:
ping, traceroute, telnet, ftp
, and
talk


from any
machine to any other in our LAN.


Q4
:


Try pinging three machines.


Record their
response times.


Telnet to two other machines, not in your group, both as root and
as guest.


Record the success/failure of this attempt.

Concluding Activities

1.

Shut down the Linux OS properly:


Press Control
-
Alt
-
Delete simultaneously.
Wait for Linux to sa
y "Rebooting" and then the BIOS screen display to appear,
and at that moment ...

2.

Turn the power off on the front panel, and disconnect the power cable.


To turn
the AT&T PC off, you must press the front orange button first and then press the
side orange b
utton.

3.

Disconnect the ribbon cable and power cable from the Linux hard disk. Set this
hard disk aside.

4.

Return the PC to the way it was when you began this lab. Return all components
to your TA. Follow the instructions given by the TA.

Achievement Test

W
rite your answers to the questions marked (Q1 to Q4) in the above procedure, and turn
them in to your TA as you leave the lab.




Appendix A: Acronyms

FTP

File Transfer Protocol

FDDI

Fiber Distributed Data Interface

IP

Internet Protocol

LAN

Local Area N
etwork

MAC

Media Access Control

NIC

Network Interface Card

NNTP

Network News Transfer Protocol

RFC

"Request For Comment" a formally submitted document

SMTP

Simple Mail Transfer Protocol

TCP

Transmission Control Protocol

UDP

User Datagram Protocol

W
AN

Wide Area Network

WWW

World Wide Web