Computer Networking Part 2 TCP/IP Protocol

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8 Νοε 2013 (πριν από 3 χρόνια και 11 μήνες)

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Computer Networking Part 2
Rev 4.

TCP/IP Protocol


Object:


Transmission Control Protocol/Internet Protocol (TCP/IP) is of great
interest since this is what makes World Wide Web browsers like Netscape and
Internet Explorer work! TCP/IP also supports other

interesting programs like
‘Ping’ and ‘Telnet’. We’ll explore each of these in this second networking
laboratory.


Introduction:



Part one of this Networking series used a network protocol called
NetBEUI. This is an IBM standard popular with Windows 3.1
1. Another protocol
is IPX/SPX by Novell Netware, popular with Windows 95. Both of these
protocols can be loaded at once for use by a computer network that may need
them. We used these to communicate with other personal computers on the
college computer

network. We transferred files, and also executed files from a
remote computer.



Part two of the Networking series will make use of the World Wide Web, a
subset of the network we refer to as the Internet. The college has a high speed
connection to the In
ternet called a T1 connection. It communicates at 1.5 million
bits per second. This is fast if there are only a few users. However, many of you
have experienced time delays caused by a hundred users on this connection to
the outside world at a time.



W
e use TCP/IP to connect to the WWW using Netscape. Netscape
sends a request out to retrieve a ‘home page’ from somewhere. In order for the
page to return, each personal computer must have a unique address so that it
can be delivered to the correct locati
on.



These addresses are in a ‘dotted four’ form. One of BCC’s ‘Internet
Protocol’ addresses is 192.203.130.1. This is our Alpha 1 mainframe computer
that holds student computer accounts.



The PC that you are using, has a particular and unique IP addr
ess
assigned to it. This is the only way that some site in Australia would know how to
get a message back to you and only you. The largest IP address is
255.255.255.255. You may recognize that in hexadecimal, this is FF.FF.FF.FF.
Yes, there is a connec
tion between this and our ‘digital’ world. The college has 3
‘groups’ of IP addresses that it has been allocated by NYSERNET, an Internet
service used by SUNY:



These run from 192.203.130.xxx through 192.203.132.xxx. xxx can vary
from 000 to 255. Some

of the possible numbers are reserved, but to simplify
this, the number of BCC accounts is 3 x 255 or 765. (This is really simplified..)



The world could have 255x255x255x255 addresses or 4,228,250,655. In
the early days of the Internet, this seemed a v
ery large number. Not anymore!
We’re living with it. There are hundreds of thousands of web sites, each of which
has many PC’s. So far the system works pretty well. Slow downs occur during
the day. You may notice that if one site is slow (Yahoo is a goo
d example),
another may be fast ( MSNBC). This reflects the popularity of the site and it’s
ability to respond to a request.


We’ll be exploring IP addresses in a number of ways.


Activities:



Before using Netscape, we need to ‘test’ the connection of ou
r personal
computer to the network. To do this we use a utility called ‘Ping’. We will ‘Ping’
our mainframe and hopefully get a response. This is like saying “ Are you there”?



Go Into Windows, shell to DOS…




(Start/Programs/
MS
-
DOS Prompt)


At the DOS prompt, you should be able to typ
e:



c:>

ping 192.203.130.2



You should get a response that tells you the number of milliseconds that it
took to get a signal back from the Alpha. If this works, your PC is connected
using TCP/IP to the mainframe.



Now lets ‘Ping’ the outside world. .w
ww.m
icrosoft.
com



Ping them. If you get a response, our T1 connection is certainly working!
Record the time it takes to ‘ping’ a remote server.


Note their IP address here _______________________.



The personal computer that you are using has two IP’s associated with it. One is
differe
nt for each machine, your unique world wide address. The other is the
same for each machine, put on reserve by the Internet ‘overseers’. This is

127.0.0.1. Try pinging 127.0.0.1. This will be your own machine responding to
your ping.



Try pinging some

of the other locations (IP’s) in the list below:



127.0.0.1


The PC you are on




_____


www.ucla.edu


IP found: _______
__
_____
_____


_____



www.latrobe.edu.au


IP: ______________
_____


_____



www.micros
oft
.com



IP: ___________________


__
___


Yahoo !



IP:

_______________


_____



Nex
t…
try ‘Telnet’.



Telnet is a program that lets you connect to a remote computer. There
are a variety of ‘Telnet’ programs available.



Select Start / Run and type in ‘Telnet’.



This will bring up a terminal that wil
l allow you to connect to a remote computer.


You’re a little spoiled in that you’re used to connecting to our Alpha using DEC
Pathworks. This is the mainframe software that allows Kermit, Sethost, or VT320
to use NetBEUI or IPXSPX to tie into the mainfram
e. We’re going to use TCP/IP
instead.


To use Telnet, you have to supply the IP of the host. Try telnetting to the BCC
server at 192.203.130.2. You will have to ‘connect’ to that IP address. An
alternate BCC IP is 192.203.130.7. Try both of these.


You

should be able to
try

log on to the Alpha. What happens? Try logging on to
a different remote computer. Rochester Institute of Technology is at rit.edu. Try
telnetting to rit.edu to see what happens.


There are many computers that you can Telnet into. U
sually you need an
account and password for actual access. But you can still at least talk to the
‘front door’ of a remote machine you don’t have an account on.


For Windows 95 users:



Tracert

is a program that allows you to see the progress of a request

heading to a remote http site. Select Start / Run, and enter:




tracert www.yahoo.com


to see the various ‘hops’ made from site to site to get to Yahoo. You may prefer
to do this from a DOS window.



Next… OK, in Windows, bring up Netscape!



You are a
ccustomed to typing in an ‘http’ address to get to a location on
the Internet. Http stands for ‘hyper text transfer protocol’. There’s also ftp, file
transfer protocol, but this is another story.



In Netscape, go to the CBS home page by entering:




htt
p://www.cbs.com


Watch the bottom of Netscape carefully……

first, Netscape goes out and tries
to find the actual Internet Protocol address (IP… dotted four) for www.cbs.com.
This is referred to as Domain Name Service. Somewhere, there is a Domain
Name Serv
er that is trying to match your request up with an IP. The world wide
web works on IP’s, not those ‘words’ you use.



If you don’t have a Domain Name Server to do DNS for you, you can’t get
anywhere since you don’t know the IP of the location you are tryi
ng to get to.
Today, we’re going to use IP’s directly to get to some interesting sites. You’re
going to be a sort of ‘reverse’ Domain Name Server and record the http
addresses of the sites you visit. Ie: fill in the blanks….



Instead of typing http:www
/.. etc, just enter the IP number directly. The
response time in retrieving a home page should be faster as you are not
requiring some remote server to perform DNS for you! See if you notice the
difference.


IP Address

Site

Comments

204.146.18
.
33



20
4.146.15.5



207.68.137.59



192.35.39.40



131.172.20.21



207.68.146.11



128.230.1.48



128.153.4.31



209.67.0.214



204.177.130.1



128.174.5.27



164.67.80.80



128.17
1.44.83



202.38.128.58



152.2.25.83





5/1/98

ACDixon