Unit 3: TCP/IP Protocol

kindlyminnowΔίκτυα και Επικοινωνίες

26 Οκτ 2013 (πριν από 3 χρόνια και 9 μήνες)

99 εμφανίσεις

Unit
3
:

TCP/IP Protocol


Section 3
: TCP Applications and Command Line Utilities

In this section you will learn about configuring TCP/IP addresses and
subnet masks.

At the end of this section you should be able to
:

1.

Identify and describe the Application
layer protocols

2.

Identify TCP/IP

command line

utilities and their use in
troubleshooting




Objective 1: Identify and Describe Application Protocols

TCP/IP application layer protocols use the top three layers of the OSI model as shown below:





For purpos
es of discussion, the TCP/IP application layer protocols can be divided into the following 5
categories:

Web

HTTP and HTTPS

File Transfer

FTP, TFTP, SCP, and SFTP

Mail and Messaging

SMTP, POP, IMAP

NNTP

Remote Control

Telnet and SSH

Remote Desktop
Protocol (RDP)

Management

NTP

SNMP


In this section we will investigate each of these categories and associated applications.



Web Protocols

HTTP (HyperText Transfer protocol)

Used by Web servers and Browsers

(Read page 46)

Web servers

listen to

Port 80 b
y default

HTTPS

Encrypted or secure Web sites



noted by padlock symbol on browser.

Requires logging with username and password

Uses port 443

Uses Secure Socket Layer (SSL) at Presentation layer (See security on page 600
-
601)

File Transfer Protocol
s

FTP
(File Transfer Protocol)

Original TCP/IP protocol that uses TCP ports 20 and 21 for reliable transfer of
data and program files.

Has a text based command line interface or often used with special client
software such as FileZilla

No encryption, transfers f
ile in clear text so data may be picked up by other
systems through eavesdropping.



TFTP (Trival File Transfer)

Uses UDP port 69



(No acknowledgements, may miss packets)

Used by diskless workstations to load software

Used to upload configuration data to
switches/routers

Secure File Transfer options


Uses SSL (See page 600)


Read page 602 for description of following utilities:


SCP (Secure Copy)


SFTP (Secure FTP)





Mail and Messaging Protocols

Read pages 500
-
503 in text book.

SMTP (Simple Mail
Transfer Protocol)

Uses port 25

Outgoing mail between mail servers


POP3 (Post Office Protocol version 3)

Uses port 110

Used by most clients to download mail from server

Mail managed on the client side


IMAP

Uses port 143

Allows management of mail on the
server

NNTP (Network News Transfer Protocol)

One of original Internet Protocols used for new feeds and groups

Uses port 119

NNTP (Network News Transfer Protocol)

Read description on page 171

Uses port 119

Uses newsgroups to distribute exchange informatio
n on specific topics


Remote Control Protocols


Allows access to another computer or server from a client

Telnet

Read material on page 168

Text based terminal for command input from remote console


uses telnet client

Clear text


no encryption

Uses port
23


SSH

(Secure Shell)

Read page 601

Secure version of Telenet using SSL encryption

Uses port 22




Remote Desktop Protocol

Service and client built into Windows

Read material on pages 333
-

335

Uses port 3389
(On Network Plus exam)



Remote Desktop
Setup


Remote Computer

Requires Windows 7 Professional or higher

Give system fixed IP address

Configure remote users with password

Open Windows firewall port 3389 (RDP)




Router

Open port 3389 and use port forwarding to connect port 3389 to IP address
of computer running Remote Desktop

Client

Start | All Programs | Accessories

Specify name or IP address of RDP service




Network Management Protocols

Simple Network Management Protocol (SNMP)

Described on page 743

Uses port 161

Agents run on devices


Repo
rt traffic information

to management console software

Management console

uses polling process to collect information and store in MIB
(Management Information Base)

More coverage in
chapter 15.


Network Time Protocol (NTP)

Read page 171

Uses port 123

Keeps
time synchronized across Internet

Simple protocol uses UDP for efficiency



Objective 2:
Identify TCP/IP commands
and their use in Troubleshooting

Command line utilities are text based commands that may be u
sed to document and trouble shoot
network configu
ration and environment.

Most of the commands are intended to be entered from the
Windows command prompt. To o
pen a command prompt in Windows

you need to



Click
Start



Enter
CMD

and press Enter


In some cases you may need to run a command in administrator mod
e. Perform the following steps
to open a command prompt window in administrative mode:



Click
Start
, click
All Programs
, and click
Accessories



Right click the
Command Prompt

option and click
Run as administrator
.



If necessary, enter the administrator’s password

In this section we will discuss using following command line utilities:



IPCONFIG



PING



TRACERT



NetStat



Route



NSLookup



IPCONFIG Command



Used to view Windows computer configuration



IPCONFIG



IPCONFIG /All




Used to update IP configuration



IPCONFIG /release



IPCONFIG /renew



IPCONFIG /display DNS



IPCONFIG /flushDNS



Linux version

IFCONFIG



Ping Command

Packet Internet Groper



part of original TCP protocol

Used to send a series of packets to another computer a
nd receive echo
acknowledgements.



uses ICMP echo commands

Ping command syntax:

PING IP_Address or Name

Switches:

-
n (specify number of ping packets, default is 4)

-
t (continuous ping)


Often used as follows to troubleshoot network communications:

PING
Loopback address (127.0.0.1) to test IP stack on computer

PING destination computer to test configuration and traffic

PING default gateway to check configuration



TraceRT Command

(mtr in Linux)

Uses ICMP Echo requests to

help determine path of packets and

any bottlenecks or
network failures

Includes time of each hop on network path

Often affected by firewalls on public networks
. Firewalls can block the ICMP echo
packets, resulting in timeouts. Time outs are indicated by a “*” on the screen



Command Syntax:

TRACERT IP_Address or DNS name






NetStat Command

Used to view status of network connections

Can be used to help identify hacker attacks by checking ports in use

Command Syntax



NetStat
-
a (available TCP and UDP ports)



NetStat


n (Lists currently connected hosts and port)



NetStat

r (Display router table)




NSLookup Command

(Dig in Linux)

Used to test DNS configuration or obtain information on DNS servers.




Route Command

Used to view router table and check for valid ro
ute configuration

Used to add or remove static routes

Syntax to view table: Route

print





Command Usage



Typically start with IPCONFIG to check configuration



IPCONFIG /All



Test communication with local host



PING 127.0.0.1



Test communication with gateway



PING 192.168.1.1



Test communication with device on another network



PING IP_Address (of device on destination network)



Test the path to the remote network



PING IP_Address (of device on destination network)



Check DNS names usage



NSLOOKUP
domain name



Loo
k for malware or hacker attack



NetStat
-
n




Chapter
4

Selected
Review Questions

2. What field in an IP datagram can be used to indicate that a packet should be routed before any
other packets?

Page 143

3. What happens to an IP datagram when its TTL
reaches 1?

Page 144

5. What is the function of ARP?

Page 146

6. Which of the following applications would be best suited to using UDP?

Page 142

13. If you are connected to a network that uses DHCP, and you need to terminate your Windows
Vista workstation’s

DHCP lease, which of the following commands would you use?

Page 155

14. At a minimum, what fields would you find in a hosts file?

Page 162

15. What devices are the highest authorities in the domain name system hierarchy?

Page 162
-
163

20. What method of tr
ansmission does a workstation use to send an ARP request?

Page 146

23. You have just set up a new wireless network in your house, and you want to determine
whether your Linux laptop has connected to it and obtained a valid IP address. Which of the
followin
g commands will allow you to find the information you need?

Page 149


25. Which of the following protocols assists in determining whether packets reached their
destinations?

Page 145



Chapter
10

Selected
Review Questions

11. You have decided to use PAT o
n your small office network. At minimum, how many IP
addresses must you obtain from your ISP in order for all five clients in your office to be able
to access servers on the Internet?

Page 499

12. You have offered to help a friend set up her e
-
mail client
software. She knows the e
-
mail
address that her ISP assigned her. Which of the following pieces of information will you need
to configure her e
-
mail software to successfully send messages?

Page 501

13. Which two of the following are benefits of using IMAP4

relative to POP3?

Page 502

14. What Network layer protocol does the TRACERT and TraceTroute utility use to obtain its
information about paths between a source and destination?

Page 511

15. Which of the following commands allows you to view the routing table on your Linux or
Windows workstation? (Choose all that apply.)

Page 513

16. When you use the
mtr

or Tracert command to assess the path from your office
workstation to a server on you
r company’s WAN that’s located in Spain, what is the first hop
the
mtr

command will display?

Page 512

17. If you know that your colleague's TCP/IP host name is JSMITH, and you need to find out
his IP address, which of the following commands should you type

at your shell prompt or
command prompt?

Page 508

18. Suppose your office's only DNS server was down, and you wanted to view the DNS
address record for your company's domain. Which of the following Linux based TCP/IP
utilities would allow you to do this? (
What command in Windows?)

Page 509

19. What Linux utility might you use to find out whether your ISP's router is responsible for
the poor network performance your organization experiences on a particular afternoon?

Page 512

20. Which of the following comma
nds reveals the default gateway addresses for all the hosts
to which a router is connected?

Page 513
-
514