Introduction to TCP/IP Protocols

screechingagendaNetworking and Communications

Oct 26, 2013 (3 years and 7 months ago)

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Network+ Guide to Networks, 6
th

Edition


4
-
1





Chapter
4


Introduction to TCP/IP Protocols



At a Glance


Instructor’s Manual Table of Contents




Overview




Objectives




Teaching Tips




Quick Quizzes




Class Discussion Topics




Additional Projects




Additional Resources




Key Terms





Network+ Guide to Networks, 6
th

Edition


4
-
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Lecture Notes


Overview


A protocol is a rule that governs how networks communicate. Protocols define the standards for
communication between network devices. Without protocols, devices could not
interpret the
signals sent by other devices, and data would go nowhere. In this chapter, the student will learn
about the most commonly used networking protocols, their components, and their functions.
This chapter is not an exhaustive study of protocols,
but rather a practical guide to applying
them.


In the sections that follow, the student will learn about the networking protocol suite that is

used on virtually all LANs and WANs today

-

TCP/IP. Other protocol suites, such as IPX/SPX,

NetBIOS, and AppleTa
lk, do exist. However,
these

protocols have been replaced by TCP/IP on
modern networks.



Chapter Objectives


After reading this chapter and completing the exercises, the student will be able to:



Identify and explain the functions of the core TCP/IP protoc
ols



Explain the

TCP/IP
model and how it

corresponds to

the OSI model



Discuss addressing schemes for TCP/IP in IPv4 and IPv6

and explain how addresses are
assigned automatically using DHCP (Dynamic Host Configuration Protocol)



Describe the purpose and
implementation of DNS (Domain Name System)



Identify the well
-
known ports for key TCP/IP services



Describe common Application layer TCP/IP protocols

are used



Teaching Tips


Characteristics of TCP/IP (Transmission Control Protocol/ Internet
Protocol)


1.

Introduce the TCP/IP protocol
.


2.

Emphasize that it is a suite of
specialized protocols

and provide examples.


3.

Note the additional terms that are use
d

to reference the TCP/IP protocol suite.


4.

Briefly discuss the history of TCP/IP.


5.

Explain why TCP/IP has bec
ome so popular.


6.

Define the term routable and explain its importance in large networks.


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7.

Discuss why flexibility is important in the TCP/IP suite.



The TCP/IP
Model


1.

Introduce the concept of TCP/IP
model
.


2.

Discuss that the model
roughly
lines up with the
OSI model consolidating the seven
layers into only four layers.


3.

Explain that the layers are Application (OSI Application/Presentation/Session),
Transport, Internet (OSI Network), and Network Access (OSI Data Link and Physical).


4.

Remind students that the T
CP/IP model developed after the protocols were in
widespread use.



The TCP/IP Core Protocols


1.

Introduce

the concept of TCP/IP core protocols.


2.

Describe where the core protocols operate in the OSI model.


3.

Mention the two most significant core protocols.


TCP (Transmission Control Protocol)


1.

Introduce TCP (Transmission Control Protocol)

and describe its purpose.


2.

Mention the layer of the OS
I

model in which it operates.


3.

Explain
characteristics of the Transport layer
that affect
TCP transmissions.


4.

Use Figure
4
-
2

to illustrate
the
format of a TCP segment.


5.

Explain how the segment becomes the IP datagram’s “data
.



6.

Describe the fields belong
ing

to the TCP segment.


7.

Use Figure 4
-
3

to walk through an example interpreting a TCP segment.


8.

Use
F
igure 4
-
4

to illustrate how a TCP connection is established.


9.

Emphasize the contents of the three segments transmitted.


UDP (User Datagram Protocol)


1.

Introduce

UDP (User Datagram Protocol)

and describe its purpose.

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2.

Mention the layer of the
OSI model

in which it o
perates.


3.

Explain characteristics of the Transport layer that affect UDP transmissions.


4.

Describe a situation that makes UDP valuable.


5.

Use Figure 4
-
5

to illustrate the
format of a UDP segment.


6.

Describe the fields belong
ing

to the UDP segment.


7.

Contrast
the UDP segment in Figure 4
-
5

with the much larger TCP segment

in
F
igure 4
-
2
.


IP (Internet Protocol)


1.

Introduce
IP (Internet Protocol)

and describe its purpose.


2.

Mention the layer of the
OSI model

in which it operates.


3.

Remind students that at the Network

layer of the OSI model, data is formed into
packets.


4.

Explain that in the IP protocol, the packet is called an IP datagram.


5.

Explain the purpose of the IP datagram.


6.

Explain characteristics of the IP protocol.


7.

Use Figure
4
-
6

to illustrate

the format of a
n IP datagram.


8.

Describe the fields belong to the IP datagram.


9.

Use Figure 4
-
7 to walk through an example interpreting an IP datagram.


10.

Use Figure 4
-
8 to illustrate the format of an IPv6 packet header, and figure 4
-
9 to
illustrate an example of an IPv6
packet.


11.

Ensure students understand the length and other structural differences between IPv4 and
IPv6 packets.


Teaching

Tip

Students may find the original RFC standards at
http://www.
rfc
-
editor.org/categories/rfc
-
standard.html




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IGMP (Internet Group Management Protocol)


1.

Introduce the
IGMP (Internet Group Management Protocol or Internet Group Multicast
Protocol)

and describe its purpose.


2.

Mention the layer of the
OSI model

in which
IGMP
operates.


3.

Define and explain the term multicasting.


ARP (Address Resolution Protocol)


1.

Introduce

ARP (Address Resolution Protocol) and describe its purpose.


2.

Define an ARP table and d
escribe

how it helps ARP operate efficiently.


3.

Use Figure 4
-
10

to
illustrate what an ARP table might look like.


4.

Introduce the two types of entries an ARP table can contain.


5.

Define and describe dynamic ARP table entries.


6.

Define and

describe
static ARP table entries.


7.

Describe how the ARP utility is accessed and what it

provides.


ICMP (Internet Control Message Protocol)


1.

Introduce ICMP (Internet Control Message Protocol) and describe its purpose.


2.

Mention the layer of the OSI model in which ICMP operates.


3.

Describe the types of errors ICMP may report.


4.

Emphasize that
ICMP cannot correct the errors it reports.


Teaching

Tip


Students may find
more information on
Address Resolution Protocol (ARP)

at
http://technet.microsoft.com/en
-
us/library/cc7583
57.aspx





IPv4 Addressing


1.

Review the two types of addresses networks recognize.


2.

Define an IP address.


3.

Explain the makeup of an IP address.

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4.

Mention the two types of information an IP address may contain.


5.

Explain how to determine the network class.


6.

Describe the three types of network classes used for LANs in traditional IP addressing.


7.

Use Table 4
-
4

to illustrate characteristics of the three commonly used classes of
TCP/IP
-
based networks.


8.

Mention the existence of Class D and Class E addresses and
note that they are rarely
used.


9.

Explain the possible combinations used to identify networks and hosts in an IP address.


10.

Explain the use of the number zero as a placeholder.


11.

Explain the use of the number 255 in broadcast transmissions.


12.

Describe how
a po
rtion of each IP address contains clues about the network class.


13.

Use Figure 4
-
8 to illustrate IP addresses and their classes.


14.

Explain the need for a new addressing scheme to meet IP address demands.


15.

Define and explain the loopback address.


16.

Define and e
xplain a loopback test.


17.

Explain the Windows command used to view IP information.


18.

Explain the UNIX and Linux command used to view IP information.


19.

Use Figure 4
-
12

to illustrate results of the
ipconfig /all

command o
n a Windows
workstation
.


20.

Use Figure 4
-
1
3

to illustrate results of the
ifconfig
-
a

command on a UNIX or
Linux workstation.


Binary and Dotted Decimal Notation


1.

Define and explain dotted decimal notation.


2.

Mention that each number in a dotted decimal address has a binary equivalent.


3.

Explain how
to convert a dotted decimal address to its binary equivalent.


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Subnet Mask


1.

Define and describe a subnet mask
.


2.

Explain the components of a subnet mask.


3.

Explain how subnet masks are assigned.


4.

Define the term net mask.


5.

Define and explain subnetting.


6.

Use

Table 4
-
5

to illustrate default subnet mask values.


Teaching

Tip


Students may find more information on understanding TCP/IP addressing and
subnetting basics at
http://support.microsoft.com/kb/164015





IPv6 Addressing


1.

Review
the increased length of IPv6 addresses
.


2.

Explain the hexadecimal notation used for IPv6 addresses.


3.

Remind students of the proper way to use IPv6 shorthand notation for addresses.


4.

Explain

to students that an IPv6 address can demonstrate the address’ scope, whether
that is a single node, group or a special group.


5.

Explain the Format Prefix of IPv6 addresses.


Teaching

Tip


Students may find more information on IPv6 concepts at

http://technet.microsoft.com/en
-
us/library/cc785929.aspx





Assigning IP Addresses


1.

Review how IP addresses are monitored and handed out.


2.

Mention that every node on a network must have a
unique IP address.


3.

Explain what happens if duplicate IP addresses exist on a network.


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4.

Explain how to assign IP address manually.


5.

Define the term static address.


DHCP (Dynamic Host Configuration Protocol
)


1.

Define and explain
DHCP (Dynamic Host
Configuration Protocol).


2.

Mention the layer of the
OSI model

in which DHCP operates.


3.

Explain how DHCP operates noting the differences from BOOTP.


4.

Describe the reasons for implementing DHCP.


DHCP Leasing Process


1.

Define and explain DHCP leasing.


2.

Explain

how a client obtains its DHCP
-
assigned address.


3.

Explain how the length of time a lease remains in effect is determined.


4.

Explain how to configur
e

the DHCP service.


5.

Describe the steps negotiate the client’s first lease.


6.

Use Figure 4
-
11 to illustrate the

DHCP leasing process.


Terminating a DHCP Lease


1.

Explain how a DHCP lease expire
s
.


2.

Explain how to release TCP/IP settings on a computer running the Windows XP
operating system.


3.

Explain how to obtain a new IP address on a Windows XP workstation.


Private

and Link
-
Local Addresses


1.

Remind students that a client cannot communicate without a valid IP address.


2.

Explain the link
-
local address and Zeroconf (Zero Configuration) protocol.


3.

Explain how Microsoft handles the problem of no DHCP server to assign a
valid DHCP
address.


4.

Explain how APIPA (Automatic Private IP Addressing) operates.


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5.

Describe

the drawbacks of the IP address assigned by APIPA.


6.

Discuss how to check whether a computer running a Windows operating system is
using APIPA.


7.

Explain why it is a
cceptable to leave APIPA enabled.


Teaching

Tip


Students may find out more on how to use automatic TCP/IP addressing without a
DHCP server at
http://support.microsoft.com/kb/220874





Quick Quiz 1


1.

TCP/IP is a ____ of protocols
.

a.

series

b.

set

c.

selection

d.

suite

Answer:
D


2.

TCP (Transmission Control Protocol) operates in the ___ layer of the OSI model.

Answer: Transport


3.

____ is a Network layer protocol that reports on the success or failure of data
delivery.

Answer: ICMP (Internet Control Message Protocol)


4.

With DHCP, a device borrows, or ____ an IP address while it is attached to the
network
.

Answer:
leases


5.

True or
F
alse:
It is unacceptable to leave APIPA enabled if it is not needed.

Answer:
False


Sockets and Ports


1.

Introduce a process and the need for a unique process address.


2.

Define and explain a port number.


3.

Define and explain a process’s socket.


4.

Describe

the advantage of using port numbers.


5.

Use Figure 4
-
1
5

to illustrate
a virtual
connection for the Telnet service.


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6.

Define the range for port numbers.


7.

Explain the three types of port numbers
:

a.

Well known

b.

Registered ports

c.

Dynamic and/or Private Ports


8.

Use
Table 4
-
6

to illustrate

commonly used TCP/IP port numbers
.


9.

Explain the editable,

text
-
based file servers maintain
ed

for ports.


Teaching

Tip


Students may find more information
on
network ports used by key Microsoft Server
products at
:

http://www.microsoft.com/smallbusiness/support/articles/ref_net_ports_ms_prod.mspx






Host Names and DNS (Domain Name System)


1.

Note that TCP/IP addressing involves numbers.


2.

Explain how this is great for computer
s
; however, most people can remember
words
better than numbers.


3.

Define and explain a host.


4.

Define and explain a host name.


Domain Names


1.

Define and explain a domain.


2.

Define and explain a domain name.


3.

Explain what is meant by a fully qualified host name.


4.

Define and explain labels noting
that each label represents a level in the domain naming
hierarchy.


5.

Explain how domain names are registered.


6.

Use Table 4
-
7

to illustrate ICANN
-
approved top
-
level domains.


7.

Note that ICANN has approv
ed 240 country code
top
-
level domains.


8.

Explain the advan
tage of reserving a domain name.


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9.

Describe host and domain names restrictions.


Host Files


1.

Describe how ARPAnet used HOSTS.TXT.


2.

Explain why ARPAnet’s arrangement became outdated.


3.

Explain why it is important to know about host files.


4.

Use
Figure 4
-
16

to illustrate an example of such a host file.


5.

Explain where host files are stored in Windows and UNIX/Linux.


DNS (Domain Name System)


1.

Introduce and describe
DNS (Domain Name System or Domain Name Service).


2.

Explain the meanings of DNS.


3.

Describe why
th
e DNS service is divided into three components.


4.

Define

and describe resolvers
.


5.

Define and describe n
ame

servers.


6.

Define and describe a
namespace.


7.

Use Figure 4
-
17

as an example to illustrate
d
omain name resolution.


8.

Explain how resource records come in
many different types, depending on their
function.


9.

Describe the fields in a resource record.


10.

Explain how DNS was updated in the past and how it is updated today.


Configuring DNS


1.

Explain how to manually configure the values in a workstation’s TCP/IP pro
perties.


2.

Use Figure 4
-
18

to illustrate a Windows
7

Internet Protocol (TCP/IP) Properties dialog
box.


DDNS (Dynamic DNS)


1.

Define and describe DDNS (Dynamic DNS)
.


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2.

Note that DDNS does not take the place of DNS.



Teaching

Tip


Students may find more
information on D
NS

at
http://technet.microsoft.com/en
-
us/network/bb629410.aspx




Application Layer Protocols


1.

Explain how
A
pplication layer protocols work over TCP or UDP plus IP.


2.

Remind students of
A
pplication layer protocols discussed earlier.


3.

Introduce the new
A
pplication layer protocols.


Telnet


1.

Define and explain Telnet.


2.

Explain the security
concern
with using Telnet.


3.

Mention a more secure alternative.


FTP (File Transfer P
rotocol)


1.

Define and explain FTP

(File Transfer Protocol).


2.

Describe how FTP commands work.


3.

Define and describe anonymous logons.


4.

Review
some
useful FTP commands and their syntax.


5.

Define and explain graphical FTP clients.


6.

Describe how a student may use

FTP in the Web browser.


7.

Describe how a student may use FTP from a modem.


8.

Explain the security concern with using FTP.


9.

Mention a more secure alternative.


TFTP (Trivial File Transfer Protocol)


1.

Define and explain TFTP

(Trivial File Transfer Protocol).


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2.

Explain the advantages and drawbacks with TFTP.


3.

Explain the security concern with TFTP.


NTP (Network Time Protocol)


1.

Define and explain NTP

(Network Time Protocol)


1.

Explain the critical nature of NTP.


2.

Explain why NTP benefits from UDPs quick,
connectionless nature at the Transport
layer.


PING (Packet Internet Groper)


1.

Define and explain Ping

(Packet Internet Groper)
.


2.

Explain how Ping uses ICMP services.


3.

Note that an IP address
or
a host name may be pinged.


4.

Use Figure 4
-
1
9

to illustrate examples of a successful and an unsuccess
ful P
ing test.


5.

Describe what happens when the loopback address is pinged. Note the significance of
this action in terms of troubleshooting.


6.

Describe the different Ping command options, switches, and

the syntax of the
command.


7.

Explain how to get help with the Ping command.


Teaching

Tip


Students may find more information on OSI layers at
http://computer.howstuffworks.com/osi1.htm






Quick Quiz 2


1.

IPv6 addresses are composed of ____ bits.

a.

32

b.

64

c.

128

d.

256

Answer:
C


2.

Which IPv6 address type represents a

single interface on a
device?

a.

Unicast

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b.

Multicast

c.

Anycast

d.

Singlecast

Answer:
A


3.

Every process on a machine is assigned a
(n)

____ number.

Answer:
port


4.

A domain name is represented by a series of character strings, called labels, separated
by
____
.

Answer: dots


5.

True or
F
alse: Host files are the best automated solution for assigning IP addresses.

Answer: False


6.

True or
F
alse: Telnet

is
ge
nerally
considered to be
insecure.

Answer:
True



Class Discussion Topics


1.

As a class,
compare and contrast Telnet and FTP.


2.

D
iscuss whether there
are
additional components that could be added to the IPv4
protocol to enhance its usefulness
.



Additional
Projects


1.

Have each student research five graphical
FTP
interfaces and write a report
summarizing their findings. The report should include a comparison of features, price,
security, and popularity.


2.

The future of the Internet
will

lie with IPv6.
Have the
students research
the components
of the protocol and compare the various TCP/IPv6 layers with the OSI model.
The
report should also include a section
discuss
ing
additional functions or components that
would be beneficial in IPv6
.



Additional Resources


1.

IB
M TCP/IP RedBook

http://www.redbooks.ibm.com/abstracts/gg243376.html



2.

TCP/IP Fundamentals for Microsoft Windows: Overview

http://technet.microsoft.com/en
-
us/library/bb726983.aspx



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3.

IPv6

http://www.ipv6.org



4.

Microsoft IPv6

http://technet.microsoft.com/en
-
us/network/bb530961.aspx



5.

Internet Protocol Version 6 Basics

http://h20195.www
2.hp.com/v2/GetPDF.aspx/4AA3
-
5764ENW.pdf




Key Terms




Address Resolution Protocol

See

ARP.



address resource record

A type of DNS data record that maps the IP address of an
Internet
-
connected device to its domain name.



alias

A nickname for a node’s host na
me. Aliases can be specified in a local host file.



anycast address

A type of address specified in IPv6 that represents a group of
interfaces, any one of which (and usually the first available of which) can accept a
transmission. At this time, anycast addre
sses are not designed to be assigned to hosts,
such as servers or workstations, but rather to routers.



APIPA (Automatic Private IP Addressing)

A service available on computers running
one of the Windows operating systems that automatically assigns the comp
uter’s
network interface a link
-
local IP address.



ARP (Address Resolution Protocol)

A core protocol in the TCP/IP suite that belongs
in the

Network layer of the OSI model. ARP obtains the MAC (physical) address of a
host, or node,

and then creates a local
database that maps the MAC address to the host’s
IP (logical) address.



ARP cache

See

ARP table.



ARP table

A database of records that maps MAC addresses to IP addresses. The ARP
table

is stored on a computer’s hard disk where it is used by the ARP utility
to supply
the MAC

addresses of network nodes, given their IP addresses.



Automatic Private IP Addressing

See

APIPA.



Avahi

A version of Zeroconf available for use with the Linux operating system.



Bonjour

Apple’s implementation of the Zeroconf group of protocols.



country code

TLD A top
-
level domain that corresponds to a country. For example, the

country code TLD for Canada is .ca, and the country code TLD for Japan is .jp.



datagram

See data packet.



DDNS (D
ynamic DNS)

A method of dynamically updating DNS records for a host.
DDNS

client computers are configured to notify a service provider when their IP
addresses change,

then the service provider propagates the DNS record change across
the Internet

automatica
lly.



DHCP (Dynamic Host Configuration Protocol)

An Application layer protocol in the
TCP/IP

suite that manages the dynamic distribution of IP addresses on a network. Using
DHCP to

assign IP addresses can nearly eliminate duplicate
-
addressing problems.



DHCP

scope

The predefined range of addresses that can be leased to any network
device on

a particular segment.

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DHCP server

A server that manages IP address assignment, maintaining information
about

which addresses are allowable, which are available, and which
have already been
associated

with a host.



DHCPv4

The version of DHCP used with IPv4. DHCPv4 uses port number 67 for
client
-
to
-
server communications and port number 68 for server
-
to
-
client
communications.



DHCPv6

The version of DHCP used with IPv6. DHCPv6 us
es port number 546 for
client
-
to
-
server communications and port number 547 for server
-
to
-
client
communications.



diskless workstation

A workstation that doesn’t contain a hard disk, but instead relies

on a small amount of read
-
only memory to connect to a ne
twork and to pick up its

system files.



DNS (Domain Name System or Domain Name Service)

A hierarchical way of
tracking

domain names and their addresses, devised in the mid
-
1980s. The DNS
database does not

rely on one file or even one server, but rather is d
istributed over
several key computers

across the Internet to prevent catastrophic failure if one or a few
computers go down. DNS

is a TCP/IP service that belongs to the Application layer of
the OSI model.



DNS cache

A database on a computer that stores info
rmation about IP addresses and
their

associated host names. DNS caches can exist on clients as well as on name servers.



DNS server

See

name server.



DNS zone

A portion of the DNS namespace for which one organization is assigned

authority to manage.



domain

A

group of computers that belong to the same organization and have part of
their

IP addresses in common.



domain name

The symbolic name that identifies a domain. Usually, a domain name is

associated with a company or other type of organization, such as a uni
versity or military
unit.



Domain Name Service

See

DNS.



Domain Name System

See

DNS.



dotted decimal notation

The shorthand convention used to represent IPv4 addresses
and

make them more easily readable by humans. In dotted decimal notation, a decimal
number

between 0 and 255 represents each binary octet. A period, or dot, separates each
decimal.



dual
-
stack

A type of network that supports both IPv4 and IPv6 traffic.



dynamic ARP table entry

A record in an ARP table that is created when a client
makes an

ARP req
uest that cannot be satisfied by data already in the ARP table.



Dynamic DNS

See

DDNS.



Dynamic Host Configuration Protocol

See

DHCP.



Dynamic Host Configuration Protocol version 4

See

DHCPv4.



Dynamic Host Configuration Protocol version 6

See

DHCPv6.



dynamic
IP address

An IP address that is assigned to a device upon request and may

change when the DHCP lease expires or is terminated. BOOTP and DHCP are two
ways of

assigning dynamic IP addresses.



Dynamic Ports

TCP/IP ports in the range of 49,152 through 65,535,

which are open for

use without requiring administrative privileges on a host or approval from IANA.



echo reply

The response signal sent by a device after another device pings it.

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echo request

The request for a response generated when one device pings anot
her
device.



File Transfer Protocol

See

FTP.



flow

A sequence of packets issued from one source to one or many destinations.
Routers

interpret flow information to ensure that packets belonging to the same
transmission arrive

together. Flow information may al
so help with traffic prioritization.



Format Prefix

A variable
-
length field at the beginning of an IPv6 address that indicates

what type of address it is (for example, unicast, anycast, or multicast).



FQDN (fully qualified domain name)

A host name plus doma
in name that uniquely

identifies a computer or location on a network.



FTP (File Transfer Protocol)

An Application layer protocol used to send and receive
files via

TCP/IP.



fully qualified domain name

See

FQDN.



fully qualified host name

See

FQDN.



hop

A term

used to describe each trip a unit of data takes from one connectivity device
to

another. Typically, hop is used in the context of router
-
to
-
router communications.



hop limit

See

TTL.



host file

A text file that associates TCP/IP host names with IP addresses
.



host name

A symbolic name that describes a TCP/IP device.



hosts

The name of the host file used on UNIX, Linux, and Windows systems. On a
UNIX
-

or

Linux
-
based computer, hosts is found in the /etc directory. On a Windows
-
based

computer, it is found in the
%systemroot%
\
system32
\
drivers
\
etc folder.



ICMP (Internet Control Message Protocol)

A core protocol in the TCP/IP suite that
notifies

the sender that something has gone wrong in the transmission process and that
packets were

not delivered.



ICMPv6

The versio
n of ICMP used with IPv6 networks. ICMPv6 performs the
functions

that ICMP, IGMP, and ARP perform in IPv4. It detects and reports data
transmission

errors, discovers other nodes on a network, and manages multicasting.



ifconfig

A TCP/IP configuration and ma
nagement utility used with UNIX and Linux

systems.



IGMP (Internet Group Management Protocol or Internet Group Multicast
Protocol)

A

TCP/IP protocol used on IPv4 networks to manage multicast transmissions.
Routers use

IGMP to determine which nodes belong to

a multicast group, and nodes use
IGMP to join

or leave a multicast group.



Internet Control Message Protocol

See

ICMP.



Internet Control Message Protocol version 6

See

ICMPv6



Internet Group Management Protocol
See

IGMP.



Internet Group Multicast Protocol

See

IGMP.



internetwork

To traverse more than one LAN segment and more than one type of

network through a router.



IP datagram

See

IP packet.



IP next generation

See

IPv6.



IP packet

The IP portion of a TCP/IP frame that acts as an envelope for data, holding

information necessary for routers to transfer data between subnets.



IP version 4 Link Local

See IPv4LL.



ipconfig

The utility used to display TCP/IP addressing and domain name information in

the Windows client operating systems.



IPng

See

IPv6.

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IPv4 IP versi
on 4
, the Internet Protocol standard released in the 1980s and still
commonly

used on modern networks. It specifies 32
-
bit addresses composed of four
octets. It lacks the

security, automatic addressing, and prioritization benefits of IPv6. It
also suffers
from a

limited number of addresses, a problem that can be resolved by
using IPv6 instead.



IPv4LL (IP version 4 Link Local)

A protocol that manages automatic address
assignment

among locally connected nodes. IPv4LL is part of the Zeroconf group of
protocols
.



IPv6 (IP version 6)

A newer standard for IP addressing that is gradually replacing the

current IPv4 (IP version 4). Most notably, IPv6 uses a newer, more efficient header in
its

packets and allows for 128
-
bit source and destination IP addresses. The use
of longer

addresses will allow for many more IP addresses to be in circulation. IPv6 also provides

automatic addressing, better security, and prioritization features.



label

A character string that represents a domain (either top
-
level, second
-
level, or
thi
rd
-
level).



lease

The agreement between a DHCP server and client on how long the client can use
a

DHCP
-
assigned IP address. DHCP services can be configured to provide lease terms
equal to

any amount of time.



link
-
local address

An IP address that is automati
cally assigned by an operating system
to

allow a node to communicate over its local subnet if a routable IP address is not
available.

ICANN has established the range of 169.254.0.0 through 169.254.254.255 as
potential

link
-
local IPv4 addresses. IPv6 link
-
l
ocal addresses begin with FE80.



loopback address

An IP address reserved for communicating from a node to itself
(used

mostly for troubleshooting purposes). The IPv4 loopback address is always cited
as

127.0.0.1, although in fact, transmitting to any IP add
ress whose first octet is 127 will

contact the originating device. In IPv6, the loopback address is represented as ::1.



loopback test

An attempt to contact one’s own machine for troubleshooting purposes.
In

TCP/IP
-
based networking, a loopback test can be p
erformed by communicating with
an IPv4

address that begins with an octet of 127. Usually, this means pinging the
address 127.0.0.1.



mask

See

subnet mask.



multicast address

A type of address in the IPv6 that represents multiple interfaces,
often

on multiple

nodes. An IPv6 multicast address begins with the following
hexadecimal field:

FF0x, where x is a character that identifies the address’s group
scope.



multicasting

A means of transmission in which one device sends data to a specific
group

of devices (not n
ecessarily the entire network segment) in a point
-
to
-
multipoint
fashion.



name server

A server that contains a database of TCP/IP host names and their
associated

IP addresses. A name server supplies a resolver with the requested
information. If it cannot

re
solve the IP address, the query passes to a higher
-
level name
server.



namespace

The database of Internet IP addresses and their associated names distributed

over DNS name servers worldwide.



net mask

See

subnet mask.



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network class

A classification for TCP
/IP
-
based networks that pertains to the
network’s

potential size and is indicated by an IP address’s network ID and subnet
mask. Network

Classes A, B, and C are commonly used by clients on LANs; network
Classes D and E are

reserved for special purposes.



ne
twork ID

The portion of an IP address common to all nodes on the same network or

subnet.



Network Time Protocol

See

NTP.



NTP (Network Time Protocol)

A simple Application layer protocol in the TCP/IP
suite used

to synchronize the clocks of computers on a net
work. NTP depends on UDP
for Transport

layer services.



octet

One of the 4 bytes that are separated by periods and together make up an IPv4

address.



Packet Internet Groper

See

PING.



ping

To send an echo request signal from one node on a TCP/IP
-
based network to

another, using the PING utility. See also PING.



PING (Packet Internet Groper)

A TCP/IP troubleshooting utility that can verify that
TCP/IP

is installed, bound to the NIC, configured

correctly, and communicating with
the network.

PING uses ICMP to send echo request and echo reply messages that
determine the validity

of an IP address.



ping6

The version of the PING utility used on Linux computers that run IPv6.



port number

The address on a host where an application makes itself available to

incoming data.



private address

An IP address used only on an organization’s internal network. Certain
IP

address ranges are reserved for private addresses. Private addresses cannot be us
ed to

communicate over the Internet.



Private Port

See

Dynamic Ports.



public address

An IP address that is valid for use on public networks, such as the
Internet.

An organization assigns its hosts public addresses from the range of addresses
assigned to it

by Internet numbering authorities.



Registered Ports

The TCP/IP ports in the range of 1024 to 49,151. These ports are

accessible to network users and processes that do not have special administrative
privileges.

Default assignments of these ports must be re
gistered with IANA.



resolver

Any host on the Internet that needs to look up domain name information.



resource record

The element of a DNS database stored on a name server that contains

information about TCP/IP host names and their addresses.



root server

A
DNS server maintained by ICANN and IANA that is an authority on how
to

contact the top
-
level domains, such as those ending with .com, .edu, .net, .us, and so
on.

ICANN oversees the operation of 13 root servers around the world.



routable

The protocols that
can span more than one LAN because they carry Network

layer and addressing information that can be interpreted by a router.



socket

A logical address assigned to a specific process running on a computer. Some

sockets are reserved for operating system functi
ons.



static ARP table entry

A record in an ARP table that someone has manually entered
using

the ARP utility. Static ARP table entries remain the same until someone manually
modifies

them with the ARP utility.



static IP address

An IP address that is manual
ly assigned to a device and remains
constant

until it is manually changed.

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subnet

A part of a network in which all nodes shares a network addressing component

and a fixed amount of bandwidth.



subnet mask

In IPv4 addressing, a 32
-
bit number that, when combi
ned with a device’s
IP

address, indicates what kind of subnet the device belongs to.



subnetting

The process of subdividing a single class of network into multiple, smaller
networks.



subprotocols

The specialized protocols that work together and belong to a
protocol
suite.



switch

The letters or words added to a command that allow you to customize a utility’s

output. Switches are usually preceded by a hyphen or forward slash character.



TCP (Transmission Control Protocol)

A core protocol of the TCP/IP suite. TCP
belongs to

the Transport layer and provides reliable data delivery services.



TCP/IP (Transmission Control Protocol/Internet Protocol)

A suite of networking
protocols

that includes TCP, IP, UDP, and many others. TCP
/IP provides the foundation
for data

exchange across the Internet.



TCP/IP core protocols

The major subprotocols of the TCP/IP suite, including IP, TCP,
and UDP.



Telnet

A terminal emulation protocol used to log on to remote hosts using the TCP/IP

protocol.
Telnet resides in the Application layer of the OSI model.



TFTP (Trivial File Transfer Protocol)

A TCP/IP Application layer protocol that
enables file

transfers between computers. Unlike FTP, TFTP relies on UDP at the
Transport layer and

does not require a
user to log on to the remote host.



Time to Live

See

TTL.



TLD (top
-
level domain)

The highest
-
level category used to distinguish domain
names

for

example, .org, .com, and .net. A TLD is also known as the domain suffix.



top
-
level domain

See

TLD.



Transmission
Control Protocol

See

TCP.



Transmission Control Protocol/Internet Protocol

See

TCP/IP.



Trivial File Transfer Protocol

See

TFTP.



TTL (Time to Live)

A number that indicates the maximum duration that a packet can
remain

on the network before it is discarded.
Although this field was originally meant to
represent units

of time, on modern networks it represents the number of router hops a
datagram has endured.

The TTL for datagrams is variable and configurable, but is
usually set at 32 or 64. Each time a

datagram

passes through a router, its TTL is reduced
by 1.When a router receives a datagram

with a TTL equal to 1, the router discards that
datagram.



UDP (User Datagram Protocol)

A core protocol in the TCP/IP suite that sits in the

Transport layer of the OSI model
. UDP is a connectionless transport service.



unicast address

A type of IPv6 address that represents a single interface on a device.
An

IPv6 unicast address begins with either FFC0 or FF80.



User Datagram Protocol

See

UDP.



Well Known Ports

The TCP/IP port nu
mbers 0 to 1023, so named because they were
long

ago assigned by Internet authorities to popular services (for example, FTP and
Telnet), and

are, therefore, well known and frequently used.



Zero configuration

See

Zeroconf.



Zeroconf (Zero configuration)

A co
llection of protocols that assigns link
-
local
addresses,

performs DNS functions, and discovers services, such as print services,
available to the node.

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zone file

A text file associated with a DNS zone that contains resource records
identifying

domains and
their IP addresses.



zone transfer

In DNS, the act of copying a primary name server’s zone file to the

secondary name server to ensure that both contain the same information.