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Guide to Net working Essentials, Fifth Edition



6
-
1



Chapter 6


Network Communications and 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




Technical Notes for
Hands
-
On Projects


Guide to Net working Essentials, Fifth Edition



6
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Lecture Notes


Overview


Chapter 6 offers an introduction to network communications and protocols. Students
learn about the function of different protocols in a network. They also learn about the
different common protocol suites, with

a special focus in the TCP/IP protocol suite.



Objectives




Explain the function of protocols in a network



Describe common protocol suites



Teaching Tips


Protocols


1.

Explain why
protocols

are needed to enable computer communications.


The Function of Pro
tocols


1.

Explain that as protocols serve their functions in the OSI model, they might work at one
or many layers. Introduce the term
protocol stack

and provide a few examples of
existing protocol stacks (including
TCP/IP
). Note that levels of a protocol sta
ck map to
their functions in the OSI model.


2.

Connectionless Versus Connection
-
Oriented Protocols
. Describe the difference between
connectionless

and
connection
-
oriented

protocols.


Teaching

Tip


For more information on connectionless vs. connection
-
orient
ed protocols, see:
www.inetdaemon.com/tutorials/theory/

concepts/connection
-
oriented_vs_connectionless.shtml
.




3.

Routable Versus Nonroutable
Protocols
. Describe the difference between
routable
and
nonroutable

protocols. Provide examples of each of these types.


Teaching

Tip


For more information on routable vs. non
-
routable protocols, see:
http://ezinearticles.com/?Routing,
-
Routed,
-
and
-
Non
-
Routable
-
Protocols&id=13286
.



Guide to Net working Essentials, Fifth Edition



6
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Protocols in a Layered Architecture


1.

Use Figure 6
-
1 to recap the functions of each layer of the OSI model.


2.

Use Figure 6
-
2 to show
how the tasks required for network communication combine to
form three major protocol types: application, transport, and network.


3.

Network Protocols
. Briefly describe each of the following common network protocols:
IPv4
,
IPX
, and
IPv6
. Note that IPv6 addre
sses some of the weaknesses of IPv4.


4.

Transport Protocols
. Explain that transport protocols can use connection
-
oriented
(reliable) or connectionless (best
-
effort) delivery. Briefly describe each of the following
common transport protocols:
TCP
,
SPX
, and
Ne
tBIOS/NetBEUI
.


Teaching

Tip


Note that NetBIOS also runs over TCP/IP and IPX/SPX, so using NetBIOS
doesn’t require using NetBEUI.





Application Protocols
. Explain that application protocols provide services to client
applications. Briefly describe each
of the following common application protocols:
SMTP, FTP,
SNMP
,
NCP
, and
AFP
.



Quick Quiz 1


1.

When a set of protocols works cooperatively, it’s called a(n) ____________________
or protocol suite.

Answer: protocol stack


2.

What is a connectionless protocol?

A
nswer: Protocols that use connectionless delivery place the data on the network and
assume it will get through, in much the same way people rely on the U.S. Postal Service
to deliver their mail when they drop it in a mailbox. However, much like the Postal
Service, delivery is not always guaranteed, so connectionless protocols aren’t entirely
reliable. However, connectionless protocols are fast because they require little overhead
and don’t waste time establishing, managing, and tearing down connections. Whe
n a
connectionless protocol transports data across a network, higher layers handle packet
sequencing and sorting, thereby allowing faster communication.


Guide to Net working Essentials, Fifth Edition



6
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3.

What is the difference between routable and nonroutable protocols?

Answer: Protocol suites that funct
ion at the Network layer are called routable or routed
protocols, whereas protocol suites that don’t are called nonroutable. Because routing
operates at the Network layer, the routable/nonroutable attribute applies primarily to
protocols that operate at th
is layer.


4.

____________________ is the TCP/IP protocol responsible for reliable delivery of
data.

Answer:

Transmission Control Protocol (TCP)


Transmission Control Protocol


TCP


Common Protocol Suites


1.

Explain that because most protocols contain a combina
tion of components to make
communications work correctly, these components are usually bundled as a protocol
suite.


2.

Note that common protocol suites are: TCP/IP, IPX/SPX, NetBIOS/NetBEUI, and
AppleTalk. Stress that TCP/IP dominates the networking arena to

the point of making
most of the other suites nearly obsolete.


Transmission Control Protocol/Internet Protocol (TCP/IP)


1.

Provide a brief history of TCP/IP’s creation and evolution.


2.

Explain that although the TCP/IP suite predates the OSI model by nearly a

decade, its
protocols and functions are quite similar. Use Figure 6
-
3 to show TCP/IP’s relation to
the OSI model.


3.

Stress that more than any other protocol suite, TCP/IP uses highly compartmentalized
and specialized protocols.


4.

TCP/IP Network Layer Protoc
ols
. Describe the role of
IPv4
,
ICMP
, and
ARP
. To see
how Ping works with ICMP, students should take a look at Simulation 6
-
1.


Teaching

Tip


Explain that communication using ARP can occur only between two systems on
the same network; holding a conversati
on with a host that must be reached
through a router requires sending the frame to the router, which forwards it to its
final destination.



Teaching

Tip


ARP is open to ARP spoofing (also called ARP poisoning) attacks, which
constitute a serious securit
y risk. Read more about this type of attack at
http://en.wikipedia.org/wiki/ARP_spoofing
.




Guide to Net working Essentials, Fifth Edition



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5.

IP, ICMP, and ARP in Action
. Use Figure 6
-
4 to show how IP, ICMP, and ARP work
together to accomplish c
ommunication between two computers. You may use the mail
delivery analogy to help explain the process. Simulation 6
-
2 will help students visualize
this process. Use Figure 6
-
5 to show the progression of building a frame, from an ICMP
message to an IP packe
t to a data frame. Stress that although the example described uses
an ICMP message, the process is much the same for any type of IP message.


Teaching

Tip


You can find an animation showing the use of ARP at
http://netbook.cs.purdue.edu/anmtions/anim15_1.htm
.




6.

TCP/IP Transport Layer Protocols
. Describe the role of the
TCP

protocol. Briefly
describe TCP’s three
-
way handshake process. Describe the role of the
UDP

protocol,
stressing the d
ifferences with TCP. Note that UDP is used by NFS and DNS.


Teaching

Tip


For an animation of TCP’s three
-
way han摳ha步Ⱐsee
htt瀺//net扯潫⹣s⹰urd略⹥du/a湭tions/a湩m㈰弱O桴m
.




Teachi
ng

Tip


For an animation of TCP’s sliding window mechanism for flow control, see
htt瀺//net扯潫⹣s⹰urd略⹥du/a湭tions/a湩m㈰弴O桴m
.




Teaching

Tip


For an animation of TCP’s sliding w
in摯d mechanism f潲 relia扬e 摡ta 摥liveryⰠ
see
htt瀺//net扯潫⹣s⹰urdue⹥d甯a湭tions/a湩m㈰張Ohtm
.





TCP/IP Application Layer Protocols
. Briefly describe the role of each of the followin
g
application layer protocols:
DNS
,
HTTP
,
FTP
,
Telnet
,
SMTP
.


IP Addressing


1.

Explain how to interpret IPv4 addresses. Introduce the terms
octet

and
dotted decimal
notation
. Stress that IPv4 addresses have two parts: network and host ID.


2.

Explain the role o
f classes in IPv4 addresses. Briefly describe each of the available
classes (A, B, C, D, and E).


3.

Describe the role of the reserved
loopback address

and introduce the term
localhost
.


4.

List the addresses that the
IETF

reserved for private networks (in class
es A, B, and C).
Stress that these addresses cannot be routed across the Internet, so
NAT

should be used
to enable computers with private addresses to access the Internet. Explain that IPv6
eliminates the need for private addressing because it provides a 1
28
-
bit address space
(versus IPv4’s 32 bits).

Guide to Net working Essentials, Fifth Edition



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Teaching

Tip


Explain that a number of public and private companies around the world, known
as IP address registries, cooperatively manage the total collection of valid IP
addresses. This activity occurs unde
r the control of the Internet Assigned
Numbers Authority (IANA), a public nonprofit agency responsible for Internet
addressing and address management.



5.

Classless Interdomain Routing (CIDR)
. Explain how
CIDR

works. Describe the
importance of CIDR in makin
g efficient use of IPv4’s limited address space. Use one or
more examples to show students how to interpret CIDR’s notation. Introduce the term
subnetting
.


6.

Why Subnet?

Describe the advantages of subnetting networks. Explain that subnetting
reduces the si
ze of
broadcast domains
, which in turn makes networks more scalable and
efficient.


7.

Subnet Masks
. Use one or more examples to show how to apply and interpret
subnet
masks
. Show how to create default subnet masks.


Teaching

Tip


Explain that all devices on

a single logical network (where each device can
communicate with another device without going through a router; sometimes
called a network segment) must share the same network address, and, therefore,
must also use the same subnet mask.



8.

Some Simple Bin
ary Arithmetic
. Use Table 6
-
1 and one or more examples to show how
to convert decimal to binary numbers. Use an example to describe the steps required to
convert binary to decimal numbers. Explain that each octet in a subnet mask always
consists of a serie
s of zero or more 1s, followed by a series of zero or more 0s, as Table
6
-
2 shows. Use Table 6
-
3 to show the low
-
order bit patterns. Explain that if you
memorize the values of the powers of 2, from 0 through 7, you can calculate this table
quickly. Use an
example and Table 6
-
4 to show how to calculate a subnet mask. Use
Figure 6
-
6 to explain with another example how to calculate a subnet mask. Subnetting
can be hard to grasp for students at first. The more they practice, the better. Introduce
the term
super
netting
. Explain that supernetting permits consecutive IP network
addresses to be combined and viewed in a single logical network. Use an example to
show how to calculate supernets. Make sure students understand the advantages of
supernetting.


Teaching

T
ip


There are several good subnetting and supernetting tutorials. One cited in the
book is
www.learntosubnet.com
. Other good resources and tutorials can be found
in the links section at the end of this document
.



Guide to Net working Essentials, Fifth Edition



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9.

Network Address Translation (NAT)
. Explain that although subnetting and supernetting
can help alleviate the IP address shortage problem, they simply make more efficient use
of existing addresses.
Network Address Translation (NAT)

helps considerably m
ore by
allowing an organization to use private IP addresses while connected to the Internet.
Use Figure 6
-
7 to explain how NAT works. Explain that an extension of NAT, called
Port Address Translation (PAT), allows several hundred workstations to access the

Internet with a single public Internet address. In Simulation 6
-
3, students can see how
NAT and PAT work; both go a long way toward extending the life of IPv4 addresses.


Teaching

Tip

For an excellent tutorial on NAT, see
www.howstuffworks.com/nat.htm
.


10.

Dynamic Host Configuration Protocol (DHCP)
. Describe the role of
DHCP
. Stress the
advantages of using this protocol. Briefly describe how DHCP works (including the role
of DHCP servers and clients). I
ntroduce the term
APIPA
. Explain that in an
APIPA
-
enabled OS, if no answer is received after a client issues a DHCP request, the computer
assigns itself an address (169.254.x.x).


Teaching

Tip


Note that all major operating systems today include a DHCP cl
ient service, and
most server operating systems include the DHCP server component.



11.

Internet Protocol Version 6 (IPv6)
. Explain that
IPv6

solves the following problems of
IPv4: limiting 32
-
bit address space, lack of built
-
in security, a sometimes complic
ated
setup, and lack of built
-
in QoS.


12.

IPv6 Addresses
. Explain how to interpret IPv6 addresses, both in longhand and
shorthand notation. Explain that addresses have a three
-
part addressing hierarchy: a
public topology, a site topology, and an interface ide
ntifier (derived from the MAC
address on the host’s NIC).


Other Protocol Suites


1.

Explain that other protocol suites are sometimes used on older networks, where the need
to change to TCP/IP is not warranted, or in environments suited to the suite’s feature
s.


2.

NetBIOS and NetBEUI
. Provide a brief history of this protocol suite. Stress that from
their inception, NetBIOS and NetBEUI were designed to work in small to medium
networks of 2 to 250 computers. Note that NetBIOS used with TCP/IP or IPX/SPX is
still a
round, but Microsoft has discontinued support for NetBEUI starting with
Windows XP. Figure 6
-
8 shows the Microsoft protocol suite and its relationship to the
OSI model. Describe the role of the redirector and
SMB
. Stress that SMB file sharing is
also suppo
rted by most Linux and UNIX systems. Explain that although Figure 6
-
8
shows NetBEUI operating at the Network layer, it is actually a nonroutable protocol and
skips this layer. Explain that NetBIOS operates at the Session layer to provide peer
-
to
-
peer netwo
rk application support. Note that a unique 15
-
character name identifies each
computer in a NetBIOS network.

Guide to Net working Essentials, Fifth Edition



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Explain that a NetBIOS broadcast advertises a computer’s name. Explain that NetBIOS
is connection
-
oriented but can use connectionless communication
s. Note that although
it is closely related to NetBEUI, NetBIOS can use a number of other lower
-
layer
protocols, including TCP/IP and IPX/SPX, for transport and lower
-
layer services. Stress
that NetBIOS is a nonroutable protocol, but it can be routed when
using a routable
protocol for transport. Describe the role of NetBEUI.


3.

IPX/SPX
. Provide an introduction to the role of this protocol suite. Note that currently,
TCP/IP is the protocol suite of choice for networking, even in NetWare. Explain that
NWLink
is

the Microsoft implementation of the IPX/SPX protocol suite. Use Figure 6
-
9
to show the protocols that compose the NWLink suite and their corresponding layers in
the OSI model. Note that computers on an IPX/SPX network must use the same
Ethernet frame type

to communicate successfully.


Teaching

Tip


For more information about IPX/SPX and Novell NetWare, you can visit
www.protocols.com/pbook/novel.htm
.




4.

AppleTalk
. Provide a brief description of th
is protocol suite. Describe the role of zones
in AppleTalk.


Teaching

Tip

For more information on these protocols and others, see
www.protocols.com
.


Implementing and Removing Protocols


1.

Use Figure 6
-
10 to expla
in that in most operating systems, adding or removing
protocols is relatively easy.


2.

Stress that adding unnecessary protocols can have a detrimental effect on network
performance.


3.

Explain that when multiple protocols are installed, the operating system mu
st be
configured carefully to prioritize the use of each protocol. This priority is referred to as
the protocol binding order.



Quick Quiz 2


1.

The ____________________ suite is the most commonly used protocol suite in the
networking world.

Answer: TCP/IP


2.

What is UDP?

Answer: The User Datagram Protocol (UDP) is a connectionless transport layer
protocol from the TCP/IP protocol suite.

Guide to Net working Essentials, Fifth Edition



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3.

In IPv4 addresses, the four decimal numbers are separated by periods in a notation
referred to as ____________________.

Answe
r:
dotted decimal


4.

What is subnetting?

Answer: Subnetting is the process of dividing a single network address into two or more
subnetwork addresses, each with fewer available host IDs than the original network
address.



Class Discussion Topics


1.

What is th
e difference between subnetting and supernetting?


2.

In which kinds of situations would an application developer choose to use UDP instead
of TCP for data transport?



Additional Projects


1.

Ask students to compile a list of protocols that belong to the TCP/IP

suite. They should
include a brief description of the role of each protocol. Additionally, for any
Application layer protocol, students should indicate if the protocol works on top of TCP
or if it works on top of UDP. Why is it common to say that the TCP/
IP protocol suite
follows an
hourglass model
?


2.

Ask students to find out why real
-
time multimedia streaming applications (e.g., VoIP)
are implemented on top of UDP and not on top of TCP.



Additional Resources


1.

Internet Protocol Suite:

http://en.wikipedia.org/wiki/TCP/IP



2.

Connection Oriented vs. Connectionless:

www.inetdaemon.com/tutorials/theor
y/concepts/connection
-
oriented_vs_connectionless.shtml



3.

Routing, Routed, and Non
-
Routable Protocols:

http://ezinearticles.com/?Routing,
-
Routed,
-
and
-
Non
-
Routabl
e
-
Protocols&id=13286



4.

IPv4:

http://en.wikipedia.org/wiki/IPv4



5.

IPv4 Address Space:

www.iana.org/assignments/ipv4
-
address
-
space



Guide to Net working Essentials, Fifth Edition



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6.

IPX/S
PX:

http://en.wikipedia.org/wiki/IPX/SPX



7.

NetWare Protocols:

www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/netw
arep.htm



8.

IPv6:

http://en.wikipedia.org/wiki/IPv6



9.

IP Version 6 Working Group Charter:

www.ietf.org/html.charters/ipv6
-
charter.html



10.

ICMP:

http://en.wikipedia.org/wiki/ICMP



11.

Address Resolution Protocol:

http://en.wikipedia.org/wiki/Address_Resolution_Protocol



12.

TCP vs. UDP:

www.skullbox.net/tcpudp.php



13.

Comparative analysis


TCP


UDP:

www.laynetworks.com/Comparative%20analysis
_TCP%20Vs%20UDP.htm



14.

Classless Inter
-
Domain Routing:

http://en.wikipedia.org/wiki/Classless_Inter
-
Domain_Routing



15.

IP Address Subnetting Tutorial:

www.ralphb.net/IPSubnet/



16.

IP Addressing and Subnetting for New Users:

www.cisco.com/warp/public/701/3.html



17.

IP Subnetting, Variable Subnetting, and CIDR (Supernetting):

www.gtoal.com/subnet.html



18.

Dynamic Host Configuration Protocol:

http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol



19.

How Network Address Translation Works:

www.howstuffworks.com/nat.htm



20.

Network Address Translation:

http://en.wikipedia.org/wi
ki/Network_address_translation



21.

NetBEUI:

www.comptechdoc.org/independent/networking/guide/netnetbeui.html




Guide to Net working Essentials, Fifth Edition



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Key Terms




Address Resolution Protocol (ARP)


A protoco
l in the TCP/IP suite used to resolve
logical IP addresses to physical MAC addresses.



AppleTalk File Protocol (AFP)


The Macintosh remote file
-
management protocol.



application protocol


A type of protocol that works in the upper layers of the OSI
model t
o provide application
-
to
-
application interaction.



automatic private IP addressing (APIPA)


A special range of addresses that starts
with 169.254 and is used by a computer when no DHCP server responds to a DHCP
request.
See also
Dynamic Host Configuration
Protocol (DHCP).



broadcast domain


The extent to which a broadcast frame is forwarded from device
to device without going through a router. An IP network or subnet is also referred to as
a broadcast domain.



Classless Interdomain Routing (CIDR)


An IP add
ressing method in which address
classes no longer dictate the part of an IP address designated as the network portion.
With CIDR, a network administrator can assign however many bits are appropriate to
the network design.



connectionless


A type of protoco
l that sends data across the network to its
destination without guaranteeing receipt.



connection
-
oriented


A type of protocol that establishes a formal connection
between two computers, guaranteeing that data will reach its destination.



Domain Name System

(DNS)


ATCP/IP protocol used to associate a computer’s IP
address with a name.



dotted decimal


The format of an IP address, expressed as four decimal numbers
separated by a period.



Dynamic Host Configuration Protocol (DHCP)


A TCP/IP protocol that allo
ws
automatic IP address and subnet mask assignment.



File Transfer Protocol (FTP)


A TCP/IP protocol used for file transfer and
manipulation services.



Hypertext Transfer Protocol (HTTP)


The protocol used to transfer Web pages
from a Web server to a Web b
rowser.



Internet Control Message Protocol (ICMP)


A TCP/IP protocol used to send
information and error messages.



Internet Protocol version 4 (IPv4)


TCP/IP’s primary network protocol; it provides
addressing and routing information.



Internet Protocol vers
ion 6 (IPv6)


An updated version of IPv4 created to solve
some problems inherent in that protocol, such as a somewhat limiting 32
-
bit address
space, lack of built
-
in security, a sometimes complicated setup, and a lack of built
-
in
Quality of Service.



Inter
network Packet Exchange/Sequenced Packet Exchange (IPX/SPX)


IPX is
Novell’s protocol for packet routing and forwarding. In this protocol suite, IPX serves
many of the same functions that IP does in the TCP/IP suite. SPX is Novell’s
connection
-
oriented pr
otocol that supplements IPX by providing reliable transport.



localhost


A special DNS host name that refers to whatever IP address is assigned to
the machine where this name is referenced. (Think of it as a special way to access the
current IP address on
any computer.)



loopback address


A special DNS host name that refers to the reserved Class A
address 127.0.0.1, used to confirm that a computer’s IP configuration works.

Guide to Net working Essentials, Fifth Edition



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NetBIOS Extended User Interface (NetBEUI)


A network protocol developed by
IBM and M
icrosoft specifically to provide transport services for NetBIOS. NetBEUI is
not routable. In addition, it’s nearly obsolete and is no longer supported on current
Windows operating systems.



NetWare Core Protocol (NCP)


Novell’s upper
-
layer protocol that pr
ovides all
client/server functions.



Network Address Translation (NAT)


A process by which an organization can
assign private IP addresses to workstations; those addresses are translated to public IP
addresses when accessing the Internet.



Network Basic Inp
ut/Output System (NetBIOS)


A protocol that establishes and
manages communications between computers and provides naming services.



nonroutable


A protocol that doesn’t include Network layer or network address
information.



NWLink


The Microsoft implement
ation of the IPX/SPX protocol suite.
See also
Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX).



octet


A grouping of eight binary digits or bits (“oct” means eight), usually expressed
as a decimal number. An octet is one of the four decima
l values that make up an IP
address.



protocols


The rules and procedures for communicating.



protocol stack


An ordered collection of networking protocols that together provide
end
-
to
-
end networked communications between a sender and a receiver.



routable


A protocol that includes Network layer information and can be forwarded
by a router.



Server Message Block (SMB)


The message format used by DOS and Windows to
share files, directories, and devices. SMB file sharing is also supported by most Linux
and UN
IX operating systems.



Simple Mail Transport Protocol (SMTP)


A TCP/IP protocol used to send mail
messages across a network. SMTP is the basis for e
-
mail on the Internet.



Simple Network Management Protocol (SNMP)


A TCP/IP protocol used to
monitor and man
age network devices.



subnet mask


A 32
-
bit dotted decimal number used to signify which part of an IP
address is the network portion and which part is the host portion. The subnet mask
consists of a string of binary 1s followed by a string of binary 0s. Th
e binary 0s mask
the host portion of an IP address. A binary 1 signifies that the corresponding bit in the
IP address belongs to the network portion of the IP address, and a binary 0 signifies that
the corresponding bit in the IP address belongs to the hos
t portion.



subnetting


The process whereby a single network address is divided into two or
more subnetwork addresses, each with fewer available host IDs than the original
network address.



supernetting


The operation of “borrowing” bits from the network p
ortion of an IP
address to combine a group of contiguous IP addresses. For supernetting to work, the
group of IP addresses must be contiguous.



Telnet


A TCP/IP protocol that provides remote terminal emulation.



Transmission Control Protocol (TCP)


The cor
e of the TCP/IP suite. TCP is a
connection
-
oriented protocol responsible for reformatting data into packets and reliably
delivering those packets.



Transmission Control Protocol/Internet Protocol (TCP/IP)


A protocol suite that
supports communication betwe
en heterogeneous systems. TCP/IP has become the
standard communications protocol for the Internet.

Guide to Net working Essentials, Fifth Edition



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transport protocol


A protocol type responsible for providing reliable
communication sessions between two computers.



User Datagram Protocol (UDP)


A connec
tionless TCP/IP protocol that provides
fast data transport.



Technical Notes for Hands
-
On Projects


Hands
-
On Project 6
-
1: In this project, students use the Windows XP Control Panel.


Hands
-
On Project 6
-
2: In this project, students use the Windows XP Contr
ol Panel and the
ipconfig command
-
line utility.


Hands
-
On Project 6
-
3: In this project, students use the Windows XP Control Panel.


Hands
-
On Project 6
-
4: In this project, students use the ping and ipconfig command
-
line
utilities.


Hands
-
On Project 6
-
5: Thi
s project requires the Netstat utility.


Hands
-
On Project 6
-
6: This project requires a Web browser and Internet access.