CHAPTER 9
Supporting TCP/IP, DNS using Windows XP
INTRODUCTION TO TCP/IP
TCP (Transmission Control
Protocol / Internet Protocol) is the
communication language between
2 computers connected through
Internet.
 It is a standard that defines how
electronic devices should be
connected to the Internet & how
the transmission is done between
them.
 It uses client/server
communication & usually pointto-point communication.

CONFIGURING & TROUBLESHOOTING
TCP/IP (TERMS)
UNDERSTANDING IP ADDRESS
Every computer has a unique identifier number
called IP Address. Ex: 192.68.20.50
 Computers can not understand decimal format,
so it uses binary form.



Ex: 11000000.010001000.00010100.00110010
The 4 numbers in IP Address are called octets
(cause they have 8 positions in binary form). Add
all and you get 32, which is why IP address are
considered 32 bit numbers.
CONVERTING OCTET TO DECIMAL
IP ADDRESSES : NETWORKS & HOSTS
Octets are used to create classes of IP address that can
be assigned for particular businesses, government &
other entities based on size.
 Octet can be split into : Network ID & Host ID

Network ID – contains the first octet & used to identify the
network the computer belongs to
 Host ID – contains the last octet & identifies the actual
computer on the network.

IP ADDRESSES : NETWORKS & HOSTS
SUBNET MASK
Subnet mask is required for TCP/IP to work & used to
determine whether a host is in the local subnet or on
other remote network.
 Subnet mask help to determine which portion of an IP
address is the network & host parts of the address.
 Network bits are represented by the 1s in the mask &
host bits are represented by 0s

SPECIAL ADDRESS
PRIVATE ADDRESS
Every network interface that is directly connected to
the Internet must have IP address registered with
Internet Assigned Numbers Authority (IANA).
 Private address prevents IP address conflicts between
addresses.
 IANA has set aside 3 address ranges for use by
private / non-Internet connected networks.

10.0.0.0 to 10.255.255.255.255
 172.16.0.0 to 172.31.255.255
 192.168.0.0 to 192.168.255.255


Only public address registered with IANA is visible
to the Internet.
ASSIGNING IP ADDRESS

Static IP addressing


Dynamic Host Configuration Protocol (DHCP)


Allows to manually configure IP address if DHCP & APIPA
not available. Time consuming & prone to error on larger
networks.
Provides automatic configuration of IP address & other
client configurations in a network with 1 / more DHCP
servers. Default addressing method in Windows XP
Professional & address might change over time.
Automatic Private IP Addressing (APIPA)

Automatically assigns a private IP address when DHCP
server is unavailable. Computers using APIPA address can
only communicate with other computers using APIPA
addresses.
ASSIGNING IP ADDRESS

Alternate IP Configuration

Allows a single interface to make use of more than 1
IP address as long as only 1 is used at a time. New in
Windows XP Professional & allows computers to use
one address & if that attempt is not successful then
to make another preconfigured attempt.
AUTOMATIC PRIVATE IP ADDRESSING
(APIPA)
APIPA serves as a DHCP server failover mechanism &
makes it easier to configure & support small local area
network.
 The computer selects an IP address from a range of
addresses (169.254.0.0 to 169.254.255.255) reserved by
the IANA for that purpose.
 Once the computer has assigned itself an IP address, it
can communicate over TCP/IP with other computers on
the LAN.
 DHCP messages notifies the user when they are
switched between DHCP addressing & APIPA.

PROCESS FOR THE APIPA FEATURES
Windows XP Professional TCP/IP attempts to find a
DHCP server on the attached network to obtain a
dynamically assigned IP address.
 In the absence of a DHCP server during start up (when
server down for maintenance) the client cannot obtain
an IP address.
 APIPA generates an IP address in the form of
169.254.x.y (where x & y is the client’s randomly
generated unique identifier) & a subnet mask of
255.255.0.0

WHEN APIPA WILL BE USEFUL
No previous IP address & no DHCP server
 Previous IP address & no DHCP server
 Lease expires and no DHCP server

TESTING TCP/IP CONNECTIONS

Windows XP provides a number of tools for
troubleshooting network connectivity problems.
Ping – This tool allows you to check for connectivity between
devices on the network
 Ipconfig – This tool used to view current TCP/IP
configuration information for a computer.
 Tracert – this tool helps you to figure out exactly where
along the route the breakdown happened.
 Pathping – A combination of ping & tracert. Displays
information about packet lost between source & destination &
used to determine which particular router / subnet might be
having network problem.

DOMAIN NAME SYSTEM (DNS)
Is a naming system that is used in TCP/IP networks
to translate computer names to IP addresses.
 It is easier as user don’t have to remember 12 digit
numbers. Ex: www.yahoo.com, the name is translated
into a number by DNS process.
 Another key element of DNS are:
 DNS servers run by Companies
 Internet Service Providers (ISPs)
 Ex: www.google.com is translated by DNS to
216.239.51.99, if DNS fails then you will have to type
in the 12 digits number in the URL.

DOMAIN NAME SPACE
Naming scheme that provides the hierarchical
structure for the DNS database. Based on the concept
of a tree of named domains.
 Branch level – more than 1 name is used to identify a
collection of named resources.
 Leaf level – single name used once at that level to
indicate a specific resource.
 Root level – represented by single period.
 DNS database is indexed by name, so each domain
must have a name. the parents domain is added to its
child domain(subdomain).
 A domain’s name identifies its position in the
hierarchy.

DOMAIN NAME SPACE

The hierarchical structure of the domain namespace
consists of:
Root domain
 Top-level domain – grouped by organization type /
geographical location controlled by IAB.
 Second-level domain – registered to individuals /
organizations by a number of different domain registry
companies. Ex: cosmopoint.com then cas.cosmopoint.com
 Host names – refers to specific computer on the Internet /
private network.


FQDN – Fully Qualified Domain Name. Ex:
computer1.cas.cosmopoint.com
DOMAIN NAMING GUIDELINES
Limit the number of domain levels.
 Use unique names
 Use simple names
 Avoid lengthy domain names
 Use standard DNS characters & unicode
characters.
