TODAY
INTERNET ADDRESSING
TCIP/IP
NAT, IP, TCP, UDP, CONFIGURATION, DNS, DHCP,
WINS
LAB 8: CONFIGURE DHCP SERVER
NETWORK ADDRESS TRANSLATION (NAT)
Allows unregistered private network addresses to communicate
with legally registered IP addresses
 Advantages

Hides internal IP addresses, thus providing security
 Eliminates need for multiple registered IP addresses
 Allows multiple ISDN (Integrated Services Digital Network) connections
to be combined into one Internet connection

IP CONFIGURATION
DOMAIN NAME SYSTEM (DNS)
Makes it easy to identify and find hosts on Internet
 When domain name is entered, it is converted to its IP
address

FULLY QUALIFIED DOMAIN NAME (FQDN)
Needed to locate a host on a large network
 Example of an FQDN: station2.xyzcorp.com
*A combination of the host name and domain name.

Operating systems such as Linux, and Windows 2000 and
later follow the rules of Fully Qualified Domain Names
when creating their network structure.
(FQDN VS NETBIOS NAME)
Fully Qualified Domain Name is limited to 63 characters.
 NetBIOS names is a computer name limited to 15
characters.
 Many symbols allowed in NetBIOS names cannot be
used in FQDN.

(;:”<>*+=\/?,)

To allow for communication between legacy systems
and ones that use host names the computer names are
converted automatically.
DNS STRUCTURE AND OPERATION

Hierarchical structure
 Root - The authoritative name servers
that serve the DNS root zone
 Top-level domains—
.com,.edu,.gov,.net,.org
 Second-level domains—mit.edu
 Subdomains(any level domain located
beneath the secondary domain)—
campus.mit.edu, faculty.mit.edu
 AKA (lower-level domain)
DNS STRUCTURE AND OPERATION

Resolver A software program located on a host that queries a
DNS server to resolve a host name to an IP address
• Once
information
is found it is
returned to
the resolver
• If top level •
server
cannot
resolve
request it is•
passed on
to the root
sever
Domain names
are placed in
cache for future
requests.
If not in cache
Top level DNS is
contacted
Research .mit.edu
• DNS server the
host is connected
to as part of a
workgroup or
domain.
• OR it could be an
ISP
WINDOWS INTERNET NAMING SERVICE (WINS)
Windows NT server operating systems used WINS to
resolve NetBIOS names to IP addresses
 Windows 2000 and later use the Dynamic DNS, which
incorporates the WINS and DNS features

IP, TCP, AND UDP
Three most commonly used protocols in TCP/IP suite
 IP establishes a link between nodes but does not verify
the data is delivered correctly – connectionless protocol
 TCP ensures packets arrive intact and in correct order connection-oriented
 TCP can break large amounts of data into smaller
packets and UDP cannot
 UDP sends a single packet to transmit control
information and data - connectionless protocol

TCP OR UDP
 The
selection of TCP or UDP depends on
three factors
 The software used in the upper layers of
the OSI model
 The amount of data to be sent
 If a connectionless or connectionoriented transport of data is desired
OSI MODEL AND TCP/IP
UDP FRAME
UDP and TCP Rely
on the IP Frame
format for IP
address
Destination and
source
Used to transfer
small blocks of
data and
commands
TCP FRAME
Used to reassemble
data in a correct
order
IP FRAME
Final step is to
encapsulate the
entire set of
protocol frames
in a frame
matching the
network standard
e.g Ethernet
ASSIGNING IP ADDRESSES
Static addressing or dynamic addressing can be used to
assign IP addresses to hosts
 A static IP assignment is entered manually when the NIC
is configured
 A server running the Dynamic Host Configuration
Protocol (DHCP) issues an IP address to a host when it
joins the network
 (dynamic IP assignment) an IP address that is issued
automatically. Typically when a computer boots and
joins the network.
 The default DHCP IP lease period is 8 days.

DYNAMIC ADDRESSING
AUTOMATIC PRIVATE IP ADDRESSING (APIPA)
Used when the host is unable to access a DHCP server
 Host automatically generates an IP address in the range
of 169.254.0.1 to 169.254.255.254
 Uses the APIPA address to communicate with other
workstations on the same segment.
 This addressing is compatible with all Microsoft products
starting with Windows 98
 This was not necessary in previous operating systems
due to NetBEUI protocol which uses MAC addresses to
communicate with workstations on the same segment

TCP/IP PORTS AND SOCKET
A port number combined with an IP address (socket) is
used to create a virtual connection
 E.G. 192.168.20.45:80
 Socket technology allows multiple, simultaneous
services to run between a server and a workstation.

EXAMPLES OF WELL-KNOWN PORT NUMBERS
Service or Protocol
Port Number
FTP
20, 21
SSH
22
Telnet
23
SMTP
25
DNS
53
TFTP
69
HTTP
80
POP3
110
NNTP
119
NTP
123
IMAP4
143
HTTPS
443