Chapter 4
TCP/IP Networking
4.1 – History of TCP/IP
4.2 – IP Addressing
4.3 – Name Resolution
4.4 – TCP/IP Protocols
History of TCP/IP
Origins and Growth of TCP/IP
• The U.S. Defense Department Advanced
Research Projects Agency (DARPA)
produced the designs and experimental
networks that evolved into the public
Internet.
• DARPA also accelerated the spread of
Transmission Control Protocol /Internet
Protocol (TCP/IP) by including it in
distributions of the UNIX operating system.
Origins and Growth of TCP/IP
Origins and Growth of TCP/IP
• It took 38 years for radio to
achieve what is called "universal
service".
• Television is now taken for
granted as a source of news and
entertainment.
• It took 59 years to achieve
"universal service”.
• The Internet has achieved most
of its explosive growth within the
past ten years and is now
beginning to absorb elements of
the telephone and television
systems.
• No other technology can match
this achievement.
The TCP/IP Network Model
• The TCP/IP network model
closely resembles the OSI
reference model and is the
predominant protocol suite
used in networking today.
• The TCP/IP network model
contains four layers, unlike
the OSI model, which
contains seven layers.
The TCP/IP Network Model
• The application layer of the
TCP/IP model defines many of
the applications that are used in
networks.
• It determines protocol and data
syntax rules at the application
level.
• Transfer Protocol (FTP), Trivial
File Transfer Protocol (TFTP),
Simple Mail Transfer Protocol
(SMTP), Internet Message
Access Protocol (IMAP), Post
Office Protocol version 3 (POP3),
Simple Network Management
Protocol (SNMP), and Telnet.
The TCP/IP Network Model
• TCP/IP transport layer
defines only Transmission
Control Protocol (TCP) and
User Datagram Protocol
(UDP).
• It provides reliability and
flow control.
• Reliability is achieved
through a sequence of
acknowledgements that
guarantee the delivery of
each packet.
• Flow control is achieved
through the windowing.
The TCP/IP Network Model
• Both TCP and UDP use
port numbers to pass
data to the upper layers.
• Port numbers help define
and keep track of all the
different types of
conversations that are
taking place throughout
the network.
The TCP/IP Network Model
• The Internet layer of the TCP/IP
model defines addressing and
path selection.
• This is the same function as the
network layer in the OSI model.
• Routers use Internet layer
protocols to identify an
appropriate path for data packets
as they travel from network to
network.
• Protocols defined at this layer are
IP, Internet Control Message
Protocol (ICMP), Address
Resolution Protocol (ARP), and
Reverse Address Resolution
Protocol (RARP).
The TCP/IP Network Model
• IP provides the routers with the ability, or addressing,
to move data to the desired destination.
• ICMP provides control and messaging capabilities,
which are used when there is a problem somewhere
in the network.
• ICMP is used to send a message back to the host,
informing it that the destination host was unreachable
and is also the basis for the ping and traceroute
commands.
• ARP is used to find the MAC address of a host,
switch, or router, when given its IP address.
• RARP is used when the MAC address of a host is
known, but the IP address is not known.
The TCP/IP Network Model
• The network interface layer
maps to the data link and
physical layers of the OSI
model.
• This layer defines TCP/IPspecific functions related to
the preparation of data for
transmission over the
physical media, including
addressing.
• It also specifies what types
of media can be used for
the data transmission.
TCP/IP and
Network Operating Systems
• Today, all NOS vendors
have adopted the TCP/IP
protocol suite for carrying
data between client and
server systems.
• Although the older
proprietary protocols remain
in use, TCP/IP is the
standard that is
implemented by all the NOS
vendors.
IP Addressing
IPv4 Addressing
• For any two systems to
communicate, they must be
able to identify and locate
each other.
• IP addresses are used to
locate other computer
systems when data must
travel and be forwarded by
other network hardware
• Each computer in a TCP/IP
network must be given at
least one unique identifier,
or address.
IPv4 Addressing Overview
• By using the network identifier, IP can deliver
a packet to the destination network.
• Once the packet arrives at a router connected
to the destination network, IP must then locate
the particular point where the destination
computer is connected to that network.
IPv4 Addressing Overview
• Every IP address has two
parts.
– One part identifies the network
to which the system is
connected
– Second part identifies that
particular system on the
network
• This kind of address is
called a hierarchical
address, because it contains
different levels and because
of the fact that the address
can be broken down into two
parts, with each parts being
used as an identifier.
IPv4 Addressing Overview
• Inside a computer, an IP
address is stored as a 32bit sequence of 1s and 0s.
• To make the IP address
easier to use, it is usually
written as four decimal
numbers. separated by
periods.
• Each part of the address is
called an octet because it is
made up of eight binary
characters.
IPv4 Addressing Overview
• IP addresses are divided
into classes to define the
large (Class A), medium
(Class B), and small (Class
C) networks.
• Knowing the class of an IP
address is the first step in
determining which part of
the address identifies the
network and which part
identifies the host.
Class A Addresses
• In a Class A address, the first number (octet) is the
network portion, and the last three numbers are the host
portion.
• The format is Network.Host.Host.Host, or N.H.H.H.
• Only 1-126 is valid for Class A networks because network
127.0.0.0 is reserved.
• The IP address 127.0.0.1 is known as the "local loopback"
address, and is used to test the NIC of the local system.
Class B Addresses
• A Class B IP address divides the network portion
from the host portion between the second and
third octet.
• The format is N.N.H.H.
• If the first octet in an IP address is greater than
127 but less than 192, it is a Class B address.
Class C Addresses
• A Class C IP address divides the network portion
from the host portion between the third and fourth
octet.
• The format is N.N.N.H.
• If the first octet of the IP address is greater than
191 but less than 224, it is a Class C address.
Class D and E Addresses
• Class D and Class E addresses are used for
special purposes.
• Class D is reserved for a technique called
multicast, and Class E addresses are used for
experimental purposes.
• Commercial organizations use classes A, B, or C
addresses to identify networks and hosts.
The IPv4 Address Crisis
•
The Internet faced the situation
where it appeared that growth
would be limited or even stopped
because the Internet address space
could become exhausted.
• In response, Internet engineers
developed a set of techniques to
make more efficient use of the
Internet address space.
• Among these techniques was the
subnetting.
• Subnetting is the process of
splitting a network portion of an IP
address, which allows an
administrator to partition or divide a
network.
The IPv4 Address Crisis
• Subnetting takes the IP
address, which is divided
into a network portion and a
host portion, and then
divides it further by adding a
third part, the subnet
number.
• The result is an address that
has the form network
number, subnet number, and
host number.
The IPv4 Address Crisis
• It is important to know
the difference between
private IP addressing
and public IP
addressing.
• They are private
addresses because
they are only known to
the company
administrator and not
known to the public.
The IPv4 Address Crisis
• NAT enables companies to keep
their private addresses secure and
not known to the public.
• NAT is enabled on a router or a
gateway device, which translates all
of the incoming and outgoing traffic
through the known, or public IP
addresses.
• The Internal IP address is different
and kept private from the external
public address that is exposed to
others through the Internet.
• The public IP addresses are what
allow people within the company to
access networks outside of the LAN.
IPv6
• Internet Protocol version 6 (IPv6) is the next
generation protocol designed to replace the current
version of the Internet Protocol, IPv4.
• IPv6 fixes a number of problems in IPv4, such as the
limited number of available IPv4 addresses.
• It will also add many improvements to IPv4 in routing
and in various network configuration tasks.
• IPv6 is expected to gradually replace IPv4, with the
two coexisting for a number of years during a
transition period.
Subnetting
• Subnets are similar to the
American telephone
numbering system.
• It is divided into area codes,
which are divided into
exchanges, and further
divided into individual
connections.
• Subnet addresses specify a
network number, a subnet
number, within the network,
and a host number within
the subnet.
Subnetting
• It is important to know how
many subnet/networks are
needed and how many
hosts will be allowed to be
on that network.
• With subnetting, the
network is not limited to the
standard Class A, B, or C
subnet masks and there is
more flexibility in the
network design.
Name Resolution
Overview of Name Resolution
• By their numerical form addresses are difficult to
remember and to manage. This is true when there is
a need to change addresses to adapt to changing
network conditions.
• Names are easy to work with. The technique that
allows names to represent network addresses is
called name resolution.
Hostnames and Host Tables
• On the network, each computer is
given a unique name to identify it.
This name is used to communicate
with a particular computer.
• To reach another computer, the
network needs to use the IP
address of that computer.
• Host tables are lists that can be
configured in each computer,
associating the names of the
computers in the network with the
IP address host table.
• The table includes the IP address
and the name that is mapped to
that address.
The Domain Name System
• Specialized servers within the
network accomplish the work of
translating names into
addresses.
• The DNS works like directory
assistance in the phone system.
• Using the phone system, a
person's name and address
may be known, but not their
phone number.
• A call to the directory assistance
produces the phone number that
matches the name and address.
Name Services and the NOS
• In a NOS, user programs
can access network devices
and services by name.
• All NOSs use DNS to
translate computer names
into IP addresses.
WINS
• To resolve or map the
NETBIOS names used by
applications into IP
addresses, Microsoft added
Windows Internet Naming
Service (WINS) as an
extension to DNS.
• WINS automates the
process of translating
NETBIOS names into IP
addresses so packets can
be properly delivered to
devices or services.
TCP/IP Protocols
Overview of TCP/IP protocols
• A protocol is a set of messages
that is exchanged between
systems in a defined sequence
in order to accomplish a specific
networking task.
• TCP/IP is a "suite" or collection
of different protocols, each one
performing a specialized task.
• In a well-functioning network, the
individual protocols are
coordinated so that, taken
together, they deliver network
services to application programs.
Address Resolution Protocol (ARP)
• The first system knows that the
second is located somewhere
on the network but does not
know its exact location on the
network.
• The source will broadcast an
ARP request to find the MAC
address of the intended
destinations MAC address.
• The signal sent is a broadcast
message and all the devices in
the LAN will hear it.
• Only the destination device will
respond to the ARP request.
Internet Control Message Protocol (ICMP)
• ICMP provides a set of error
and control messages to
help track and resolve
network problems.
• ICMP is used to send a
“destination unreachable”
message when there is an
error somewhere in the
network that is preventing
the frame or packet from
being forwarded to the
destination device.
Internet Control Message Protocol (ICMP)
• It includes a type of message,
called an Echo Request, which
can be sent from one host to
another to see if it is reachable
on the network.
• If it is reachable, the destination
host will reply with the ICMP
Echo Reply message.
• The Ping program uses ICMP to
send Echo Request messages
and to receive the Echo Reply
messages.
• An ICMP echo-request is
generated by the Ping command.
Transmission Control Protocol (TCP)
• The Transmission Control
Protocol (TCP) has the job
of guaranteeing that
messages arrive at their
destination, or if they cannot
be delivered, informing the
application programs of the
failure.
• Once a TCP connection is
made between two
applications, all the
messages flow from the
origin to the destination
over that logical connection.
User Datagram Protocol (UDP)
• User Datagram Protocol (UDP)
provides an "unreliable" service
to applications that can tolerate
a loss of some messages but
still function.
• Streams of video or audio data
fall into this category.
• UDP is:
– fast
– unreliable
– assumes applications will
retransmit on error
– often use diskless workstations
DHCP Services
• Dynamic Host Configuration
Protocol (DHCP) enables
computers on an IP network
to extract their configurations
from a DHCP server.
• When a computer on the
network needs an IP address,
it sends a request to a DHCP
server.
• The DHCP server can then
provide the host computer
with all the configuration
information it needs.
Hypertext Transport Protocol (HTTP)
• The Hypertext Transport
Protocol (HTTP) transfers
World Wide Web pages
between web browser client
programs like Netscape
Communicator or Internet
Explorer, and web servers
where web pages are
stored.
• HTTP defines the exact
format of the requests that
the browser sends as well
as the format of the replies
that the server returns.
File Transfer Protocol (FTP)
• FTP is a general-purpose
protocol that can be used to
copy all types of files from
one computer to another.
• FTP makes use of the TCP
reliable transport services to
establish a logical
connection between the
systems.
• FTP is one of the most
heavily used protocols on
the Internet.
Telnet
• Telnet enables interactive
terminal communications
with remote systems as if
they were directly
connected to the terminal,
even though there may be
many networks separating
the terminal from the
remote system.
• Users can type
commands to the system
as if they were directly
connected to it.
SMTP
• Simple Mail Transfer
Protocol (SMTP) is a
protocol for sending e-mail
messages between servers.
• The messages can then be
retrieved with an e-mail
client using either Post
Office Protocol (POP) or
Internet Message Access
Protocol (IMAP).
POP3
• Post Office Protocol version
3 (POP3) is a common mail
service protocol that is used
by ISPs that provide
Internet and e-mail service
to home customers.
• POP3 permits a workstation
to retrieve mail that the
server is holding.
IMAP
• Internet Message Access
Protocol (IMAP) is a newer email protocol that is more robust
than POP3.
• It is a method for accessing
electronic mail or bulletin board
messages that are kept on a
mail server.
• It is fully compatible with
Multipurpose Internet Mail
Extension (MIME) Internet
messaging standards, and it
allows message access and
management from more than
one computer.