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TCP/IP
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Figure 24-1
An Internet According to TCP/IP
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Figure 24-2
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TCP/IP and the OSI Model
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Comparison between OSI and TCP/IP
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Figure 24-3
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IP Packet
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Figure 24-4
Internet Address
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Figure 24-5
Internet Classes
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Figure 24-6
IP Addresses in Decimal Notation
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Figure 24-7
Class Ranges of Internet Addresses
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Figure 24-8
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Network and Host Addresses
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Figure 24-9
A Network with Two Levels of Hierarchy
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Figure 24-10
A Network with Three Levels of Hierarchy
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Figure 24-11
Addresses with and without Subnetting
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Figure 24-12
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Masking
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Figure 24-12
Private and Reserved Addresses
The following addresses are reserved for private
use. They are typically non-routing.
Network address
Default mask
10.0.0.0
255.0.0.0
172.16.0.0
255.240.0.0
192.168.0.0
255.255.0.0
127.0.0.0 is reserved for loopback and is
used for internal testing on the local machine.
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Figure 24-12
Where Do I Get an IP Address?
Three regional Internet registries assign
Internet Protocol addresses –
•ARIN
•RIPE
•NCC
•APNIC
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Figure 24-12
Where Do I Get an IP Address?
Because IP addresses are in such short supply
due to inefficient assignment of addresses,
it’s nearly impossible anymore
for anyone but an Internet Service Provider
to get an address from one of these agencies.
We now get our addresses from our Internet
Service Providers.
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Figure 24-12
Classes and Classless
Class A - supports 16 million hosts on each
of 127 networks
Class B - supports 65,000 hosts on each
of 16,000 networks
Class C - supports 254 hosts on each
of 2 million networks
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Figure 24-12
Classes and Classless
Of the total address space:
50% is assigned to class A networks
25% is assigned to class B networks
12.5% is assigned to class C networks
A very small fraction of class A addresses
have been assigned to workstations.
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Figure 24-12
Classes and Classless
Because of this inefficient assignment of
addresses, longer addresses and the idea of
classless addresses was developed.
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Figure 24-12
IPv4 vs IPv6
IPv6 was developed because of the shortage of
IP addresses.
IPv4- 32 bit addresses, about 4 billion
IPv6- 128 bit addresses, about 4 billion billion
However, if these addresses are not assigned
efficiently, even this may not be enough
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Figure 24-12
IPv4 vs IPv6
Along with IPv6, a classless structure was
proposed. Networks were defined on the bit
level, rather than at a multibit level
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Figure 24-12
CIDR
CIDR stands for Classless InterDomain Routing.
It is also sometimes called Supernetting.
The idea is to subnet based at the bit.
CIDR notation looks like this:
•Class A = /8
•Class B = /16
•Class C = /24)
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Figure 24-12
CIDR
The number after the “/” is the number of bits
in the subnet mask
Class A = /8
For example: 9.0.0.0, with subnet mask of
255.0.0.0, or 11111111.0.0.0
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Figure 24-12
CIDR
The number after the “/” is the number of bits
in the subnet mask
Class B = /16
129.233.0.0, subnet mask 255.255.0.0,
11111111.11111111.0.0
Class C = /24)
192.60.128.0, subnet mask 255.255.255.0,
11111111.11111111.11111111.0
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Figure 24-12
CIDR
What happens if you want a network larger
than 254 nodes? Say, about 1000?
You can combine 4 class C addresses,
192.60.128.0-192.60.131, and change the
subnet mask.
192.60.128.0 /22, subnet mask 255.255.252.0,
11111111.11111111.11111100.00000000
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Figure 24-12
CIDR
The network address is calculated by ANDing the
associated class C IP addresses.
192.60.128.0
192.60.129.0
192.60.130.0
192.60.131.0
192.60.128.0
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(11000000.00111100.10000000.00000000)
(11000000.00111100.10000001.00000000)
(11000000.00111100.10000010.00000000)
(11000000.00111100.10000011.00000000)
(11000000.00111100.10000000.00000000)
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Local Login
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Remote Login
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Telnet
Telnet is a terminal emulation program for TCP/IP networks such as
the Internet. The Telnet program runs on your computer and
connects your PC to a server on the network. You can then enter
commands through the Telnet program and they will be executed as
if you were entering them directly on the server console. This
enables you to control the server and communicate with other
servers on the network. To start a Telnet session, you must log in to
a server by entering a valid username and password. Telnet is a
common way to remotely control Web servers.
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FTP
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FTP
File Transfer Protocol, or FTP, is a protocol used to upload
files from a workstation to a FTP server or download files
from a FTP server to a workstation. It is the way that files
get transferred from one device to another in order for the
files to be available on the Internet. When ftp appears in a
URL it means that the user is connecting to a file server and
not a Web server and that some form of file transfer is going
to take place. Most FTP servers require the user to log on to
the server in order to transfer files.
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HTTP
In contrast, Hyper Text Transfer Protocol, or HTTP, is a
protocol used to transfer files from a Web server onto a
browser in order to view a Web page.
Unlike FTP, where entire files are transferred from one
device to another and copied into memory and then disk,
HTTP only transfers the contents of a web page into a
browser for viewing. FTP is a two-way system as files
are transferred back and forth between server and
workstation. HTTP is a one-way system as files are
transported only from the server onto the workstation's
browser. When http appears in a URL it means that the
user is connecting to a Web server and not a file server.
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SNMP Concept
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SNMP Messages
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Figure 24-13
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ARP
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TFTP
Abbreviation of Trivial File Transfer Protocol, a simple
form of the File Transfer Protocol (FTP). TFTP uses the
User Datagram Protocol (UDP)and provides no security
features. It is often used by servers to boot diskless
workstations, X-terminals, and routers.
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NFS
Abbreviation of Network File System, a client/server
application designed by Sun Microsystems that allows
all network users to access shared files stored on
computers of different types. NFS provides access to
shared files through an interface called the Virtual File
System (VFS) that runs on top of TCP/IP. Users can
manipulate shared files as if they were stored locally
on the user's own hard disk. Originally called Yellow
Pages.
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SMTP
• Short for Simple Mail Transfer Protocol, a protocol for
sending e-mail messages between servers.
• Most e-mail systems that send mail over the Internet use
SMTP to send messages from one server to another; the
messages can then be retrieved with an e-mail client using
either POP3 or IMAP.
• In addition, SMTP is generally used to send messages from
a mail client to a mail server. This is why you need to
specify both the POP3 or IMAP server and the SMTP
server when you configure your e-mail application.
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DNS
Short for Domain Name System. It translates domain
names into IP addresses. Because domain names are
alphabetic, they're easier to remember. A network however,
is really based on IP addresses. Every time you use a
domain name, therefore, a DNS service must translate
the name into the corresponding IP address. For
example, the domain name www.example.com
might translate to 192.0.34.166
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Bootp or Bootstrap
Short for Bootstrap Protocol, an Internet protocol that
enables a diskless device to discover its own IP
address, the IP address of a BOOTP server on the network,
and a file to be loaded into memory to boot the machine.
This enables the workstation to boot without requiring a
hard or floppy disk drive. The protocol is defined by
RFC 951. It uses TFTP, and thus UDP
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DHCP
Short for Dynamic Host Configuration Protocol, a protocol
for assigning dynamic IP addresses to devices on a network.
With dynamic addressing, a device can have a different IP
address every time it connects to the network. In some
systems, the device's IP address can even change while it
is still connected. DHCP also supports a mix of static and
dynamic IP addresses.
A DHCP server may also provide subnet mask, domain
Name, default gateway and DNS server
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Figure 24-15
UDP Datagram Format
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Figure 24-16
TCP Segment Format
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Ports
• Ports are the addresses for a process in the
TCP/UDP layer of the TCP/IP protocol
stack.
• When a workstation makes a request across
the network, it’s not enough that the reply
comes back to the same workstation. It
must also come back to the same process
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Ports
• For example, you may decide to start
downloading a file using FTP (port 21).
While doing so you also decide to look at
web pages using HTTP (port 80). The
replies will come back to the same machine,
but will be dealt with by a different process.
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Figure 24-14
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Port Addresses
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Ports
• http://support.fishnetsecurity.com/scripts/fis
hnet/portnumbers/portnumbers.asp allows
you to enter a protocol and get the port
associated with that protocol.
• http://www.iana.org/assignments/portnumbers is the site of the organization,
IANA, that assigns port numbers. It has a
complete list of ports in ASCII format
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Ports
• Ports are broken up into three sections:
– The Well Known Ports are those from 0
through 1023.
– The Registered Ports are those from 1024
through 49151
– The Dynamic and/or Private Ports are those
from 49152 through 65535
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Ports
• The Well Known Ports are assigned by the
IANA and on most systems can only be
used by system (or root) processes or by
programs executed by privileged users.
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Ports
• The Well Known Ports are assigned and
controlled by IANA. Some UDP ports you
may be familiar with include:
–
–
–
–
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69
111
161
162
TFTP
RPC
SNMP
SNMP trap
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Ports
• Some well-known TCP ports you may be
familiar with include:
–
–
–
–
–
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20
21
23
53
80
FTP data
FTP control
Telnet
DNS
HTTP
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Ports
• The Registered Ports are those from 1024
through 49151
• The Registered Ports are listed by the IANA
and on most systems can be used by
ordinary user processes or programs
executed by ordinary users.
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Ports
• The Dynamic and/or Private Ports are those
from 49152 through 65535. These can be
used by any process or user at any time,
without restriction.
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Ports
• Ports are used in the TCP [RFC793] to
name the ends of logical connections which
carry long term conversations. For the
purpose of providing services to unknown
callers, a Service Contact Port is defined.
This specifies the port used by the server,
such as a NAT server, as its contact port.
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Ports
• Ports are assigned at each end of the conversation
by the software.
• Some protocols use the same port every time,
while others choose a different port for each
conversation.
• Although both ends must assign a port number,
they don’t necessarily have to assign the same port
number.
• Both UDP and TCP use ports.
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Sockets
• A socket is a combination of the IP address
from the packet and the port number from
the TCP or UDP address field. Together
they uniquely define both the client and
process.
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IP
• Internet Protocol provides a way to get data
from network to network.
• The IP packet contains the IP address.
• It provides for a variable length data field
• It specifies which protocol it will
encapsulate (eg TCP, UDP, etc)
• It has provision to limit the life of the
packet
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IP
• It provides for fragmentation of packets as
they go from network to network
• It can handle a maximum datagram size of
65,535 bytes, which can be broken down for
other network types including FDDI
(4,352), Ethernet (1500), and X.25 (576).
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PING
• Ping is a protocol hacked together early on
in the development of networking
• Its function is to check to see if a network
device is up and running
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PING
• Ping is popularly defined as standing for Packet
INternet Groper, is the definition given by Dave
Mills, author of NTP and claimed author of PING
• Mike Muus, (died Oct. 2000 in a traffic accident),
also claimed authorship. He said that the name
had no such origin. He named it after the
echolocation method used by submariners, which,
in turn, was named after the sound the method
made.
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PING
• Whoever originally wrote it, ICMP is a protocol in
the TCP layer which uses two types of messages:
Error-Reporting and Query
• Query uses one of four types of messages,
including Echo Request and Reply.
• Ping combines the Echo Request and Reply
function of ICMP with UDP in an IP packet to
validate whether a node is functioning
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PING
• Ping Time is the time it takes for a packet to
go from the source to destination and back
again, including all delays from
intermediate routers, processing delays, and
network congestion delays.
• The ping protocol is not a single protocol.
It uses a combination of protocols; ICMP
and UDP
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