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Data and Computer
Communications
Chapter 18 – Internet Protocols
Ninth Edition
by William Stallings
Data and Computer Communications, Ninth
Edition by William Stallings, (c) Pearson
Education - Prentice Hall, 2011
Internet
internet
an interconnected set of networks where each of
the constituent networks retains its identity
end
systems
devices attached to a network
intermediate
systems
provide a communications path and perform the
necessary relaying and routing functions
bridges
acts as a relay of frames between similar networks
routers
routes packets between potentially different networks

Internetworking
Terms
TCP/IP Concepts
Differences in Networks
addressing
schemes
maximum packet size
network access mechanisms
timeouts
error recovery
status reporting
routing techniques
user access control
connection, connectionless
Connectionless Operation
Internetworking
involves connectionless
operation at the level of the Internet Protocol
(IP)
IP
initially developed for the DARPA
internet project
protocol is needed to access a particular
network
Connectionless Internetworking
Connectionless
internet facility is flexible
IP provides a connectionless service
between end systems.

Advantages:
is flexible
can be made robust
does not impose unnecessary overhead
IP
Operation
LAPF : link access
protocol for frame
(frame relay)
IP Design Issues
routing
datagram
lifetime
fragmentation and reassembly
error control
flow control
Internet Protocol (IP) v4
defined

in RFC 791
www.rfc-editor.org
part
of TCP/IP suite
two parts
specification of
interface with a
higher layer
specification of
actual protocol
format and
mechanisms
IP Services
Primitives
specifies functions to be
performed
form of primitive
implementation
dependent
Send : request
transmission of data unit
Deliver : notify user of
arrival of data unit

Parameters
used to pass data and
control information

IP Parameters
source & destination addresses
protocol
type of Service
identification
“don’t fragment” indicator
time to live
data length
option data
user data
IPv4 Header
IPv4 Header
http://www.tcpipguide.com/free/t_IPDatagr
amGeneralFormat.htm
Important:
the « Protocol » field identifies
the nature of the next header (in the data
portion of the IP packet) Ex: TCP, ICMP
http://www.iana.org/assignments/protocolnumbers/protocol-numbers.xml

IPv4 Address Formats
IP Addresses - Class A
start
with binary 0
all 0 reserved
01111111 reserved for loopback
(localhost 127.0.0.1)
range
1.x.x.x to 126.x.x.x
IP Addresses - Class B
start
with binary 10
range 128.x.x.x to 191.x.x.x
second octet also included in network
address
214 = 16,384 class B addresses
IP Addresses - Class C
start
with binary 110
range 192.x.x.x to 223.x.x.x
second and third octet also part of network
address
221 = 2,097,152 addresses
nearly all allocated

see IPv6
IP Addresses
Decimal
code to simplify address
management.
00001010

00000000 00000000 00000000 = 10.0.0.0 (classe A)
Class A examples:

BBN (4.0.0.0) , General Electric (3.0.0.0),
Hewlett-Packard (15.0.0.0), Apple (17.0.0.0), AT&T
(12.0.0.0), IBM (9.0.0.0), DEC (16.0.0.0), MIT
(18.0.0.0)

Class B example : UQAC (132.212.0.0)
IP Addresses
IP


addresses index :
http://cqcounter.com/whois/ip/
(http://www.ip2location.com/)
IP Addresses
Special cases :

"loopback address" : 127.0.0.1
Non-routable addresses :
10.0.0.0
à 10.255.255.255
172.16.0.0 à 172.31.255.255
192.168.0.0 à 192.168.255.255
if hostid = 111....1, "broadcast" in the local network

Addresses assigned by central organisations
IANA (ARIN, RIPR NCC, LACNIC and APNIC)
InterNIC: www.internic.net (http://www.internic.ca/)
Godaddy
Subnets and Subnet Masks
allows
arbitrary complexity of internetworked
LANs within organization
insulate overall internet from growth of network
numbers and routing complexity
site looks to rest of internet like single network
each LAN assigned subnet number
host portion of address partitioned into subnet
number and host number
local routers route within subnetted network
subnet mask indicates which bits are subnet
number and which are host number
IP Addresses and Subnet Masks
Subnet mask:

Allows to define netid and subnetid
Subnets and Subnet Masks
When

the default gateway is actually used
Decision based on netmask
Subnets and Subnet Masks
Obtaining an IP address
DHCP
:
dynamic host configuration protocol
belongs to the application layer
uses UDP port 68 on the client and port 67 on
the server
see figure in

http://wiki.cas.mcmaster.ca/index.php/Dynamic_
Host_Configuration_Protocol

Information sent by DHCP server
Default gateway
Domain name
Name servers …
Address Resolution Protocol
(ARP)
Address Resolution Protocol
(ARP)
Sequence of events :
•See
http://www.tcpipguide.com/free/t_ARPAddressSpecificationandGeneralOperation-2.htm
To read the arp table on a PC :
arp -a