Fiber Optical Networks and Data Communication

FarhanGhafoor7 15 views 59 slides Jul 03, 2024
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Slide Content

Software Engineering Departments
COE (College of Engineering
Lecture 11
Network Layer:
Logical Addressing
Computer Communication and Networks
Engr. Farhan Ghafoor

19.2
19-1 IPv4 ADDRESSES
AnIPv4addressisa32-bitaddressthatuniquelyand
universallydefinestheconnectionofadevice(for
example,acomputerorarouter)totheInternet.
Address Space
Notations
Classful Addressing
Classless Addressing
Network Address Translation (NAT)
Topics discussed in this section:

19.3
An IPv4 address is 32 bits long.
Note

19.4
The IPv4 addresses are unique
and universal.
Note

19.5
The address space of IPv4 is
2
32
or 4,294,967,296.
Note

19.6
Figure 19.1 Dotted-decimal notation and binary notation for an IPv4 address

19.7
Numbering systems are reviewed in
Appendix B.
Note

19.8
ChangethefollowingIPv4addressesfrombinary
notationtodotted-decimalnotation.
Example 19.1
Solution
Wereplaceeachgroupof8bitswithitsequivalent
decimalnumber(seeAppendixB)andadddotsfor
separation.

19.9
ChangethefollowingIPv4addressesfromdotted-decimal
notationtobinarynotation.
Example 19.2
Solution
Wereplaceeachdecimalnumberwithitsbinary
equivalent(seeAppendixB).

19.10
Findtheerror,ifany,inthefollowingIPv4addresses.
Example 19.3
Solution
a.There must be no leading zero (045).
b.There can be no more than four numbers.
c.Each number needs to be less than or equal to 255.
d.A mixture of binary notation and dotted-decimal
notation is not allowed.

19.11
In classful addressing, the address
space is divided into five classes:
A, B, C, D, and E.
Note

19.12
Figure 19.2 Finding the classes in binary and dotted-decimal notation

19.13
Findtheclassofeachaddress.
a.00000001000010110000101111101111
b.11000001100000110001101111111111
c.14.23.120.8
d.252.5.15.111
Example 19.4
Solution
a.The first bit is 0. This is a class A address.
b.The first 2 bits are 1; the third bit is 0. This is a class C
address.
c.The first byte is 14; the class is A.
d.The first byte is 252; the class is E.

19.14
Table 19.1 Number of blocks and block size in classful IPv4 addressing

19.15
In classful addressing, a large part of the
available addresses were wasted.
Note

19.16
Table 19.2 Default masks for classful addressing

19.17
Classful addressing, which is almost
obsolete, is replaced with classless
addressing.
Note

19.18
Figure19.3showsablockofaddresses,inbothbinary
anddotted-decimalnotation,grantedtoasmallbusiness
thatneeds16addresses.
Wecanseethattherestrictionsareappliedtothisblock.
Theaddressesarecontiguous.Thenumberofaddresses
isapowerof2(16=2
4
),andthefirstaddressisdivisible
by16.Thefirstaddress,whenconvertedtoadecimal
number,is3,440,387,360,whichwhendividedby16
resultsin215,024,210.
Example 19.5

19.19
Figure 19.3 A block of 16 addresses granted to a small organization

19.20
In IPv4 addressing, a block of
addresses can be defined as
x.y.z.t /n
in which x.y.z.t defines one of the
addresses and the /ndefines the mask.
Note

19.21
The first address in the block can be
found by setting the rightmost
32 − nbits to 0s.
Note

19.22
Ablockofaddressesisgrantedtoasmallorganization.
Weknowthatoneoftheaddressesis205.16.37.39/28.
Whatisthefirstaddressintheblock?
Solution
Thebinaryrepresentationofthegivenaddressis
11001101 00010000 00100101 00100111
If we set 32−28 rightmost bits to 0, we get
11001101 00010000 00100101 0010000
or
205.16.37.32.
This is actually the block shown in Figure 19.3.
Example 19.6

19.23
The last address in the block can be
found by setting the rightmost
32 − n bits to 1s.
Note

19.24
FindthelastaddressfortheblockinExample19.6.
Solution
The binary representation of the given address is
11001101 00010000 00100101 00100111
If we set 32 − 28 rightmost bits to 1, we get
11001101 00010000 00100101 00101111
or
205.16.37.47
This is actually the block shown in Figure 19.3.
Example 19.7

19.25
The number of addresses in the block
can be found by using the formula
2
32−n
.
Note

19.26
FindthenumberofaddressesinExample19.6.
Example 19.8
Solution
Thevalueofnis28,whichmeansthatnumber
ofaddressesis2
32−28
or16.

19.27
Anotherwaytofindthefirstaddress,thelastaddress,and
thenumberofaddressesistorepresentthemaskasa32-
bitbinary(or8-digithexadecimal)number.Thisis
particularlyusefulwhenwearewritingaprogramtofind
thesepiecesofinformation.InExample19.5the/28can
berepresentedas
11111111 11111111 11111111 11110000
(twenty-eight1sandfour0s).
Find
a.Thefirstaddress
b.Thelastaddress
c.Thenumberofaddresses.
Example 19.9

19.28
Solution
a.ThefirstaddresscanbefoundbyANDingthegiven
addresseswiththemask.ANDinghereisdonebitby
bit.TheresultofANDing2bitsis1ifbothbitsare1s;
theresultis0otherwise.
Example 19.9 (continued)

19.29
b.ThelastaddresscanbefoundbyORingthegiven
addresseswiththecomplementofthemask.ORing
hereisdonebitbybit.TheresultofORing2bitsis0if
bothbitsare0s;theresultis1otherwise.The
complementofanumberisfoundbychangingeach1
to0andeach0to1.
Example 19.9 (continued)

19.30
c.Thenumberofaddressescanbefoundby
complementingthemask,interpretingitasadecimal
number,andadding1toit.
Example 19.9 (continued)

19.31
Figure 19.4 A network configuration for the block 205.16.37.32/28

19.32
The first address in a block is
normally not assigned to any device;
it is used as the network address that
represents the organization
to the rest of the world.
Note

19.33
Figure 19.5 Two levels of hierarchy in an IPv4 address

19.34
Figure 19.6 A frame in a character-oriented protocol

19.35
Each address in the block can be
considered as a two-level
hierarchical structure:
the leftmost nbits (prefix) define
the network;
the rightmost 32 − n bits define
the host.
Note

19.36
Figure 19.7 Configuration and addresses in a subnetted network

19.37
Figure 19.8 Three-level hierarchy in an IPv4 address

19.38
AnISPisgrantedablockofaddressesstartingwith
190.100.0.0/16(65,536addresses).TheISPneedsto
distributetheseaddressestothreegroupsofcustomersas
follows:
a.Thefirstgrouphas64customers;eachneeds256
addresses.
b.Thesecondgrouphas128customers;eachneeds128
addresses.
c.Thethirdgrouphas128customers;eachneeds64
addresses.
Designthesubblocksandfindouthowmanyaddresses
arestillavailableaftertheseallocations.
Example 19.10

19.39
Solution
Figure19.9showsthesituation.
Example 19.10 (continued)
Group1
Forthisgroup,eachcustomerneeds256addresses.This
meansthat8(log2256)bitsareneededtodefineeach
host.Theprefixlengthisthen32−8=24.Theaddresses
are

19.40
Example 19.10 (continued)
Group2
Forthisgroup,eachcustomerneeds128addresses.This
meansthat7(log2128)bitsareneededtodefineeach
host.Theprefixlengthisthen32−7=25.Theaddresses
are

19.41
Example 19.10 (continued)
Group3
Forthisgroup,eachcustomerneeds64addresses.This
meansthat6(log264)bitsareneededtoeachhost.The
prefixlengthisthen32−6=26.Theaddressesare
NumberofgrantedaddressestotheISP:65,536
NumberofallocatedaddressesbytheISP:40,960
Numberofavailableaddresses:24,576

19.42
Figure 19.9 An example of address allocation and distribution by an ISP

19.43
Table 19.3 Addresses for private networks

19.44
Figure 19.10 A NAT implementation

19.45
Figure 19.11 Addresses in a NAT

19.46
Figure 19.12 NAT address translation

19.47
Table 19.4 Five-column translation table

19.48
Figure 19.13 An ISP and NAT

19.49
19-2 IPv6 ADDRESSES
Despiteallshort-termsolutions,addressdepletionis
stillalong-termproblemfortheInternet.Thisand
otherproblemsintheIPprotocolitselfhavebeenthe
motivationforIPv6.
Structure
Address Space
Topics discussed in this section:

19.50
An IPv6 address is 128 bits long.
Note

19.51
Figure 19.14 IPv6 address in binary and hexadecimal colon notation

19.52
Figure 19.15 Abbreviated IPv6 addresses

19.53
Expandtheaddress0:15::1:12:1213toitsoriginal.
Example 19.11
Solution
Wefirstneedtoaligntheleftsideofthedoublecolonto
theleftoftheoriginalpatternandtherightsideofthe
doublecolontotherightoftheoriginalpatterntofind
howmany0sweneedtoreplacethedoublecolon.
Thismeansthattheoriginaladdressis.

19.54
Table 19.5 Type prefixes for IPv6 addresses

19.55
Table 19.5 Type prefixes for IPv6 addresses (continued)

19.56
Figure 19.16 Prefixes for provider-based unicast address

19.57
Figure 19.17 Multicast address in IPv6

19.58
Figure 19.18 Reserved addresses in IPv6

19.59
Figure 19.19 Local addresses in IPv6
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