Date post: | 06-Apr-2018 |
Category: |
Documents |
Upload: | sahil-wadhwa |
View: | 221 times |
Download: | 0 times |
of 37
8/2/2019 IPv4Overview
1/37
IPv4 Overview
8/2/2019 IPv4Overview
2/37
IP Protocol
This is host to host network layer connection less datagram
protocol with no guarantee of reliability. It is a unreliable protocol
bz it does not provide any error and flow control. It can only
detect the error and discard the corrupted packet.
IP Datagram
Packet in IP layer are called datagram.it is a variable length packet
with two parts Header and Data .The header is 20-60 bytes in
length and contains information required for routing and delivery.
data field is of variable length.
8/2/2019 IPv4Overview
3/37
Structure of IP frame header
8/2/2019 IPv4Overview
4/37
Version (VER). This 4-bit field defines the version of the IP protocol. Currently
the version is 4. However, version 6 may totally replace version 4 in the
future. This field tells the IPv4 software running in the processing machine that the
datagram has the format of version 4. All fields must be interpreted as specified
in the fourth version of the protocol. If the machine is using some other version of
IPv4, the datagram is discarded rather than interpreted incorrectly.
Header length (HLEN). This 4-bit field defines the total length of the datagram
header in 4-byte words. This field is needed because the length of the header
is variable (between 20 and 60 bytes). When there are no options, the header length
is 20 bytes, and the value of this field is 5 (5 x 4 = 20). When the option field is
at its maximum size, the value of this field is 15 (15 x 4 = 60).
Services. This is 8-bit field. This field, previously called service type, is now called
differentiated services.it defines the class of datagram for quality of service purpose.
Total length field defines the total length of the datagram including the header.
Length of data =total length - header length
Since the field length is 16 bits, the total length of the IPv4 datagram is limited to
65,535 (216 - 1) bytes, of which 20 to 60 bytes are the header and the rest is data.
8/2/2019 IPv4Overview
5/37
Identification:--This 16-bit field identifies a datagram originating from the source
host. When a datagram is fragmented, the value in the identification field is copied
to all fragments . The identification number helps the destination in reassembling
the datagram. It knows that all fragments having the same identification value
must be assembled into one datagram.
Flags:- This is a 3-bit field. The first bit is reserved and it should be zero. The
second bit is called the do not fragment bit. If its value is 1, the machine must not
fragment the datagram . If its value is 0, the datagram can be fragmented if
required. The third bit is called the more fragment bit. If its value is 1, it means the
datagram is not the last fragment; there are more fragments after this one. If its
value is 0, it means this is the last or only fragment.
More fragmentation bitDo not fragment bit Reserved bit
Fields Related to Fragmentation
8/2/2019 IPv4Overview
6/37
Fragmentation offset
This 13-bit field shows the relative position of this fragment with respect to the
whole datagram. It is the offset of the data in the original datagram measured in
units of 8 bytes.
8/2/2019 IPv4Overview
7/37
The bytes in the original datagram are numbered 0 to 3999. The first fragment
carries bytes 0 to 1399. The offset for this datagram is 0/8 =O. The second
fragment carries bytes 1400 to 2799; the offset value for this fragment is 1400/8
= 175. Finally, the third fragment carries bytes 2800 to 3999. The offset value
for this fragment is 2800/8 =350. Remember that the value of the offset ismeasured in units of 8 bytes. This forces hosts that fragment datagrams to
choose a fragment size so that the first byte number is divisible by 8.
Time to live. A datagram has a limited lifetime in its travel through an internet.
This field was designed to hold a timestamp, which was decremented by each
visited router. The datagram was discarded when the value became zero. all themachines must have synchronized clocks and must know how long it takes for
a datagram to go from one machine to another. this field is used mostly to
control the maximum number of routers visited by the datagram. When a
source host sends the datagram, it stores a number in this field. This value is 2
times the maximum number of routes between any two hosts. Each router thatprocesses the datagram decrements this number by 1.If this value is zero, the
router discards the datagram .
8/2/2019 IPv4Overview
8/37
This field is needed because routing tables in the Internet can
become corrupted . A datagram may travel between two or more
routers for a long time without ever getting delivered to thedestination host. This field limits the lifetime of a datagram .
this field is also used to intentionally limit the journey of the
packet. if the source wants to confine the packet to the local
network, it can store 1 in this field. When the packet arrives at the
first router, this value is decremented to 0, and the datagram is
discarded
8/2/2019 IPv4Overview
9/37
A no-operation option is a I-byte option used as a filler between options.
An end-of-option option is a I-byte option used for padding at the end of the option
field. It, however, can only be used as the last option.
A record route option is used to record the Internet routers that handle the datagram. Itcan list up to nine router addresses. It can be used for debugging and management
purposes.A strict source route option is used by the source to predetermine a route for the datagram
as it travels through the Internet. The sender can choose a route with a specific type of
service, such as minimum delay or maximum throughput. Alternatively, it may choose a
route that is safer or more reliable for the sender's purposeA loose source route option is similar to the strict source route, but it is less rigid. Each
router in the list must be visited, but the datagram can visit other routers as well.
A timestamp option is used to record the time of datagram processing by a router.
Knowing the time a datagram is processed can help users and managers track the
behavior of the routers in the Internet. We can estimate the time it takes for a datagram
to go from one router to another.
8/2/2019 IPv4Overview
10/37
Checksum
First the value of the checksum field is set to O. Then the entire header is
divided into 16-bit sections and added together. The result (sum) is
complemented and inserted into the
checksum field . The checksum in the IP packet covers only the header, not the
data. There are two good reasons for this.
First, all higher-level protocols that encapsulate data in the IP datagram have
a checksum field that covers the whole packet. Therefore, the checksum forthe IP datagram does not have to check the encapsulated data.
Second, the header of the IP packet changes with each visited router, but the
data do not. So the checksum includes only the part that has changed. If the
data were included, each router must recalculate the checksum for the whole
packet, which means an increase in processing time.
8/2/2019 IPv4Overview
11/37
Services provided by IP
Addressing32 bit address used by intermediate router to select a path
through the network for the packet. FragmentationIP packet may be split in to smaller packets. This permit a
large packet to travel through a n/w that can handle the smaller packets.
Packet time outtime to live
Address Space. IP uses 32-bit addresses . An address space is the total number of addresses
used by the protocol. IP uses 32-bit addresses, which means that the address
space is 232 or 4,294,967,296 (more than 4 billion).
8/2/2019 IPv4Overview
12/37
Protocol
This 8-bit field defines the higher-level protocol that uses the services of
the IP layer. An IP datagram can encapsulate data from several higher-levelprotocols such as TCP, UDP, ICMP, and IGMP. This field specifies the final
destination protocol to which the IP datagram is delivered. since the IP protocol
carries data from different other protocols, the value of this field helps the receiving
network layer know to which protocol the data belong
8/2/2019 IPv4Overview
13/37
Source address. This 32-bit field defines the IP address of the source. This fieldmust remain unchanged during the time the IP datagram travels from the source
host to the destination host.
Destination address. This 32-bit field defines the IP address of the destination .This field must remain unchanged during the time the IP datagram travels from the
source host to the destination host.
OptionsOptions, as the name implies, are not required for every datagram. They can be
used for network testing and debugging.
8/2/2019 IPv4Overview
14/37
IP Address
8/2/2019 IPv4Overview
15/37
IP Addresses:
Classful Addressing
8/2/2019 IPv4Overview
16/37
An IP address is a
32-bitaddress.
8/2/2019 IPv4Overview
17/37
The IP addressesare
unique.
8/2/2019 IPv4Overview
18/37
RULE:
addr15addr1
addr2
addr41addr31
addr226
....
....
..
....
If a protocol usesNbits to
define an address,the address space is 2N
because each bit can have two
different values (0 and 1)andNbits can have 2Nvalues.
8/2/2019 IPv4Overview
19/37
The address space of IPv4 is
232
or4,294,967,296.
An address space is the total number of addresses used by the
protocol.
8/2/2019 IPv4Overview
20/37
01110101 10010101 00011101 11101010
Binary Notation
8/2/2019 IPv4Overview
21/37
Dotted-decimal notation
8/2/2019 IPv4Overview
22/37
Every router and host on internet has a unique IP address .all IP address are of
32 bit and they use source and destination field of the IP header. The first part
of address is called network ID which identify the network on the internet and
second called the host ID used to identify the individual host on that network.
Classes of IP address :-
8/2/2019 IPv4Overview
23/37
Netid and hostid
8/2/2019 IPv4Overview
24/37
In classful addressing,
the address space is
divided into five classes:A,B, C,D, andE.
8/2/2019 IPv4Overview
25/37
Class Ranges of Internet Addresses
8/2/2019 IPv4Overview
26/37
Class A address
The n/w field is of 7 bit and the host field is of 24 bits . One bit is used for the class
type. So the n/w field can have numbers b/w 0 to 127. but the host number ranges from
0.0.0.0 to 127.255.255.255. hence in class A there can be 127 types of n/ws. bit 0 in fist
field indicates that it is class A n/w address.
27 26 25 24 23 22 21 20
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 1
.0 1 1 1 1 1 1 1
Samewaytotal number of host will be ranges from 0. 0.0.0 to 127. 255.255.255
0 7 bit / network ID 24 bit host ID
0
127
32 bit
8/2/2019 IPv4Overview
27/37
Millions of class A addressesare wasted.
8/2/2019 IPv4Overview
28/37
Class B address
The first field defines the class type and second field defines the
networks. And last field defines the hosts. The n/w field values lies
b/w 128 to 191.the first block covers the address from
128.0.0.0 to 128.255.255.255 and last block covers from 191.0.0.0 to
191.255.255.255.
10 14 bit / network id 16 bit / host id
10 (6 bit) 000000 8 bit( 00000000) Host id (8 + 8 )
Range from 0 to 255
Ranges from 128 to 191
32 bit
Range from 0 to 255
Range from 0 to 255
14 bits (6 + 8)
8/2/2019 IPv4Overview
29/37
Many class B addressesare wasted.
8/2/2019 IPv4Overview
30/37
Class C address32 bit
110 Network ID ( 21 bit) Host ID (8 bit)
110 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Host ID(8 bit)
21 bits(5+8+8)
110 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 HostID(8 bit)
272625 24 23 22 21 20 27 26 25 24 23 22 21 20 27 26 25 24 23 22 21 20
00192
110 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 HostID(8 bit)
223
255255
0
255
192.0.0.0
223.255.255.255
8/2/2019 IPv4Overview
31/37
Class C address32 bit
110 Network ID ( 21 bit) Host ID (8 bit)
110 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Host ID(8 bit)
21 bits(5+8+8)
110 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 HostID(8 bit)
272625 24 23 22 21 20 27 26 25 24 23 22 21 20 27 26 25 24 23 22 21 20
00192
110 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 HostID(8 bit)
223
255255
0
255
192.0.0.0
223.255.255.255
8/2/2019 IPv4Overview
32/37
Class D address
1110 Multicast ID
32 bit
1 1 1 0 4 bit 8 bit 8 bit 8 bit
1 1 1 0 0 0 0 0 00000000 0000000 0000000
27 26 25 24 23 22 21 20
00
0224
224.0.0.0
1 1 1 0 1 1 1 1 11111111 11111111 1111111127 26 25 24 23 22 21 20
239
255255 255
239.255.255.255
8/2/2019 IPv4Overview
33/37
Class D addresses
are used for multicasting;
there is only
one block in this class.
Cl E dd
8/2/2019 IPv4Overview
34/37
Class E address
1111 Reserved for future use
32 bit
1 1 1 1 4 bit 8 bit 8 bit 8 bit
1 1 1 1 0 0 0 0 00000000 0000000 0000000
27 26 25 24 23 22 21 20
00
0240
240.0.0.0
1 1 1 1 1 1 1 1 11111111 11111111 1111111127 26 25 24 23 22 21 20
255
255255 255
255.255.255.255
8/2/2019 IPv4Overview
35/37
Class E addresses are reserved
for special purposes;most of the block is wasted.
Fi di th dd l
8/2/2019 IPv4Overview
36/37
Finding the address class
8/2/2019 IPv4Overview
37/37
Finding the class in decimal notation