IP Addressing Part1 2016

8/17/2019 IP Addressing Part1 2016

http://slidepdf.com/reader/full/ip-addressing-part1-2016 1/64

1

Network Layer:Internet Protocol



2

INTERNETWORKINGINTERNETWORKING

In this section, we discuss internetworking, connecting In this section, we discuss internetworking, connecting

networks together to make an internetwork or annetworks together to make an internetwork or an

internet.internet.

Need for Network Layer

Internet as a Datagram Network

Internet as a Connectionless Network

Topics discussed in this section:To

pics discussed in this section:



3

Figure Links between two hosts



4

Figure Network layer in an internetwork



5

Figure Network layer at the source, router, and destination



6

Figure Network layer at the source, router, and destination (continued)



Switching at the network layer in theInternet uses the datagra a!!roach to

!acket switching"


http://slidepdf.com/reader/full/ip-addressing-part1-2016 8/64#

$ounication at the network layer inthe Internet is connectionless"


http://slidepdf.com/reader/full/ip-addressing-part1-2016 9/64%

IPv4IPv4

The Internet Protocol ersion ! ( The Internet Protocol ersion ! ( IP! IP! ) is the deliery ) is the deliery

mechanism used by the T"P#IP protocols.mechanism used by the T"P#IP protocols.

Datagram

Fragmentation

Checksum

Options

Topics discussed in this section:To pics discussed in this section:


http://slidepdf.com/reader/full/ip-addressing-part1-2016 10/641&

The Internet has chosen the datagram approach to switching

in the network layer. It uses the universal addresses definedin the network layer to route packets from the source to the

destination.



Datagram

Packets in the IPv4 layer are called datagrams. Figure

shows the IPv4 datagram format.



Figure Position o$ IP! in T"P#IP protocol suite



Figure IP! datagram $ormat



15

Figure 20. %erice type or di$$erentiated serices

a. Precedence is a ,-bit subfield ranging from ' $''' in binary% to $ in

binary%. The precedence de.ines the !riority o. the datagra in issues

such as congestion. If a router is congested and needs to discard some

datagrams" those datagrams with lowest !recedence are discarded

.irst"

b. T/* bits is a 4-bit subfield with each bit having a s!ecial eaning"

0lthough a bit can be either ' or " one and only one o. the /its can

ha-e the -alue o. 1 in each datagram. The bit patterns and their

interpretations are given in Table.



16

Figure %erice type or di$$erentiated serices



17

0he !recedence su/.ield was !art o.-ersion 4 /ut ne-er used"



1#

!a"le Types o$ serice

!!lication !rogras can reuest a s!eci.ic ty!e o. ser-ice. The

defaults for some applications are shown in Table ne+t



1%

!a"le &e$ault types o$ serice



2&

2" i..erentiated Ser-ices: In this interpretation" the .irst 6 /its ake u!

the code!oint su/.ield" and the last 2 /its are not used. The codepoint

subfield can be used in two different ways.

a%1hen the 3 rightost /its are &s" the 3 le.tost /its are inter!reted

the sae as the !recedence /its in the service type interpretation. In

other words" it is compatible with the old interpretation.

b%1hen the 3 rightost /its are not all &s" the 6 /its de.ine 64 ser-icesbased on the priority assignment by the Internet or local authorities

according to Table . 0he .irst category contains 32 ser-ice types2 the

second and the third each contain 16"

The first category $nu/ers & 24 """ 62+ is assigned by the Internetauthorities $I(TF%. The second category (3 7 11 15 63% can be used

by local authorities $organi3ations%. The third category $1 5 % 61% is

temporary and can be used for e+perimental purposes.



21

!a"le 'alues $or codepoints

i..erentiated Ser-ices: In this interpretation" the first # bits make up the

codepoint subfield" and the last & bits are not used. The codepoint subfield

can be used in two different ways.



22

0he total length .ield de.ines the totallength o. the datagra including the

header"

0otal length. This is a In-bit field that defines the total length $header

plus data% of the IPv4 datagram in bytes.



23

Figure ncapsulation o$ a small datagram in an thernet $rame



24

Figure Protocol $ield and encapsulated data

Protocol" This )-bit field defines the higherle-el !rotocol that uses the

services of the IPv4 layer. 0n IPv4 datagram can encapsulate data fromseveral higher-level protocols such as TP" DP" I5P" and I65P.



25

!a"le Protocol alues

#$ample



26

n IP! packet has arried with the $irst * bits as shown:

++++++

The receier discards the packet. -hy

%olution

There is an error in this packet. The 4 leftmost bits (0100)

show the version, which is correct. The next 4 bits (0010)

show an invalid header length (2 × 4 = 8). The minimum

number of bytes in the header must be 20 . The packet has

been corrupted in transmission.

#$ample

l



27

In an IP! packet, the alue o$ /LN is +++ in binary.

/ow many bytes o$ options are being carried by this

packet

%olution

The HLEN value is 8, which means the total number of

bytes in the header is 8 × 4, or 32 bytes. The first 20 bytes

are the base header, the next 12 bytes are the options.

0ample

l



2#

In an IP! packet, the alue o$ /LN is 1, and the alue

o$ the total length $ield is +0++2*. /ow many bytes o$

data are being carried by this packet

%olution

The HLEN value is 5, which means the total number of

bytes in the header is 5 × 4, or 20 bytes (no options). The

total length is 40 bytes, which means the packet is

carrying 20 bytes of data (40 − 20).

0ample

# l



2%

$hecksu. The checksum concept and its calculation.

Source address. This ,&-bit field defines the IPv4 address of the source.

This field must remain unchanged during the time the IPv4 datagram

travels from the source host to the destination host.

estination address" This ,&-bit field defines the IPv4 address of thedestination. This field must remain unchanged during the time the IPv4

datagram travels from the source host to the destination host.

#$ample

# l



3&

n IP! packet has arried with the $irst $ew he0adecimal

digits as shown.

+0!1++++2*+++++++++2 . . .

/ow many hops can this packet trael be$ore being

dropped The data belong to what upper3layer protocol

%olution

To find the time-to-live field, we skip 8 bytes. The time-to-

live field is the ninth byte, which is 01. This means the packet can travel only one hop. The protocol field is the

next byte (02), which means that the upper-layer protocol

is IGMP.

#$ample

ragentation



31

ragentation

0 datagram can travel through different networks. (ach router

decapsulates the IPv4 datagram from the frame it receives"processes it" and then encapsulates it in another frame.

8a9iu 0rans.er nit (80+

(ach data link layer protocol has its own frame format in most

protocols. /ne of the fields defined in the format is the ma+imumsi3e of the data field.

To make the IPv4 protocol independent of the physical network"

the designers decided to make the ma+imum length of the IPv4

datagram e7ual to #8"8,8 bytes.

Fi ld R l t d t F t ti



32

Fields Related to Fragmentation

0 datagram can travel through different networks. (ach router

decapsulates the IPv4 datagram from the frame it receives"processes it" and then encapsulates it in another frame.

8a9iu 0rans.er nit (80+

(ach data link layer protocol has its own frame format in most

protocols. /ne of the fields defined in the format is the ma+imumsi3e of the data field.

To make the IPv4 protocol independent of the physical network"

the designers decided to make the ma+imum length of the IPv4

datagram e7ual to #8"8,8 bytes.




33


Identi.ication" This #-bit field identifies a datagram originating from

the source host. The combination of the identification and source IPv4

address must uni7uely de.ine a datagra as it lea-es the sourcehost.

lags" This is a ,-bit field. The first bit is reserved. The second bit is

called the do notfragment bit. If its value is " the machine must not

fragment the datagram. If it cannot pass the datagram through anyavailable physical network" it discards the datagram and sends an

I5P error message to the source host $see hapter &%. If its value

is '" the datagram can be fragmented if necessary. The third bit is

called the more fragment bit. If its value is " it means the datagram is

not the last fragment2 there are more fragments after this one. If itsvalue is '" it means this is the last or only fragment.

ragentation o..set" This ,-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 ) bytes.



34

Figure 4a0imum trans$er unit (4T5)



2&"35

!a"le 4T5s $or some networks



36

Figure 6lags used in $ragmentation



37

Figure 6ragmentation e0ample

/riginal datagram are numbered ' to ,999.



0ample



3%

packet has arried with an 4 bit alue o$ +. Is this the

$irst $ragment, the last $ragment, or a middle $ragment

&o we know i$ the packet was $ragmented

%olution

If the M bit is 0, it means that there are no more

fragments; the fragment is the last one. However, we

cannot say if the original packet was fragmented or not. A

non-fragmented packet is considered the last fragment.

0ample

#$ample



4&

packet has arried with an 4 bit alue o$ . Is this the

$irst $ragment, the last $ragment, or a middle $ragment

&o we know i$ the packet was $ragmented

%olution

If the M bit is 1, it means that there is at least one more

fragment. This fragment can be the first one or a middle

one, but not the last one. We don’t know if it is the first

one or a middle one; we need more information (the

value of the fragmentation offset).

#$ample

0ample



2&"41

packet has arried with an 4 bit alue o$ and a

$ragmentation o$$set alue o$ +. Is this the $irst $ragment,

the last $ragment, or a middle $ragment

%olution

Because the M bit is 1, it is either the first fragment or a

middle one. Because the offset value is 0, it is the first

fragment.

0ample

0ample



42

packet has arried in which the o$$set alue is ++.

-hat is the number o$ the $irst byte &o we know the

number o$ the last byte

%olution

To $ind the number o$ the $irst byte, we multiply the o$$set

alue by *. This means that the $irst byte number is *++.

-e cannot determine the number o$ the last byte unless

we know the length.

0ample

0ample



43

packet has arried in which the o$$set alue is ++, the

alue o$ /LN is 1, and the alue o$ the total length $ield

is ++. -hat are the numbers o$ the $irst byte and the last

byte

%olutionThe first byte number is 100 × 8 = 800. The total length is

100 bytes, and the header length is 20 bytes (5 × 4), which

means that there are 80 bytes in this datagram. If the first

byte number is 800, the last byte number must be 879.

0ample

0ample



44

6igure shows an e0ample o$ a checksum calculation $or

an IP! header without options. The header is diided

into 73bit sections. ll the sections are added and the

sum is complemented. The result is inserted in the

checksum $ield.

0ample



45

$hecksu" Then the entire header is divided into #-bit sections and

added together. The result $sum% is complemented and inserted into thechecksum field. The checksum in the IPv4 packet covers only the header"

not the data.

!tions" The header of the IPv4 datagram is made of two parts: a fi+edpalt and a variable part. The fi+ed part is &' bytes long and was discussed

in the previous section. The variable part comprises the options that can be

a ma+imum of 4' bytes.

/ptions" as the name implies" are not re7uired for a datagram. They can be

used for network testing and debugging.

;o /peration" 0 noo!eration o!tion is a I-byte option used as a filler

between options.



46

(nd of /ption. 0n end-of-option option is a I/yte o!tion used .or

!adding at the end of the option field. It" however" can only be used as the

last option.

<ecord <oute. 0 record route option is used to record the Internet routers

that handle the datagram. It can list u! to nine router addresses. It can

be used for debugging and management purposes.

*trict *ource <oute. 0 strict source route option is used by the source to

predetermine a route for the datagram as it travels through the Internet.

=oose *ource <oute. 0 loose source route option is similar to the strict

source route" but it is less rigid.

Timestamp. 0 timestamp option is used to record the tie o. datagra

!rocessing /y a router" The time is e+pressed in milliseconds from

midnight" niversal time or 6reenwich mean time. >nowing the time a

datagram is processed can help users and managers track the behavior of

the routers in the Internet.



47

Figure 0ample o$ checksum calculation in IP!



4#

Figure Ta0onomy o$ options in IP!



2&"4%

IPv6IPv6

The network layer protocol in the T"P#IP protocolThe network layer protocol in the T"P#IP protocol

suite is currently IP!. lthough IP! is well designed,suite is currently IP!. lthough IP! is well designed,

data communication has eoled since the inception o$data communication has eoled since the inception o$

IP! in the 89+s. IP! has some de$iciencies that IP! in the 89+s. IP! has some de$iciencies thatmake it unsuitable $or the $ast3growing Internet.make it unsuitable $or the $ast3growing Internet.

%d&antages

'acket Format

#$tension (eaders


6



5&

IPv6IPv6

Despite all short-term solutions" such as subnetting" classless

addressing" and ;0T" address depletion is still a long-term problem in

the Internet.

The Internet must accommodate real-time audio and video

transmission. This type of transmission re7uires minimum delay

strategies and reservation of resources not provided in the IPv4

design.

The Internet must accommodate encryption and authentication of data

for some applications. ;o encryption or authentication is provided by

IPv4.

%d&antages

'acket Format

#$tension (eaders




51

Figure IP7 datagram header and payload



52

Figure 6ormat o$ an IP7 datagram



53

!a"le Ne0t header codes $or IP7



54

!a"le Priorities $or congestion3controlled tra$$ic



56

!a"le "omparison between IP! and IP7 packet headers



57

Figure 0tension header types



5#

!a"le "omparison between IP! options and IP7 e0tension headers



5%

TRANSITION FROM IPv4 TO IPv6TRANSITION FROM IPv4 TO IPv6

ecause o$ the huge number o$ systems on the ecause o$ the huge number o$ systems on the

Internet, the transition $rom IP! to IP7 cannot Internet, the transition $rom IP! to IP7 cannot

happen suddenly. It takes a considerable amount o$happen suddenly. It takes a considerable amount o$

time be$ore eery system in the Internet can moe $romtime be$ore eery system in the Internet can moe $rom

IP! to IP7. The transition must be smooth to preent IP! to IP7. The transition must be smooth to preent

any problems between IP! and IP7 systems.any problems between IP! and IP7 systems.

Dual )tack

!unneling

(eader !ranslation




6&

Figure Three transition strategies



61

Figure &ual stack



62

Figure Tunneling strategy



63

Figure /eader translation strategy



!a"le /eader translation

IP Addressing Part1 2016

Documents

Transcript of IP Addressing Part1 2016