The Saigon CTT Semester 1 CHAPTER 10 Wael Yousif.

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Semester 1Semester 1

CHAPTER 10CHAPTER 10

Wael YousifWael Yousif

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ContentContent

• IP Address Classes.

• Subnetting and Creating a Subnet.

• Network Layer and Path Determination.

• IP Address within the IP Header.

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IP ADDRESS CLASSESIP ADDRESS CLASSES

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IP network addressIP network address

• Network layer addresses are 32 bits long.

• The are presented as four octets in dotted decimal format.

• The IP address has two components: Network ID and Host ID.

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IP address formatIP address format

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Binary and decimal conversionBinary and decimal conversion

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Why we need to know B-D conversionWhy we need to know B-D conversion

• Use of calculators is discouraged for one simple reason :

No calculators are allowed on the CCNA exam.

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Fast conversionFast conversion

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Exercise: Exercise: DEC – BIN DEC – BIN

203

11001011

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Exercise: Exercise: BIN – DECBIN – DEC

10100010

162

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Network ID and host IDNetwork ID and host ID

• Network ID :– Assigned by Internet Network Information

Center.

– Assigned by upper organization.

– Identifies the network to which a devices is attached.

• Host ID :– Assigned by a network administrator.

– Identifies the specific device on that network.

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Bits on the IP addressBits on the IP address

• Network Bits :

– Identifies network ID

– Identifies class of the IP address

– All of host bits are 0

• Host Bits :

– Identifies host ID

– All of bits are 0: reserved for network address

– All of bits are 1: reserved for broadcast address

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IP address classesIP address classes

• Different class addresses reserve different amounts of bits for the Network and Host portions of the address

• Provide the flexibility required to support different size networks

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IP address classes:IP address classes: Class A Class A

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IP address classes:IP address classes: Class A Class A

• The first bit of a Class A address is always 0.

• The first 8 bits to identify the network part of the address.

• Possible network address from 1.0.0.0 to 127.0.0.0.

• The remaining three octets can be used for the host portion of the address.

• Each class A network have up to 16,777,214 possible IP addresses.

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IP address classes:IP address classes: Class B Class B

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IP address classes:IP address classes: Class B Class B

• The first 2 bits of a Class B address is always 10.

• The first two octets to identify the network part of the address.

• Possible network address from 128.0.0.0 to 191.255.0.0.

• The remaining two octets can be used for the host portion of the address.

• Class B network have up to 65.534 possible IP addresses.

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IP address classes:IP address classes: Class C Class C

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IP address classes:IP address classes: Class C Class C

• The first 3 bits of a Class C address is always 110.

• The first three octets to identify the network part of the address.

• Possible network address from 192.0.0.0 to 223.255.255.0.

• The remaining last octet can be used for the host portion of the address.

• Class C network have up to 254 possible IP addresses.

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IP address classes:IP address classes: Summary Summary

• 1.0.0.0 - 126.0.0.0 : Class A.

• 127.0.0.0 : Loopback network.

• 128.0.0.0 - 191.255.0.0 : Class B.

• 192.0.0.0 - 223.255.255.0 : Class C.

• 224.0.0.0 < 240.0.0.0 : Class D, multicast.

• >= 240.0.0.0 : Class E, reserved.

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Network addressNetwork address

• Network address provide a convenient way to refer to all of the addresses on a particular network or subnetwork.

• Two hosts with differing network address require a device, typically a router, in order to communicate.

• An IP address that ends with binary 0s in all host bits is reserved for the network address.

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Broadcast addressBroadcast address

• Broadcast goes to every host with a particular network ID number.

• An IP address that ends with binary 1s in all host bits is reserved for the directed broadcast address.

• An IP address with binary 1s in all network bits and host bits is reserved for the local broadcast address.

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Local broadcast addressLocal broadcast address

STOP

255.255.255.255

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Directed broadcast addressDirected broadcast address

Broadcast addressBroadcast address

192.168.20.0

192.168.20.255

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Example: Example: 172.16.20.200172.16.20.200

• 172.16.20.200 is Class B address

• Network portion: 172.16

• Host portion: 20.200

• Network address: 172.16.0.0

• Broadcast address: 172.16.255.255

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Private addressesPrivate addresses

• According to RFC-1918.

• Organizations make use of the private Internet address space for hosts that require IP connectivity within their enterprise network, but do not require external connections to the global Internet.

• Class A: 10.0.0.0.

• Class B: 172.16.0.0 - 172.31.0.0.

• Class C: 192.168.0.0 - 192.168.255.0.

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Preparation for LABPreparation for LAB

• 10.4: IP address classes.

• Lab companion:

– 10.4.1.

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Lab 10.4.1:Lab 10.4.1: Step 1 Step 1

• Review IP address classes and their characteristics.

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Lab 10.4.1:Lab 10.4.1: Step 2 Step 2

1. What is the decimal and binary range of the first octet of class B IP addresses?

– Decimal: 128 – 191

– Binary:   10000000 – 10111111

2. Which octet(s) represent the network portion of a class C IP address?

– The first three octets

3. Which octet(s) represent the host portion of a class A IP address?

– The last three octets

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Lab 10.4.1:Lab 10.4.1: Step 3 Step 3

Host IP AddressAddress

ClassNetwork Address

Host Address

Broadcast Address

218.14.55.137

123.1.1.15

150.127.221.244

194.125.35.199

175.12.239.244

C 218.14.55 137 218.14.55.255

A 123 1.1.15 123.255.255.255

B 150.127 221.244 150.127.255.255

C 194.125.35 199 194.125.35.255

B 175.12 239.244 175.12.255.255

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Lab 10.4.1:Lab 10.4.1: Step 4 – Valid address Step 4 – Valid address

• 150.100.255.255

• 175.100.255.18

• 195.234.253.0

• 100.0.0.23

• 188.258.221.176

• 127.34.25.189

• 224.156.217.73

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ReviewReview

• Classes of IP address and range of IP on each class.

• Determine network portion and host portion in a IP address.

• Understand about broadcast addresses.

• Understand about valid host address.

• Binary and Decimal conversion.

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SUBNETTING SUBNETTING

AND AND

CREATING A SUBNETCREATING A SUBNET

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Why we need to divide network?Why we need to divide network?

• Network administrators sometimes need to divide networks, especially large ones, into smaller networks:– Reduce the size of a broadcast domain.

– Improve network security.

– Implement the hierarchical managements.

• So we need more network addresses for your network. But I want the outside networks see our network as a single network.

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Divide network by threeDivide network by three

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SubnettingSubnetting

• Subnetworks are smaller divisions of network.

• Subnet addresses include the Class A, Class B, or Class C network portion, plus a subnet field and a host field.

• To create a subnet address, a network administrator borrows bits from the original host portion and designates them as the subnet field.

• Subnet addresses are assigned locally, usually by a network administrator.

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– Number of subnets created = 2 ^ (Number of bits borrowed from the host section)

– Number of subnets Available = 2 ^ (Number of bits borrowed from the host section) – 2

– Number of hosts created per subnet = 2 ^ (Number of bits remaining under the host section)

– Number of hosts available per subnet =2 ^ (Number of bits remaining from the host section) – 2

What are the rules?What are the rules?

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How many bits can I borrow?How many bits can I borrow?

• The minimum bits you can borrow is:

2 bits.

• The maximum bits you can borrow is:

A: 22 bits ~ 222 - 2 = 4.194.302 subnets.

B: 14 bits ~ 214 - 2 = 16.382 subnets.

C: 06 bits ~ 206 - 2 = 62 subnets.

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T • Two addresses are reserved for the following:– Network Identifier.

– Network Broadcast Address.

• What is a network Identifier– The first IP address in a network, Known as the

cable identifier, Represents the entire network, All host bits are turned off (0s).

• What is a Broadcast Address?– The last IP address in a network, used to

communicate with all the hosts in the network, All host bits are turned On (1s).

Why are we loosing 2?Why are we loosing 2?

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– Loosing IPs.

– The outside world does not have any knowledge of our Subnetting plan.

• How can we fix those two problems?

– Loosing IPs. Router Configuration.

– Subnetting Plan.

– Subnetmask

Subnetting Challenges!!Subnetting Challenges!!

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What is a SubnetmaskWhat is a Subnetmask

– Special 32-bit number that, when combined (Logically Anded) with a device’s IP address, determines which network and subnetwork that particular device belongs to.

For an external host to communicate with 166.144.63.12, the router will need to interpret the Subnetmask Information.

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Subnet maskSubnet mask

• “Extended Network Prefix”.

• Determines which part of an IP address is the network field and which part is the host field.

• 32 bits long.

• Divided into four octets.

• Network and Subnet portions all 1’s.

• Host portions all 0’s.

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– All bits under the network and subnetwork sections are turned on (1s).

• What is Default Subnetmask?

– The subnet mask that will be used if you do not specify one in your TCP/IP configuration.

• 255.0.0.0 for Class A

• 255.255.0.0 for Class B

• 255.255.255.0 for Class C

How is the Subnet Mask Is Written in Binary?How is the Subnet Mask Is Written in Binary?

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SubnettingSubnetting

How would your subnet mask look if you borrow 3 host bits from class C network??

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Subnet mask:Subnet mask: Example Example

• 172.16.65.100 / 255.255.240.0.

• 10101100.00010000.01000001.01100100.

• 11111111.11111111.11110000.00000000.

• 10101100.00010000.01000001.01100100.

• Class B network:– 16 bits for network portion.

– 4 bits for subnet portion.

– 12 bits for host portion.

• Subnet address: 172.16.64.0.

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• Combination of software and hardware that enable two different network segments to exchange data.– The IP address of a router’s port through which a network is

connected to the router.

– Every device has a default gateway.

What is a Gateway?What is a Gateway?

Case 1Case 1

1. Suppose you are given the IP address 195.5.5.0 and wish to connect Springfield and Bedrock to Southpark. Create an IP addressing scheme that will meet the following requirements:

– A: Each subnet must support between 25 and 30 devices.

– B: You must have enough subnets to address each network.

i. What is the subnet mask for this network?

ii. What is the broadcast address of the 3rd subnet?

iii. On the diagram, assign a subnet address to each network and give each router interface an appropriate IP address for that network.

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Case 2Case 2

• Given the IP address 199.199.199.172 with a subnet mask of 255.255.255.192. Answer the following:

a.What is the subnet address of the network containing the given IP address?

b.What is the broadcast address of the network containing the given IP address?

c.How many bits were borrowed?

d.How many subnets have been created?

e.How many host address per subnet?

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Boolean algebra reviewBoolean algebra review

• Boolean operators:

–AND.

–OR.

–NOT.

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ANDAND operator operator

1 AND 1 = 1

1 AND 0 = 0

0 AND 1 = 0

0 AND 0 = 0

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OROR operator operator

1 OR 1 = 1

1 OR 0 = 1

0 OR 1 = 1

0 OR 0 = 0

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NOTNOT operator operator

NOT 1 = 0

NOT 0 = 1

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Boolean algebra examplesBoolean algebra examples

1010 AND 0110 = 0010

1010 OR 0110 = 1110

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Why we need to know Boolean ops?Why we need to know Boolean ops?

• Network layer performs the Boolean operations in order to find the network ID of a subnet

• Example: – 172.16.65.100 AND 255.255.240.0

– Network address: 172.16.64.0

IP Address

ANDSubnet Mask

=Network and

Subnet address

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Subnetting exampleSubnetting example

• Given network 172.16.0.0.

• We need 8 usable subnets and up to 1000 hosts on each subnet.

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Calculating a subnetCalculating a subnet

1. Determine the class of network and default subnet mask.

2. Determine how many bits to borrow. Determine the subnet mask and the actual number of subnets and hosts.

3. Determine the ranges of host address for each subnet. Choose the subnets that you want to use.

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Calculating a subnet:Calculating a subnet: STEP 1 STEP 1

• Determine the Class of network

Class B

• Determine the default subnet mask

255.255.0.0

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Calculating a subnet:Calculating a subnet: STEP 2 STEP 2

• Number of subnets <= 2n - 2 with n is number of bits that are borrowed.

• Number of hosts <= 2m - 2 with m is number of bits that are remained.

• Determine how many bits to borrow from the host portion from requirement:

– 8 subnets.

– 1000 hosts on each subnet.

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Calculating a subnet:Calculating a subnet: STEP 2 (Cont.) STEP 2 (Cont.)

• Choose n = 4:

– Number of possible subnets is:

24 - 2 = 14– Number of possible hosts on each subnet is:

2(16-4) - 2 = 4094

• Other choice n = 5 , n = 6 ?

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Calculating a subnet:Calculating a subnet: STEP 2 (Cont.) STEP 2 (Cont.)

The subnet mask: 255.255.240.0.

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Calculating a subnet:Calculating a subnet: STEP 3 STEP 3

• Determine the subnets and the ranges of host address for each subnet. Including:

Sub-network addresses

Range of usable IP addresses

Sub-network broadcast addresses

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Calculating a subnet:Calculating a subnet: STEP 3 (Cont.) STEP 3 (Cont.)

• Determine the subnets from 4 borrowed bits from the host portion (last 2 bytes):

• 1st subnet: .00000000.00000000

• 2nd subnet: .00010000.00000000

• 3rd subnet: .00100000.00000000

• …

• 15th subnet: .11110000.00000000

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Calculating a subnet:Calculating a subnet: STEP 3 (Cont.) STEP 3 (Cont.)

NoSub-network

addressPossible host address

Broadcast address

Use?

0 172.16.0.0 172.16.0.1 – 172.16.15.254 172.16.15.255 N

1 172.16.16.0 172.16.16.1 – 172.16.31.254 172.16.31.255 Y

2 172.16.32.0 172.16.32.1 – 172.16.47.254 172.16.47.255 Y

.. .. .. .. ..

.. .. .. .. ..

13 172.16.208.0 172.16.208.1 – 172.16.223.254 172.16.223.255 Y

14 172.16.224.0 172.16.224.1 – 172.16.239.254 172.16.239.255 Y

15 172.16.240.0 172.16.240.1 – 172.16.255.254 172.16.255.255 N

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Calculating a subnet:Calculating a subnet: STEP 3 (Cont.) STEP 3 (Cont.)

• Using subnets No.1 to No.8.

• Assign IP addresses to hosts and interfaces on each network. IP address configuration.

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Addresses are loose by subnetting.Addresses are loose by subnetting.

• Network administrator must strike a balance between the number of subnets required, the hosts per subnet that is acceptable, and the resulting waste of addresses.

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ReviewReview

• Why we need to divide a network.

• What is the subnetting.

• What is the subnet mask.

• How to create subnet addresses.

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Teaching topology (10.7.6)Teaching topology (10.7.6)

Work

group

Work

group

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NETWORK LAYER NETWORK LAYER

AND AND

PATH DETERMINATIONPATH DETERMINATION

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A network layer. Why?A network layer. Why?

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Network layerNetwork layer

• Segment network and control flow of traffic.

• Move data through a set of networks.

• Logical Addressing, use a hierarchical addressing scheme.

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Network segmentation. Why?Network segmentation. Why?

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Network segmentationNetwork segmentation

• Control network traffics and reduce broadcast traffics.

• Separate computer networks is managed by a single administration - Autonomous systems.

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Communication among networksCommunication among networks

• Networks operate in much the same manner.

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RouterRouter

• Routers connect separate networks.

• Routers make best path decisions based on Layer 3 information.

• Routers actually switch packets from incoming ports to appropriate outgoing ports.

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Data relayingData relaying

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Path determinationPath determination

• Path determination is the process that the router uses to choose the next hop in the path for the packet to travel to its destination based on the link bandwidth, hop, delay ...

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Network layer addressingNetwork layer addressing

• Network address + Host address: Hierarchical Addressing Schemes.

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Flat Addressing SchemeFlat Addressing Scheme

1

2

3

4

5

6

A B

1 – A1

2 – A2

3 – A3

1 – A2 – A3 – A4 – B5 – B6 – B

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Hierarchical Addressing SchemeHierarchical Addressing Scheme

A1

A2

A3

B1

B2

B3

A B

1 – A1

2 – A2

3 – A3

A – LocalB – Switch to B

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Hierarchical Addressing SchemeHierarchical Addressing Scheme

InternationalGateway

DomesticSwitch

LocalSwitch

84 8 9321044

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Network addressNetwork address

• The network address helps the router identify a path within the network cloud.

• The router uses the network address to identify the destination network of a packet within an internetwork.

• Network address is assigned by higher-level administrator. Host address is assigned manually or automatically by manager of that network.

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ReviewReview

• Why it’s necessary to have a network layer.

• Why we need to segment networks.

• What are the roles of router in network.

• Compare flat and hierarchical addressing schemes.

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IP ADDRESS WITHIN IP ADDRESS WITHIN

THE IP HEADERTHE IP HEADER

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Network layer datagramNetwork layer datagram

• At the network layer, the data is encapsulated within packets (also known as datagrams).

• Packet includes header - addressing and other control information - and actual data - whatever is passed down from the higher layers.

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IP header formatIP header format

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IP header format:IP header format: Version Version

• 4 bits.• Indicates the version of

IP currently used.– IPv4 : 0100– IPv6 : 0110

• 4 bits.• Indicates the version of

IP currently used.– IPv4 : 0100– IPv6 : 0110

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IP header format:IP header format: Header length Header length

• 4 bits.• IP header length : Indicates the

datagram header length in 32 bit words (4 bits), and thus points to the beginning of the data.

• 4 bits.• IP header length : Indicates the

datagram header length in 32 bit words (4 bits), and thus points to the beginning of the data.

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IP header format:IP header format: Service type Service type

• 8 bits.• Specifies the level of importance

that has been assigned by a particular upper-layer protocol.• Precedence. • Reliability. • Speed.

• 8 bits.• Specifies the level of importance

that has been assigned by a particular upper-layer protocol.• Precedence. • Reliability. • Speed.

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IP header format:IP header format: Total length Total length

• 16 bits.• Specifies the length of the

entire IP packet, including data and header, in bytes.

• 16 bits.• Specifies the length of the

entire IP packet, including data and header, in bytes.

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IP header format:IP header format: Identification Identification

• 16 bits.• Identification contains an integer

that identifies the current datagram.• Assigned by the sender to aid in

assembling the fragments of a datagram.

• 16 bits.• Identification contains an integer

that identifies the current datagram.• Assigned by the sender to aid in

assembling the fragments of a datagram.

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IP header format:IP header format: Flags Flags

• 3 bits.• The second bit specifying whether the

packet can be fragmented .• The last bit specifying whether the packet

is the last fragment in a series of fragmented packets.

• 3 bits.• The second bit specifying whether the

packet can be fragmented .• The last bit specifying whether the packet

is the last fragment in a series of fragmented packets.

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IP header format:IP header format: Fragment offset Fragment offset

• 13 bits.• The field that is used to help piece together

datagram fragments.• The fragment offset is measured in units of

8 octets (64 bits). • The first fragment has offset zero.

• 13 bits.• The field that is used to help piece together

datagram fragments.• The fragment offset is measured in units of

8 octets (64 bits). • The first fragment has offset zero.

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IP header format:IP header format: Time to Live Time to Live

• 8 bits.• Time-to-Live maintains a counter that

gradually decreases to zero, at which point the datagram is discarded, keeping the packets from looping endlessly.

• 8 bits.• Time-to-Live maintains a counter that

gradually decreases to zero, at which point the datagram is discarded, keeping the packets from looping endlessly.

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IP header format:IP header format: Protocol Protocol

• 8 bits.• Indicates which upper-layer protocol receives

incoming packets after IP processing has been completed• 06 : TCP• 17 : UDP

• 8 bits.• Indicates which upper-layer protocol receives

incoming packets after IP processing has been completed• 06 : TCP• 17 : UDP

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IP header format:IP header format: Header checksum Header checksum

• 16 bits.• A checksum on the header only,

helps ensure IP header integrity.

• 16 bits.• A checksum on the header only,

helps ensure IP header integrity.

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IP header format:IP header format: Addresses Addresses

• 32 bits each.• Source IP Address• Destination IP Address

• 32 bits each.• Source IP Address• Destination IP Address

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IP header format:IP header format: Options Options

• Variable length.• Allows IP to support various options,

such as security, route, error report ...

• Variable length.• Allows IP to support various options,

such as security, route, error report ...

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IP header format:IP header format: Padding Padding

• The header padding is used to ensure that the internet header ends on a 32 bit boundary.

• The header padding is used to ensure that the internet header ends on a 32 bit boundary.

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HomeworkHomework

• www.ietf.org and RFC-760.

• Groups presentations:

– Internet Protocol Overview.

– Packet fragment fields.

– Type of services field.

– Option field.

Th

e S

aig

on

CT

T

ReviewReview

• Detail of IP packet header.

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e S

aig

on

CT

T

Preparation for LABPreparation for LAB

• Lab companion:

– 10.6.6.

– 10.7.5.

– 10.7.7.

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e S

aig

on

CT

T