1 kyung hee university part 4 : network layer. 2 kyung hee university role and position of network...
TRANSCRIPT
![Page 1: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/1.jpg)
11
Kyung Hee University
Part 4 :Part 4 :Network LayerNetwork Layer
![Page 2: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/2.jpg)
22
Kyung Hee University
Role and Position of Network LayerRole and Position of Network Layer
Network layer in the Internet model is responsible for
carrying a packet from one computer to another
It is responsible for host-to-host delivery.
Position of network layer
![Page 3: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/3.jpg)
33
Kyung Hee University
Duties of Network LayerDuties of Network Layer
![Page 4: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/4.jpg)
44
Kyung Hee University
Chapter 19Chapter 19
Host-to-host DelivHost-to-host Delivery :ery :
Interworking, AddrInterworking, Addressing, essing,
and Routingand Routing
![Page 5: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/5.jpg)
55
Kyung Hee University
19.1 Internetworks19.1 Internetworks
The physical and data link layers of a network operate
locally
![Page 6: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/6.jpg)
66
Kyung Hee University
Links in an InternetworkLinks in an Internetwork
![Page 7: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/7.jpg)
77
Kyung Hee University
Network Layer in an InternetworkNetwork Layer in an Internetwork
![Page 8: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/8.jpg)
88
Kyung Hee University
Network Layer at the SourceNetwork Layer at the Source
![Page 9: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/9.jpg)
99
Kyung Hee University
Network Layer at a RouterNetwork Layer at a Router
![Page 10: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/10.jpg)
1010
Kyung Hee University
Network Layer at the DestinationNetwork Layer at the Destination
![Page 11: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/11.jpg)
1111
Kyung Hee University
SwitchingSwitching
Virtual circuit approach – relationship between all packets
belonging to a message is preserved – a single route is
chosen, and all packets take that route
Datagram approach – each packet is treated independently
of all others – thus, packets in the same message can take
different routes, and possibly arrive out of order
![Page 12: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/12.jpg)
1212
Kyung Hee University
Datagram ApproachDatagram Approach
![Page 13: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/13.jpg)
1313
Kyung Hee University
Internet as a Connectionless NetworkInternet as a Connectionless Network
In a connection-oriented service, the source first
makes connection with the destination before sending
a packet.
They are sent on the same path in sequential order.
In a connectionless service, the network layer protocol
treats each packet independently, with each packet
having no relationship to any other packet.
![Page 14: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/14.jpg)
1414
Kyung Hee University
19.2 Addressing19.2 Addressing
For a host to communicate with any other host
Need a universal identification system
Need to name each host
Internet address or IP address is a 32-bit address that
uniquely defines a host or a router on the internet
The IP addresses are unique in the sense that two
devices can never have the same address. However, a
device can have more one address.
![Page 15: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/15.jpg)
1515
Kyung Hee University
NotationNotation
Binary notation
01110101 10010101 00011101 11101010
32 bit address, or a 4 octet address or a 4-byte address
Decimal point notation
![Page 16: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/16.jpg)
1616
Kyung Hee University
Notation (cont’d)Notation (cont’d)
Hexadecimal NotationHexadecimal Notation
- 8 hexadecimal digits- 8 hexadecimal digits
- Used in network programming- Used in network programming
0111 0101 1001 0101 0001 1101 1110 1010
75 95 1D EA
0x75951DEA
![Page 17: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/17.jpg)
1717
Kyung Hee University
Classful AddressingClassful Addressing Occupation of address space
In classful addressing, the address space is divided into five classes: A, B, C, D, and E.
Finding the class in binary notation
![Page 18: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/18.jpg)
1818
Kyung Hee University
Classful Addressing (cont’d)Classful Addressing (cont’d)
Finding the address class
![Page 19: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/19.jpg)
1919
Kyung Hee University
Classful Addressing (cont’d)Classful Addressing (cont’d)
Finding the class in decimal notation
![Page 20: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/20.jpg)
2020
Kyung Hee University
Example 4Example 4
Find the class of each address:
a. 227.12.14.87
b. 252.5.15.111
c. 134.11.78.56
Solution
a. The first byte is 227 (between 224 and 239); the class is D.
b. The first byte is 252 (between 240 and 255); the class is E.
c. The first byte is 134 (between 128 and 191); the class is B.
![Page 21: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/21.jpg)
2121
Kyung Hee University
Netid and HostidNetid and Hostid
Each IP address is made of two parts; netid and hostid.
Netid defines a network; hostid identifies a host on that network.
![Page 22: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/22.jpg)
2222
Kyung Hee University
Netid and Hostid (cont’d)Netid and Hostid (cont’d)
IP addresses are divided into five different classes: A, B, C, D, and E
![Page 23: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/23.jpg)
2323
Kyung Hee University
Classes and Blocks Blocks in class A
Class A is divided into 128 blocks with each block having a different netid.
Millions of class A addresses Millions of class A addresses are wasted.are wasted.
![Page 24: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/24.jpg)
2424
Kyung Hee University
Classes and Blocks (cont’d) Class B is divided into 16,384 blocks with each block having a diffe
rent netid
Many class B addresses Many class B addresses are wasted.are wasted.
![Page 25: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/25.jpg)
2525
Kyung Hee University
Classes and Blocks (cont’d)
Class C is divided into 2,097,152 blocks with each block having a diff
erent netid.
The number of addresses in The number of addresses in a class C block a class C block is smaller than is smaller than the needs of most the needs of most organizationsorganizations
![Page 26: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/26.jpg)
2626
Kyung Hee University
Classes and Blocks (cont’d)
Class D addresses are used for multicasting;
there is only one block in this class.
Class E addresses are reserved for special purposes;
most of the block is wasted.
![Page 27: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/27.jpg)
2727
Kyung Hee University
Network AddressNetwork Address
The network address is the first address.
The network address defines the network to the rest of t
he Internet.
Given the network address, we can find the class of th
e address, the block, and the range of the addresses in
the block
In classful addressing, the network address
(the first address in the block) is the one that is assigne
d to the organization.
![Page 28: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/28.jpg)
2828
Kyung Hee University
Network Address (cont’d)Network Address (cont’d)
Network address : an address with the hostid all set to 0s
![Page 29: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/29.jpg)
2929
Kyung Hee University
A Sample Internet with Classful AddressA Sample Internet with Classful Address
Token Ring LAN (Class C), Ethernet LAN (Class B), Ethernet LAN (Class A) ,
Point-to-point WAN, A Switched WAN
![Page 30: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/30.jpg)
3030
Kyung Hee University
Subnetting and SupernettingSubnetting and Supernetting
Subnetting
A network is divided into several smaller networks with each subnetwork (or subnet) having its subnetwork address
Supernetting
Combining several class C addresses to create a larger range of addresses
IP Addresses are designed with two levels of hierarchy
![Page 31: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/31.jpg)
3131
Kyung Hee University
SubnettingSubnetting
Classes A, B, C in IP addressing are designed with two levels of hierarchy (not subnetted)
Netid and Hostid
![Page 32: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/32.jpg)
3232
Kyung Hee University
Subnetting (cont’d)Subnetting (cont’d) Further division of a network into smaller networks called subnetworks
R1 differentiating subnets
![Page 33: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/33.jpg)
3333
Kyung Hee University
Subnetting (cont’d)Subnetting (cont’d)
Three levels of hierarchy : netid, subnetid, and hostid
![Page 34: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/34.jpg)
3434
Kyung Hee University
Subnetting (cont’d)Subnetting (cont’d)
Three steps of the routing for an IP datagram
Delivery to the site, delivery to the subnetwork, and delivery to the host
Hierarchy concept in a telephone number
031
![Page 35: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/35.jpg)
3535
Kyung Hee University
Default MasksDefault Masks
Class In BinaryIn Dotted-
DecimalUsing Slash
A11111111 00000000 00000000 00000000
255.0.0.0 /8
B11111111 11111111 00000000 00000000
255.255.0.0 /16
C 11111111 111111111 11111111 00000000 255.255.255.0 /24
• When a router receives a packet, it needs to route it• Uses mask to determine the subnetwork address• Routers outside the organization use default mask• Routers inside use a subnet mask
![Page 36: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/36.jpg)
3636
Kyung Hee University
Comparison of a default mask and a subnet mask
• Number of subnets is determined by number of extra 1s in the subnet mask.
• 2n = 23 = 8 subnets
![Page 37: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/37.jpg)
3737
Kyung Hee University
Supernetting Supernetting
A block of class x addresses
For example,
An organization that needs 1,000 addresses can be granted four class C addresses
![Page 38: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/38.jpg)
3838
Kyung Hee University
Supernetting (cont’d)Supernetting (cont’d)
4 class C addresses combine to make one supernetwork
![Page 39: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/39.jpg)
3939
Kyung Hee University
19.3 Routing 19.3 Routing
Next-hop routing
![Page 40: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/40.jpg)
4040
Kyung Hee University
Routing (cont’d)Routing (cont’d)
Network-specific routing
• Don’t have an entry for every host connected to the same
physical network
• Instead, only have one entry to define the destination network
![Page 41: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/41.jpg)
4141
Kyung Hee University
Routing (cont’d)Routing (cont’d)
Host-specific routing
![Page 42: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/42.jpg)
4242
Kyung Hee University
Routing (cont’d)Routing (cont’d)
Default routing
![Page 43: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/43.jpg)
4343
Kyung Hee University
Static and Dynamic Routing TablesStatic and Dynamic Routing Tables
Static routing table : containing information entered
manually
Dynamic routing table
updating periodically using one of the dynamic routing protocols such as RIP, OSPF, or BGP
Whenever there is a change in the Internet, the dynamic routing protocols update all the tables in the routers.
![Page 44: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/44.jpg)
4444
Kyung Hee University
20.2 IP datagram20.2 IP datagram
![Page 45: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/45.jpg)
4545
Kyung Hee University
IP Datagram (cont’d)IP Datagram (cont’d)
Version : for IP version4, it is 4
Header Length : Defining the length of the datagram
header in 4 byte words
![Page 46: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/46.jpg)
4646
Kyung Hee University
IP Datagram (cont’d)IP Datagram (cont’d)
Differentiated Services
The first 6 bits : codepoint subfield (DSCP : differentiated services code point)
Values for codepoints
Category Codepoint Assigning Authority
1 XXXXX0 Internet
2 XXXX11 Local
3 XXXX01 Temporary or experiment
![Page 47: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/47.jpg)
4747
Kyung Hee University
IP Datagram (cont’d)IP Datagram (cont’d)
Total Length : head + data
Defining the total length of the datagram including the header
Length of data = total length – header length
Limited to 65,535 (216 – 1) bytes
Encapsulation of a small datagram in an Ethernet Frame
![Page 48: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/48.jpg)
4848
Kyung Hee University
IP Datagram (cont’d)IP Datagram (cont’d) Fields related to fragmentation
Identification : 16 bit-field Datagram id that is originated by the source host
– Therefore, Source IP address + datagram id (identification) All fragments having same identification number Identification No. to be used for the destination in
reassembling the datagram
Flags : 3 bit-field D : Do not fragment (1)
– If it can not pass the datagram through any available physical network, it discards the datagram and send ICMP error message to the source host
M : More fragment (0) – 0 : last fragment or only fragment
![Page 49: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/49.jpg)
4949
Kyung Hee University
IP Datagram (cont’d)IP Datagram (cont’d) Fragmentation offset : 13-bit field
Showing relative position of this fragment with respect to the whole datagram
Measured in units of 8 bytes : forcing hosts or routers that fragment datagrams to choose the size of each fragment so that the first byte number is divisible by eight
![Page 50: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/50.jpg)
5050
Kyung Hee University
IP Datagram (cont’d)IP Datagram (cont’d)
Time to live
Used to control the maximum number of hops (routers) visited by the datagram
If the value is Zero, the routers discarded If the source wants to confine the packet to the local
network, it can store 1 in this field
![Page 51: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/51.jpg)
5151
Kyung Hee University
IP Datagram (cont’d)IP Datagram (cont’d)
Fragmentation
The format and size of the received frame depend on the protocol used by the physical network
* MTU (Maximum Transfer Unit) : When a datagram is encapsulated in a frame, the total size of the datagram must be less than this maximum size
![Page 52: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/52.jpg)
5252
Kyung Hee University
IP Datagram (cont’d)IP Datagram (cont’d)
MTUs for different networks
Protocol MTU
Hyperchannel 65,535
Token ring (16Mbps) 17,914
Token ring (4Mbps) 4,464
FDDI 4,352
Ethernet 1,500
X.25 576
PPP 296
• Hyperchannel : Network Systems Corporation, 1988 (RFC 1044)
![Page 53: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/53.jpg)
5353
Kyung Hee University
IP Datagram (cont’d)IP Datagram (cont’d)
Value Protocol1 ICMP2 IGMP6 TCP8 EGP
17 UDP89 OSPF
Protocol
Defining the higher level protocol that uses the services of the IP layer
TCP, UDP, ICMP, and IGMP Multiplexing data from different higher level protocols
![Page 54: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/54.jpg)
5454
Kyung Hee University
IP Datagram (cont’d)IP Datagram (cont’d)
Example of Checksum Calculation
![Page 55: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/55.jpg)
5555
Kyung Hee University
![Page 56: 1 Kyung Hee University Part 4 : Network Layer. 2 Kyung Hee University Role and Position of Network Layer o Network layer in the Internet model is responsible](https://reader030.vdocuments.net/reader030/viewer/2022032801/56649de35503460f94ad9de3/html5/thumbnails/56.jpg)
5656
Kyung Hee University
20.4 IPv6 Address20.4 IPv6 Address
IPv6 address consists of 16 octets; it is 128 bits long