Network Layer
- use
- manages device addressing
- tracks the location of devices on the network.
- determines the best path to move data from source to the destination
- routers used in this layer
- ip address
- source and destination address headers are added
- routing is done
- protocols
- IP
- IPv6
- SCP
- ARP
- RARP
- ICMP
- IGMP
- pdu
- packets
IP Addressing
- IP Address - consists of two parts
- network id - identify the network
- host id - get the host
-
Where is port number then?
- if you visit a web page in the browser then
- you are using
http
which has a predefined port no -80
-
the service that is used to convert the domain name to is called Domain name Service.
- port number is used to identify a particular process in the host
For well known services the port number is already
predefined and fixed
http
- 80https
smtp
- 25ftp
- 21
- even though your intention is to reach
google.com
you are visiting DNS firsts and then getting IP address of google.com and then visiting the google home page. -
This is actually overhead which is also called DNS overhead.
-
\(2^32\) ip address possible if we use 32-bit number
IP address types
- class A - starts with
0
- class B - starts with
10
- class C - starts with
110
- class D - starts with
1110
-
class E - starts with
1111
-
class A - \(2^7\) networks and \(2^{24}\) hosts
- class B - \(2^{14}\) networks and \(2^{16}\) hosts
- class C - \(2^{21}\) networks and \(2^8\) hosts
- class D - used for multicasting
- class E - used for military application
class | ip | subnet | use |
---|---|---|---|
A | 1-127.x.x.x |
255.0.0.0 |
huge corporations |
B | 128-191.x.x.x |
255.255.0.0 |
big companies |
C | 192-223.x.x.x |
255.255.255.0 |
small companies |
D | 224-239.x.x.x |
multicast | |
E | 240-255.x.x.x |
research/development |
but some are reserved for private use in each class
- class A -
10.0.0.0
-10.255.255.255
- class B -
172.16.0.0
-172.16.0.0
- class C -
192.168.0.0
-192.168.255.255
Note
127
-0111
1111
-+ 64 + 32 + 16 + 15
191
-1011
1111
-128 + + 32 + 16 + 15
223
-1101
1111
-128 + 64 + + 16 + 15
239
-1110
1111
-128 + 64 + 32 + + 15
255
-1111
1111
-128 + 64 + 32 + 16 + 15
how to remember
127
+ 64 - 191191
+ 32 - 223223
+ 16 -255
so we can recognize the class of ip using first four bit
Starting Bit | Class |
---|---|
0 |
A |
10 |
B |
110 |
C |
1110 |
D |
1111 |
E |
subnetting
- dividing network in smaller networks