Subnet mask - range calculation

how to calculate subnet mask?

e.g - 200.10.10.0 --> usable host 16

what is 6th usable subnet range?
: from here we know every subnet must have 16 hosts..
so 6th usable subnet range is from 6th to 7th subnet
6th subnet address = 16 x 6 = 96
7th subnet address = 16 x 7 = 112

the answer is : 200.10.10.96 to 200.10.10.111


what is subnet number for 4th usable subnet?
: 16 x 4 = 64

the answer is : 200.10.10.64


what is subnet broadcast address for the 3rd usable subnet?
: take 4th subnet becoz the broadcast address of 3rd subnet is before 4th subnet address.
16 x 4 =64

the answer is : 200.10.10.63


what are the assignable address for the 5th usable subnet?
: 16 x 5 = 80 ; 16 x 6 = 96
range 200.10.10.80 to 200.10.10.95 ... then exclude address and broadcast

the answer is : 200.10.10.81 to 200.10.10.94

Data Can Be Corrupted During Transmission

Data can be corrupted during transmission. For reliable communication, errors must be detected and corrected.

Single-Bit err vs Burs err --> only 1 err vs more than 1

Error detection uses the concept of redundancy, which means adding extra bits for detecting errors at the destination.

CRC is one of Detection Method (lain²: parity check [vrc + lrc], checksum)
crc use polynomial as divisor. e.g. x7 + x5 + x² + x + 1 --> 10100111

b4 sent, generate remainder as redundant bit.
e.g data=100100 divisor=1101

then sent data+remainder

receive.. (data+remainder) divide 1101 must get remainder '0'. else --> error.
in data correction, can use Hamming Code.

place a redundant bit to take care of every single bit of data..
then put the redundant bit.. r8, r4, r2, r1
do check.. if error, calculate which bit is error...