fragmentation

Question

The following IPv4 header, shown in hex below, is received for an IP packet at its destination.
4500 003c 1c46 4000 4017 c311 aca8 0101 aca8 0102
Using the Internet checksum algorithm, determine if there were any errors in the transmission?:

 

1.  Single bit error
2.  Double bit error
3.  More than 2 bit error
4. No error

Answer 1

IP header is given as :-  4500 003C 1C46 4000 4017 C311 ACA8 0101 ACA8 0102

Checksum is = C311

To calculate checksum of given header. Add in chunks of 16 bit excluding header checksum

4500 + 003C + 1C46 + 4000 + 4017 +ACA8 + 0101 + ACA8 + 0102 = 23CEC

Here 2 is carry, so add it again  =  3CEC + 2 = 3CEE

Now add it with checksum = 3CEE + C311 = FFFF

now flip every bit = 0000

That means no error

Comments

which calculator??

---

I am using real calculator ( CASIO- fx-991ES ) :p

---

suppose if there is error  then will it possible to know how many bit error is there ?

I think we cannot state that with check sum. so answer will directly be no error.