Header Checksum Field in IPv4 Header || Lesson 76 || Computer Networks || Learning Monkey ||

Header Checksum Field in IPv4 Header
We will try to understand Header Checksum Field in IPv4 Header in this class.
We have already discussed the Time to Live TTL field in the IPv4 header in our previous class.
Header Checksum Field in IPv4 Header
How to calculate the header checksum?
Divide the IP header into 16-bit words, sum each of them up, and finally do one’s complement of the sum. Then the value generated out of this operation would be the checksum.
We will consider a header and group the header bits as the 16-bit group to understand this.
The grouping of the bits of the header checksum is done as shown below.
STEP 1: Grouping the header bits
STEP 2: Summing up each group
STEP 3: One’s Compliment of the Final Sum
The final result is placed in the header checksum field and send to the receiver.
How the checksum is verified at the receiver?
After receiving the packet the header checksum value is removed and replaced with all zeros.
Now the same procedure is repeated and compared with the value sent by the sender.
If both the values are the same then the packet is forwarded to the upper layer else discarded.
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[@mohsinqureshi6850]

this is some next level explanation , hats off

[@occy222]

Thank you so much sir for good knowledge

[@raulcasquinha]

Thank you a lot for the fast and simple explanations with good examples

[@LearningMonkey]

Have a great learning in CSE

[@franciscorepetto2482]

You save my life man. Thank you very much

[@sureshthervy]

Bro really excellent ....clearly explained...

[@sureshthervy]

What is the exact data present in the data field of header?

[@somnathyadav2836]

As TTL field changes at every router then TTL field will be defferent on sender and receiver.
Then how header checksum will verify error??

[@endunry]

Everyone changing the Header needs to update the Checksum accordingly. Otherwise the checksum wouldnt be that useful (im just guessing that, but that would make sense to me)