IP Header Doubt

Question

https://gateoverflow.in/2062/gate2014-3-28

In the above question we are subtracting the header length from the IP paxket to find out number of IP fragments.

But in this question https://gateoverflow.in/8255/gate2015-2-52

Why we are adding the header length to the UDP datagram to find number of IP fragments?

 

 

Comments

Is it because in the first question every IP packet would have a header length which needs to be deducted.

But in the 2nd question datagram header is needed in the next layer. Also in the Network layer the datagram would be given added IP header.

 

So can we conclude in every case IP header should be deduced before calculation of IP fragments?

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in 2nd question, it's clearly written that 8880 bytes of user data so header will be added before user data.

Only first fragment contain UDP header else don't, right?

This makes sense too, as router don't need UDP header and at the destination, after reassembly at the destination, it's going to be one packet anyway.
To travel intermediate routers we don't need UDP header.

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Yes.. Its true