IPv4 Header unused fields

[Shakey9]

Hi,

Can some explain to me which fields are currently virtually unused in the IPv4 header?

Did some google search, suggested that 40bytes of the options field is unused but I am not sure if this is true?

The other think I came across was Check sum field is unnecessary as the TCP layer checks for the errors including source and des addresses.

Any information on this subject will be very much appreciated.

 

[MarkhP]

Have a look through this. It may give some assistance.

http://www.tcpipguide.com/free/t_IPDatagramGeneralFormat.htm

 

[SamBones]

The IP header is placed around the TCP packet. That means the TCP header checksum doesn't include the IP header since it was added at a lower layer. The IP header's checksum covers both the IP datagram and the TCP packet it's carrying as a payload.

So yes, they are both needed.