I read in 2-3 places that length of IP header may change during transit from source to destination with routers in-between. However, no explanation was given as to why it might change.
According to me, the only way the length of IP header could change is when length of options field would change. For example, we have record route option where the IP address gets added each time to options field when it passes through each router giving us the entire route from source to destination. So here as IP address is added each time, the length of option field is changing.
Is this reasoning correct?