> Computing the checksum is a nuisance, and it is usually inadequate, so it is allowed to be zero in IPV4, but not IPV6. If IPv6 disallows simpy zeroing the fi

> Computing the checksum is a nuisance, and it is usually inadequate, so it is allowed to be zero in IPV4, but not IPV6. If IPv6 disallows simpy zeroing the field, that sounds like it's not just a nuisance. > I have never seen an actual use of UDP that looked at the port numbers, although firewalls often use them for filtering. I don't know what you're saying here. UDP's ports model isn't optional in any sense, it's just like TCP's. If you run several UDP-based services on your server, port numbers are how the server knows which packets are destined for which processes.