Re: [TUHS] core

Well, the division into 'net' and 'rest' does not appear to have been a hard one at that point, as it later became. Yes... interesting! Yeah, small stuff like that got added/moved/removed around a lot. It made packet processing in routers quite different; routing lookups, the routing table, etc became much more complex (I remember that change)! Also in hosts, which had not yet had their understanding of fields in the addresses lobotomized away (RFC-1122, Section 3.3.1). Yes, the impact on code _elsewhere_ in the stack was minimal, because the overall packet format didn't change, and addresses were still 32 bits, but... Yeah, there was a lot of discussion about whether they were properly part of the internetwork layer, or the transport. I'm not sure there's really a 'right' answer; PUP: http://gunkies.org/wiki/PARC_Universal_Packet made them part of the internetwork header, and seemed to do OK. I think we eventually decided that we didn't want to mandate a particular port name size across all transports, and moved it out. This had the down-side that there are some times when you _do_ want to have the port available to an IP-only device, which is why ICMP messages return the first N bytes of the data _after_ the IP header (since it's not clear where the port field[s] will be). But I found, working with PUP, there were some times when the defined ports didn't always make sense with some protocols (although PUP didn't really have a 'protocol' field per se); the interaction of 'PUP type' and 'socket' could sometimes be confusing/problemtic. So I personally felt that was at least as good a reason to move them out. 'Ports' make no sense for routing protocols, etc. Overall, I think in the end, TCP/IP got that all right - the semantics of the 'protocol' field are clear and simple, and ports in the transport layer have worked well; I can't think of any places (other than routers which want to play games with connections) where not having ports in the internetwork layer has been an issue. Noel