I apologize that the quality of this message will be somewhat limited by pressures of time and having to use a really weird Microsoft keyboard that leaves me prone to speeling mistakes, but I couldn't resist some of the things being talked about in this thread. Phil Howard <phil@charon.milepost.com> writes:
The transition to IPv6 is clearly going to have some difficulties. We are waiting on:
1. Network equipment, with translation translation have to have translations routing software includes translation
Bingo! The thing that amazes me about people who are fans of IPv6 is that they have realized that NAT is THE fundamental scaling technology for the Internet. Translation of addresses, whether it is between IPv4 and IPv4 or involves protocol translations as well (as is the case in IPv4->IPv6->IPv4, or IPv6->IPv4->IPv6), is simply the most practical and effective way of overcoming the two principal scaling problems of the Internet, namely the narrowness of the IPv4 address and the fact that deployed routing protocols simply suck. Observe that so long as a translatable subset of transport layer options are used, there is absolutely no difference between NAT between IPv4 addresses and protocol translation between IPv4 and IPv6. Moreover, in the latter case, you are not restricted to IPv6s4 (who comes up with these acronyms anyway? Does anyone mind if I call IPv4 IP? If you do, well, tough.) The technical goal is that end to end services will work, period, in all cases. This is possible provided that the higher order protocols do not make invalid assumptions about the transport layer. Most importantly, just as CIDR requires that protocol implementations respect that IP addresses may change over time, NAT as THE new fundamental scaling technology requires that protocol implementations respect that IP addresses may change over space as well. That is, so long as protocols do not assume that an IP address is the same from the point of view of all locations throughout the concatenated Internet, they will do just fine with either NAT or protocol translation or both. Returning to the observation that NAT and protocol translation are semantically equivalent from an end-to-end perspective, we now need to consider whether simple address translation or protocol translation is a better idea.
But just having [network routing software] translating IPv4 <-> IPv6s4 is not enough. We will need to manage the new IPv6 network.
Deployed base is a strong engineering consderation in an industry which is experiencing enormous growth. NAT has the advantage that reasonably designed existing technologies ought not even notice that NAT is happening. Protocol translation, on the other hand, requires, as you say, new management techniques, which will generally involve lots of learning time on the part of lots of engineers and operators, wherever the new protocol is deployed. The fact is, that there may be a reason to deploy a new protocol that makes this worthwhile, however, you should also note that so long as a translation between transport layers is straightforward, there is no reason why the new protocol needs to be IPv6. In fact, I welcome IPv6's fan base working on protocol translation because there are also some more interesting experimental protocols which could be deployed in precisely the same fashion that do not suffer some of the brokenesses of IPv6. Most notably:
Routing issues will become different in IPv6.
This is simply untrue. Routing issues are EXACTLY the same in IP and IPv6, the only difference is the width of the addresses, which worsens the poor scaling properties of IP with current routing protocols. The only attractive (and this is very very very speculative) aspect of the IPv6 address scheme is that it may be wide enough to experiment with something like using a modified IS-IS that works on multiple hierarchical areas encoded as fields in the IPv6 address, with the thought of using that to supplant current interdomain routing protocols. I'm sure this thought will go over well with the IPv6 crowd...
If IPv6 allocations will have varying sizes like CIDR, then we might continue to have issues of size based route filtering.
Please understand that the size-based filtering is done to limit the number of prefixes carried, and that this is completely independent of IP vs IPv6. If the number of prefixes must be kept to some maximum by filtering at, say, the 19 bit mark, the same maximum will be maintained even if the address space is much wider, and the straightforward way of doing that is to retain filters at the 19 bit mark.
OTOH, with the right methods of allocating IPv6 space, no one should ever have to come back to get more space. Eventually that should mean fewer routes as IPv4/IPv6s4 closes down. Route filtering should be encouraged on IPv4 space and prohibited on IPv6 space, at that point, IMHO.
Could you pleace elaborate? I am completely lost by your logic here. Sean.