Re: [v4v6interim] "IPv4->IPv6 is hard"
Fred Baker <fred@cisco.com> Fri, 17 October 2008 15:56 UTC
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From: Fred Baker <fred@cisco.com>
To: Iljitsch van Beijnum <iljitsch@muada.com>
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Cc: v4v6interim@ietf.org
Subject: Re: [v4v6interim] "IPv4->IPv6 is hard"
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On Oct 17, 2008, at 3:40 AM, Iljitsch van Beijnum wrote: > So you _don't_ want to solve the situation where an IPv4-only host > gets to talk to any given IPv6 host. > > I think it would be fair to call _that_ scenario "hard". > > However, I think there are others who are interested in solving this > case. Correct on both points. NAT-PT tries to connect any IPv4 to any IPv6, and winds up with some "interesting" operational complexity as a result. I think that if you want to go after that problem for real, the solution you come up with is going to have comparable complexity and weaknesses. Willing to be proven wrong, but that's what it looks like to me. However, using an IPv4 address mapped into an IPv6 address as SIIT does, we can provide access to a subset of IPv6 nodes - the ones that have such an address in addition to their standard IPv6 address. We can describe a relatively simple mechanism that will address most requirements for quite a while. I would far rather go for the low hanging fruit and let those who want to solve the bigger problem do so without slowing the relatively easy part down. In my mind, it is in large part a question of requirements. Would it be nice to enable any IPv4 node to access any IPv6 node? of course. But is that really needed? I don't think so. As I said in email during the interim, you really have two application cases - client/server (the web and POP/IMAP being examples, and SMTP when it is configured to upload mail from an application like OutLook to a corporate/ISP mail server), and peer-to-peer. SMTP is peer-to- peer between MTAs (TCP sessions are created in both directions), and applications like BitTorrent are obviously peer-to-peer. Obviously you need any client to be able to access any server. Given that there are often several orders of magnitude more clients than servers in such applications, I have a relatively small translation requirement - I don't need any computer to any computer, I only need for IPv6 clients to be able to access IPv4 servers (mapped address in the client or stateful NATs comparable to present NAT44 will work), and IPv4 clients to access IPv6 servers (simply done with a mapped address). For peer to peer applications like SMTP, using mapped addresses makes it relatively simple to support them. Since one expects them to be the bulk of application traffic, stateless translation has some real benefits there as well. Why does one expect that? Well, if one MTA serves 10,000 MUAs that each upload less than 100 messages a day, that MTA is at any given time talking with only a few of them, perhaps 10-100. But it will be constantly chatting with the next MTA upstream as it sends its clients' 10,000*100 messages along. For peer to peer applications like BitTorrent, while what would otherwise be called "clients" in fact open TCP-like connections willy- nilly, they have rules about how they open them. They tend to open a few connections that they leave open for a long time and use bidirectionally, so opening a connection in the IPv6->IPv4 direction works also to move content from the IPv4 domain to the IPv6 domain. Within each domain, connections generally work, and content can be moved where it needs to be. Using NAT44-like technology, IPv6 systems can access IPv4 systems readily. IPv4 systems won't be able to access IPv6-native peers, but they won't need to as the content will already be in their domain. So I don't think we need any<->any access anywhere near as much as we need the much simpler ability to have IPv4 systems access IPv6 *servers*, systems that have stable addresses that are generally assigned to them anyway. _______________________________________________ v4v6interim mailing list v4v6interim@ietf.org https://www.ietf.org/mailman/listinfo/v4v6interim
- [v4v6interim] "IPv4->IPv6 is hard" Fred Baker
- Re: [v4v6interim] "IPv4->IPv6 is hard" Mark Townsley
- Re: [v4v6interim] "IPv4->IPv6 is hard" Fred Baker
- Re: [v4v6interim] "IPv4->IPv6 is hard" Iljitsch van Beijnum
- Re: [v4v6interim] "IPv4->IPv6 is hard" Ed Jankiewicz
- Re: [v4v6interim] "IPv4->IPv6 is hard" Fred Baker
- Re: [v4v6interim] "IPv4->IPv6 is hard" Randy Bush
- Re: [v4v6interim] "IPv4->IPv6 is hard" Ed Jankiewicz
- Re: [v4v6interim] "IPv4->IPv6 is hard" Randy Bush
- Re: [v4v6interim] "IPv4->IPv6 is hard" Ed Jankiewicz
- Re: [v4v6interim] "IPv4->IPv6 is hard" Eric Vyncke (evyncke)
- Re: [v4v6interim] "IPv4->IPv6 is hard" Fred Baker
- Re: [v4v6interim] "IPv4->IPv6 is hard" Fred Baker
- Re: [v4v6interim] "IPv4->IPv6 is hard" Xing Li
- Re: [v4v6interim] "IPv4->IPv6 is hard" marcelo bagnulo braun
- Re: [v4v6interim] "IPv4->IPv6 is hard" Fred Baker
- Re: [v4v6interim] "IPv4->IPv6 is hard" Xing Li
- Re: [v4v6interim] "IPv4->IPv6 is hard" Xing Li
- Re: [v4v6interim] "IPv4->IPv6 is hard" marcelo bagnulo braun
- Re: [v4v6interim] "IPv4->IPv6 is hard" Mark Townsley
- Re: [v4v6interim] "IPv4->IPv6 is hard" Rémi Després
- Re: [v4v6interim] "IPv4->IPv6 is hard" Xing Li