I have a firewall appliance that does VOIP just fine, in fact I have 4 Vonage devices behind my Firebox x1250 and they have no issues at all.
I have entire medical centers behind firewall appliances, using NAT, where there are VOIP based systems for some departments - and they work across a site-site VPN through the firewalls.
And I have yet to actually experience one that is broken and I started with the first NAT router that was released for residential use and have used Linksys, D-Link, Netgear, 3COM, CISCO devices without breaking anything.
A residential/home user is safer behind a NAT router than directly connected to the internet. While NAT is not a security feature, a 1:MANY NAT does offer "protection" from unsolicited traffic - and that is a very big protection when talking about the typical ignorant users home computer(s).
4864 Local Network Protection for IPv6. G. Van de Velde, T. Hain, R. Droms, B. Carpenter, E. Klein. May 2007. (Format: TXT=95448 bytes) (Status: INFORMATIONAL)
An artifact of the way blocks of IP addresses were handed out in the
1970s through mid 1990s. Initially, you got the next larger size of a /24, /16 or /8. This attitude is shown by the effective use of a single host with _two_ slant eights (0.0.0.0 and 127.0.0.0) verses two (or more) /32s. If you look at the way blocks are being handed out now (2009), the majority of new blocks are smaller than /20s (255.255.240.0 or fffff000 - 4094 usable addresses)
At the moment, it's not solved by IPv6 either. Ignoring work (because of an NDA), just one of the four ISPs I regularly use provides real IPv6 addresses. If you look world wide, that is above the average. On
15 September 2009, the five Regional Internet Registries (AfriNIC, APNIC, ARIN, LACNIC and RIPE) had allocated or assigned 2,923,334,816 IPv4 addresses (78.87 percent of non-RFC3330 address space) in 97651 networks. They've also allocated or assigned 1.103e33 IPv6 addresses (0.026 percent of the non-RFC5156 address space) in 3697 networks. You're posting with a .se domain - Sweden had 870 IPv4 blocks and just
66 IPv6 blocks. Great - there are a jillion IPv6 addresses (the _smallest_ assigned blocks are 4 /64s, each of which is 1.845e18 addresses - six billion times the total current IPv4 space) but if the only way I can get to them is through the equivalent of NAT, and that adds 6 to _20_ hops to the path (latency), it's not doing me a whole lot of good. Chicken? Egg? Sure, eventually IPv6 is going to save the planet, but that day isn't in sight yet, and until then, NAT and RFC1918 is going to remain an important part.
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