On Mon, 2006-04-24 at 11:56 -0700, Alex Pankratov wrote: > We've recently added UPnP support to our client software and > now I got some server-side stats and they are most interesting. > > Check this out - > > Roughly a half of all clients that reported success talking to > their 'routers' and establishing TCP/UDP port mappings were > still inaccessible from an outside via their mapped ports.
Interesting. Some reasons for this I can think of are as follows: - If I recall, UPnP on a NAT that is behind yet another NAT doesn't work well (since the UPnP Internet Gateway Device on most NATs typically doesn't act as a client for the outer NAT's UPnP IGD). This comes into play when some connects a wireless router to their existing wired-only NAT or something. - UPnP doesn't have nice crash semantics. If an application registers a mapping, crashes, is restarted, and re-registers the same mapping, some NATs ignore the new registration while other NATs silently reap the old mapping. The first case would result in broken behavior. - On the flip side, if two different applications register the same mapping, the latter mapping may silently override the former mapping or alternatively, the latter may get silently ignored. Either way, one of the applications suffers. > Anyone care to comment or compare this to their own numbers ? While I don't have numbers, I suspect UPnP success rate (for NATs that support UPnP) would depend on the application as well as the topology common for the target user population. As a side note, if you want to test UPnP functionality, target Japanese users -- based on anecdotal evidence, UPnP seems far more popular in the far east than anywhere else. cheers, -- Saikat
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