[Serusers] NAT Traversal Technique Survey

[jh at lohi.eng.song.fi]

Jiri Kuthan writes:

 > technique:    UPnP
 > requirements: NATs and phones with UPnP support; Messenger and 
 >               snom are known to support UPnP; there is linux
 >               support for it

but how many nat boxes support upnp?  last time i looked at ms upnp
page, the list was very short.

 > technique:    ALG
 > requirements: SIP-capable NAT (like Intertex or Cisco/PIX)

i like this one.  cisco ios nat that is built in every cisco router
now has sip alg.  you must have very recent ios version though.

 > technique:    STUN
 > requirements: STUN-enabled phone (like k-phone, snom)
 > limitations:  doesn't work over symmetric NATs (words-of-mouth propaganda
 >               has been telling me that many residential NATs are fortunately
 >               not symmetric, but I don't know how objective this information
 >               really is)

we have tried kphone's stun in all mojor dsl providers in finland that
nat their customers and haven't had problems with any.  in some cases
you have to run stund in your outbound proxy and not in some other ip
address. 

-- juha