[Serusers] NAT ping and consumer router

[Jiri Kuthan]

At 04:13 PM 8/25/2004, Jesus Rodriguez wrote:
>That's like known SBCs work. Before, they sent an OPTIONS packet but last
>software versions modify the Expire of the 200 OK from REGISTER so is the
>UA the one that sends a new REGISTER and generates traffic from the
>internal side every 30 seconds. These REGISTER are not forwarded to the
>proxy. The SBC keeps a table where saves the "real" REGISTER expire sent to
>the proxy. This way you don't flood the proxy with all those REGISTER.

Which appears like a questionnable benefit -- I mean it does not seem to
make a big difference to me if the extra REGISTER load is put on SER PC
or some other PC in front of it... (Not mentioning what other pain SBCs
cause -- I just spent a good part of day/night reviewing a network setup
in which such an SBC caused real harm.)

I objected several ideas on this mailing list, like ALGs, SBC, and other
in-network NAT/SIP patches, so I should perhaps state what I consider
a good idea. First it takes good NAT support in end-devices. Creating
network-based patches to deal with NAT-incapable devices just creates
a great amount of complexity which typically breaks other things. Make
clients detect connectivity using STUN, perhaps ICE, let it send keep-alive,
implement SIP stack correctly, be symmetric, etc. That's something which
is achievable short-term, it is also buyer's responsibility to buy those
that get it right.

Long-term removing indeterminism from NATs as in IETF/behave is another
important acchitectural activity.

If people ask me how to make SIP/NAT stable right now, regardless of sanity,
my preference is to find a good UAC and stick to it. (I have to admit
I don't have a specific recommednations -- the capabilities change rapidly
fimrware by firmware in a pace I can't follow.) Configure SER to help
by reducing registration intervals, using a voice proxy, sending pings.


-jiri