No, not a B2BUA. Each element would have a virtual UA function "in
parallel" to its regular function (e.g. being a proxy). And indeed, one
way to implement this would be to keep either one (one way) or two
(opposite ways) flows active between them.
Like so:
|-----------| |-----------|
| Proxy | | Proxy |
|-----------| |-----------|
| UA | <---------->| UA |
|-----------| |-----------|
Each "UA" would implement both a simple registrar and a UAC performing
registration. It could also be setup asymmetrically, with the (smaller)
IP-PBX doing a single registration towards the (bigger) Service provider
network. Registration expiry would denote a loss of connectivity.
Regards,
Jeroen
Christer Holmberg wrote:
Hi,
So, you are proposing that each element should be a B2BUA, and both elements
then register towards each other and use Outbound???
Regards,
Christer
-----Original Message-----
From: Jeroen van Bemmel [mailto:[EMAIL PROTECTED]
Sent: 25. kesäkuuta 2008 22:57
To: Hadriel Kaplan
Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; [email protected];
Christer Holmberg
Subject: Re: [Sip] Progress draft-holmberg-sip-keep: proxy-to-proxy use case
Hadriel, Markus,
Instead of standardizing keep-alives between proxies, how about we define a "virtual
UA" on each element (similar to the one described in
RFC3261 section 16.7 point 6) to be used to provide this functionality?
(using existing outbound functionality, perhaps both ways)
Regards,
Jeroen
Hadriel Kaplan wrote:
Yes I am of that same opinion - that any real "IP-PBX" or whatever big
enough NOT to be doing Registration, and to instead do static provisioning or DNS, would be given a static hole/DMZ address in their firewall/NAT. But some of my customers have told me otherwise. (interestingly mostly in APAC region) There's also some concern that while a static entry is there for inbound TCP connections, the PBX creates outbound ones to the service provider which are ephemeral port sources and need to live for very long durations (though why they can't just do TCP keepalive is beyond me, but I'm no expert).
But anyway, the big issue we've seen is that we need both the PBX and the
service provider box to detect failure before an active call/request attempt is
made; to trigger alternate route selection without waiting for transport
failure, and as a method to detect liveness again and revert. Today that's
almost exclusively done with Options requests as far as I've seen, and lots of
people don't seem to like that.
-hadriel
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Wednesday, June 25, 2008 3:11 PM
To: [EMAIL PROTECTED]; Hadriel Kaplan;
[EMAIL PROTECTED]; [email protected]
Cc: [EMAIL PROTECTED]
Subject: RE: [Sip] Progress draft-holmberg-sip-keep: proxy-to-proxy
use case
Hi,
I'm a bit sceptical about the need for keep-alives between proxies.
It is of course entirely possible that an enterprise PBX is connected
to (or peering with) a service provider proxy through a NAT and/or a
firewall. However, wouldn't such a NAT or firewall be under the
administration of either the enterprise itself or its ISP (who quite
often would be the SIP service provider), and the required port
forwardings or firewall rules could be set through administration.
This means that there would not be need for keepalive traffic to
implicitely keep the mapping/pinhole open.
Or are there really deployment cases where there are SIP PBXs behind
unadministrated NATs or firewalls?
Wouldn't we then need keepalives for SMTP as well, or how has the
e-mail infrastructure managed to solve this problem?
Markus
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