On Oct 7, 2008, at 4:41 PM, Paul Kyzivat wrote:
The question is: why would a *single* UA establish two distinct
contacts and register them for the same AOR?
Because it has two different network interfaces, with two separate IP
addresses, and it wants to use them both in case one of those contacts
fails. Keepalive is then used so that the proxy-registrar can note a
failed Contact.
This is the classic dual-homed node use case, and it affects
everything from DNS entries to BGP route advertisement. It's a general
thorn in the sides of people who think of networks as acyclical graphs
or trees. Sometimes, leaf nodes have multiple stems for good reasons.
And, as you say, the edge proxies may be "access network
dependent", so
it may not even be possible to e.g. register the wlan contact via
the 3g
edge proxy, etc.
So you are saying that the contact addresses are themselves access
network dependent??? So that the ip address of the contact is only
accessible via a particular access network and proxy?
This *really* isn't the internet, is it!!!
This isn't just a registration problem.
Imagine an enterprise that's connected to two ISPs. Each ISP provides
an SBC for the enterprise.
Now you need two sets of telephone-routing tables to reach that
enterprise.
--
Dean
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