This time I want to discuss one of the problems we see with Diameter and introduce a work being done to overcome this problem.
Capabilities exchange is one of the fundamental and most important mechanisms in Diameter, it is taking place in the beginning of each session, and allows peers to define the basic parameters/capabilities for the session (version number, supported Diameter apps, security mechanisms, etc…)
But what if the capabilities on one of the sides change during the session ? what if the sessions are being kept open for long time and in this time an upgrade or configuration change in one of the clients/servers involved takes place ?
The way Capabilities exchange is defined in RFC 3588 is that it can take place only in the inception of a session, so if there is a change during the session it means we need to tear down all the existing sessions involved and restarted in order for the updated capabilities to be taken into account – not very efficient you’ll agree.
But worry no more, the cure is on the way, a new IETF Diameter draft is here to help - The Diameter Capabilities Update Application.
A work led by Glen Zorn, whom is one of the driving forces behind Diameter since his Cisco days.
This work defines a new Diameter application intended to allow the dynamic update of a subset of Diameter peer capabilities over an existing connection.
Because the new proposed Capabilities Update application operates over an existing transport connection, modifications of certain capabilities is prohibited.
There are a lot of heated discussions going on in the Diameter swamp around this new work – some security issues have being raised, but I think those will be handled also.
This is a blessed and important work (I can see all of you with Gx interface related work scars nodding your heads) and let’s hope we will have this draft approved soon.
I personally believe with service providers complaining on the amount of signaling in Diameter and the delays involved in some of sessions set up times – this new work is very important and sheds bright healthy light into one of the dark corners of the Diameter 3588 RFC.