Hmm, I've seen enough Cisco EMEA keynotes to know that unless its John Chambers, then they are optional ;-) So a slightly later start for day 1 (techtorial day is really day zero!) of the conference - glad to see they listened to the feedback years ago from the advisory council ;-)
So Call Admission Control (CAC from now on) - what is it about? Opening statement - "Video killed the network administrator" - One of the major focuses of this year's networkers is Video. It was pointed out that the session could fit 65 people in the room, but 100 people had registered for the session, so if the excess people had subscribed to the session for a video feed at just 384kbps - that would have be more than 10 Mbps of bandwidth to service the excess attendees (yes the session was full - and people were standing at the back).
CAC takes two forms based on whether it is topology aware or not (there are actually four primary CAC mechanisms but Cisco only supports two of them). Topology unaware CAC is best used on hub and spoke topologies, it is provided using either Cisco Unified Communications Manager (CUCM) locations, or gatekeeper zones. It is not suitable for topologies where there are multiple paths, or hierarchical topologies.
Topology aware CAC is provided by RSVP. RSVP is an old protocol that got a really bad wrap when it tried to do the whole QoS process. Newer techniques using a mix of DiffServ(DSCP-based) and IntServ(RSVP-based) QoS techniques means that RSVP is the new preferred CAC mechanism. RSVP sends a message from the source to the destination to check that the required bandwidth can be reserved before the call setup proceeds. RSVP does require that some of the routers within the path between source and destination are RSVP enabled. If a hop is not RSVP enabled, the reservation request is passed transparently to the next hop.
The original RSVP requirement expected the endpoints to be RSVP aware (i.e. intelligent endpoints), with the advances in Cisco Unified Communications Manager (CUCM) and related devices, this functionality is now moved to an RSVP agent which is an IOS device "near" to the endpoint (controlled by media resource groups) which provides the initial reservation request for the endpoint.
The session was very focused on RSVP, and the presenter’s (Vanessa again from the presence techtorial) opinion was that RSVP will become the standard CAC method and that combined with SAF – see a posting coming soon – h.323 gatekeepers will start to fade away.
One take away regarding CAC that Vanessa made provides a good analogy for non-technical people - "CAC is this - If a boat is made for 5 people and a you let a sixth person get in the boat, you all drown!"
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