Service Advetisement Framework (SAF) is a method to transport discovery information that would typically resides locally across Wide Area Networks. A SAF-enabled network will transport encapsulated messages and distribute those as it they were part of an IP routing protocol.
Current Cisco implementation leverage EIGRP as a transport medium, independent of the actual routing protocol; could be a BGP, OSPF or IS-IS routed network.
The first application I want to spend a bit more time on is Call-Control Discovery.
Problematic with a large number Call-agent is to have them inter-working and in particular adjusting dial-plan amongst and between them. Previous to SAF, two options were offered as depicted below:
You’ll note that in both case the operational overhead and technical complexity can ramp up pretty quickly as the number of call-agents to inter-work is growing.
Cisco Unified Communications is using a new service, CCD, that leverages SAF to exchange call routing information, automatically, between multiple SAF-enabled call control systems (like CUCM, CUCME, CUBE). This permits those systems to update their call routing table dynamically.
The call-control, being a SAF-client, is sending CCD information to the first connected SAF-forwarder, a router in this case. CCD is contained in a SAF Advertisement, itself having a header and ‘service data’ payload.
Terminology:
SAF Client: any application wishing to advertise a service to the network or request a service from the network or both
SAF Forwarder: router feature – provides relationship between client and framework, stores service information and propagates it to other forwarders
Service: any information that a SAF client wishes to advertise and “consume” (e.g., dial plans for CCD)
SAF Advertisement: carries service information, consists of SAF Header and Service Data
Non-SAF Node: any router that does not run the SAF protocols
How does it work ?
In the following example, you have the San Jose site updating, via the SAF-enabled network, the New-York office with its call routing information.
Then New-York office is also sending its CCD to the SAF-enabled network, and by which San Jose call-control also gets updated call routing information.
Now a third call-control, London, is added to the scheme, the CCD does not need to be re-send by the call-control as it’s the SAF-agent that will update the new call-control, without other intervention. In the meantime, London’s CCD will be propagated across the SAF-enabled network.
If for any reason the IP path becomes unavailable to a specific call agent, the network will update itself the call routing information, alerting the other call-control to use the PSTN path to reach those location.
And the beauty of this, it all happened without any administrative actions with regards to the call-routing…. great isn’t it 🙂
Stay tuned to an upcoming post on how to configure CUCM to use SAF.
Filed under: Borderless Networks, Collaboration | Tagged: CCD, CUCM, IOS, medianet, SAF, UC Manager, UCM | Leave a comment »