TVOICE – SAF and CCD- Understanding How SAF and CCD Works

Intro..If you’re one for “revolutionary technology,” you’ll absolutely love this Nugget! The Service Advertising Framework (SAF) and Call Control Discovery (CCD) protocols represent an evolution in designing voice network by allowing the Call Agents (and SAF Forwarders) to do the dial plan work for you. Tune into this Nugget to learn more! 

Understanding SAF and CCD

Advertises services around the network, the same as a dynamic routing protocol would advertise routes.

CCD is the 1st Cisco service to use SAF (Call Control Discovery)

Two Components:

-SAF Forwarders
-SAF Clients

SAF Client/Forwarder Communication

Call Agent = UCM/VG/CUBE

Call Agent can advertise UCM info to a SAF Forwarder

SAF is engine behind CCD, CCD is the payload/info carried by SAF.

Forwarders just send onto neighbours and don’t care about the content
Clients received the payload and process it.

SAF-FP used by Forwarders
SAF-CP used by Clients (Internal and External)

Forwarders are always routers.

Internal Client = Device acting as a Forwarder and Client in 1. Cisco router as a VG and router for example.

External Client = Example is UCM with no Forwarder.

SAF Routing (Engine)

  • Cisco designed SAF as a service routing protocol
  • Used many of EIGRP characteristics
  • Neighbor discovery via Multicast default
  • Support Unicast/Static neighbors including distant neighbors
  • SAF clients and forwarders use keepalives to detect death

What is CCD? (Cargo)

  • Allow call agents to advertise DN/PSTN numbers
  • Relies on SAF
  • Allows call agents (CUCM, CME, VG) to exchange voice routes
  • Eliminates the need for gatekeepers/SIP proxy servers
    Dynamic, provides PSTN failover
  • Allows digit transformations on PSTN failover using ToDID rules

More CCD detail..

CUCM is a SAF client, exchanges routes with a SAF forwarder

Route Filtering can be used (Prefix, Pattern, IP, SAF, Client ID)

Same Destination Number can be learned multiple times (CUCM CLUSTER) – Load balancing is used

CCD PSTN backup totally different than AAR (Which focuses on bandwidth)

External Client will advertise IP, DN and ToDID (PSTN Transformation Digits) info to Forwarder.

ToDID = Discard Digits:Add Digits