In normal SIP call, the CCM act as SIP proxy interconnecting 2 SIP endpoint in a conversation. And once the conversation is started, the CCM takes a step back.
How about for CUCM-SME, in the deployment guide, it is written that the SME supports 48 calls and 9000 concurrent calls. What is the concurrent calls in this context? Does this means that CUCM-SME involves throughout the conversation between 2 endpoints?