Clearspan® Product Overview R19 Aastra – 2740-0072014 Clearspan® is a Registered Trademark of Aastra Technologies Ltd. Page 35 of 932.4.2.3 Internal Call FlowsShown in the following diagram (Figure 19), the last situation is where a Clearspan SIP user placesan “internal” call to another user serviced by the same Clearspan node. Please note that this is notto imply that the users must be collocated at the same physical site, because as mentioned earlier,the Clearspan solution supports the ability to service dispersed sites. The flows for the internal callsare naturally somewhat simpler than those for either Outbound or Inbound calls, since there is noneed to involve the service provider (assuming that the calls are routed over the internal networkeven if both “internal” parties are at different physical locations). The SIP Signaling traverses the customer LAN to reach the Clearspan node (1) and (2). Upon being processed by the Clearspan server complex, the signaling is forwarded overthe customers’ LAN to route to the remote endpoint (3) and (4). Upon completing the call set-up, the RTP media stream is routed directly between the twoendpoints, without having to traverse through the Clearspan server complex. Also, aspreviously mentioned, the two endpoint need not both be SIP endpoints.Figure 19. Clearspan Internal Signaling and Call Flows.Shown in the following diagram (Figure 20), for internal calls, the call set-up is handled within theClearspan node itself, and we see that the process involves the following servers:Upon completing the call setup, the RTP flows directly from the initiating SIP endpoint, to the calledparty SIP endpoint.
