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vcs expressway internetworking question

So i have an issue and am curious if any one can explain.

So i have a control and expressway setup and when I dial on an internal endpoint outbound to an endpoint on the Internet as an IP address via SIP, and the endpoint on the Internet only talks h323, the expressway tries to send out a SIP-Invite. Which it is merely forwarding on from the control. Well and good. The SIP invite is sent until a 30 second timeout si reached. The expressway will then send out a h323_setup and the call connects. All well and good.




If I do the same thing, but this time dial the IP address via h323 from my endpoint, a SIP Options is sent as oppose to the invite, and the expressway NEVER attempts to send a h323 setup after the 30-second SIP timeout. Does anyone know why that it is?


To recap,

1) why does the interworking send a SIP options, as opposed to a SIP invite?

2) Why does the expressway never try h323?


Diagram:                                                                (only sip between control and expressway)

internal Endpoint dialing IP address via SIP -> Control -> expressway -> IP_address
                                                              (Invite)       (invite)          (invite)
                                                              after 30 second time out (h323_setup)


internal endpoint dial IP address via h323 -> Control -> expressway -> IP_address
                                                         (h323)     (sip options)       (sip options)
                                                       after 30 second time out no (h323_setup)




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