The current version of H.450.6 is such that in a GK-routed environment, it becomes impossible for a GK to remain in control of the Call Waiting service and still be able to notify the served endpoint about the fact that there are calls waiting.
The reason for this is that the Recommendation only specifies a means for the served endpoint to notify the calling users/endpoints about the fact that there call "is waiting". The served endpoint uses incoming call setups to implement the service.
As a result, a GK has no choice but to propagate call setups to the served endpoint to let it know about incoming calls. This means that both the GK and the served endpoint implement Call Waiting, there will most likely be some unwanted service interaction.
For this purpose I propose to make the following modifications to H.450.6:
- 7.3 is split up into two parts (7.3.1 and 7.3.2). - The text that is now in 7.3 goes into 7.3.1. - The new section (7.3.2) will contain the following text:
--start of new text ---
"7.3.2 Call waiting notification to served user
A GK/Proxy may implement the Call Waiting service. In this case, the GK/Proxy may send a cwNotification Invoke APDU to the served endpoint. The GK/Proxy shall send the cwNotification Invoke APDU in either a FACILITY message of an existing call or in a SETUP message for a new call- independent signalling connection. If a new call-independent signalling connection is initiated, it shall be established in accordance with the procedures specified in 6.2/H.450.1."
--end of text---
The ASN.1 to be added is the following:
---Start of ASN.1-----
cwNotification OPERATION ::= { -- Sent from GK to served endpoint
ARGUMENT cwNotificationArg RETURN RESULT FALSE ALWAYS RESPONDS FALSE CODE local:xxx }
cwNotificationArg ::= SEQUENCE { nbOfCalls NbOfCalls OPTIONAL, waitingCalls SEQUENCE SIZE (0..65535) OF WaitingCall, extensionArg SEQUENCE SIZE (0..255) OF MixedExtension OPTIONAL ... }
WaitingCall ::= SEQUENCE { waitingNumber EndpointAddress OPTIONAL, -- if not present, waitingPosition must be present callId CallIdentifier OPTIONAL, -- to be used if waitingNumber is not present ... }
NbOfCalls ::= INTEGER (0..65535)
---End of ASN.1---
Some carifications for the above ASN.1:
- Since the operation defines a notification, no (return) result is required.
- Because the GK/Proxy may have more than one calls waiting, a "nbOfParties" field is added. This field, when present, will contain the number of parties that the GK/Proxy has currently waiting for the served endpoint.
- Since it may be possible that presentation restrictions or screening apply to a call, it is possible to only convey the callId and not the calling party's "number" to the served endpoint.
- The "waitingParties" element contains a list of parties that are currently waiting. The number of calls that can be waiting is set at the same number as the maximum number of calls that can be parked according to the H.450.5 Recommendation.
Regards,
Frank
----------------------------------------------------- Frank Derks |Tel +31 35 6893238 | ServWare |Fax +31 35 6891030 | Philips Business Communications|P.O. Box 32 | |1200 JD Hilversum | |The Netherlands | ----------------------------------------------------| E-mail: mailto:frank.derks@philips.com | WWW: http://www.sopho.philips.com | -----------------------------------------------------
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