VoIP Now: H.323 protocols and their applications

September 06, 2005

H.323 protocols and their applications - Part 2

H.450 is a set of standards similar to the QSIG standards that detail services for ISDN networks. H.450 defines the Supplementary Services for the H.323 protocol. These include Call Transfer and Call Diversion. The H.450 protocol works with the H.225 protocol and its messages do not have a header.

H.450.1: It relates to the procedures for controlling the supplementary services between H.323 applications. It elaborates a signaling protocol that is common to all H.323 supplementary services and is based on the generic functional protocol for Private Integrated Services Network (PISN).

H.450.2: It is based on H.450.1 and is a Call Transfer supplementary service in H.323 networks. This protocol enables a user to transfer his call with another user to a third user without having to establish a call with the third user.

H.450.3: It is based on H.450.1 and is a Call Diversion supplementary service in H.323 networks. Call Forwarding Unconditional (SS-CFU), Call Forwarding Busy (SS-CFB), Call Forwarding No Reply (SS-CFNR), and Call Deflection (SS-CD) are the services that are included in this protocol. These services are applicable during call establishment and enable the diversion of a call to another specified endpoint, which may be a voicemail or a cell phone number. The reason for the diversion, such as unavailable or busy, is specified by H.450.3 to the destination endpoint, thereby allowing it to respond accordingly.

H.450.4: It is based on H.450.1 and is a Call Hold (SS-HOLD) supplementary service in H.323 networks. It enables the interruption and re-establishment of communication between users. SS-HOLD is applicable to the audio as well as video data streams. The caller can put the receiver on hold to carry out other activities and at the other end, the other person can too initiate another call without disturbing the held call, if he so wishes.

H.450.5: It is based on H.450.1 and is a Call Park (SS-PARK) supplementary service in H.323 networks. It enables a user (Parking User) to park a call (parked to endpoint); it results in the parking endpoint achieving idle status. The Parked User experiences filler music, video, or images while he is parked. A user can pick up a parked call or an alerting call using Call Pickup. Every authorized user of the H.323 network can avail this supplementary service irrespective of the gatekeeper zone.

H.450.6: Call waiting (SS-CW) operates when an endpoint is busy with another call or another application, such as emails. The caller is made aware of the endpoint being busy and has the option of either ending the calling or leaving a message waiting callback. The potential receiver can accept, reject, or ignore the call. SS-CW occurs when all other options such as active, waiting, etc have been exhausted.

H.450.7: It deals with Message Waiting Indications that may be voicemail, fax, teletex, etc. It is a general purpose mechanism in which a Message Center notifies the Served User at whose end A Message Waiting lamp lights up. Message related information such as the type of message, subject, and relevance can also be highlighted. Automated message retrieval and a callback request are possible in an H.323 environment.

H.450.8: It deals with Calling Party Name Presentation in which the receiver gets to see the name of the caller. The calling endpoint or gatekeeper provides the name of the caller for gatekeeper routed calls. The gateway obtains the name of the calling party from the switched circuit network and passes it to the packet network.

H.450.9: It elaborates on the Completion of Calls to Busy Subscribers (SS-CCBS). SS-CCBS notifies a caller if the receiver is busy, the receiver's endpoint can monitor activity at its end and inform the caller when it is free, upon receiving the information, the caller's endpoint then attempts to complete the call.

H.450.10: It is a Call Offer (SS-CO) supplementary service that allows a calling user to wait till the receiver reacts to the call. The receiver can accept the call after the resources become available to him. The receiver can ignore the call offered or try to make resources available by releasing or placing on hold other calls.

H.450.11: A served user can interrupt an established call by invoking Call Intrusion (SS-CI). A Call Intrusion results in the third user either being held, invited to a conference call, or force-released. The options available with a Call Intrusion depend upon the level of authorization with the served user.

H.450.12: It deals with the ANF-CMN service that allows for the exchange of Common Information, such as Feature Identifiers, Feature Values and Feature Controls. This information can serve as a foundation for the indications to the local user or for filtering requests. ANF-CMN endpoints can receive solicited and unsolicited services that can be offered as a combination.

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September 6, 2005 in Solutions | Permalink