Cisco Systems H.323 appendix Asymmetric Codec Treatment, Empty Capability Set, Hairpin

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Chapter 3 Provisioning the Cisco HSI

HSI Feature Configuration

•Configuring G.726 on the Cisco HSI

•Configuring G.729 Annex and G.729 Annex B

Asymmetric Codec Treatment

The Asymmetric Codec Treatment feature averts the potential for inconsistencies in codec selection, which can result if the open channel requests are sent by each endpoint at nearly the same time, so that neither side has received an open channel request prior to sending one. In practice, such asymmetric conditions occur only for slow start calls. When there is a fast start recipient, both channels agree to use the same codec in unison.

The Asymmetric Codec Treatment support is enabled if this parameter is present and set to anything other than “”. For example, support is enabled if the parameter is explicitly set to “Enabled.” To enable Asymmetric Codec Treatment, enter the following command:

Example:

prov-add:name=sys_config_static, asymmetrichandlingsupported = "Enabled"

Empty Capability Set

The Empty Capability Set feature enables an H.323 endpoint to send a TCS message with empty capabilities during a call. The TCS message causes the audio channels to close. This action enables the negotiation and opening of new audio channels.

The Empty Capability Set feature is useful when the H.323 endpoint wishes to change the audio codec during a call or if the endpoint needs to divert the media streams to a different location. Typically, the feature is used to place a call on hold to disable the media stream until the user presses the Resume button.

The Empty Capability Set feature on the HSI requires no provisioning.

H.323 Hairpin

The H.323 Hairpin feature can be used to connect a call between two H.323 endpoints without using resources on the media gateway. For example, the PGW can respond to the dialled number in an incoming H.323 call by routing the call to another HSI (perhaps the same HSI) rather than routing the call to the PSTN. In this case, the originating and terminating HSIs establish the call normally but pass the H.245 address of the H.323 endpoints. This enables the two endpoints to use H.245 to negotiate media channels with each other directly, independent of the HSI.

The H.323 Hairpin feature on the HSI requires no provisioning. However, to operate throughout the system, H.323 Hairpin must be enabled on the PGW. On the PGW, you enable H.323 Hairpin through a trunk group property by issuing the following commands:

prov-add:trnkgrpprop:name="2000",AllowH323Hairpin="1" prov-add:trnkgrpprop:name="3000",AllowH323Hairpin="1"

Note H.323 Hairpin must be enabled for both the ingress and egress EISUP trunk groups.

 

 

Cisco H.323 Signaling Interface User Guide

 

 

 

 

 

 

OL-4806-01 Rev. A14

 

 

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Contents Provisioning the Cisco HSI Description MML Configuration CommandsCommand Command DescriptionVerifying the Configuration Introduction to MML Command Operation for HSIInitiating an MML Session to Enable Dtmf on the HSI Example System Configuration DataReverting to the Base Configuration Static System DataParameter Type Description Parameter, set it to Enabled Changing Static System Data Issue the command restart-softwconfirmDynamic System Data Parameter Description DefaultOVLDLEVEL1THRESHLOWER OVLDLEVEL1PERCENTOVLDLEVEL3PERCENT OVLDLEVEL1FILTEROVLDLEVEL3THRESHUPPER AlarmdebouncetimeOVLDLEVEL3FILTER OVLDLEVEL3THRESHLOWERParameters Nonprovisionable DataMML Provisionable Data System ParametersNull Parameter Name Description Type Example Update TypeParameter Name Description Type Example RAS ParametersAllowCallsWhenNonReg If this parameter is present, it String H323ESP Parameter Name Type UpdateINTEGER0,1 Parameter Name Parameter Value Description Codec SelectionQuick Reference for Important Parameters 14presents important static system data parameters Parameter Name Parameter Values Description VSCBPORTNUMBER1/2 VSCBIPADDR1/2Parameter Name Parameter Value HSI Feature ConfigurationHairpin Asymmetric Codec TreatmentEmpty Capability Set 38 Fax Configuring T.38 Fax on the Cisco Pstn GatewayConfiguring T.38 Fax on a Cisco IOS H.323 Gateway Configuring T.38 Fax on a Cisco IOS Mgcp GatewayHSI Support for Tech Prefixes Configuring Clear Channel on the Cisco HSIClear Channel Parameters Example Value Example Configuration Configuring G.726 on the Cisco HSI Configuring the Payload Type for the Mgcp Parameter Example Value Configuration ExampleConfiguring Cisco HSI g726-generic OL-4806-01 Rev. A14 Parameter Configuring G.729 Annex and G.729 Annex BOL-4806-01 Rev. A14
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H.323 specifications

Cisco Systems H.323 is a set of standards designed for transmitting audio, video, and data over packet-switched networks. It is a critical technology that enables real-time communication and has become integral to the world of VoIP (Voice over Internet Protocol) and video conferencing applications. Originally developed by the ITU-T, H.323 has been widely adopted and implemented by Cisco Systems, allowing organizations to leverage reliable and scalable communication solutions.

One of the standout features of H.323 is its ability to support interoperability among varying equipment and platforms. This means that devices from different manufacturers can communicate seamlessly, which is vital in a diverse technical environment. H.323 does this by defining protocols that handle signaling, media transport, and control, ensuring that various systems can work together effectively.

Key technologies utilized within H.323 include H.225 and H.245 signaling protocols. H.225 is responsible for call setup and management, establishing communication between endpoints. In contrast, H.245 manages the negotiation of media channels, allowing devices to configure themselves based on the capabilities of each other. This adaptability is crucial for dynamic network conditions typical in VoIP applications.

Another defining characteristic of H.323 is its support for multiple types of multimedia communication, including point-to-point and multipoint calls. This flexibility supports everything from simple audio calls to complex videoconferencing setups, where many participants can share video and audio streams concurrently. Cisco enhances this capability through its hardware and software offerings, optimizing performance for conference calls.

H.323 also features robust error resilience mechanisms. This ensures that real-time data, which is typically sensitive to delays and losses, can be transmitted with minimal disruption. Moreover, it facilitates quality of service (QoS) implementation, allowing organizations to prioritize voice and video traffic over less critical data services, thereby improving the overall user experience.

In conclusion, Cisco Systems H.323 stands out as a comprehensive solution for real-time communication over packet-based networks. Its main features, including interoperability, multimedia support, and enhanced error resilience, position it as a relevant technology in both corporate and personal communication settings. As organizations continue to adopt cloud and hybrid communication models, H.323 remains a reliable backbone for ensuring connectivity and collaboration across diverse platforms.
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