Chapter 3 Provisioning the Cisco HSI

H.323 Stack Configuration

Codec Selection

The Cisco HSI negotiates the media stream codec to establish a match between the PSTN MGCP media gateway (for example, the Cisco AS5xxx series or Cisco MGX series) and the H.323 endpoint or gateway. To match codecs, the MGCP gateway must be configured to match what is expected at the H.323 end. Similarly, the Cisco HSI also must be configured with the same codecs.

The Cisco HSI receives a list of codecs from the MGCP gateway and matches the listed codecs to the codecs that are configured on the HSI. The HSI advertises all of the successful matches in the H.245 terminalCapabilitySet messaging with the H.323 endpoint.

It is important to determine and configure the “frames-per-packet” value correctly on the Cisco HSI per codec. If “frames-per-packet” value is incorrect, the codec may not be negotiated successfully between the HSI and the H.323 endpoint.

It is also important to configure the MGCP gateway correctly. The gateway should be configured to provide “static payload” values for the required codecs, rather than dynamic payload types (see Table 4 in RFC 3551, Schulzrinne and Casner).

Quick Reference for Important Parameters

Table 3-13, Table 3-14, Table 3-15, and Table 3-16can be used in initial HSI configuration. The tables present parameters that you might use frequently to align the Cisco HSI with an existing PSTN or Voice over IP network.

Table 3-13presents important call control parameters.

Table 3-13 Common Call Control Parameters

 

Parameter Name

Parameter Value

Description

 

 

 

 

 

 

 

A_CC_oLinecall

0—Unknown

Calling party's category

 

 

 

 

10—Ordinary

 

 

 

 

 

 

 

 

 

A_CC_Clir

0—No indication

Address presentation restricted indicator

 

 

 

 

1—Presentation allowed

 

 

 

 

 

 

 

2—Presentation restricted

 

 

 

 

 

 

 

3—Address not available

 

 

 

 

 

 

 

 

 

A_CC_ANumDataSI

0—None

Screening indicator

 

 

 

 

1—User provided not verified

 

 

 

 

 

 

 

2—User provided verified passed

 

 

 

 

 

 

 

3—User provided verified failed

 

 

 

 

 

 

 

4—Network provided

 

 

 

 

 

 

 

 

 

A_CC_oIsdnAllTheWay

0—ISDN user part not used all the way

Forward call indicator, ISUP indicator

 

 

 

 

1—ISDN user part used all the way

 

 

 

 

 

 

 

 

 

A_CC_oIsdnPref

0—ISDN user part preferred all the way

Forward call indicator, ISUP preference

 

 

 

 

1—ISDN user part not required all the

 

 

 

 

 

 

 

way

 

 

 

 

 

 

 

2—ISDN user part required all the way

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Cisco H.323 Signaling Interface User Guide

 

 

 

 

 

 

 

 

 

 

3-18

 

 

 

OL-4806-01 Rev. A14

 

 

 

 

 

 

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Cisco Systems H.323 Codec Selection, Quick Reference for Important Parameters, Parameter Name Parameter Value Description
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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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