A H.323 Support and Compliance

This Appendix briefly describes the H.323 Version 2 support and compliance including:

The Excel H.323 implementation enhances the Excel platform software to comply with the mandatory requirements of the H.323 Version 2 specification. This feature enhances the existing Voice over IP offering of the VDAC-ONE card for RTP bearer channels.

• Real-time Transport Protocol/Real-time Transport Control Protocol (RTP/RTCP)

• DTMF generation/detection: Supported by the DSP-ONE
Card. (G.711 CODEC only)

The Excel H.323 implementation enables the Excel platform to send and receive all the REQUIRED or mandatory fields in the H.323 Version 2 messages.

The Excel H.323 implementation enhances the Excel platform software to comply with the mandatory requirements of the H.323 Version 2 specification. This includes the Lightweight Registration Feature. H.323 Version 2 defines a lightweight registration procedure that still requires the full registration, but uses an abbreviated renewal procedure to update the gatekeeper and subsequently reduces overhead.

Lightweight registration requires each endpoint to specify a Time-to-Live (TTL) value in its Registration Request (RRQ) message. When a gatekeeper receives an RRQ message from the Excel platform with a TTL value, it returns an updated TTL timer value in a Registration Confirmation (RCF) message to the endpoint. Prior to the TTL timer expiring, the endpoint sends an RRQ message with the KeepAlive field set to "Yes", which refreshes the existing registration.

An H.323 Version 2 endpoint is not required to indicate a time-to-live in its registration request. If the endpoint does not indicate a time-to-live, the gatekeeper assigns one and sends it to the gateway in the RCF message. No configuration changes are permitted during a lightweight registration.

Dual-Tone Multi-Frequency (DTMF) is the tone generated on a touch-tone phone when you press keypad digits. During a call you might enter the DTMF to access Interactive Voice Response (IVR) systems such as voicemail, calling card services, and so on. DTMF is transported the same way as voice in the PSTN.

• H.323 provides the DTMF digit support using the User Input Indication (UII) H.245 message.

• Media gateways or the VDAC-ONE card can provide DTMF digits in separate RTP packet formats.

• Media streams can accurately transmit DTMF digits "in-band" using high bit-rate CODECS. Media gateways or the VDAC-ONE card with high bit-rate CODECS can reproduce DTMF digits in the same manner as it creates voice packets.

Converged networks contain media gateways and other devices with high bit-rate and/or low bit-rate CODECS. High bit-rate CODECS, such as G.711, G.726, and G.727, reproduce DTMF digits accurately. However, low bit-rate CODECS, such as G.729, and G.723.1 require DTMF tones to be put in a separate RTP payload format because they cannot reproduce DTMF tone signals accurately enough for automatic recognition. Using separate RTP payload formats for both high and low bit-rate CODECS is one way to address DTMF tone reproduction in a standard way in the IP media stream.

The Excel platform is capable of supporting all methods of handling DTMF digits for ultimate partner flexibility. The current plan for DTMF digit support in this version of the Excel platform system is as follows:

• In-band DTMF digit support with VDAC-ONE for high bit-rate CODECS such as G.711, G.726, and G.727:

A 'hookflash" indication is a brief on-hook condition that occurs during a call. For example during a call, a phone user quickly depresses and then releases the hook switch on their telephone. It is not long enough to be interpreted as a signal to disconnect the call, but telephone switches and PBXs are frequently programmed to intercept hookflash indications and use them as a way to allow a user to invoke supplemental services. For example, your local service provider may allow you to enter a hookflash as a means of switching between calls if you subscribe to a call waiting service.

In the traditional telephone network, a hookflash results in a voltage change on the telephone line. Since there is no equivalent of this voltage change in an IP network, the ITU H.245 standard defines a message representing a hookflash. To send a hookflash indication using this message, an H.323 endpoint sends an H.245 User Input Indication message containing a "signal" structure with a value of "!". The value represents a hookflash indication.

The Excel platform H.323 implementation includes support for relaying hookflash indications using the H.245 User Input Indication message.

CODEC negotiation allows the gateway to offer several CODECS during the H.245 capability exchange phase and ultimately settle upon a single common CODEC during the call setup. This increases the probability of establishing a connection because there is a greater chance of overlapping audio capabilities between endpoints. During the call setup phase, the gateway uses the highest priority CODEC selected from the list that it has in common with the remote endpoint. It also adjusts to the CODEC selected by the remote endpoint so that a common CODEC is established for the receive and transmit audio directions.

IMTC stands for the International Multimedia Telecommunications Consortium, Inc., a non-profit corporation comprising more than 120 organizations around the globe. The IMTC's mission is to promote and facilitate the development and implementation of interoperable, multimedia, conferencing solutions based on open international standards -- particularly the multimedia conferencing standards adopted by the International Telecommunication Union (ITU), as well as other standards organizations.

IMTC iNOW! stands for "interoperability NOW!". IMTC iNOW! is an industry initiative to achieve interoperability as soon as possible between different vendor's IP telephony equipment platforms. IMTC iNOW! is not a standard and it is not proprietary.

IMTC iNOW! is an initiative that is supported by the major players in IP telephony including Excel, with new supporters being added all the time. Supporters of this initiative have committed to building or buying equipment that follows the IMTC iNOW! Profiles, publicly available documents that draw upon existing standards such as H.323. Any vendor that follows these Profiles will have the blueprint to build or operate IMTC iNOW! compliant equipment.

The Excel platform H.323 Version 2 offering does not operate on Release 5.x. If you are planning to use an Excel platform H.323 Version 2 Platform, your software requires Release 8.0 or later and the following hardware:

Elements	Supported	Notes
Call Direction: (O)riginate/(R)ecieve	Yes
GRQ/GCF RRQ/RCF URQ/UCF	Yes
BRQ/BCF	Yes
IRQ/IRR/IACK/INAK	Yes
GK Routed Call	Yes
Gateway Resource Availability	No
PreGranted ARQ	Yes
Q.931 Connection	Yes
Fast Start	Yes
Overlapped Sending	No
H.245 Tunneling	No
Q.931 Multiplexing	No
H.245 Connection Establishment	Yes
Empty Term Cap Set	Yes
MC Cascading	No
Supplementary Services H.450	No
ReplacementFor	No
Request Mode	No	Future Release
CommunicationModeCommand	No
H.235	No
T.38 FoIP	No	Future Release
IP Addressing	Yes
E.164 Alias Addressing	Yes
H.323 ID Alias Addressing	Yes
UniCast RTP/RTCP	Yes
MultiCast RTP/RTCP	No
G.711	Yes
G.726	No
G.723.1	Yes
G.722/G.722.1	No
G.728	No
G.729 (A, B)	Yes	G.729C is not supported
H.261	No
H.263	No
Data Channel (T.120)	No

Elements	Supported	Notes
SRV Discovery	No	Future Release
TXT Discovery	No	Future Release
A Record Discover	No	Future Release
Pre-Configured ID Discovery	Yes
GRQ Discover	Yes
GRQ/GCF RRQ/RCF URQ/UCF	Yes
GK Routed Call	Yes
Pre-Granted ARQ	Yes
Q.931 Connection	Yes
Fast Start	Yes
H.245 Tunneling	No
Lightweight RRQ(Keep Alive)	Yes
H.323 Annex J Authentication	No
H.323 Annex J Integrity	No
E.164 Addressing	Yes
E-mail Addressing	Yes
Keypad entries (Q.931 Info Msg.)	No
Alternate GK	Yes
Status Inquiry/Status	Yes
Unicast RTP/RTCP	Yes
G.711	Yes
G.723.1	Yes
G.729 (A, B)	Yes	G.729C is not supported
H.245v4	No	Future Release
H.245v6 syntax for Fax	No	Future Release
Interoperability with Simple Endpoint Type (SET) devices implementing the minimum requirements as defined by H.323 Annex F	No	Future Release

• This feature provides support for the ITU H.323 V2 teleconferencing standard.

ITU-T standard defines a set of call control, channel setup, and codec specifications for transmitting real-time voice and video over networks that do not offer guaranteed service or quality of service.

Internet Protocol. Part of the TCP/IP family of protocols used to route messages and tracks the addresses of nodes.

Real-Time Transport Protocol. Supports transport of real-time data like interactive voice and video over packet-switched networks.

International Telecommunications Union (UN)

The Registration, Admission, and Status messages communicated between two H.323 entities for example between an Endpoint and a Gatekeeper.

Real-Time Transport Control Protocol.

Call signaling protocol for setup and termination of calls.

A device that translates calls between an IP network and another network, typically the PSTN.

An H.323 entity on the network that provides address translation and controls access to the network for H.323 terminals and other end points. The gatekeeper may also provide other services to the endpoints such as bandwidth management and locating gateways.

Session-Initiation Protocol. A signaling protocol used for establishing sessions in an IP network. A session could be a simple, two-way telephone call, or it could be a collaborative multi-media conference session.

Interworking is a software feature within the Excel platform call control layer that enables protocol conversion by analyzing and converting Network Signaling (NS) Layer 3 information.

Voice over Internet Protocol. The delivery of voice information in digital form in discrete packets rather than in the traditional circuit-committed protocols of the public-switched telephone network (PSTN).

Voice Data Access Concentrator Card. Performs two-way conversion between circuit-switched data and packet-switched Ethernet data required by packetized voice applications such as VoIP.

Coder/Decoder. A CODEC converts voice signals from their analog form to digital signal acceptable to modern digital transmission systems.

Digital Signal Processor

DTMF. Method by which the digits (0-9) and symbols (* and #) are generated from a handset, represented by two tones, one high and one low frequency (touchtone dialing).

See Integrated Voice Response.

Public Switched Telephone Network

Address format for ISDN networks. The international public telecom-munications numbering plan. A standard set by ITU-T for addressing telephone numbers. See ITU Recommendation E.164 (1991).

An H.323 terminal or gateway, or MCU. An endpoint can call and be called. It generates and/or terminates the information stream.

The Matrix Controller Series 3 card is based on Motorola’s 750 PowerPC processor (68750). It is often referred to as the Matrix Controller.