Avaya BCM 2.0 IP Telephony Manual de usuario descargar pdf (Pagina 42)

42 Engineering guidelines

Enterprise Edge 2.0 IP Telephony Configuration Guide P0911590 Issue 02

• Interoperability with other IP gateways. A terminating gateway must support

CED fax tone detection, and start the procedure as described in previous

paragraphs. An originating gateway must support the H.323 Request Mode

procedure, but does not need to detect fax tones. The originating gateway must

additionally be capable of supporting the large G.711 packets used for fax

transmission.

• In order for the gateways to revert to a G.711 clear channel, the terminating fax

machine must issue a CED tone when answering the call. Manually started fax

transmissions, where the user at the terminating end first talks with the

originating user before setting the terminating fax to receive the document, are

not supported.

• Fax machines allow a maximum round trip delay of 1200 ms. Media processing

in the two gateways introduces a round trip delay of approximately 300 ms, and

the delay caused by the jitter buffer. If a 250 ms jitter buffer is used, IP latency

must never exceed (1200 - (300 + (2 x 250))) = 400 ms round trip delay, or

approximately 200 ms one way.

Fallback threshold

Fallback threshold has two parameters, the receive fallback threshold (Rx) and the

transmit fallback threshold (Tx), set on a per site pair basis.

The Setting QoS section on page 26 and Measuring Intranet QoS section on page 27

describe the process to determine the appropriate QoS level for operating the voice

network. Site pairs can have very different QoS measurements, either because some

traffic flows are local, while other traffic flows are inter-continental. The installer

or administrator can consider setting a higher QoS level for the local sites compared

to the international sites, keeping cost of international WAN links down.

Normally, set the fallback threshold in both directions to the same QoS level. In site

pairs where the applications are so that one direction of flow is more important, the

installer or administrator can set up asymmetric QoS levels.

Enterprise Edge uses routes to determine which outgoing facilities to use. A given

destination code can have an alternate route configured. The alternate route is used

if the main route is not available to process calls. For example, calls use the alternate

route if all lines in the line pool are busy. See the Enterprise Edge Programming

Operations Guide for more information.

IP trunks can use this capability. Unique to IP trunks is the ability to take advantage

of the QoS monitoring capability that is part of IP telephony. If fallback

functionality enabled, any QoS damage in the intranet which causes any monitored

remote gateway to exceed its threshold results in the configuration of an alternate

route (if configured). Until the QoS improves, IP trunks are all considered busy.

Enable QoS monitoring for the required destination in the Modifying the Remote

Gateway Configuration table on page 66. To prevent a few bad sites from starting

fallback, disable the QoS monitoring for remote gateways which have QoS

problems until solved.

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Avaya BCM 2.0 IP Telephony Manual de usuario Pagina 42

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