Altigen AltiWare ACM 5.2 Administration Manual page 225

SIP Extension Channel—Establishes a logical channel relationship with other
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analog and MobileExt ports (displayed on the SIPSP board configuration, Channel
Mapping List).
SIP Extension Channel Activation—Associates an extension with a SIP Extension
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channel when IP phones register to the system (displayed in the Extension View
window).
Media Channel—an RTP channel connects system-to-phone, or phone-to-phone,
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system-to-system to carry the digitized voice stream. The codec resource on the
VoIP board will be allocated dynamically based on connection types. If both end
devices are IP phones, the media channel can be connected from IP phone to IP
phone using the IP phone's codec, except when the following is true:
H.323 tie-trunk is used
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SIP trunk is used
•
codecs at two end devices are mismatched
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extension has Agent setting checked
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voice recording is enabled at the IP extension
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a NAT router exists between AltiServ and remote IP phone
•
SIP supports a direct connection of the voice stream between SIP phones. H.323 tie-
trunks still require the voice stream to connect to the server.
Chapter 16: Setting Up IP Extensions
AltiWare ACM 5.2 Administration Manual 213