Gateway-Controlled Modem Relay
Beginning with Cisco IOS Release 12.4(4)T, Cisco supports gateway-controlled negotiation
parameters for modem relay. This new affection is a non-negotiated, bearer-switched
mode for modem carriage that does not absorb call-agent-assisted agreement during
the alarm setup. Instead, the agreement ambit are configured anon on the gateway.
These gateway-controlled agreement ambit use NSEs to announce the switchover
from articulation to articulation bandage abstracts to modem relay.
Upon audition a 2100 Hz tone, the absolute aperture sends an NSE 192 to the originating
gateway and switches over to modem pass-through. The absolute aperture also
sends an NSE 199 to announce modem relay. If this accident is accustomed by the originating
gateway, the alarm occurs as modem relay. If the accident is not recognized, the alarm occurs as
modem pass-through.
Because Cisco modem broadcast uses configured parameters, it removes the signaling
dependency from the alarm abettor and allows modem broadcast abutment absolute of call
control. Cisco modem broadcast can be deployed over any alarm abettor that is able of setting
up a articulation affiliation amid gateways, including Cisco Unified Communications
Manager, Cisco Unified Communications Manager Express, and the Cisco BTS and PGW
soft switches.
The gateway-controlled modem broadcast ambit are enabled by absence back Cisco
modem broadcast is configured. Interestingly, back Cisco modem broadcast is configured, gateway
XID constant agreement is consistently enabled. Aperture XID ambit are negotiated
using the SPRT protocol.