DRAG DROP
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Explanation/Reference:
Cisco 642-437 Exam
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H.225 is responsible only for setting up the call and routing it to the proper destination. H.225 does not haveany mechanism for exchanging capabilities or setting up and tearing down media streams. The called H.323 device is responsible for sending the IP address and port number that are used to establish the TCPconnections for H.245 signaling. This information can be sent by the called device in either the Alerting orConnect message. When the originating H.323 device receives the IP address and port number for H.245negotiations, it initiates a second TCP connection to carry out the necessary capabilities exchange andlogical channel negotiations. This TCP session is primarily used to do four things:
Master/slave determination-This is used to resolve conflicts that might exist when two endpoints in a callrequest the same thing, but only one of the two can gain access to the resource at a time. Terminalcapabilities exchange-This is one of the most important functions of the H.245 protocol. The two mostimportant capabilities are the supported audio codecs and the basic audio calls. Logical channel signaling-This indicates a one-way audio stream. With H.323 version 2, it is possible to open and close logicalchannels in the middle of a call. Because H.245 messages are independent of the H.225 signaling, a callcan still be connected in H.225 even if no logical 56
Cisco 642-437 Exam
channels are open. This is typical with such features as hold, transfer, and conference. DTMF relay-Because voice networks typically do not carry DTMF tones inband because of compression issues, thesetones are carried on the signaling channel. Ensure that the type of DTMF relay configured on your gatewayis compatible with your gatekeeper. http://www.cisco.com/en/US/docs/ios/12_3/vvf_c/voice_troubleshooting/old/vts_h323.html#wp106