http://www.networkDictionary.com/chinese/protocols/h225.php
H.225 is a primary protocol in the H.323 VoIP architecture defined by ITU-T, which is a standard for narrowband video telephony services in H.200 / AV.120-Series Recommendations. It mainly handles transmission path issues, including one or more network packets, where the configuration and management provides no guarantee service QoS, which cannot be equal to N-ISDN equivalent, and its additional protection or recovery mechanism is far exceeded by REC commission. The function of the agent. For the terminal, H.320 is very necessary. H.225 describes how to operate video, audio, data, and control information on the network package to provide H.323 equipment session services. H.225 There are two main parts: call signaling and RAS (registration, access allowance, and status).
The call control signaling of H.225 is used to establish a H.323 end point connection, which is achieved by exchange H.225 protocol information on the call signaling channel. The call signaling channel can be located between the end points and offices between two H.323 endpoints. The H.225 details the use and support of Q.931 signaling information. The TCP port 1720 of the IP network needs to create a reliable TCP call control channel that completes the initialization of the Q.931 call control information, thereby implementing connection, maintenance, and call separation. When there is a gateway exists in the network domain, the H.225 call installation information may also be exchanged by direct call signaling through custom routing call signaling GKRCs. Guan Gu is used to determine the option of the RAS access information exchange. Once there is a valid, H.225 information can be exchanged directly between endpoints.
H.225 / RAS (registration, access allowance) is a protocol between endpoints and gates. RAS is primarily used to enable registration between endpoints and gates, access allows control, bandwidth conversion, status, and removal programs. A RAS channel is primarily used to exchange RAS information, and the signaling channel is between a terminal and a gates prior to establishing any other channel.
Protocol structure
12348 BitProtocol Discriminator00 000Length of Call Reference BitsCall Reference Value 0MESSAGE TYPEINFORMATION Elements
Protocol Discriminator - Distinguish between network users call control information and other information. Length of call REF - Call reference value size. Call Reference Value - Identify calls or facilities, local network user interface registration / delete requests, applied to special information. Size may reach 2 optets. Message Type - Identification of functional information Elements - defines two types of information elements: an eight-bit information element and a variable length information element. As follows:
148 Bit1ieicontents Of IE
18 Bit1ie Identifier
18 BIT1IELENGTH OF Contents of Iecontents of IE (Variable)
Main RAS information:
Information Function RegistrationRequest (RRQ) Sends a request from the terminal or gateway to the registration, and the wandere can be approved or rejected (RCF or RRJ). AdmissionRequest (ARQ) From the terminal to the Defold Access to the request, the Gate can approve (ACF or ARJ). BandwidthRequest (brq) requests a request for switching bandwidth allocation from the terminal to the termination, and the values can be approved or rejected (BCF or BRJ). DISENGAGEREQUEST (DRQ) If the request is sent from the end point to Defold, the DRQ will notify the Defold end point is abandoned; if the request is sent from Defold to the end point, then DRQ will force the call to end. Gate can approve (DCF or DRJ). If DRQ is sent by Defold, the end point must be replied to DCF. InforeQuest (IRQ) Sends Status Information Request from Off to Terminal. InforquestResponse (IRR) responds to IRQ. From the terminal to the delegation actively transmitted in a predetermined interval. RAS TIMERS AND REQUEST IN Progress (RIP) is the default timeout value recommended by the RAS information, and if the response is not received and retry. Related protocols RTP, RTSP, SIP, Megaco, H.248, Q.931, H.323, H.245 Source H.225 is an ITU-T (http://www.itu.int/itu- /)standard. Related Links http://www.javvin.com/protocol/H225v5.pdf: Call signaling protocols and media stream packetization for packet-based multimedia communication systems Version 5http: //www.h323forum.org/papers/: H.323 papers And Documents
