Q.931协议分析培训教材
该消息由网络侧向被叫用户发送的，用来标识该被叫用户已经被授予该连接通路。该消息也会由主叫用户向网络侧发送，用来确认对称的通路连接控制过程。
LAPD: 0 R (F) I-frame (NR=2e NS=5e) Q.931-BRI: ref=0x001a CONN ACK < 1: ( 9) 2751348
< 00 01 bc 5c 46 02 00 1a 0f
LAPD: 0 R (F) I-frame (NR=54 NS=4f) Q.931: ref=0x0062 CONN ACK > 2: ( 9) 2751348
> 00 01 9e a8 08 02 00 62 0f 消息内容：
? Q.931\\Q.931-BRI：协议鉴别语，同SETUP消息； ? Ref=0x0062\\Ref=0x001a：呼叫参考，但F位值为0；
? CONN ACK：消息类型，八位字节编码：0f，详见Q.931协议Table4-2。
2.1.2.7 DISC （DISCONNECT）
Table Q.931 – DISCONNECT message content
Message type: DISCONNECT Significance: Global Direction: Both Information element Protocol discriminator Call reference Message type Cause Progress indicator Display Signal Reference (subclause) 4.2 4.3 4.4 4.5 4.5 4.5 4.5 Direction Both Both Both Both (Note 1) n ? u n ? u Type M M M M O (Note 2) O (Note 3) O (Note 5) Length 1 2-* 1 4-32 2-4 (Note 4) 2-3 NOTE 1 – Included in the network-to-user direction if the network provides in-band tones. See Annex D for usage in the user-to-network direction. NOTE 2 – Included by the network if in-band tones are provided. However, the user may include the progress indicator and provide in-band tones. See Annex D. In such cases, the network will ignore this information element and will not convey the in-band tones. 项目管理和技术支持部 22
Q.931协议分析培训教材
NOTE 3 – Included if the network provides information that can be presented to the user. NOTE 4 – The minimum length is 2 octets; the maximum length is network dependent and is either 34 or 82 octets. NOTE 5 – Included if the network optionally provides additional information describing tones.
该消息由用户发起，请求网络侧释放该连接通路。
LAPD: 0 R (F) I-frame (NR=30 NS=63) Q.931-BRI: ref=0x001a DISC Cause (2) cause=16 < 1: ( 13) 2751891
< 00 01 c6 60 46 02 00 1a 45 08 02 80 90
LAPD: 0 R (F) I-frame (NR=57 NS=54) Q.931: ref=0x0062 DISC Cause (2) cause=16 > 2: ( 13) 2751891
> 00 01 a8 ae 08 02 00 62 45 08 02 80 90 消息内容：
? Q.931\\Q.931-BRI：协议鉴别语，同SETUP消息； ? Ref=0x0062\\Ref=0x001a：呼叫参考，但F位值为0；
? DISC：消息类型，八位字节编码：45，详见Q.931协议Table4-2
? Cause：呼叫中断原因，8位字节编码：08，DISCONNECT消息必须包含该信息单
元，各Cause不同值的含义见附录，详细内容请参阅Q.931协议。
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Q.931协议分析培训教材
2.1.2.8 REL
Table Q.931 – RELEASE message content
Message type: RELEASE Significance: Local (Note 1) Direction: Both Information element Protocol discriminator Call reference Message type Cause Display Signal Reference (subclause) 4.2 4.3 4.4 4.5 4.5 4.5 Direction Both Both Both Both n ? u n ? u Type M M M O (Note 2) O (Note 3) O (Note 5) Length 1 2-* 1 2-32 (Note 4) 2-3 NOTE 1 – This message has local significance; however, it may carry information of global significance when used as the first call clearing message. NOTE 2 – Mandatory in the first call clearing message, including when the RELEASE message is sent as a result of an error handling condition. NOTE 3 – Included if the network provides information that can be presented to the user. NOTE 4 – The minimum length is 2 octets; the maximum length is network dependent and is either 34 or 82 octets. NOTE 5 – Included if the network optionally provides additional information describing tones.
该消息是由网络侧发向用户的，用来标识连接通路已经被切断，并且网络侧已经准备释放该信道和呼叫参考。接受端收到该消息后，将在发出RELEASE COMPLETE后释放该信道并准备释放该呼叫参考值。
LAPD: 0 C (F) I-frame (NR=55 NS=57) Q.931: ref=0x8062 REL Cause (2) cause=16 < 2: ( 13) 2751891
< 02 01 ae aa 08 02 80 62 4d 08 02 82 90
LAPD: 0 C (F) I-frame (NR=64 NS=30) Q.931-BRI: ref=0x801a REL Cause (2) cause=16
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Q.931协议分析培训教材
> 1: ( 13) 2751891
> 02 01 60 c8 46 02 80 1a 4d 08 02 82 90 消息内容：
? Q.931\\Q.931-BRI：协议鉴别语，同SETUP消息； ? Ref=0x8062\\Ref=0x801a：呼叫参考，但F位值为1；
? REL：消息类型，八位字节编码：4d，详见Q.931协议Table4-2； ? Cause：呼叫中断原因，8位字节编码：08。
2.1.2.9 REL COM
Table Q.931 – RELEASE COMPLETE message content
Message type: RELEASE COMPLETE Significance: Local (Note 1) Direction: Both Information element Protocol discriminator Call reference Message type Cause Display Signal Reference (subclause) 4.2 4.3 4.4 4.5 4.5 4.5 Direction Both Both Both Both n ? u n ? u Type M M M O (Note 2) O (Note 3) O (Note 5) Length 1 2-* 1 2-32 (Note 4) 2-3 NOTE 1 – This message has local significance; however, it may carry information of global significance when used as the first call clearing message. NOTE 2 – Mandatory in the first call clearing message, including when the RELEASE COMPLETE message is sent as a result of an error handling condition. NOTE 3 – Included if the network provides information that can be presented to the user. NOTE 4 – The minimum length is 2 octets; the maximum length is network dependent and is either 34 or 82 octets. NOTE 5 – Included if the network optionally provides additional information describing tones.
该消息由用户侧发出，用来标识本端已经释放该呼叫的信道和呼叫参考值，该信道可以再次被利用，接受端可以释放相应的呼叫参考值。
LAPD: 0 R (F) I-frame (NR=31 NS=64)
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Q.931协议分析培训教材
Q.931-BRI: ref=0x001a REL COM < 1: ( 9) 2751893
< 00 01 c8 62 46 02 00 1a 5a
LAPD: 0 R (F) I-frame (NR=58 NS=55) Q.931: ref=0x0062 REL COM > 2: ( 9) 2751893
> 00 01 aa b0 08 02 00 62 5a 消息内容：
? Q.931\\Q.931-BRI：协议鉴别语，同SETUP消息； ? Ref=0x0062\\Ref=0x001a：呼叫参考，但F位值为0；
? REL COM：消息类型，八位字节编码：5a，详见Q.931协议Table4-2。
2.1.2.10 REGISTER
除了上面提到的FACILITY消息外，在无线市话系统中还有REGISTER消息被用来提供辅助业务。
Table – REGISTER message content
Message type: REGISTER Significance: Local Direction: u ?n Information element Protocol discriminator Call reference Message type Facility
LAPD: 0 R (F) I-frame (NR=1b NS=1e) Q.931-BRI: ref=0x004d REGISTER Unknown (1C) (35) < 1: ( 46) 158929
< 00 01 3c 36 46 02 00 4d 64 1c 23 91 a1 20 02 01 < 4d 06 07 03 a2 31 87 6c 01 08 31 12 86 01 01 40
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Reference (subclause) Direction u ?n u ?n u ?n u ?n Type M M M O Length 1 3 1 2-64