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配置数字中继(T1/E1,PRI) 需要了解的

VoIP88商城 / 2010-04-26

呵呵,突然发现.论坛里的很多朋友已经有了数字卡,可以参考james.zhu大大发的关于asterisk配置数字中继的汇总贴(在本分区的硬件相关的置顶部分).再次,我简单把一些基础的常识用中文表达出来,不足之处,欢迎大家指正

ISDN PRI的基本配置
控制器类型(T1/E1)
组帧(frame)和线路编码(line code)
时钟控制
交换机类型(switchtype)
时隙识别
RBS
D信道串行端口的配置
接受模拟呼叫

控制器类型
E1 TDM  支持2.048 Mbps 通信链路,将它划分为32个时隙,每间隔为64 kbps
T1 TDM  支持1.544 Mbps  通信链路,将它划分为24 个时隙,每间隔为64 kbps,其中  8 kbps  信道用于同步操作和维护过程。  
T1 控制器应用于北美和日本,而欧洲和中国则更多地采用 E1

组帧与线路编码
组帧和线路编码是由 ISP 提供的属性。
T1-->
在一正常的 T1 帧中,192 位用于数据,1 个位用于组帧。但是在T1中这个单独的位不能简单自如地来传送保持T1线路同步的信令信息。因此,人们创建了超帧格式(superframe format,SF)来处理这个问题。SF也就是 D4,由12 个T1帧组成,这12个组帧位要经历下面的 12 位模式:100011011100。也就是说,第 1 个帧中的组帧位为 1,下面 3 个帧的组帧位为 0,再下两个帧的组帧位为1,直到12位模式结束。一旦到达了最后,就再重新开始。接收器通过在 12 个帧的每193个位中寻找这种特定的模式,就可以建立帧的同步。
另一种组帧方法,称为 T1 扩展超帧格式(extendedsuperframeformat,ESF)。在 ESF 中,24 个帧组成一组,产生了24个组帧位。这些组帧位可分解为以下3种功能:


D信道串行接口配置
既然用户已经定义了时隙的数量,就需要识别哪一个信道将为D信道。一旦识别出D信道的时隙,用户就需要为其配置其他的一些属性。因为所有的T1线路都使用最后一条信道24作为D信道,而E1线路使用第15条信道为D信道,所以配置D信道并不困难。

T1的四种格式
IDA-P = ISDN PRI on T1 (ITU-T standard), using 4ESS protocol
IDA-M = DTMF on T1 (can use US CAS Global Call or direct DTMF+A/B bit programming)
IDA-R = R1 tones on T1 (rarely available now)
IDA-C = ITU C7(SS7) on T1 (D/240SC-T1 be the bearer circuit, and SIU/PCCS6 as signalling GW)

告警信息
RED ALARM
The signal is not being recieved at the local end. The switch then TRANSMITS a YELLOW alarm towards the far end.

YELLOW ALARM
The far end is SENDING you a signal saying they do not see you. BUT obviously you are seeing them, because you see the YELLOW signal they are sending!

RED ALRM is a local alarm. It means there is no signal present at the T1 card in the PBX. Most likely the problem is towards the CO. A loopback plug will confirm this. If you plug in the Loopback, and the system goes out of RED, then there is problem with the circuit.

YELLOW ALARM - A lot of folks get this wrong. It is a RECIEVED ALARM. Just by the fact that you are getting it, means you see the other side. What it is telling you though, is that the far side does NOT see you and they are sending a YELLOW to let you know that.

T1 (Non PRI) - If you loop these back, the channels will go idle and you WILL TRY TO SEND CALLS! be careful when looping back during business hours when this T1 is still a possible route choice.

T1 (PRI) - Looping these back will only bring the T1 in service. The DCH will not establish, since it is seeing itself, and one side has to be master and one side has to be slave. Looping a PRI causes the DCH to see a Slave to Slave, or Master to Master DCH connection, and it will not bring the channels into idle.
 

http://bbs.voip88.com/thread-512-1-1.html

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