CMPP通信方式 - 王茜翻译
CMPP Communication Mode

SP与ISMG之间、ISMG之间进行信息交互时，可以采用长连接方式，也可以采用短连接方式。所谓长连接，指在一个TCP连接上可以连续发送多个数据包，在TCP连接保持期间，如果没有数据包发送，需要双方发链路检测包以维持此连接。短连接是指通信双方有数据交互时，就建立一个TCP连接，数据发送完成后，则断开此TCP连接，即每次TCP连接只完成一对CMPP消息的发送。
When messages interact between SP and ISMG as well as between ISMGs, both the long connection mode and the short connection mode can be used. A long connection means that multiple data packets can be sent consecutively on one TCP connection; to maintain the TCP connection, both sides need to send link test packets to the other if no data packets are sent out. A short connection means a TCP connection is established only when there are data interacting between the communication parties; after data are sent, the TCP connection will be terminated, which means each TCP connection only completes one pair of CMPP messages submission.

1. 长连接Long Connection
通信双方以客户-服务器方式建立TCP连接，用于双方信息的相互提交。当信道上没有数据传输时，通信双方应每隔时间C发送链路检测包以维持此连接，当链路检测包发出超过时间T后未收到响应，应立即再发送链路检测包，再连续发送N-1次后仍未得到响应则断开此连接。
Both sides establish a TCP connection in the client-server mode for the two-way submission of messages. When there are not data being transmitted on the channel, both sides shall send link test packets every time interval C to maintain the connection. When the sending of a link test packet is not responded after a period of T, another link test packet shall be sent out immediately. If no response is received after a consecutive sending of N-1 times, the connection shall be terminated.

参数C、T、N原则上应可配置，现阶段建议取值为: C=3分钟，T=60秒，N=3。
In principle the parameters C, T and N are configurable. On this stage the recommended values are: C=3 minutes, T=60 seconds, and N=3.

网关与SP之间、网关之间的消息发送后等待T秒后未收到响应，应立即重发，再连续发送N-1次后仍未得到响应则停发。现阶段建议取值为: T=60秒，N=3。
If there is no response received T seconds after a message is sent between the gateway and SP or between gateways, it shall be resent. If no response is received after a consecutive sending of N-1 times the sending shall be canceled. On this stage the recommended values are: T=60 seconds, N=3.

消息采用并发方式发送，加以滑动窗口流量控制，窗口大小参数W可配置，现阶段建
议为16，即接收方在应答前一次收到的消息最多不超过16条。
Messages are sent via the concurrent method supervised by sliding window flow control. The size of the window Parameter W is configurable. On this stage the recommended value is 16, which means the maximum number of messages the receiver receives for one time before responding is 16.

长连接的操作流程举例如图5所示:
The operation flow of a long connection is illustrated in Figure 5:

2. 短连接 Short Connection

通信双方以客户-服务器方式建立TCP连接，应答与请求在同一个连接中完成。系统采用客户/服务器模式，操作以客户端驱动方式发起连接请求，完成一次操作后关闭此连接。
Both sides establish a TCP connection in the client-server mode. Requests and responses are exchanged in the same connection. The system adopts the client/server mode. The operation is client-initiated: The client initiates a connection request, and terminates this connection after one operation.

网关与SP之间、网关之间的消息发送后等待T秒后未收到响应，应立即重发，再连续发送N-1次后仍未得到响应则停发。现阶段建议取值为: T=60秒，N=3。
In case no response is received T seconds after a message between the gateway and SP or between gateways is submitted, it must be resent immediately. The sending shall be stopped when no response is received after a consecutive sending of N-1 times. On this stage the recommended values are: T=60 seconds, N=3.

短连接的操作流程举例如图6所示:
The operation flow of a short connection is illustrated in Figure 6:

3.本协议中涉及的端口号
Port Numbers Appeared in the Protocol
Port number Application
7890 Long connections (between SPs and gateways)
7900 Short connections (between SPs and gateways or between gateways)
7930 Long connections (between gateways)
9168 Short connections (between ISMGs and tandem gateways)

4.交互过程中的应答方式
Responding Modes during the Interactions

在SP与ISMG之间、SMC与ISMG之间及ISMG之间的交互过程中均采用异步方式，即任一个网元在收到请求消息后应立即回送响应消息。举例如图7所示:
The asynchronous mode is used for interactions between SP and ISMG, between SMC and ISMG, and between ISMG and ISMG. That is to say, any network unit shall return a responding message immediately after it receives a request message. Figure 7 is an illustration: