Zhongshan GPRS DTU digital terminal traffic control strategy 1) Mobile charging method for GPRS traffic At present, mobile companies calculate GPRS according to the billing method, but in practice they also impose some restrictions. There are two main aspects. One aspect is to limit the free time. When there is no data communication for a long time, the mobile gateway automatically disconnects the communication connection (for the TCP protocol, it directly disconnects the link; for the UDP protocol, it reclaims the assigned NAT port number). For this disconnection time, the TCP protocol is much larger than the UDP protocol. In many places, the TCP protocol allows a few minutes of idle time, while the UDP protocol allows only a few tens of seconds of idle time. In addition, when the mobile company calculates the traffic, it does not necessarily follow the real byte calculation, but specifies a minimum flow. When a time period, if only one packet is sent, then no matter what The actual size of the packet is calculated on the basis of the minimum traffic, such as 1K bytes. Even if calculated in this way, the actual heartbeat flow needs to occupy about 10M bytes per month. Mobile currently has 20 yuan, 50 yuan monthly package of small traffic, allowing users to use 20M bytes -50M bytes of traffic every month, by reason, in many GPRS industry applications should also be sufficient. However, in real situations, there is often a flow of out of control, which exceeds the expected phenomenon! 2) Analysis of GPRS DTU traffic out of control In the actual GPRS application system, users may often find that the GPRS traffic statistics from the mobile company often exceed their expectations, and even the phenomenon of "explosion of fees" occurs. This situation is mainly due to the fact that the GPRS DTU terminal products used by users do not have thorough traffic control, resulting in a large amount of invalid traffic. In general, the GPRS DTU traffic composition mainly includes four parts: We have two categories to illustrate: A.Flow stabilized: [User application data], [Heartbeat] When the user system design is reasonable and the parameters are set properly, then [user application layer data] and [heartbeat packet] basically do not cause the traffic to exceed the expected situation. B. Uncertain traffic type: [Create network connection], [Junk data] Causes a lot of traffic. [Garbage data] is when a GPRS DTU is in a GPRS network, it will receive a considerable amount of spam with unknown content. This is to calculate the traffic, and it may account for a large proportion of the traffic. Example (At present, the phenomenon of spam in the GPRS network is widespread. One explanation may be attack data or probe packets from other computer viruses that access the GPRS network). After analyzing the reasons that caused the traffic to exceed expectations, let's take a look at the strategies adopted by the public domain of GPRS DTU digital terminal traffic control: A. Control strategies for [Heartbeat] section for [User Application Tier Data]: Public Mountain GPRS DTU can be divided into keep online mode and wake up online mode. When users use frequent data communication and need frequent two-way communication, GPRS DTU is generally used to maintain online mode. When the amount of user application data is very small, wake-up online mode can also be considered. Wake-up online mode can be further subdivided into local control command wake-up, user data packet wake-up, automatic wake-up at regular time, central dial-up wake-up, central SMS wake-up and several methods. The wake-up mode can significantly reduce GPRS traffic. B. Traffic Control Policy for [Create Network Connection]: Public Hill GPRS DTU implements a method of intelligent judgment on the part of [establishing a network connection]. When the center cannot be connected, it avoids the generation of a large number of invalid connection packets. GPRS DTU support Retry connection time interval setting, for example, retry connection once every 5 minutes instead of continuously retrying connection, or retry connection in increments of time. (For example, according to 10 seconds, 20 seconds, 40 seconds, ...increment) to effectively avoid large traffic in the [establish network connection] section. C. Traffic Control Policy for [Spam]: In the situation where many GPRS DTU manufacturers are incapable of dealing with the phenomenon of spam data, the company has exclusively implemented a technology that automatically avoids garbage data. One feature of spam data is that it does not appear for all IPs, when a GPRS device is When time is received for a junk packet, if you replace an IP address, you can effectively avoid continuing to receive more junk data. The core idea is actually simple and easy to understand. The method of changing the IP address is also easy to implement. That is, re-fast GPRS dial-up, so as to assign a new IP address and re-establish a handshake with the center. However, judging that the GPRS device receives garbage data requires a prerequisite, that is, it must implement a complete PPP protocol and TCP/IP protocol within the GPRS DTU. That is, the GPRS DTU has IP. Layer data packet processing capability, because the GPRS device knows the IP address of the legal data center and the IP address of the DNS server, it can judge the received data packet at the IP layer if the IP packet The source IP address is not an IP address from a legitimate data center, nor is it a legitimate DNS server IP address. By the way, at present, some manufacturers' GPRS DTU devices use the built-in protocol stack of the GPRS wireless module. In this case, since the GPRS wireless module's built-in protocol stack has encapsulated the IP layer, Open only the data of TCP and UDP channels, so it can not determine the existence of garbage packets, let alone automatic avoidance. The use of self-implemented PPP and TCP/IP protocol stacks allows them to effectively identify garbage packets. When user data is not lost, they automatically switch IP addresses quickly and avoid garbage data. Attacks can effectively avoid the generation of garbage traffic, and ensure that the effective bandwidth and processor resources of GPRS are not consumed by garbage traffic, further enhancing the reliability of GPRS communications.
[Create Network Connection Package], [User Application Layer Data], [Heartbeat Packet], [Junk Data]
[Creating a Network Connection] The reason for the instability is that when the data center is closed or the GPRS DTU fails to establish a connection with the center for some reason, the DTU will try to establish a connection repeatedly, which will lead to
3) GPRS DTU digital terminal traffic control strategy
Excerpt from <Zhongshan GPRS DTU Digital Application Basics> http://