ntp network time server and dual Cheese Li showing the new features
ntp network time server rely on GPS clock server to obtain the standard clock signal information from the GPS geostationary satellite through a GPS antenna, then Network Time System These clock information transmitted in the network on the basis of NTP, the network needs a clock signal equipment such as computers and other equipment can be synchronized with the standard clock signal.
Currently, the typical application is to use the NTP protocol NTP protocol in the LAN computer equipment involved in clock synchronization, and along with network switching equipment, the establishment of a clock with the network. The network may be composed of the same server clock, two clocks server, client, and transmitting the routing interconnect therebetween. Master clock reference clock server directly usually GPS satellite positioning system. Two clock synchronization server via a network server master clock, two clocks through the NTP protocol server clock information is transmitted to other hosts within the LAN.
First, pay attention to achieve when using
( . 1) GPS antenna is no source antenna , which is to ensure that the GPS receiver and the satellite synchronization key member, and its erection correct or not directly related to the performance of the GPS clock. To ensure the GPS antenna close star effect, the installation should be set up as far as possible , such as roof, roofs, balconies, terraces and other places, far away from the emission source adjacent frequency points, avoid woods, floors, towers and other buildings on the block antenna, around the high voltage power lines from interference sources should be a strong electric field and the magnetic field and the like . When the antenna should be parallel to the horizontal, is fixedly mounted on a base or stand, note that the antenna is attached to the roof, it should be lower than the height of the lightning rod.
( 2) With the network number of layers increases, the time accuracy will be lowered, to limit the total number of layers in 15 layers or less. In the actual design application should minimize the number of stages, if too many layers, not only increases the complexity of the network, and will reduce the time synchronization accuracy and reliability, we can synchronize the important level of equipment to points based on the time Floor.
( 3) In order to prevent, NTP protocol also provides authentication and encryption function employed. If the network is not a closed structure, core management security layer device time service is very important, if subjected to, it will affect a wide range of services. So you can use when necessary verification requirements set timing and access control policies combine to prevent unauthorized access to core equipment and changes to ensure accurate time within the network, reliability and security .
Two, NTP network time server uses and characteristics
ntp network time server output generally second pulse, pulse division, pulse, the serial data signal embodiment, timing accuracy is required for the mode to be selected according to the LAN device. Requirements for time accuracy of milliseconds or less, generally use serial communication, a certain time to read their satellite time correction time interval by a host; requirements for time accuracy in the case of milliseconds or less, may utilize pulse output signal, by shaking clock and other hardware devices, serial communication signal timing correction.
SYN2136 type Compass NTP network time server
Core functions:
1) to the GPS timing signals to establish a time reference;
2) to provide 4 NTP Network Time Interface and 2 IRIG-B code signal;
3) The front panel display date, day, hour, number of teeth and satellite working condition;
4) Support windows, LINUX, UNIX, SUN SOLARIS , IBM AIX operating systems such as time synchronization;
5) supports the NTP & v1.v2.v3 V4 (RFC1119 & 1305), the SNTP (RFC2030) protocols such as ;
6) supports the DHCP function, all LAN port network device, to automatically obtain an IP address;
7) Excellent safety performance, providing firewall protection, enable the SYN-flood defenses, which greatly improve the security of the internal network, reducing risk;
8) Support heartbeat detection, multiple time servers or multiple network ports can be set to the same IP, mutually redundant backup;
9) Support WEB, SSH encrypted communication parameter management and monitoring software provided;
10) Support of WEB firmware upgrade, backup parameters and provide import, the system transmits local log and remote log function;
11) provide hardware and software watchdog design, the QoS function (traffic monitoring) and network diagnostics;
12) parameter setting file can be imported and exported;
13) the network configuration page English switch provided username and password and host name;
14) load, running time, memory status and other real-time traffic and real-time monitoring;
15) 显示实时链接，包括客户端访问时间服务器的IP、通信协议和交互数据量，并以图表形式展示历史数据。
北斗高精度时频服务器
北斗高精度时频服务器顾名思义就是从北斗卫星上获取一个标准的高精度时间信息，通过内部高科技技术处理之后，使得北斗时间信息通过其他接口往出发时间信息及标准的频率信息。
时频服务器组件
北斗高精度时频服务器的组件有：天线，天线安装支架，主机，连接线。
天线：天线也叫授时天线、卫星天线等等，就是用获取卫星的标准时间信号，通过线缆介质传输给主机，一般情况下，传输的距离有限制，标准30米，如需更长，需要做信号放大处理。
主机：主机里内含北斗接收机，通过天线在北斗卫星上获取标准的时钟信息，通过芯片及主板的高精度解析处理后，通过主机的NTP接口，PTP接口，串口接口，B码接口，频率输出接口等输出一些标准时间频率信息。
gps时间同步服务器的组成及使用
gps时间同步服务器系统由设备主机及天线组成
1、gps时间同步服务器是一款由gps卫星上获取时间，将时间信息作已处理后通过某种接口（网口、串口、irig-b码、1PPS等等）进行输出，从而来给其他设备进行校时，每种接口的使用方法都不大一样，详细的使用方法请联系我公司销售人员。
2、授时天线是指接受卫星向外发射的载波信号，利用授时天线获取到卫星的标准时间信息，授时天线就是接受卫星载波信号的一种接收装置，然后对获取的信号处理，传输给主机进行处理，然后输出各种接口。授时天线应可靠地工作，减少环境的影响及周围电磁/电波的影响，因此，授时天线必须防雷设计、抗干扰设计放在重点考虑范围内。
3、在固定安装架设天线之前，建议用户先进行卫星信号及天线的的测试，正常获得卫星信号后，确认天线无任何收星问题后，再上楼安装，以便正确判断是是主机问题还是天线问题。
4、授时接收天线需架设于室外如阳台/露台/屋顶，周围空旷没有任何的电磁/电波干扰，天线顶端白色蘑菇头的视场不应有成片障碍物如建筑物、树林、信号发射塔等等，以免阻挡卫星信号的接收，天线所需的电源由本机通过天线馈线（同轴电缆）提供。
时间服务器结构
gps网络时间服务器所搭建的系统主要是由GPS卫星天线、时间服务器主机、交换机，客户终端等组成。
2.1GPS卫星天线
GPS卫星天线就是通过接受卫星传播出来的时间信号和定位信号， GPS卫星信号分为L1和L2，其中L1为开放的民用信号。天线的长度一般有30、50、80、100、150、200米等长度由客户自己根据实际情况进行选择。
2.2时间服务器主机
时间服务器是通过GPS天线接收卫星信号，内部经过高科技处理和运算，通过网口（RJ45口）对外发出NTP v1.v2.v3&v4(RFC1119&1305)，HTTP/SSL/HTTPS（RFC2616)，802.11b/g/n，SNTP(RFC2030)，SNMP，SSH/SCP,MD5（RFC1321）IPV4、IPV6、IPv4/IPv6 Hybrid,Telnet（RFC854），NTP Unicast，Broadcast，Multicast，等协议，常见可用于给电脑、摄像头、NVR、服务器及其他常见的客户终端进行授时。时间服务器里内置GPS接收机是GPS接收机的核心部件， GPS接收机接收卫星信号, GPS 信号包括 2 种载波( L1、L2) 和 2 种伪噪声码 ( P 码、C/A 码) 。我们使用卫星接受器接收的数据是经过美国的伪噪声码对原始码进行调制后, 再将噪声码调制在载波上形成的。实际上我们使用的是 C/A 码―粗码, 全球都能免费使用, P码是精确码, 不对民用开放。接收机在接收到卫星信号后, 其内部硬件电路和软件通过对接收到的信息进行解码和处理, 能从中提取并输出 2 种时间信号: 一是间隔为 1s 的同步脉冲信号 1PPS ( 电平为3V) ,还有一种是串口时间信息， 它是与 1PPS 脉冲相对应的。
2.3交换机
当时间服务器的网口接入至交换机时，交换机就可以把一个输入网口分为多个输出网口供下面的终端使用，如果一个交换机不够用的话，下面可接数十个交换机进行扩展使用。
2.4客户终端
客户终端指的是用户需要同步的终端，常见的终端比如电脑、摄像头、NVR、服务器及其他常见的客户终端需要进行授时的终端等等。
三、授时协议分析
当前使用的时码协议主要有三种：它们是Daytime(RFC-867)、Time(RFC-868)和Network Time Protocol。网络时间协议是当前最复杂、最高级、同步精度最高的时码协议。其中SNMP和TNMP是广泛使用的两种网络时码协议。在时间服务器上安装网络时间服务器软件，在局域网内的其他计算机上安装NTP客户端软件，客户端软件可作为背景任务连续、周期性地运行，不断得到服务器的更新信息。
优势分析
应用NTP的卫星时间同步系统，通过GPS或“北斗”导航设备终端获取高精度时间信息，并将该时间信息作为时间源提供给局域网综合系统，能够保证局域网系统时间源的准确性，同时，以UDP组播形式实现同网段内各测试设备之间的时间同步，应用NTP时间同步原理并以UDP客户机形式实现跨网段测试设备之间的时间同步，既考虑了系统运行的效率问题，又满足了卫星综合测试系统时间精确的毫秒的要求，可有效解决现有综合测试系统校时软件所不能实现的广域网环境下综合测试系统的时间同步问题。
采用 GPS 接收设备接收GPS信息，并与服务器相连，校正时钟源服务器的时间。
授时终端定时向授时服务器发送 NTP 包请求校时基准时钟，获
得基准时钟后通过应用软件校正本计算机系统时钟使其与授时服务器的时钟同步。