联网监控DVR技术在ADSL环境中的应用Application of network monitoring DVR technology in ADSL environment

　　联网监控：DVR技术在ADSL环境中的应用  Application of network monitoring DVR technology in ADSL environment

　　随着计算机网络技术的不断发展、完善，以及宽带的逐渐普及，基于Internet的网络视频监控解决方案应在众多的监控系统中。对于安防所涉及的网络视频监控系统在很多场所下，价格成为一个相对比较敏感的因素。以往的网络视频监控系统，基本上都是基于局域网或者光纤专网。但是一些监控场所无法保证这样的网络条件，如果常年租用光纤线路，每年需要的投入太大，而ADSL宽带现在已经非常普及且整体成本很低，一些不需要24小时不间断的外网浏览地点可以采用这种方式节省资金。那么，针对ADSL环境的应用，DVR需要具备什么样的技术呢?
With the continuous development and perfection of computer network technology and the popularization of broadband, the network video monitoring solution based on Internet should be in a large number of monitoring systems. For the network video surveillance system involved in security, the price becomes a relatively sensitive factor in many places. In the past, network video surveillance systems are basically based on LAN or optical fiber private network. But some monitoring sites do not guarantee such network conditions. If fiber lines are rented for years, the annual cost is too large, and ADSL broadband is now very popular and the overall cost is low, and some 24 hours of uninterrupted web sites can be saved in this way. So, what technology does DVR need for ADSL environment?
 

　　pppoE和DDNS

　　PPPoE是point-to-point protocol over ethernet的简称，可以使以太网的主机通过一个简单的桥接设备连到一个远端的接入集中器上。目前流行的宽带接入方式adsl就使用了PPPoE协议。

　　但是采用了动态IP接入方式的ADSL，会遇到这样一个问题。每次用户通过ADSL拨号连接Internet时，ISP通常会分配给用户一个公共IP地址，这时候Internet上的其他用户就可以通过这个IP地址访问该计算机。但是，因为这个IP地址是动态的，也就是说一旦断线，下次再连接Internet的时候，ISP将会分配另一个不同的公共IP地址。这样就导致了用户通过 Internet访问DVR时每次都要现场人员查看分配的IP地址是什么，再去访问。这么复杂的访问方式谁愿意去使用呢?所以DDNS技术便成了DVR必备的网络技术之一。

　　DDNS(Dynamic Domain Name Server)是动态域名服务的缩写!DDNS是将用户的动态IP地址映射到一个固定的域名解析服务上，用户每次连接网络的时候客户端程序就会通过信息传递把该主机的动态IP地址传送给位于服务商主机上的服务器程序，服务项目器程序负责提供DNS服务并实现动态域名解析。

　　采用DDNS技术的DVR，通过PPPoE拨号连接后，自动拨号连入Internet，并通过DHCP方式获取动态公网IP地址。将从域名服务提供商(如花生壳、3322.org)处获取的域名、用户名、密码输入监控设备，外网用户可通过该域名访问监控设备。

　　UPnP

　　什么是 UPnP?Universal Plug and Play(通用即插即用)。从字面上很容易理解这个使得监控产品走向民用市场的技术。以往的视频监控系统专业性很强，在Internet网络进行远程访问时，可以通过端口映射、域名解析等技术，在路由器上进行设置后即可使得监控系统可以在外网进行访问。但是面对监控产品民用化的时代，在小区内对路由器进行设置是不现实的(因为一个小区里面的路由普通用户是无法接触的)，而且普通用户也并非每个人都会设置。那么UPnP技术便很好地解决了这个问题，它的网络地址转换和NAT穿越技术帮助用户实现了只需输入监控设备的地址便可以直接远程浏览监控画面。目前市场上主流的IPC厂商都已支持该技术如AXIS 211，Tiandy TC-NC8100S;但DVR厂商采用此技术的还比较少，小路数的DVR产品未来还是需要UPnP技术来提高产品竞争力。

UPnP is what? Universal Plug and Play(Universal Plug and Play). It's literally easy to understand the technology that allows surveillance products to move to the civilian market. Previous professional video monitoring system is very strong, in the Internet network for remote access, you can through the port mapping, domain name resolution, such as technology, makes the monitoring system after the Settings on the router can be outside the net for a visit. But in front of the era, MinYongHua monitoring products within the community for Settings of the router is not realistic (because of a village inside routing ordinary users are unable to contact), and ordinary users is not set for everyone. The UPnP technology has solved the problem very well, it's network address translation and NAT through technology to help users realize the address simply type monitoring equipment can directly browse remote monitoring picture. Currently, the mainstream IPC manufacturers in the market have all supported this technology, such as AXIS 211, Tiandy tc-nc8100s. However, few DVR manufacturers have adopted this technology. In the future, small-circuit DVR products still need UPnP technology to improve their competitiveness.