Simple services, like stock quote services or temperature services with no quality of service guarantee and available at no charge.
简单服务，类似股票行情服务或温度服务等没有服务质量担保、且可以免费获得的服务。
Network providers do not guarantee a certain quality of service, but merely promise to do their best. That may not matter for personal e-mails, but it does for time-sensitive data such as video.
网络提供者们不担保某种程度的服务质量，仅承诺将尽力而为，这可能对个人电邮不算什么，但是对时间敏感的数据比如视频就很重要了。
Network providers do not guarantee a certain quality of service, but merely promise to do their best.
网络供应商并未保证特定质量的服务，而仅仅承诺了尽其所能。
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