The HTTP protocol supports a method head, which is designed to return only HTTP headers, but no content.

HTTP协议支持方法HEAD，它设计成仅返回http头而不返回内容。

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Tunneling (RFC 2893) : it allows you to encapsulate one packet head into the other and one protocol will communicate with others through the encapsulation in the other protocol.

隧道技术(RFC 2893)：是指将一种协议报头封装在另一种协议报头中，这样，一种协议就可以通过另一种协议的封装进行通信。

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Review and revise clinical documents like protocol, case report form, etc, ensure it get approval from country medical director and appropriate central medical head.

审核修改临床研究协调员撰写的临床研究方案，病例表格等研究文件，保证得到区域和总部相关部门的批准；

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The Head of Protocol at the Foreign Office confirmed this view, which means that, despite twelve years of service, Mrs Jimenez has never, legally, been a member of the mission.

BBC: NEWS | UK | Magazine | Diplomatic immunity? Not from the taxman