Which one of the following protocols uses both UDP and TCP ports for the transport layer operation?（）
- A、FTP
- B、TFTP
- C、SMTP
- D、Telnet
- E、DNS
正确答案:E
答案解析:有
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思科认证考试
思科认证考试
Which one of the following protocols uses both UDP and TCP ports for the transport layer operation?（）
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