今天在客户这里给客户解决一个关于ftp认证慢的问题.
连接后需要等待一段时间才能够进行认证.但是在认证后传输文档是速度很快的.
根据感觉这个东西是dns方面的问题.
经过在google上面查找终于找到了关于这个方面的资料.

Logins to the ftp server take a long time, after that things run smooth

Possible causes: IDENT (RFC931) lookup is enabled in WU-FTPD. This has a timeout of 10 seconds. If the protocol (port 113) gets blocked by a firewall or suchlike, it will wait for timeout. If it is 30 seconds and you are using Redhat >= 7 with xinetd, disable AUTH in inetd as well. Change the entries in /etc/xinetd.d/ftp that read: 

log_on_success       = DURATION USERID
log_on_failure       = USERID
Remove the 'USERID' from both. Any other time period: DNS is broken for the IP address the connection is coming from.


按照上面的方法经过配置后从新起动xined.就一切ok了:)