能PING通服务器，但不能访问

sufferyxw

os：sco unix5.07+informix7.31
现象：前天都正常，昨天开始能ping通，但是用telnet,ftp报拒绝访问，系统重启后可以访问，过10多分钟又不能访问了，各位有没有碰到过这种情况？能不能提供检查问题的步骤？先谢谢大家了！非常急！
日志如下：

Mon Jan  5 09:59:51 2009

09:59:51  Event alarms enabled.  ALARMPROG = '/usr/informix/etc/log_full.sh'
09:59:57  DR: DRAUTO is 0 (Off)
09:59:57  Informix Dynamic Server Version 7.31.UC7    Software Serial Number AAC#J529250
09:59:58  Informix Dynamic Server Initialized -- Shared Memory Initialized.
09:59:58  Physical Recovery Started.
09:59:58  Physical Recovery Complete: 96 Pages Restored.
09:59:58  Logical Recovery Started.
10:00:09  Logical Recovery Complete.
        106 Committed, 0 Rolled Back, 0 Open, 0 Bad Locks

10:00:10  Dataskip is now OFF for all dbspaces
10:00:10  On-Line Mode
10:00:10  Checkpoint Completed:  duration was 0 seconds.
10:08:30  Requested shared memory segment size rounded from 8000KB to 8192KB

Mon Jan  5 10:08:31 2009

10:08:31  Event alarms enabled.  ALARMPROG = '/usr/informix/etc/log_full.sh'
10:08:36  DR: DRAUTO is 0 (Off)
10:08:36  Informix Dynamic Server Version 7.31.UC7    Software Serial Number AAC#J529250
10:08:37  Informix Dynamic Server Initialized -- Shared Memory Initialized.
10:08:37  Physical Recovery Started.
10:08:37  Physical Recovery Complete: 0 Pages Restored.
10:08:37  Logical Recovery Started.
10:08:40  Logical Recovery Complete.
        5 Committed, 0 Rolled Back, 0 Open, 0 Bad Locks

10:08:41  Dataskip is now OFF for all dbspaces
10:08:41  On-Line Mode
10:08:41  Checkpoint Completed:  duration was 0 seconds.

PING服务器的时候有延迟：
reply from 192.193.120.201:bytes=32 times=141 TTL=61
reply from 192.193.120.201:bytes=32 times=172 TTL=61
reply from 192.193.120.201:bytes=32 times=195 TTL=61
reply from 192.193.120.201:bytes=32 times=180 TTL=61