[CentOS] centos server network speed check???

we have several servers on same rack and servers are all inside firewall.  Centos version from 4.X to 5.X.  sometime the connection are very slow (compare to servers on other racks also inside firewall).

we discuss with network engineer he ask us use "ping" and traceroute" to check.  Both tools response time are good but if we connect through application like Web browser, database, or DELL OPMN tool.  The response time is very very slow.  

This situation normally last 4 to 5 hours then it back to normal.  Does there has way to check "real" network response time so we can show to network engineer.  Otherwise they always say "no problem".

Thanks.