Application layer proxy

Hi ,

I am trying to identify an application proxy in Linux equivalent to MS ISA proxy. Proxy should mediate communication b/w various protocols based on port and ip adress, viz. SMTP, MSSQL , LDAP, HTTP etc.

Have googled and found DeleGate, Zorp and Squid etc. Application layer, transparent proxies.

Can someone help me understand which of these would be easier to install and suits the above mentioned requirements. Would appreciate notes on these if any of you had chance to work on.

Cheers, Murli.

squid to my best knowledge is most easiest to work with, and easy-configurable. Our corporate network currently relies on 2.5.STABLE 6

I think we can achieve Transparent Application level proxying with SQUid only for HTTP .But I am looking for application level proxying on SQUID, for SMTP, MSSQL , LDAP, HTTP etc.

Appreciate any ideas