Q:

Alert me Logical Architecture of SharePoint Farm -- Security Issue

I have a question about Logical Architecture of SharePoint Farm , My topology design consists of 3 tiers:

Front Servers
Application Servers
DB Servers

As you know we need to run Windows SharePoint Services Web Application service on web front servers. There is a connection between Web Front Servers and DB servers and there was a discussion between SharePoint Team and security team in our organization about direct connection between Front Serves and DB Servers.
Now my question is, why should there be a direct connection between Front Servers and DB Servers?

A:

Front end servers not only run Foundation Web service, but also the Timer Service (sptimerv4) which must communicate with SQL databases directly. Yes, SharePoint is secure if you set it up as such.

