Front End/BE Exchange 2003 topology over

I am planning to put a FE exchange server. The back End server is located over a slow link.
(There is only one Exchange server in the ORG). What are the benefit of having a FE server….
Some of the benefit I Know…1) you can do directory lookup in AD – Reduces overhead. 2) Use of SSL encrypt – decrypt 3)Better security benefit (you do not expose your back End Exchange server. My question is what kind of topology /architecture will allow you to reduce traffic(or performance) between the FE and BE server. Thank you in advance for all your support ?