What exactly do ipsec and ssl do?

What are the differences between the SSL-VPN and IPSec VPN in their client software, protection mechanisms, and protocols?

• Answer:

  SSL was "sold" as a clientless VPN, supposedly all you had to do was bring up a web browser, create the SSL connection to the "server" and you were good to go. In reality, all SSL-VPN implementations have some form of client software that is installed on your machine the first time you connect to the "server". However the client is very "lite-weight" and for all intents and purpose runs in the background unknown to the user. SSL-VPN servers act as a proxy for your session though. You connect to the server and the server proxies on the users behalf into the "secured network", which means it's possible to encounter some applications that the proxy doesn't understand, therefore won't work. The advantage to SSL is you can generally get through any firewall with it. To a firewall it looks like a http session. IPsec VPN (PC to secure network) uses a heavier client, one that must be pre-installed prior to session initiation. Because IPSec operates on a different IP socket, it's not uncommon for firewalls to block it. For example, if you are trying to use it from a motel or some random hot spot. IPSec does not operate like a proxy. When you are connected it's as though you are physically connected to the secured network. Any application will work through IPSec. IPSec has the advantage of being able to support what is known as a branch to branch VPN. Meaning router A connects to router B using IPSec through some public IP network (Internet), securing the communications between users off routers A and B. IPSec can be used to secure older "non-IP" applications too.