G'day,
STATEFUL PACKET INSPECTION (From Techweb)
A firewall technology that ensures that all inbound packets are the result of an outbound request. Also called "stateful packet inspection" (SPI), it was designed to prevent harmful or unrequested packets from entering the computer. For example, if you click on a link to a Web page, an HTTP request is being made to a specific URL address. All packets coming back from that URL would pass the stateful inspection and be accepted. Every so many minutes, your e-mail program queries the mail server, and returning packets from that server are allowed.
PROTOCOL ANALYSIS (from CFP V3 help files)
Protocol Analysis is key to the detection of fake packets used in denial of service attacks. Checking this option means Comodo Firewall Pro checks every packet conforms to that protocols standards. If not, then the packets are blocked
In a nutshell, SPI checks whether the packets coming into your PC are supposed to be coming in and Protocol Alanysis, looks inside those packets to ensure that they are valid when compared tothe specifications of that packet type.
Hope this helps,
Ewen :-)