How to size a firewall according to the different throughputs

[fjulianom]

Hi checkmates,

For sizing a firewall I know I have to consider many things such as max. number of concurrent connections, types of interfaces, throughputs and so on. According to the different kind of throughputs I have some doubts. Let's take 5600 SG appliance as an example, which has a firewall throughput of 20.4 Gbps, a NGFW throughtput of 5.1 Gbps, and a threat prevention throughput of 2.78 Gbps. As far as I know, briefly that means that if you don't use any UTM features you will have total throughput of 20.4 Gbps, but if you activate application control and IPS, you will have a throughput of 5.1 Gbps because the gateway has to scan the traffic, and if you also want to use the URL filtering and antivirus features, you will have a throughput of 2.78 Gbps, because the gateway has to do more even scan.

Then, my doubts are:

1. If you don't activate any UTM features, I will have 20.4 Gbps of throughput. This considers the sum of the transmited and received traffic of all the interfaces of the firewall, right?
2. If I have a users VLAN interface which uses 500 Mbps and where I want to activate URL filtering and antivirus. Will I have to consider a throughput of 2.78 Gbps?
3. If I have a mix of interfaces which uses antivirus, others which uses application control and IPS, others which only use firewall rules, will I have to add the bandwitdh of all the interfaces and consider the threat prevention throughput which is the most restrictive?
   
4. What about the VPN throughput which is 6.5 Gbps for 5600 SG appliance. Is this SSL VPN throughput? Or IPSec VPN throughput? Is this the VPN throughput if I don't activate any other UTM features or it will be decreased if I activate antivirus, IPS or other UTM feature?

Thanks in advance.

Regards,

Julián