When defining IPSec VPN tunnels, how much of a performance impact can I expect from choosing "stronger" Phase 1 settings (such as AES256/SHA1/DH5 over DES/MD5/DH1)?
For example, I'm told that AES-256 is 40% slower than AES-128 (which is reasonable, I guess), but am I right in thinking that overall "noticable" tunnel throughput is only really going to be affected if that is specified in Phase 2?
I'm thinking that specifying/prioritising stronger Phase 1 settings will just mean that the endpoints will take marginally longer to authenticate on startup (and at the lifetime intervals), rather than decreasing the throughput of the tunnel, and so I should probably prioritise IKE proposals (which are shared by all tunnels in a Cisco ASA device) by algorithm strength, rather than performance.
Am I on the right track?
(Having discussed it with some of the guys at Security.SE, I reckon I have a preference based on the security of the stronger algorithms; for now, I'm more interested in the performance aspect)