This reports the IPsec, or related, protocol type this security association uses, such as AH, ESP, or IPComp, alongside other protected protocols like OSPFv2 or RIPv2. Admins check this to confirm a tunnel is using the expected protection mechanism, since most production VPNs should show esp rather than the weaker ah or an unspec or unknown value that would indicate misconfiguration. A value of esp confirms the SA is providing encryption and authentication, as opposed to ah which only authenticates without encrypting payload.