The last count I saw, however, indicated that only four Su-30s were present, along with 12 Su-24s and 12 Su-25s, all photographed at a Syrian Naval Aviation base adjacent to Basil al-Asad [officially spelled Bassel Al-Assad in English] International Airport in Latakia. It is not known if all will be deployed there or moved elsewhere, but the Su-24s and Su-25s clearly are ground attack and interdiction fighters, used by the Soviets in Afghanistan and the Russians in Chechnya, and thus appropriate for fighting ISIS, as are the Syrian helicopters normally based there. (Though helicopters have notoriously been used for barrel-bombing civilians).
I'm not an expert on Russian air defense doctrine, but I doubt if Russia, undertaking its biggest military buildup since Afghanistan outside former Soviet space, would build what is starting to look like a military base at Latakia and a major expansion of its Navy facility at Tartus without providing perimeter defense of its own forces (the SAMs, tanks, and ground forces it is moving in as well). A lot depends on what the mission of the four Su-30s are, since they have both ground attack and air superiority capabilities.
Don't misunderstand me. I'm not defending Russia's jumping in to the Syrian civil war or their attempts to rescue the Asad regime, which they no doubt saw as on the ropes. But until we see exactly where this is going, it could still be seen as a Russian rescue effort for Asad, creating a Russian-protected area in the Asad heartland, and not necessarily a direct challenge to the US and coalition air campaign. It mostly depends on what those Su-30s are intended for.