Guys ,
Short and simple, no isis military groups are existing at that vicinity( north syria) , just el nusra (syrian turkish sunni group armed by usa and turkey ,offically known by nato against esad regime) and pyd ( kurd groups) are positioned there. Russia has been carried out air strikes to them last one month and violated Turkey's border dosen of time or more.. It is clear that Turkey as Nato member wont shoot down a Russian Fighter without States confirmation.
So for the ones who mention that Turks are trying make shield to protect Isis is
...
Try to be more sphecific...
Turkey is not over-reactive ; remember that syria shoot down Turkish fighter 2 years ago because of same reason. there is no squawk code of fighters to identify its russian or syrian, even doest not matter...