IS are not thought to possess SAMs with anything like to capability to reach 31,000 feet.
MH17 was shot down by a much longer range missile supplied by Russia. Of course in that instance the culprits boasted about it on social media, but when they realised what had really happened the posts were swiftly deleted: the exact opposite of this.
A bomb seems more likely as the plane does seem to have split apart in mid air (giving the lie to the footage in the link, which appears to show an intact aircraft)
However, if it was a bomb it would seem rather strange for it to have been on an inbound flight. Either a suicide bomber took his bomb on holiday with him first, or a non-passenger might have had it smuggled it on board at Sharm-el-Sheikh
The crew reportedly had being having technical difficulties since take off and were planning on landing at a N Sinai airfield, which also would suggest that whatever happened it was not a bomb. But who knows at the moment.