Improved techniques are disclosed for detecting instability events in data communications systems that support inter-administrative domain (inter-domain) routing. For example, a technique for detecting an instability event in a communications system supporting inter-administrative domain routing includes the following steps. At an inter-domain router, one or more features are extracted from one or more messages obtained from at least another router in the communications system. The one or more extracted features include a path length feature, a path edit distance feature, or a combination thereof. Then, the inter-domain router detects whether an instability event has occurred in the communications system based on the one or more extracted features such that an action can be effectuated. By way of example, the one or more messages may include one or more border gateway protocol update messages and the inter-domain router may be a border gateway protocol router.