Improvement of colored thread algorithm for network reachability test
Han‐Kyoung Kim, Kwang-Hui Lee · Journal of Internet Computing and services · 2009
Colored thread algorithm, suggested to be used for the label switching network, needs to be modified for the packet switching network. In this paper, it is recommended to add a merged state, besides the 3 states - null, colored and transparent - which are resulted from the behaviors of extend, rewind, stall, withdraw and merge events. The original colored thread algorithm is designed to generate a new thread and extend it to the downstream direction with unknown hop count when the thread has revisited the node that was visited. It also suggested rewinding the thread to the downstream direction by the source node, instead of rewinding it upstream direction by the revisited node. If a node received multiple threads which had a same forward equivalent class, then it checks first whether the hop counts are ascending or not. If it is in ascending order, then threads are merged. Otherwise the later thread is stalled until the former thread's color is to be changed to transparent or it is removed. This idea removes the effort of generating a new thread with unknown hop count.