Silk Road mechanics?

Is the Silk Road supposed to provide a viable land trade route across Asia? I'm playing as China and I control the two cities along it, the one in the desert Xinjiang region and one in the Samarkand area north of Persia, but it seems to end there. My resource trades with the Byzantines get cancelled when the Tamils DoWs me or the Arabians collapse. Am I supposed to build the rest of it myself? If so, what is the purpose of it in its current state? Also, is it supposed to go through the super-unstable Persia area, where the isolationist Arabs conquer and the Seljuks spawn, and all sorts of other craziness happens, and it generally remains in Independent control for most of the time?

Thanks.