Well, you have three major routes for Indian Ocean trade into the Middle East. The first, is the Red Sea route starts in Alexandria passes down the Nile into the Necho canal which debouches into Qulzum and the Red Sea. This route in OTL seems to have only gained major significance (at least for Europeans) with the collapse of the Crusader States, the conversion of the Ilk-Khans to Islam and finally and most significantly the destruction of Baghdad by Tamerlane. It was still used to supply domestic Egyptian requirements, at least in part, since it seems that the majority of its imports were brought overland via Sinai. The second route passed through the Crusader states primarily from Antioch through to Aleppo, thence to Baghdad before it finally met the Persian Gulf at Basra. This route was in OTL the most significant partially because the Crusaders could to some extent exercise some measure of control over the Muslim merchantry. It also helped that Baghdad was a major centre of consumption as well as production and that it was by far the easiest route to satisfy that. Europeans just got lucky when they took over the Levant insofar as they were able to tap it for there own primarily consumptive purposes. The third route passes into Persia via Hormuz. European merchants tend to cluster in Cyprus and Little Armenia to service it in OTL although I guess a case could be made for the Levant if the Il-Khans are playing ball. Really, this is the natural route ceteris parabis for trade. The fourth route (and largely unimportant route) passes through Genoa, the Crimea and is the route that Marco Polo used. It only worked when the Mongols had united the steppes to a tolerable extent and when the other two routes were infeasible for European trade. This final route was only ever the fall-back and wasn't otherwise profitable.
The problem we have is that none of these routes seem to be functioning very well, if at all which has wide ranging consequences from the Italian city states, through to the Levant, Egypt, Mesopotamia, the Malabar, the Coromandel, into the Straits, and all the way to China. Its the major source of revenue for the Venetians and Genoese, the Crusaders; and a major source of revenue and economic stimulation for Mesopotamia, Egypt; as well as the only reason for any economic activity in Southern India apart from subsistence and that magnificently fails as a pre-condition of state development in Malabar if not in the Coromandel; and the only reason for anything to happen in the Malay Archipelago apart from the inordinately boring Javanese hydraulic agriculture. So, yeah, I need to know this and really considering what your trying to do so should you.
