Rulers collected tolls, tariffs, and duties in their lands, and they could and did stack (similar to how you might pay state, local, and a national tax). Some of these would not necessarily only apply to outsiders (such as tolls on roads). In England, customs duties were a royal prerogative (King John introduced a duty of 1/15th the value of imports as well as exports), but in other areas you might pay the local ruler as well as a king.

The key is "how much exclusivity can the ruler control?". The Eastern Roman Empire, controlling the Bosphorus Strait and the easiest trade routes to the far East obviously had more power to influence international trade than, say, the King of Poland.

So, in the 11th century, you don't yet have real multi-city leagues (like the Hanseatic League which forms in the 12th century and really gets going in the 13th and 14th century to dominate Baltic Trade), but you do have the beginnings of guilds (London's Guildhall dates back to around 1128, so just after your date), who would attempt to organize merchants at the city level. In Italy, Venice, Genoa, Pisa, and Amalfi are merchant-led republics, and are competing heavily for Mediterranean Trade (it was Venice that was behind the sacking of Constantinople in 1204) with the Caliphate and the Eastern Roman Empire.

Trade agreements do exist at this point - the Hanseatic League famously agreed with Henry II to drop all tolls with Hanseatic merchants and allow them access to English Trade Fairs in 1157 (just after your time). Most trade agreements at this point appear to be focused on tolls, duties, market access, and (of course) tributes.

The keys to really long distance international trade at this point were control over the land routes through the Silk Road (from China through Constantinople and into Europe) and the African trade routes (through what would become Mali and Songhai) and control over access to India (with most routes controlled by the Abbasids at this time).