Depending on your country of citizenship, you may or may not need to obtain a visa to enter Canada. To find out, you may consult the relevant pages of Citizenship and Immigration Canada and the Canadian embassy and consular/visa offices in your country. Note that, depending on the visa office you apply at, the processing time could be weeks or even months, so please make sure to apply early.
If you need an invitation letter from IVNC in order to apply for a visa, please indicate this in the relevant box on the conference registration form, and a letter will be emailed to you. If you do not wish to pay the registration fee prior to ensuring that you have obtained the visa, you can still use the same registration form and submit without paying, and then make the payment later. However, please keep in mind that the registration fee will be higher if you make the payment after the early-bird deadline (01 May 2016), even if you have registered earlier.
Note that there is a new entry requirement in effect: visa-exempt foreign nationals are expected to have an Electronic Travel Authorization (eTA). Exceptions include U.S. citizens and travellers with a valid Canadian visa. For more information, please see Citizenship and Immigration Canada.