Depending on your country of citizenship, you may or may not need to obtain a visa to enter Germany. To find out, you may consult the relevant pages of Federal Foreign Office of Germany, the German 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 (02 May 2017), even if you have registered earlier.