Linking is an important component to electronic resource access and depends on a few things:
Do you want to use a static URL at the portfolio level (typically, the URL provided by the vendor or publisher)?
Do you want to use the parser parameters in the electronic collection?
Does the content require a proxy because it's a licensed resource or is the content available Open Access and therefore does not require an off-campus proxy?
Some vendors require an additional linking parameter for linking to work properly. When working with a given resource, do you need to include your library's account ID, location ID, customer ID, or other parameter so linking works properly?