When you place the %link% variable within the message body and your scenario uses a public domain name, it will automatically be shortened. The link will look like “http://is.gd/9VjDKF” to fit into one text message. If you use an IP address for your landing page the link will be not shortened.

Within the scenario settings you can choose an URL shortening service from the dropdown menu. This only works for domain names (not IP's):

The URL-shortening services may check the links. As a result, incorrect statistics will be displayed. To avoid this issue, please use Antivirus/Firewall Protection Interval, which can be set in the Base settings of the campaign.