International Simple Resale (ISR) is a methodology used by some telecom carriers to avoid or reduce payment of agreed settlement rates with other countries' carriers. ISR operators take advantage of imbalanced retail rate structures to bypass carriers and reduce costs. ISR operators tend to have small offices, connections to foreign carriers, and congregate in the same buildings. While ISR provides opportunities for low-cost international calls, it can result in significant revenue loss and damage relationships for other carriers if bypass is excessive.