Context: Just as their customers pay them for Internet access, ISPs themselves pay upstream ISPs for Internet access. An upstream ISP usually has a larger network than the contracting ISP or is able to provide the contracting ISP with access to parts of the Internet the contracting ISP by itself has no access to.

Question: Who does an ISP pay for internet access?
Answer: upstream ISPs

Question: Why does an ISP need to pay an upstream ISP?
Answer: An upstream ISP usually has a larger network than the contracting ISP

Question: What does an upstream ISP provide for an ISP?
Answer: access to parts of the Internet the contracting ISP by itself has no access to

Question: what usually has a larger network, the ISP of the customer or the upstream ISP?
Answer: upstream ISPs

Question: What do ISPs pay customers for?
Answer: Unanswerable

Question: What usually has a small network than a contracting ISP?
Answer: Unanswerable

Question: What does an upstream ISP provide for customers?
Answer: Unanswerable

Question: What does the contracting ISP have access to that the upstream ISP does not?
Answer: Unanswerable