Step 1: Understand what the question asks.
The browser has a human-friendly URL like www.example.com but the network needs a numeric IP address to actually reach the server. We need the system that bridges that gap.
Step 2: Recall the Internet's phonebook idea.
The Domain Name System (DNS) is often called the phonebook of the Internet because it maps readable names to IP numbers.
Step 3: Rule out HTTP.
HTTP is the protocol that transfers the web page once you already know where the server is; it does not look up addresses.
Step 4: Rule out SSD.
SSD is a solid-state storage device, completely unrelated to name resolution.
Step 5: Rule out SMTP.
SMTP handles sending email, not translating URLs.
Step 6: Conclude.
The only system that turns a URL into an IP address is DNS.
\[ \boxed{\text{DNS}} \]