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Science / Networking / Grade 7 / sn790

Names, Addresses and Network Delays

Separate finding an address from reaching a service, and delay from capacity.

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Learn the skill

DNS can translate a domain name into an IP address. Finding an address does not prove a service is reachable. Latency describes delay; bandwidth describes a link's data-carrying capacity. Compare measurements with matching units.

Worked example

In a simplified test, lookup takes 20 milliseconds and the later request takes 80 milliseconds. Sequential time is 20 + 80 = 100 milliseconds. A successful lookup alone does not prove that the later request will succeed.

Path A has 30 milliseconds latency and 20 megabits per second bandwidth. Path B has 70 milliseconds latency and 100 megabits per second bandwidth.
Lower delay and greater capacity need not belong to the same path.

Invented Network Tests

Path A has 30 milliseconds of latency and 20 megabits per second of bandwidth. Path B has 70 milliseconds of latency and 100 megabits per second of bandwidth. These invented values describe different properties. A separate service has a successful name lookup but a failed connection. Nothing here requires contacting a real network.

Question 1 Which service can look up an IP address for a domain name?
Question 2 Which path has lower latency?
Question 3 Which path has greater bandwidth?
Question 4 How many milliseconds greater is B's latency than A's?
Question 5 What does a successful DNS lookup with a failed connection show?