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For each host we intend to connect to, a DNS query is often issued to find the corresponding IP address of the host. The figure below indicates the entities often involved when a DNS query is issued. Root DNS Server 60 ms 100 ms TLD DNS Server 40 ms 40 ms Authoritative Local DNS Server 20 ms DNS Server 10 ms 10 ms Requesting Host Target Host DNS queries and replies are small. Let's ignore the transmission delay of the DNS queries and replies. Given the propagation delay indicated in the figure between the entities, how long does it take to receive the DNS reply? a) In case that the DNS query is cached in the local DNS server? (2 mark) b) In case that the DNS query is iterative? (2 mark) c) In case that the DNS query is recursive? (2 mark) d) Let L denote the propagation delay between the Requesting Host and the Local DNS server. Let R denote the delay between the Local to the Root DNS server. Let LT, LA, RT, and TA denote the delay between the Local-TLD, Local-Authoritative, Root-TLD, and TLD-Authoritative DNS servers respectively. Write out the formula of DNS response time for • Iterative query (2 marks) • Recursive query (2 marks) Show your work

For each host we intend to connect to, a DNS query is often issued to find the corresponding IP address of the host. The figure below indicates the entities often involved when a DNS query is issued. Root DNS Server 60 ms 100 ms TLD DNS Server 40 ms 40 ms Authoritative Local DNS Server 20 ms DNS Server 10 ms 10 ms Requesting Host Target Host DNS queries and replies are small. Let's ignore the transmission delay of the DNS queries and replies. Given the propagation delay indicated in the figure between the entities, how long does it take to receive the DNS reply? a) In case that the DNS query is cached in the local DNS server? (2 mark) b) In case that the DNS query is iterative? (2 mark) c) In case that the DNS query is recursive? (2 mark) d) Let L denote the propagation delay between the Requesting Host and the Local DNS server. Let R denote the delay between the Local to the Root DNS server. Let LT, LA, RT, and TA denote the delay between the Local-TLD, Local-Authoritative, Root-TLD, and TLD-Authoritative DNS servers respectively. Write out the formula of DNS response time for • Iterative query (2 marks) • Recursive query (2 marks) Show your work

Computer Networking: A Top-Down Approach (7th Edition)
Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN:9780133594140
Author:James Kurose, Keith Ross
Publisher:James Kurose, Keith Ross
Chapter1: Computer Networks And The Internet
Section: Chapter Questions
Problem R1RQ: What is the difference between a host and an end system? List several different types of end...
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For each host we intend to connect to, a DNS query is often issued to find the corresponding IP address of the host. The figure below indicates the entities often involved when a DNS query is issued. Root DNS Server 60 ms 100 ms TLD DNS Server 40 ms 40 ms Authoritative Local DNS Server 20 ms DNS Server 10 ms 10 ms Requesting Host Target Host DNS queries and replies are small. Let's ignore the transmission delay of the DNS queries and replies. Given the propagation delay indicated in the figure between the entities, how long does it take to receive the DNS reply? a) In case that the DNS query is cached in the local DNS server? (2 mark) b) In case that the DNS query is iterative? (2 mark) c) In case that the DNS query is recursive? (2 mark) d) Let L denote the propagation delay between the Requesting Host and the Local DNS server. Let R denote the delay between the Local to the Root DNS server. Let LT, LA, RT, and TA denote the delay between the Local-TLD, Local-Authoritative, Root-TLD, and TLD-Authoritative DNS servers respectively. Write out the formula of DNS response time for • Iterative query (2 marks) • Recursive query (2 marks) Show your work
Transcribed Image Text:For each host we intend to connect to, a DNS query is often issued to find the corresponding IP address of the host. The figure below indicates the entities often involved when a DNS query is issued. Root DNS Server 60 ms 100 ms TLD DNS Server 40 ms 40 ms Authoritative Local DNS Server 20 ms DNS Server 10 ms 10 ms Requesting Host Target Host DNS queries and replies are small. Let's ignore the transmission delay of the DNS queries and replies. Given the propagation delay indicated in the figure between the entities, how long does it take to receive the DNS reply? a) In case that the DNS query is cached in the local DNS server? (2 mark) b) In case that the DNS query is iterative? (2 mark) c) In case that the DNS query is recursive? (2 mark) d) Let L denote the propagation delay between the Requesting Host and the Local DNS server. Let R denote the delay between the Local to the Root DNS server. Let LT, LA, RT, and TA denote the delay between the Local-TLD, Local-Authoritative, Root-TLD, and TLD-Authoritative DNS servers respectively. Write out the formula of DNS response time for • Iterative query (2 marks) • Recursive query (2 marks) Show your work
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