[dns-operations] IPv6 Connectivity on Firefox

[Fatemah Alharbi]

Hello,

I am a PhD student at UC Riverside, CA, USA. I am conducting experiments using Firefox to test Ipv6 connectivity and I would appreciate your cooperation and help to answer the following questions. 

Experiment 1:
By default, Firefox has Ipv6 enabled. When I visit a particular website, Firefox always sends 2 DNS queries: A query(For IPv4 address) and AAAA query (for IPv6 address). It always prefers the IPv4 address, why?

Experiment 2:
Please see the attached file: block_A_record_google.pcapng. I blocked the IPv4 response packets (for the A queries) of the domain name clients1.google.com to see how Firefox would behave if it gets only the AAAA response. Even if Firefox gets a positive response for the AAAA query, it ignores the response and keeps asking for the Ipv4 address! Why?

Does that have anything to do with my ISP Ipv6 connectivity? My ISP, Charter, doesn’t support Ipv6 connectivity to residential customers yet. If so, how Firefox does know that my ISP doesn’t support Ipv6 connectivity? How does Firefox know that the host triggering the DNS requests is not within an Ipv6 network?

This is the result of the Ipv6 connectivity test on Firefox (Please see the attached file: Test Your Ipv6 Connectivity-Firefox.pdf):



Thank you for your time. I look forward to hearing from you soon.


Sincerely,
Fatemah Alharbi
PhD Student
Computer Science Department
University of California, Riverside


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