1. 1 Simplified DNS Query under IPv4/IPv6 Mixed Environment Hiroshi KITAMURA NEC Corporation kitamura@da.jp.nec.com

2. 2 Index Goals and Non-goal for today Analysis of current regular Two DNS queries method Understanding Confirmation Problems of the current Two DNS queries transaction method Proposal: 3 types of One DNS query transaction for One domain name resolving methods. 1.Two record types (AAAA and A) set Queries 2.One special new record type (e.g., AAAA+A) set Queries 3.One record type (AAAA) set Queries with transformation of A (IPv4) record entries Discussions

3. 3 Goals and Non-goal for today 1.Clarify problems of current regular Two DNS queries method 2.Propose a simplified regular DNS query method (One DNS query for One domain name resolving) Goal for today: - Notice that the current Two-DNS queries method is problematic and should be refined. Non-goal for today: - Discuss which simplified query method is suitable.

4. 4 Simple DNS Query: (used in IPv4 only era) DNS Server Client (w/ PF_INET) RecordAddress hostX Ap (IPv4) Aq (IPv4) p IPv4(A): q Queries 1 Name:hostX Type: A Answers 1 Name:hostX Type: A Addr:p(IPv4) Name:hostX Type:A Addr:q(IPv4)

5. 5 Current: DNS Server Status under IPv4 / IPv6 Mixed Environment for (one domain name) hostX –Two IPv4 addresses (p, q) are registered as A record In addition: –Two IPv6 addresses (s, t) are registered as AAAA record RecordAddress hostX Ap (IPv4) Aq (IPv4) hostX AAAAs (IPv6) AAAAt (IPv6) p IPv4(A): IPv6(AAAA): q st DNS Server

6. 6 Various Implementation types for current Two DNS queries method Type Name1st Query2nd Query Serial / Parallel 4-6 Serialfor A recordfor AAAA recordSerial Windows Vista/7 FreeBSD 6-4 Serialfor AAAA recordfor A recordSerial RFC4472 shows: not recommend now 4-6 Parallelfor A recordfor AAAA recordParallel Some Linux 6-4 Parallelfor AAAA recordfor A recordParallel At least, 4 types of implementations are known.

7. 7 4-6 (A first) Serial Type DNS Server Client (w/ PF_UNSPEC) Queries 1 Name:hostX Type: A Answers 1 Name:hostX Type: A Addr:p(IPv4) Name:hostX Type:A Addr:q(IPv4) Queries 2 Name:hostX Type: AAAA Answers 2 Name:hostX Type: AAAA Addr:s(IPv6) Name:hostX Type:AAAA Addr:t(IPv6) RecordAddress hostX Ap (IPv4) Aq (IPv4) hostX AAAAs (IPv6) AAAAt (IPv6) p IPv4(A): IPv6(AAAA): q st Popular Implementation Windows Vista/7, FreeBSD adopt this

8. 8 6-4 (AAAA first) Serial Type (RFC4472 shows) DNS Server Client (w/ PF_UNSPEC) Queries 1 Name:hostX Type: A Answers 1 Name:hostX Type: A Addr:p(IPv4) Name:hostX Type:A Addr:q(IPv4) Queries 2 Name:hostX Type: AAAA Answers 2 Name:hostX Type: AAAA Addr:s(IPv6) Name:hostX Type:AAAA Addr:t(IPv6) RecordAddress hostX Ap (IPv4) Aq (IPv4) hostX AAAAs (IPv6) AAAAt (IPv6) p IPv4(A): IPv6(AAAA): q st NOT Recommended Now! to avoid confusion RFC4472 (dnsop) should be updated??? Independence We have to remember order Independence “Issued queries” order “listed entries” order of getaddrinfo () return

9. 9 4-6 (A first) Parallel Type DNS Server Client (w/ PF_UNSPEC) Queries 1 Name:hostX Type: A Answers 1 Name:hostX Type: A Addr:p(IPv4) Name:hostX Type:A Addr:q(IPv4) Queries 2 Name:hostX Type: AAAA Answers 2 Name:hostX Type: AAAA Addr:s(IPv6) Name:hostX Type:AAAA Addr:t(IPv6) RecordAddress hostX Ap (IPv4) Aq (IPv4) hostX AAAAs (IPv6) AAAAt (IPv6) p IPv4(A): IPv6(AAAA): q st Popular Implementation, too Some Linux (after glibc2.10) adopt this

10. 10 6-4 (AAAA first) Parallel Type DNS Server Client (w/ PF_UNSPEC) Queries 1 Name:hostX Type: A Answers 1 Name:hostX Type: A Addr:p(IPv4) Name:hostX Type:A Addr:q(IPv4) Queries 2 Name:hostX Type: AAAA Answers 2 Name:hostX Type: AAAA Addr:s(IPv6) Name:hostX Type:AAAA Addr:t(IPv6) RecordAddress hostX Ap (IPv4) Aq (IPv4) hostX AAAAs (IPv6) AAAAt (IPv6) p IPv4(A): IPv6(AAAA): q st

11. 11 Understanding Confirmation Status of DNS serversBest practical solution? When IPv6 is started Number of IPv6 ready DNS servers is small WAS best practical solution at that time Now Most of the DNS servers are IPv6 ready will NOT become best practical solution anymore Q: Why we have adopted Two DNS queries method? A: Though it is less efficient, in order to avoid problems that is caused by meeting non-IPv6 ready DNS servers 1: keep IPv4(A) DNS query as it is. 2: Introduce IPv6(AAAA) DNS query independently It must be time to reconsider or refine DNS query method under IPv4/IPv6 mixed environment, NOW!

12. 12 Problems of current Two-queries method 1/2 (from technical or abstract viewpoint) Two-queries method is: –Latency is bad: wait for receiving two answers. If either one of two answers is lost, too complicated recover procedures are required. –twice much traffic (compared to one query) –complicated, inefficient and problematic. –not suitable and not optimized for current IPv4/IPv6 mixed environment. –temporal and will never last to the future IPv6 fully deployed environment.

13. 13 Problems of current Two-queries method 2/2 (from operational or end-user viewpoint) Worst problems: becomes one of the biggest obstacles Two-queries method is a hotbed to bring unsolvable problems for low-skill general end users, and it becomes one of the biggest obstacles to deploy the IPv6 to the Internet. When low-skill end users meet such problems, solution for them is “Uninstall IPv6 protocol stack”. It is clear that this is “put the cart before the horse” type bad solution, but there are no choice for them.

14. 14 One of unsolvable problems example for low-skill general end users Two types of Application implementations No A: (try once type) No loop after getaddrinfo () B: (multiple try type) recommended style has try & error loop after getaddrinfo () If an application get an unreachable IPv6 address as a first entry of getaddrinfo () return. not A: can not connect() / communicate B: takes long time (because first trial is failed)

15. 15 What we have to do NOW? Our mission is : to provide “Simplified DNS query method” that can solve technical problems and reduce to cause unsolvable problems for low-skill general end users. Hopefully, the method should be optimized for current IPv4/IPv6 mixed environment and will last to the future IPv6 fully deployed environment. We propose “One DNS query method” to accomplish this mission

16. 16 Solution Proposal: 3 types of One DNS query method for One domain name resolving We can discuss 3 types of methods. 1.Two record types (AAAA and A) set Queries 2.One special new record type (e.g., AAAA+A) set Queries 3.One record type (AAAA) set Queries with transformation of A (IPv4) record entries

17. 17 1: Two record types (AAAA and A) set Queries DNS Server Client (w/ PF_UNSPEC) Queries 1 Answers 1 Name:hostX Type: A Addr:p(IPv4) Name:hostX Type:A Addr:q(IPv4) Name:hostX Type: AAAA Addr:s(IPv6) Name:hostX Type:AAAA Addr:t(IPv6) Name:hostX Type: A Name:hostX Type: AAAA RecordAddress hostX Ap (IPv4) Aq (IPv4) hostX AAAAs (IPv6) AAAAt (IPv6) p IPv4(A): IPv6(AAAA): q st Two record types set

18. 18 2: One special new record type (e.g., AAAA+A ) set Queries DNS Server Client (w/ PF_UNSPEC) Queries 1 Answers 1 Name:hostX Type: A Addr:p(IPv4) Name:hostX Type:A Addr:q(IPv4) Name:hostX Type: AAAA Addr:s(IPv6) Name:hostX Type:AAAA Addr:t(IPv6) Name:hostX Type: special new (e.g., AAAA+A) RecordAddress hostX Ap (IPv4) Aq (IPv4) hostX AAAAs (IPv6) AAAAt (IPv6) p IPv4(A): IPv6(AAAA): q st One special new record (e.g.,AAAA+A) type set Use Pseudo-RR is also possible

19. 19 3: One record type (AAAA) set Queries with transformation of A (IPv4) record entries DNS Server Client (w/ PF_INET6) Queries 1 Answers 1 Name:hostX Type: AAAA Addr:p’(IPv6) Name:hostX Type:AAAA Addr:q’(IPv6) Name:hostX Type: AAAA Addr:s(IPv6) Name:hostX Type:AAAA Addr:t(IPv6) Name:hostX Type: AAAA RecordAddress hostX Ap (IPv4) Aq (IPv4) hostX AAAAs (IPv6) AAAAt (IPv6) p IPv4(A): IPv6(AAAA): q st RecordAddress hostX AAAAp’ (IPv6) AAAAq’ (IPv6) hostX AAAAs (IPv6) AAAAt (IPv6) Transform by using “IPv4 mapped IPv6 address” Very Unique Solution No modifications are needed on the Clients One record type (AAAA) set with IPv4 mapped address Transformation

20. 20 Effects brought by One DNS query method Simple and technical problems are solved Efficient Latency is improved Query traffic is decreased (becomes half) If you choose Type 3(AAAA only w/ mapped address), no modifications are needed on Clients.

21. 21 Discussions How do you think on this issue? Q: How many people 1.current Two-queries method is problematic? 2.shown problems are worthwhile for solving? 3.agree with going forward this I-D? 4. either of the proposed One-query methods can become good solution? Please let us know you comments. –Which types of One-query methods is preferable?