Details
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Proposal
1. Summary of the problem being addressed by this proposal
1.1.Background: What is "Lame Delegation"?
In the DNS, a lame delegation is a type of DNS misconfiguration error that occurs when a nameserver that is designated as an authoritative server for a domain name, does not return authoritative data for that name, when queried. For example, if a nameserver is delegated the responsibility for providing a name service for a zone (via NS records) and it is not actually doing it, i.e. the nameserver is neither set up as a primary nor secondary server, or is unresponsive, then the NS record is considered to be 'lame'.(RFC1912 [2]).
1.2. Impact of Lame Delegations in the Global DNS
In the in-addr.arpa and ip6.arpa zones, as applicable to this policy, the DNS records considered are NS records (as in the example above), delegating authority further down the chain of authority. With such a delegation resulting in lame responses, the most obvious issue is complete failure for the specific .ARPA sub-zone that is being delegated to. This is similar to not having any delegation in place at all: The sub-set of .ARPA records cannot be found, and so reverse DNS lookups will fail for that set of IP address resources. With no delegation in place, the failure is immediate and final. The querying client for a particular zone will get a negative response from the parent zone's nameserver, and do no further lookups.
But comparing to a lame delegation, the client receives a referral to the lame (and invalid or broken) nameserver(s). It then has to look them up by name before then querying one or more for the originally requested record. If the first nameserver in the set fails, the client may try the remainder, one by one if all are lame.
In some cases the lameness is a result of non-authority or missing records, but in others the lame nameserver is non-existent or unresponsive. In these cases, the client also has to wait for the request to time-out before trying the alternate NS, or failing completely.
In summary, lame nameserver delegations as compared to no delegation result in additional DNS traffic and a far greater time to respond for the client, with the same practical end outcome. In addition, the higher level parent zones that contain these useless and effectively invalid NS records are unnecessarily larger then needed. There is also a potential impact on any statistical data drawn from the parent zone(s).
2. Summary of how this proposal addresses the problem
2.1. Summary
This policy lays out a process to monitor nameserver records responsible for lame delegations, and a phased approach to removing these records from the DNS.
2.2. Scope of the Policy
This policy is intended to apply only to the DNS zones under in-addr.arpa and ip6.arpa managed by AFRINIC. Checks should be done for every single NS record as sourced from "domain" objects in the AFRINIC WHOIS database.
More specifically, this policy is only applicable to reverse DNS delegations managed within the AFRINIC region for AFRINIC majority RIR IP allocations and assignments.
This policy should not monitor or consider reverse DNS delegations for minority RIR IP address resources or legacy IP address resources.
3. Proposal
3.1. Process Detail
The following text will be added into the Consolidated Policy Manual:
10.7 Process for Lame Delegations
10.7.1 Monitoring / Checking
All "domain" objects in the AFRINIC WHOIS database must be periodically examined, and all "nserver" attributes extracted for checking. Each "nserver" found must be checked to:
- Respond to DNS queries.
- Reply with a valid SOA record for the associated domain with in the WHOIS database.
This periodic checking should be automated. The checks should be relatively frequent, but not so frequent as to cause any operational impact to either AFRINIC systems or the global DNS. If a nameserver fails a check for the first time, this is initially just recorded. Only after failing multiple lameness checks, should a nameserver be flagged for further action.
10.7.2 Notification
After one or more nameservers are flagged as lame, a reasonable attempt must be made to contact the person(s) responsible for the "domain" object and the DNS delegation.
All of the "admin-c", "tech-c" and "zone-c" contacts should be tried in parallel.
In addition, contact information may be extracted from associated "org" and/or "mnt-by" attributes when appropriate.
Unanswered notification communications should also be re-tried more than once before moving on to further actions.
The communication frequency, communication method(s) and number of attempts should be standardised and publicly documented.
10.7.3 Delegation Removal
Once a given nameserver had been determined to be lame for a given DNS "domain", and reasonable attempts have been made to contact a responsible person, the nameserver must then be removed from the given DNS "domain".
The nameserver must not be removed from all WHOIS objects and DNS zones, as it may not be uniformly lame for other zones it serves.
Only those nameservers flagged as lame should be removed from a given domain. The domain must not have all "nserver" attributes removed.
These removals should be automated. An optional "remarks" line may be added to the "domain" record in the database.
Should a given domain have all it's nameserver's identified as lame, and thus removed, it must then also be removed from the database, due to the "nserver" attribute being mandatory for "domain" objects.
Historical information about removed nameservers and domain objects should be archived for a reasonable amount of time and made available to the member for informational purpose.
10.7.4 Re-instatement
Once nameservers are fixed, or alternate nameservers are available for a given reverse DNS zone, the responsible person(s) would add delegation to them in the same way as a new delegation is done for a new IP assignment or allocation.
3.2 Possible Operational Impact(s)
A DNS delegation of a child-zone by lame NS records in the parent-zone will result in partial or complete failure of the child-zone.
Therefore, removing these lame records at the parent will have no further adverse effects on the child zone.
In the case of partial lameness, where not all nameservers are found to be lame, the impact will be positive: The removal of failing delegations will result in no DNS failures, rather than partial.
3.3 Sample Implementation Operations Guideline
The authors are aware that there would be significant work to be done to implement this policy. They have worked on a guideline for implementation, should the policy be passed.
A sample operational manual is available online [9] as a guideline to AFRINIC staff to use. Input and text, is welcome, but please note that this is a sample for implementation and not part of the policy.
4. Revision History
2017-03-15: First draft
5. References
5.1 Similar policies in other regions
- ARIN: Policy 2002-1: Lame Delegations in IN-ADDR.ARPA [4]
- APNIC: prop-038: Amending APNIC's lame DNS reverse delegation policy [5]
- LACNIC: Lame Delegation Policy within the Region Covered by LACNIC [6]
- RIPE NCC: No known policy at this time.
5.2 DNS misconfiguration studies
- Lame delegation in the AFRINIC database: How lame are our reverse delegations? [7]
- DNS Misconfiguration errors: Impact of Configuration Errors on DNS Robustness [8]
5.3 URI’s
[1]https://www.rfc-editor.org/rfc/rfc2119.txt
[2]https://www.ietf.org/rfc/rfc1912.txt
[4]https://www.arin.net/policy/proposals/2002_1.html
[5]https://www.apnic.net/community/policy/proposals/prop-038/
[6]http://www.lacnic.net/en/web/lacnic/manual-6
[7]http://afrinic.net/blog/165-how-lame-are-our-reverse-delegations
[8]http://web.cs.ucla.edu/~lixia/papers/09DNSConfig.pdf
5.4 Glossary
- DNS: Domain Name System
- RIR: Regional Internet Registry
- Majority RIR: Holds the parent allocation from IANA.
- Minority RIR: Administrates space within the majority allocation.
- Legacy Internet Resources: Internet number resources obtained prior to or otherwise outside the current hierarchical Internet registry system.
- SOA record: "Start Of Authority" record, at the head of every DNS zone.
Staff Assessment
Staff Assessment
| Proposal | AFPUB-2017-DNS-001-DRAFT-01 |
| Title | Lame delegations in AFRINIC reverse DNS |
| Assessed | 15 May 2017 |
1.0 Staff Understanding the Proposal
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The proposal is intended to mitigate or eliminate lame rdns DNS delegations associated with resources issued (or administratively managed) by AFRINIC.
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The proposal puts in place a process to monitor NS records responsible for lame delegations, and a phased approach to removing these records from the DNS.
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It is an update (or enhancement) to the current rDNS process outlined in the Consolidated Policy Manual (Sec 10)
2.0 Staff Comments:
- Reverse DNS space delegated from AFRINIC IP resources is approx 44% LAME according to data analysed from http://ftp.afrinic.net/pub/zones/ on 12 May 2017.
- The proposal needs to explicitly state that AFRINIC will not consider incoming "minority" resource records from other RIRs, as these records are from outside AFRINIC and beyond our control.
- The proposal should indicate explicitly if Legacy resource holders are included/excluded/affected and how.
- Regarding notifications - authors should allow AFRINIC to determine who can be notified and what process to be used. The wording "unanswered communications" could also change to refer to lack of resolution of the problem after some time, because it may happen that a communication is answered without the problem being fixed.
- On clause 10.7.4 - this clause seems unnecessary.
3.0 Comments from Legal Counsel:
- None observed
4.0 Implementation:
4.1 Timeline & Impact
(Software) development and testing will require approximately two months.
4.2 Implementation Requirements
The following actions are necessary to implement this policy as written:
- Implementing the automated "lameness" checks.
- Updating (internal) business rules to run checks prior to domain creation/updates.
- Automation of notifications sent out to contacts of records associated with lame delegations as specified in 10.7.2 as well as monthly lameness delegation reports and bi-annual lame delegation cleanup reports.
- Public lameness checker tool.
- Object archival in WHOIS (additional development also be needed to display archived objects in MyAFRINIC).
- Automation of removal of lame delegations as specified in 10.7.3
- Automation of reinstatements as specified in 10.7.4
- Documentation (and required publication) of the process detailing how the communication frequency/attempts and method(s) will be implemented.
