draft-ietf-dnsop-maintain-ds-00.txt   draft-ietf-dnsop-maintain-ds-01.txt 
dnsop O. Gudmundsson dnsop O. Gudmundsson
Internet-Draft CloudFlare Internet-Draft CloudFlare
Intended status: Informational P. Wouters Intended status: Informational P. Wouters
Expires: June 16, 2016 Red Hat Expires: September 21, 2016 Red Hat
December 14, 2015 March 20, 2016
Managing DS records from parent via CDS/CDNSKEY Managing DS records from parent via CDS/CDNSKEY
draft-ietf-dnsop-maintain-ds-00 draft-ietf-dnsop-maintain-ds-01
Abstract Abstract
RFC7344 specifies how DNS trust can be maintained in-band between RFC7344 specifies how DNS trust can be partially maintained in-band
parent and child. There are two features missing in that between parent and child. There are two features missing in that
specification: initial trust setup and removal of trust anchor. This specification: initial trust setup and removal of trust anchor. This
document addresses both these omissions. document addresses both these omissions.
Changing a domain's DNSSEC status can be a complicated matter Changing a domain's DNSSEC status can be a complicated matter
involving many parties. Some of these parties, such as the DNS involving multiple unrelated parties. Some of these parties, such as
operator, might not even be known by all organisations involved. The the DNS operator, might not even be known by all organizations
inability to enable or disable DNSSEC via in-band signalling is seen involved. The inability to disable DNSSEC via in-band signalling is
as a problem or liability that prevents DNSSEC adoption at large seen as a problem or liability that prevents some DNSSEC adoption at
scale. This document adds a method for in-band signalling of DNSSEC large scale. This document adds a method for in-band signalling of
status changes. this DNSSEC status changes.
Initial trust is considered a much harder problem, this document will Initial trust is considered a much harder problem, this document will
seek to clarify and simplify the initial acceptance policy. seek to clarify and simplify the initial acceptance policy.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 16, 2016. This Internet-Draft will expire on September 21, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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publication of this document. Please review these documents publication of this document. Please review these documents
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Removing DS . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Removing a DS Record . . . . . . . . . . . . . . . . . . 3
1.2. Introducing DS . . . . . . . . . . . . . . . . . . . . . 3 1.2. Introducing a DS record . . . . . . . . . . . . . . . . . 3
1.3. Notation . . . . . . . . . . . . . . . . . . . . . . . . 3 1.3. Notation . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.4. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. The Three Uses of CDS . . . . . . . . . . . . . . . . . . . . 4 2. The Three Uses of CDS . . . . . . . . . . . . . . . . . . . . 4
2.1. The meaning of CDS ? . . . . . . . . . . . . . . . . . . 4 2.1. The meaning of the CDS RRset . . . . . . . . . . . . . . 5
3. Enabling DNSSEC via CDS/CDNSKEY . . . . . . . . . . . . . . . 5 3. Enabling DNSSEC via CDS/CDNSKEY . . . . . . . . . . . . . . . 5
3.1. Accept policy via authenticated channel . . . . . . . . . 5 3.1. Accept policy via authenticated channel . . . . . . . . . 5
3.2. Accept with extra checks . . . . . . . . . . . . . . . . 5 3.2. Accept with extra checks . . . . . . . . . . . . . . . . 5
3.3. Accept after delay . . . . . . . . . . . . . . . . . . . 5 3.3. Accept after delay . . . . . . . . . . . . . . . . . . . 6
3.4. Accept with challenge . . . . . . . . . . . . . . . . . . 6 3.4. Accept with challenge . . . . . . . . . . . . . . . . . . 6
4. DNSSEC Delete Algorithm . . . . . . . . . . . . . . . . . . . 6 4. DNSSEC Delete Algorithm . . . . . . . . . . . . . . . . . . . 6
5. Security considerations . . . . . . . . . . . . . . . . . . . 7 5. Security considerations . . . . . . . . . . . . . . . . . . . 7
6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 7 6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 7 7.1. Normative References . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . 8 7.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 8 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
CDS/CDNSKEY [RFC7344] records are used to signal changes in trust CDS/CDNSKEY [RFC7344] records are used to signal changes in trust
anchors, this is a great way to maintain delegations when the DNS anchors, this is one method to maintain delegations that can be used
operator has no other way to inform the parent that changes are when the DNS operator has no other way to inform the parent that
needed. RFC7344 contains no "delete" signal for the child to tell changes are needed. RFC7344 contains no "delete" signal for the
the parent that it wants to change the DNSSEC security of its domain. child to tell the parent that it wants to remove the DNSSEC security
for its domain.
[RFC7344] punted the Initial Trust establishment question and left it [RFC7344] did not include a method for the Initial Trust
to each parent to come up with an acceptance policy. establishment and left it to each parent to come up with an
acceptance policy.
1.1. Removing DS 1.1. Removing a DS Record
This document introduces the delete option for both CDS and CDNSKEY. This document introduces the delete option for both CDS and CDNSKEY,
to allow a child to signal the parent to turn off DNSSEC. When a allowing a child to signal to the parent to turn off DNSSEC. When a
domain is moved from one DNS operator to another one, sometimes it is domain is moved from one DNS operator to another one, sometimes it is
necessary to turn off DNSSEC to facilitate the change of DNS necessary to turn off DNSSEC to facilitate the change of DNS
operator. Common scenarios include: operator. Common scenarios include:
1 moving from a DNSSEC operator to a non-DNSSEC capable one or one 1 alternative to doing a proper DNSSEC algorithm rollover due to
that does not support the same algorithms as the old one. operational limitations such as software limitations.
2 moving to one that cannot/does-not-want to do a proper DNSSEC 2 moving from a DNSSEC operator to a non-DNSSEC capable operator.
rollover.
3 the domain holder does not want DNSSEC. 3 moving to an operator that cannot/does-not-want to do a proper
DNSSEC rollover.
4 when moving between two DNS operators that use disjoint sets of 4 when moving between two DNS operators that use disjoint sets of
algorithms to sign the zone, thus algorithm roll can not be algorithms to sign the zone, thus an algorithm rollover can not be
performed. performed.
Whatever the reason, the lack of a "remove my DNSSEC" option is 5 the domain holder no longer wants DNSSEC enabled.
turning into the latest excuse as why DNSSEC cannot be deployed.
Turing off DNSSEC reduces the security of the domain and thus should The lack of a "remove my DNSSEC" option is cited as a reason why some
operators cannot deploy DNSSEC, as this is seen as an operational
risk.
Turning off DNSSEC reduces the security of the domain and thus should
only be done carefully, and that decision should be fully under the only be done carefully, and that decision should be fully under the
child domain's control. child domain's control.
1.2. Introducing DS 1.2. Introducing a DS record
The converse issue is how does a child domain instruct the parent it The converse issue is how a child domain instructs the parent that it
wants to have a DS record added. This problem is not as hard as many wants to have a DS record added. This problem can be solved using a
have assumed, given a few simplifying assumptions. This document few simplifying assumptions. This document makes the assumption that
makes the assumption that there are reasonable policies that can be there are reasonable policies that can be applied and will allow
applied and will allow automation of trust introduction. automation of trust introduction.
Not being able to enable trust via an easily automated mechanism is Not being able to enable trust via an easily automated mechanism is
hindering DNSSEC at scale by anyone that does not have automated hindering DNSSEC at scale for DNS hosters that do not have automated
access to its parent's "registry". access to the "registry" of the child zone's parent.
1.3. Notation 1.3. Notation
When this document uses the word CDS it implies that the same applies When this document uses the word CDS it implies that the same applies
to CDNSKEY and vice versa, the only difference between the two to CDNSKEY and vice versa. The only difference between the two
records is how information is represented. records is how information is represented.
When the document uses the word "parent" it implies an entity that is We use RRR to mean Registry Registrar Registrant in the context of
authorized to insert into parent zone information about this child DNS domain markets.
domain. Which entity this is exactly does not matter. It could be
the Registrar or Reseller that the child domain was purchased from.
It could be the Registry that the domain is registered in when
allowed. It could be some other entity when the RRR framework is not
used.
We use RRR to mean Registry Registrar Reseller in the context of DNS When the document uses the word "parent" it implies an entity that is
domain markets. authorized to insert DS records into the parent zone on behalf of the
child domain. Which entity this exactly is does not matter. It
could be the Registrar or Reseller that the child domain was
purchased from. It could be the Registry that the domain is
registered in when allowed. It could be some other entity when the
RRR framework is not used.
1.4. Terminology 1.4. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
2. The Three Uses of CDS 2. The Three Uses of CDS
In general there are three operations that a domain wants to In general there are three operations that a domain wants to
influence on its parent: influence on its parent:
1 Roll over KSK, this means updating the DS records in the parent to 1 Roll over KSK, this means updating the DS records in the parent to
reflect the new set of KSK's at the child. This could be an ADD reflect the new set of KSK's at the child. This could be an ADD
operation, a Delete operation on one or more records while keeping operation, a DELETE operation on one or more records while keeping
at least one DS RR, or a full Replace operation at least one DS RR, or a full REPLACE operation.
2 Turn off DNSSEC validation, i.e. delete all the DS records 2 Turn off DNSSEC validation, i.e. delete all the DS records.
3 Enable DNSSEC validation, i.e. place initial DS RRset in the 3 Enable DNSSEC validation, i.e. place an initial DS RRset in the
parent. parent.
Operation 1 is covered in [RFC7344], operations 2 and 3 are defined Operation 1 is covered in [RFC7344], operations 2 and 3 are defined
in this document. In many people's minds, those two later operations in this document. In many people's minds, those two later operations
carry more risk than the first one. This document argues that 2 is carry more risk than the first one. This document argues that 2 is
identical to 1 and the final one is different (but not that identical to 1 and the third one is different (but not that
different). different).
2.1. The meaning of CDS ? 2.1. The meaning of the CDS RRset
The fundamental question is what is the semantic meaning of The semantic meaning of publishing a CDS RRset is interpreted to
publishing a CDS RRset in a zone? We offer the following mean:
interpretation:
"Publishing a CDS or CDNSKEY record signifies to the parent that the "Publishing a CDS or CDNSKEY record signals to the parent that the
child is ready for the corresponding DS records to be synchronized. child desires that the corresponding DS records be synchronized.
Every parent or parental agent should have an acceptance policy of Every parent or parental agent should have an acceptance policy of
these records for the three different use cases involved: Initial DS these records for the three different use cases involved: Initial DS
publication, Key rollover, and Returning to Insecure." publication, Key rollover, and Returning to Insecure."
In short, the CDS RRset is an instruction to the parent to modify DS In short, the CDS RRset is an instruction to the parent to modify DS
RRset if the CDS and DS RRsets differ. The acceptance policy for CDS RRset if the CDS and DS RRsets differ. The acceptance policy for CDS
in the rollover case is "seeing" according to [RFC7344]. The in the rollover case is "seeing" according to [RFC7344]. The
acceptance policy in the Delete case is just seeing a CDS RRset with acceptance policy in the Delete case is seeing a (validly signed) CDS
the delete operation specified in this document. RRset with the delete operation specified in this document.
3. Enabling DNSSEC via CDS/CDNSKEY 3. Enabling DNSSEC via CDS/CDNSKEY
There are number of different models for managing initial trust, but There are number of different models for managing initial trust, but
in the general case, the child wants to enable global validation for in the general case, the child wants to enable global validation for
the future. Thus during the period from the time the child publishes the future. Thus during the period from the time the child publishes
the CDS until the corresponding DS is published is the period that the CDS until the corresponding DS is published at the parent is the
DNS answers for the child could be forged. The goal is to keep this period that DNS answers for the child could be forged. The goal is
period as short as possible. to keep this period as short as possible.
One important case is how a 3rd party DNS operator can upload its One important case is how a third party DNS operator can upload its
DNSSEC information to the parent, so the parent can publish a DS DNSSEC information to the parent, so the parent can publish a DS
record for the child. In this case there is a possibility of setting record for the child. In this case there is a possibility of setting
up some kind of authentication mechanism and submission mechanism up some kind of authentication mechanism and submission mechanism
that is outside the scope of this document. that is outside the scope of this document.
Below are some policies that parents can use. These policies assume Below are some policies that parents can use. These policies assume
that the notifications are can be authenticated and/or identified. that the notifications can be verified or authenticated.
3.1. Accept policy via authenticated channel 3.1. Accept policy via authenticated channel
In this case the parent is notified via UI/API that CDS exists, the In this case the parent is notified via UI/API that a CDS RRset
parent retrieves the CDS and inserts the DS record as requested, if exists. The parent retrieves the CDS and inserts the corresponding
the request comes over an authenticated channel. DS RRset as requested, provided that the request comes over an
authenticated channel.
3.2. Accept with extra checks 3.2. Accept with extra checks
In this case the parent checks that the source of the notification is In this case the parent checks that the source of the notification is
allowed to request the DS insertion. The checks could include allowed to request the DS insertion. The checks could include
whether this is a trusted entity, whether the nameservers correspond whether this is a trusted entity, whether the nameservers correspond
to the requestor, whether there have been any changes in registration to the requestor, whether there have been any changes in registration
in the last few days, etc, or the parent can send a notification in the last few days, etc. The parent can also send a notification
requesting an confirmation. requesting a confirmation.
The end result is that the CDS is accepted at the end of the checks The end result is that the CDS RRset is accepted at the end of the
or when the out-of-band confirmation is received. checks or when the out-of-band confirmation is received.
3.3. Accept after delay 3.3. Accept after delay
In this case, if the parent deems the request valid, it starts In this case, if the parent deems the request valid, it starts
monitoring the CDS records at the child nameservers over period of monitoring the CDS RRset at the child nameservers over period of time
time to make sure nothing changes. After number of checks, to make sure nothing changes. After some time or after a number of
preferably from different vantage points, the parent accepts the CDS checks, preferably from different vantage points in the network, the
records as a valid signal to update. parent accepts the CDS RRset as a valid signal to update its DS RRset
for this child.
3.4. Accept with challenge 3.4. Accept with challenge
In this case the parent instructs the requestor to insert some record In this case the parent instructs the requestor to insert some record
into the child domain to prove it has the ability to do so (i.e., it into the child domain to prove it has the ability to do so (i.e., it
is the operator of the zone). is the operator of the zone).
4. DNSSEC Delete Algorithm 4. DNSSEC Delete Algorithm
The DNSKEY algorithm registry contains two reserved values: 0 and The DNSKEY algorithm registry contains two reserved values: 0 and
255[RFC4034]. The CERT record [RFC4398] defines the value 0 to mean 255[RFC4034]. The CERT record [RFC4398] defines the value 0 to mean
the algorithm in the CERT record is not defined in DNSSEC. the algorithm in the CERT record is not defined in DNSSEC.
[rfc-editor remove before publication] For this reason, using the [rfc-editor remove before publication] For this reason, using the
value 0 in CDS/CDNSKEY delete operations is potentially problematic, value 0 in CDS/CDNSKEY delete operations is potentially problematic,
but we propose that here anyway as the risk is minimal. The but we propose it here anyway as the risk is minimal. The
alternative is to reserve one DNSSEC algorithm number for this alternative is to reserve a DNSSEC algorithm number for this purpose.
purpose. [rfc-editor end remove] [rfc-editor end remove]
Right now, no DNSSEC validator understands algorithm 0 as a valid Right now, no DNSSEC validator understands algorithm 0 as a valid
signature algorithm, thus if the validator sees a DNSKEY or DS record signature algorithm. If a validator sees a DNSKEY or DS record with
with this value, it will treat it as unknown. Accordingly, the zone this algorithm value, it MUST treat it as unknown. Accordingly, the
is treated as unsigned unless there are other algorithms present. zone is treated as unsigned unless there are other algorithms
present.
In the context of CDS and CDNSKEY records, DNSSEC algorithm 0 is In the context of CDS and CDNSKEY records, DNSSEC algorithm 0 is
defined and means the entire DS set MUST be removed. The contents of defined to mean that the entire DS RRset MUST be removed. The
the records MUST contain only the fixed fields as show below. contents of the CDS or CDNSKEY RRset MUST contain one RR and only
contain the fixed fields as shown below.
1 CDS 0 0 0 1 CDS 0 0 0
2 CDNSKEY 0 3 0 2 CDNSKEY 0 3 0
The keying material payload is represented by a single 0. This
There is no keying material payload in the records, just the command record is signed in the same way as regular CDS/CDNSKEY RRsets are
to delete all DS records. This record is signed in the same way as signed.
CDS/CDNSKEY is signed.
Strictly speaking the CDS record could be "CDS X 0 X" as only the Strictly speaking the CDS record could be "CDS X 0 X" as only the
DNSKEY algorithm is what signals the delete operation, but for DNSKEY algorithm is what signals the DELETE operation, but for
clarity the "0 0 0" notation is mandated, this is not a definition of clarity the "0 0 0" notation is mandated - this is not a definition
DS Digest algorithm 0. Same argument applies to "CDNSKEY 0 3 0". of DS Digest algorithm 0. The same argument applies to "CDNSKEY 0 3
0", the value 3 in second field is mandated by RFC4034 section 2.1.2.
Once the parent has verified the CDS/CDNSKEY record and it has passed Once the parent has verified the CDS/CDNSKEY RRset and it has passed
other acceptance tests, the DS record MUST be removed. At this point other acceptance tests, the parent MUST remove the DS RRset. After
the child can start the process of turning DNSSEC off. waiting a sufficient amount of time - depending the the parental
TTL's - the child can start the process of turning off DNSSEC.
5. Security considerations 5. Security considerations
This document is about avoiding validation failures when a domain This document's main goal is to avoid validation failures when a
moves from one DNS operator to another one. Turing off DNSSEC domain moves from one DNS operator to another. Turning off DNSSEC
reduces the security of the domain and thus should only be done as a reduces the security of the domain and thus should only be done as a
last resort. last resort.
In most cases it is preferable that operators collaborate on the In most cases it is preferable that operators collaborate on the
rollover by doing a KSK+ZSK rollover as part of the handoff, but that rollover by doing a KSK+ZSK rollover as part of the hand-off, but
is not always possible. This document addresses the case where that is not always possible. This document addresses the case where
unsigned state is needed. unsigned state is needed to complete a rollover.
Users SHOULD keep in mind that re-establishing trust in delegation Users SHOULD keep in mind that re-establishing trust in delegation
can be hard and take a long time thus before going to unsigned all can be hard and takes a long time. Before deciding to complete the
options SHOULD be considered. rollover via an unsigned state, all options SHOULD be considered.
A parent should ensure that when it is allowing a child to become A parent SHOULD ensure that when it is allowing a child to become
securely delegated, that it has a reasonable assurance that the CDS/ securely delegated, that it has a reasonable assurance that the CDS/
CDNSKEY that is used to bootstrap the security on is visible from a CDNSKEY RRset that is used to bootstrap the security is visible from
geographically and network topology diverse view. It should also a geographically and network topology diverse view. It SHOULD also
ensure the the zone would validate if the parent published the DS ensure the the zone validates correctly if the parent publishes the
record. A parent zone might also consider sending an email to its DS record. A parent zone might also consider sending an email to its
contact addresses to give the child a warning that security will be contact addresses to give the child zone a warning that security will
enabled after a certain about of wait time - thus allowing a child be enabled after a certain about of wait time - thus allowing a child
administrator to cancel the request. administrator to cancel the request.
This document does not introduce any new problems, but like Negative
Trust Anchor[RFC7646], it addresses operational reality.
6. IANA considerations 6. IANA considerations
This document updates the following IANA registries: "DNS Security This document updates the following IANA registries: "DNS Security
Algorithm Numbers" Algorithm Numbers"
Algorithm 0 adds a reference to this document. Algorithm 0 adds a reference to this document.
7. References 7. References
7.1. Normative References 7.1. Normative References
skipping to change at page 8, line 21 skipping to change at page 8, line 30
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997, RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC4398] Josefsson, S., "Storing Certificates in the Domain Name [RFC4398] Josefsson, S., "Storing Certificates in the Domain Name
System (DNS)", RFC 4398, DOI 10.17487/RFC4398, March 2006, System (DNS)", RFC 4398, DOI 10.17487/RFC4398, March 2006,
<http://www.rfc-editor.org/info/rfc4398>. <http://www.rfc-editor.org/info/rfc4398>.
[RFC7646] Ebersman, P., Kumari, W., Griffiths, C., Livingood, J.,
and R. Weber, "Definition and Use of DNSSEC Negative Trust
Anchors", RFC 7646, DOI 10.17487/RFC7646, September 2015,
<http://www.rfc-editor.org/info/rfc7646>.
Appendix A. Acknowledgements Appendix A. Acknowledgements
This document is generated using the mmark tool that Miek Gieben has This document is generated using the mmark tool that Miek Gieben has
developed. developed.
Authors' Addresses Authors' Addresses
Olafur Gudmundsson Olafur Gudmundsson
CloudFlare CloudFlare
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