[Docs] [txt|pdf|xml|html] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-nygren-dnsop-svcb-httpssvc) 00 01

DNSOP Working Group                                          B. Schwartz
Internet-Draft                                                    Google
Intended status: Standards Track                               M. Bishop
Expires: May 7, 2020                                           E. Nygren
                                                     Akamai Technologies
                                                        November 4, 2019


 Service binding and parameter specification via the DNS (DNS SVCB and
                               HTTPSSVC)
                   draft-ietf-dnsop-svcb-httpssvc-01

Abstract

   This document specifies the "SVCB" and "HTTPSSVC" DNS resource record
   types to facilitate the lookup of information needed to make
   connections for origin resources, such as for HTTPS URLs.  SVCB
   records allow an origin to be served from multiple network locations,
   each with associated parameters (such as transport protocol
   configuration and keying material for encrypting TLS SNI).  They also
   enable aliasing of apex domains, which is not possible with CNAME.
   The HTTPSSVC DNS RR is a variation of SVCB for HTTPS and HTTP
   origins.  By providing more information to the client before it
   attempts to establish a connection, these records offer potential
   benefits to both performance and privacy.

   TO BE REMOVED: This proposal is inspired by and based on recent DNS
   usage proposals such as ALTSVC, ANAME, and ESNIKEYS (as well as long
   standing desires to have SRV or a functional equivalent implemented
   for HTTP).  These proposals each provide an important function but
   are potentially incompatible with each other, such as when an origin
   is load-balanced across multiple hosting providers (multi-CDN).
   Furthermore, these each add potential cases for adding additional
   record lookups in-addition to AAAA/A lookups.  This design attempts
   to provide a unified framework that encompasses the key functionality
   of these proposals, as well as providing some extensibility for
   addressing similar future challenges.

   TO BE REMOVED: The specific name for this RR type is an open topic
   for discussion.  "SVCB" and "HTTPSSVC" are meant as placeholders as
   they are easy to replace.  Other names might include "B", "SRV2",
   "SVCHTTPS", "HTTPS", and "ALTSVC".

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.




Schwartz, et al.           Expires May 7, 2020                  [Page 1]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 7, 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Introductory Example  . . . . . . . . . . . . . . . . . .   5
     1.2.  Goals of the SVCB RR  . . . . . . . . . . . . . . . . . .   6
     1.3.  Overview of the SVCB RR . . . . . . . . . . . . . . . . .   7
     1.4.  Parameter for ESNI  . . . . . . . . . . . . . . . . . . .   8
     1.5.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   8
   2.  The SVCB record type  . . . . . . . . . . . . . . . . . . . .   8
     2.1.  Parameter specification via ServiceFieldValue . . . . . .   9
       2.1.1.  Presentation format . . . . . . . . . . . . . . . . .   9
     2.2.  SVCB RDATA Wire Format  . . . . . . . . . . . . . . . . .  10
     2.3.  SVCB owner names  . . . . . . . . . . . . . . . . . . . .  10
     2.4.  SvcRecordType . . . . . . . . . . . . . . . . . . . . . .  11
     2.5.  SVCB records: AliasForm . . . . . . . . . . . . . . . . .  11
     2.6.  SVCB records: ServiceForm . . . . . . . . . . . . . . . .  12
       2.6.1.  Special handling of "." for SvcDomainName in
               ServiceForm . . . . . . . . . . . . . . . . . . . . .  12
       2.6.2.  SvcFieldPriority  . . . . . . . . . . . . . . . . . .  13
   3.  Client behavior . . . . . . . . . . . . . . . . . . . . . . .  13
     3.1.  Clients using a Proxy . . . . . . . . . . . . . . . . . .  14



Schwartz, et al.           Expires May 7, 2020                  [Page 2]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   4.  DNS Server Behavior . . . . . . . . . . . . . . . . . . . . .  14
   5.  Performance optimizations . . . . . . . . . . . . . . . . . .  15
     5.1.  Optimistic pre-connection and connection reuse  . . . . .  15
     5.2.  Preferring usable records . . . . . . . . . . . . . . . .  16
     5.3.  Structuring zones for performance . . . . . . . . . . . .  16
   6.  Initial SvcParamKeys  . . . . . . . . . . . . . . . . . . . .  16
     6.1.  "alpn"  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     6.2.  "port"  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     6.3.  "esniconfig"  . . . . . . . . . . . . . . . . . . . . . .  17
     6.4.  "ipv4hint" and "ipv6hint" . . . . . . . . . . . . . . . .  17
   7.  Using SVCB with HTTPS and HTTP  . . . . . . . . . . . . . . .  18
     7.1.  Owner names for HTTPSSVC records  . . . . . . . . . . . .  19
     7.2.  Populating Alt-Used . . . . . . . . . . . . . . . . . . .  19
     7.3.  Differences from Alt-Svc  . . . . . . . . . . . . . . . .  19
       7.3.1.  Untrusted channel . . . . . . . . . . . . . . . . . .  19
       7.3.2.  Caching and granularity . . . . . . . . . . . . . . .  20
     7.4.  HTTP Strict Transport Security  . . . . . . . . . . . . .  20
   8.  Alt-Svc and SVCB/HTTPSSVC parameter for ESNI keys . . . . . .  21
     8.1.  Handling a mixture of alternatives not supporting ESNI  .  21
   9.  Interaction with other standards  . . . . . . . . . . . . . .  22
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  22
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  22
     11.1.  New registry for Service Parameters  . . . . . . . . . .  22
       11.1.1.  Procedure  . . . . . . . . . . . . . . . . . . . . .  23
       11.1.2.  Initial contents . . . . . . . . . . . . . . . . . .  23
     11.2.  Registry updates . . . . . . . . . . . . . . . . . . . .  24
   12. Acknowledgments and Related Proposals . . . . . . . . . . . .  25
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  25
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  25
     13.2.  Informative References . . . . . . . . . . . . . . . . .  28
   Appendix A.  Mapping between HTTPSSVC and Alt-Svc . . . . . . . .  29
     A.1.  Multiple records and preference ordering  . . . . . . . .  30
     A.2.  Additional examples . . . . . . . . . . . . . . . . . . .  30
   Appendix B.  Comparison with alternatives . . . . . . . . . . . .  31
     B.1.  Differences from the SRV RR type  . . . . . . . . . . . .  31
     B.2.  Differences from the proposed HTTP record . . . . . . . .  31
     B.3.  Differences from the proposed ANAME record  . . . . . . .  32
     B.4.  Differences from the proposed ESNI record . . . . . . . .  32
     B.5.  SNI Alt-Svc parameter . . . . . . . . . . . . . . . . . .  32
   Appendix C.  Design Considerations and Open Issues  . . . . . . .  32
     C.1.  Record Name . . . . . . . . . . . . . . . . . . . . . . .  33
     C.2.  Generality  . . . . . . . . . . . . . . . . . . . . . . .  33
     C.3.  Wire Format . . . . . . . . . . . . . . . . . . . . . . .  33
     C.4.  Where to include Priority . . . . . . . . . . . . . . . .  33
     C.5.  Whether to include Weight . . . . . . . . . . . . . . . .  33
   Appendix D.  Change history . . . . . . . . . . . . . . . . . . .  33
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  34




Schwartz, et al.           Expires May 7, 2020                  [Page 3]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


1.  Introduction

   The SVCB and HTTPSSVC RRs provide clients with complete instructions
   for access to an origin.  This information enables improved
   performance and privacy by avoiding transient connections to a sub-
   optimal default server, negotiating a preferred protocol, and
   providing relevant public keys.

   For example, when clients need to make a connection to fetch
   resources associated with an HTTPS URI, they currently resolve only A
   and/or AAAA records for the origin hostname.  This is adequate for
   services that use basic HTTPS (fixed port, no QUIC, no [ESNI]).
   Going beyond basic HTTPS confers privacy, performance, and
   operational advantages, but it requires the client to learn
   additional information, and it is highly desirable to minimize the
   number of round-trip and lookups required to learn this additional
   information.

   The SVCB and HTTPSSVC RRs also help when the operator of an origin
   wishes to delegate operational control to one or more other domains,
   e.g.  delegating the origin resource "https://example.com" to a
   service operator endpoint at "svc.example.net".  While this case can
   sometimes be handled by a CNAME, that does not cover all use-cases.
   CNAME is also inadequate when the service operator needs to provide a
   bound collection of consistent configuration parameters through the
   DNS (such as network location, protocol, and keying information).

   This document first describes the SVCB RR as a general-purpose
   resource record that can be applied directly and efficiently to a
   wide range of services.  As HTTPS is a primary use-case and has
   special requirements, the HTTPSSVC RR is also defined within this
   document as a special case of SVCB.  Services wishing to avoid the
   need for an [Attrleaf] label with SVCB may follow the pattern of
   HTTPSSVC and assign their own SVCB-compatible RR types.

   All behaviors described as applying to the SVCB RR also apply to the
   HTTPSSVC RR unless explicitly stated otherwise.  Section 7 describes
   additional behaviors specific to the HTTPSSVC record.  Apart from
   Section 7 and introductory examples, much of this document refers
   only to the SVCB RR, but those references should be taken to apply to
   SVCB, HTTPSSVC, and any future SVCB-compatible RR types.

   The SVCB RR has two forms: 1) the "Alias Form" simply delegates
   operational control for a resource; 2) the "Service Form" binds
   together configuration information for a service endpoint.  The
   Service Form provides additional key=value parameters within each
   RDATA set.




Schwartz, et al.           Expires May 7, 2020                  [Page 4]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   TO BE REMOVED: If we use this for providing configuration for DNS
   authorities, it is likely we'd specify a distinct "NS2" RR type that
   is an instantiation of SVCB for authoritative nameserver delegation
   and parameter specification, similar to HTTPSSVC.

   TO BE REMOVED: Another open question is whether SVCB records should
   be self-descriptive and include the service name (eg, "https") in the
   RDATA section to avoid ambiguity.  Perhaps this could be included as
   a svc="baz" parameter for protocols that are not the default for the
   RR type?  Current inclination is to not do so.

1.1.  Introductory Example

   As an introductory example for an HTTPS origin resource, a set of
   example HTTPSSVC and associated A+AAAA records might be:

   www.example.com.  7200  IN CNAME    svc.example.net.
   ; AliasForm
   example.com.      7200  IN HTTPSSVC 0 svc.example.net.
   ; ServiceForm
   svc.example.net.  7200  IN HTTPSSVC 2 svc3.example.net. ( alpn=h3
                                       port=8003 esniconfig="..." )
   svc.example.net.  7200  IN HTTPSSVC 3 svc2.example.net. ( alpn=h2
                                       port=8002 esniconfig="..." )
   svc2.example.net. 300   IN A        192.0.2.2
   svc2.example.net. 300   IN AAAA     2001:db8::2
   svc3.example.net. 300   IN A        192.0.2.3
   svc3.example.net. 300   IN AAAA     2001:db8::3
   ; Compatibility records for non-HTTPSSVC-aware clients
   example.com.      300   IN A        192.0.2.1
   example.com.      300   IN AAAA     2001:db8::1
   svc.example.net.  300   IN A        192.0.2.1
   svc.example.net.  300   IN AAAA     2001:db8::1

   In the preceding example, both of the "example.com" and
   "www.example.com" origin names are aliased to use alternative service
   endpoints offered as "svc.example.net" (with "www.example.com"
   continuing to use a CNAME alias).  HTTP/2 is available on a cluster
   of machines located at svc2.example.net with TCP port 8002 and HTTP/3
   is available on a cluster of machines located at svc3.example.net
   with UDP port 8003.  The client can use the specified ESNI keys to
   encrypt the SNI values of "example.com" and "www.example.com" in the
   handshake with these alternative service endpoints.  When connecting,
   clients will continue to treat the authoritative origins as
   "https://example.com" and "https://www.example.com", respectively.

   For services other than HTTPS (as well as for HTTPS origins with non-
   default ports), the SVCB RR and an [Attrleaf] label will be used.



Schwartz, et al.           Expires May 7, 2020                  [Page 5]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   For example, to reach an example resource of
   "baz://api.example.com:8765", the following Alias Form SVCB record
   would be used to delegate to "svc4-baz.example.net." which in-turn
   could return AAAA/A records and/or SVCB records in ServiceForm.

   _8765._baz.api.example.com. 7200 IN SVCB 0 svc4-baz.example.net.

1.2.  Goals of the SVCB RR

   The goal of the SVCB RR is to allow clients to resolve a single
   additional DNS RR in a way that:

   o  Provides service endpoints authoritative for the service, along
      with parameters associated with each of these endpoints.

   o  Does not assume that all alternative service endpoints have the
      same parameters or capabilities, or are even operated by the same
      entity.  This is important as DNS does not provide any way to tie
      together multiple RRs for the same name.  For example, if
      www.example.com is a CNAME alias that switches between one of
      three CDNs or hosting environments, successive queries for that
      name may return records that correspond to different environments.

   o  Enables CNAME-like functionality at a zone apex (such as
      "example.com") for participating protocols, and generally enables
      delegation of operational authority for an origin within the DNS
      to an alternate name.

   Additional goals specific to HTTPSSVC and the HTTPS use-case include:

   o  Connect directly to [HTTP3] (QUIC transport) alternative service
      endpoints

   o  Obtain the [ESNI] keys associated with an alternative service
      endpoint

   o  Support non-default TCP and UDP ports

   o  Address a set of long-standing issues due to HTTP(S) clients not
      implementing support for SRV records, as well as due to a
      limitation that a DNS name can not have both CNAME and NS RRs (as
      is the case for zone apex names)

   o  Provide an HSTS-like indication signaling for the duration of the
      DNS RR TTL that the HTTPS scheme should be used instead of HTTP
      (see Section 7.4).





Schwartz, et al.           Expires May 7, 2020                  [Page 6]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


1.3.  Overview of the SVCB RR

   This subsection briefly describes the SVCB RR in a non-normative
   manner.  (As mentioned above, this all applies equally to the
   HTTPSSVC RR which shares the same encoding, format, and high-level
   semantics.)

   The SVCB RR has two forms: AliasForm and ServiceForm.  SVCB RR
   entries with two non-empty fields are in AliasForm.  When more fields
   are present, this indicates that the SVCB RR is in ServiceForm.  The
   fields are:

   1.  SvcFieldPriority: The priority of this record (relative to
       others, with lower values preferred).  Applicable for the
       ServiceForm, and otherwise has value "0".  (Described in
       Appendix A.1.)

   2.  SvcDomainName: The domain name of either the alias target (for
       AliasForm) or the alternative service endpoint (for ServiceForm).

   3.  SvcFieldValue: A list of key=value pairs describing the
       alternative service endpoint for the domain name specified in
       SvcDomainName (only for ServiceForm and otherwise empty).
       Described in Section 2.1.

   Cooperating DNS recursive resolvers will perform subsequent record
   resolution (for SVCB, A, and AAAA records) and return them in the
   Additional Section of the response.  Clients must either use
   responses included in the additional section returned by the
   recursive resolver or perform necessary SVCB, A, and AAAA record
   resolutions.  DNS authoritative servers may attach in-bailiwick SVCB,
   A, AAAA, and CNAME records in the Additional Section to responses for
   an SVCB query.

   When in the ServiceForm, the SvcFieldValue of the SVCB RR provides an
   extensible data model for describing network endpoints that are
   authoritative for the origin, along with parameters associated with
   each of these endpoints.

   For the HTTPS use-case, the HTTPSSVC RR enables many of the benefits
   of [AltSvc], without waiting for a full HTTP connection initiation
   (multiple roundtrips) before learning of the preferred alternative,
   and without necessarily revealing the user's intended destination to
   all entities along the network path.







Schwartz, et al.           Expires May 7, 2020                  [Page 7]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


1.4.  Parameter for ESNI

   This document also defines a parameter for Encrypted SNI [ESNI] keys,
   both as a general SVCB parameter and also as a corresponding Alt-Svc
   parameter.  See Section 8.

1.5.  Terminology

   For consistency with [AltSvc], we adopt the following definitions:

   o  An "origin" is an information source as in [RFC6454].  For
      services other than HTTPS, the exact definition will need to be
      provided by the document mapping that service onto the SVCB RR.

   o  The "origin server" is the server that the client would reach when
      accessing the origin in the absence of the SVCB record or an HTTPS
      Alt-Svc.

   o  An "alternative service" is a different server that can serve the
      origin over a specified protocol.

   For example within HTTPS, the origin consists of a scheme (typically
   "https"), a host name, and a port (typically "443").

   Additional DNS terminology intends to be consistent with [DNSTerm].

   SVCB is a contraction of "service binding".  HTTPSSVC is a
   contraction of "HTTPS service".  SVCB, HTTPSSVC, and future RR types
   that share SVCB's format and registry are collectively known as SVCB-
   compatible RR types.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  The SVCB record type

   The SVCB DNS resource record (RR) type (RR type ???) is used to
   locate endpoints that can service an origin.  There is special
   handling for the case of "https" origins.  The presentation format of
   the record is:

   Name TTL IN SVCB SvcFieldPriority SvcDomainName SvcFieldValue

   The SVCB record is defined specifically within the Internet ("IN")
   Class ([RFC1035]).  SvcFieldPriority is a number in the range



Schwartz, et al.           Expires May 7, 2020                  [Page 8]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   0-65535, SvcDomainName is a domain name, and SvcFieldValue is a set
   of key=value pairs present for the ServiceForm.  The SvcFieldValue is
   empty for the AliasForm.

   The algorithm for resolving SVCB records and associated address
   records is specified in Section 3.

2.1.  Parameter specification via ServiceFieldValue

   In ServiceForm, the SvcFieldValue contains key=value pairs.  Keys are
   IANA-registered SvcParamKeys (Section 11.1) with both a case-
   insensitive string representation and a numeric representation in the
   range 0-65535.  Registered key names should only contain characters
   from the ranges "a"-"z", "0"-"9", and "-".  In ABNF [RFC5234],

   ALPHA_LC    = %x61-7A   ;  a-z
   key         = ALPHA_LC / DIGIT / "-"
   display-key = ALPHA / DIGIT / "-"

   Values are in a format specific to the SvcParamKey.  Their definition
   should specify both their presentation format and wire encoding
   (e.g., domain names, binary data, or numeric values).

   The SVCB format preserves the order of values and can encode multiple
   values for the same parameter.  However, clients MUST consider only
   the first appearance of a parameter unless its specification
   explicitly allows multiple values.

2.1.1.  Presentation format

   The presentation format for SvcFieldValue is a whitespace-separated
   list of the key=value pairs.  Each pair is presented in the following
   form:

   ; basic-visible is VCHAR minus DQUOTE, ";", and "\"
   basic-visible = %x21 / %x23-3A / %x3C-5B / %x5D-7E
   escaped-char  = "\" (VCHAR / WSP)
   contiguous    = *(basic-visible / escaped-char)
   quoted-string = DQUOTE *(contiguous / WSP) DQUOTE
   value         = quoted-string / contiguous
   pair          = display-key "=" value

   The value format is intended to match the definition of <character-
   string> in [RFC1035] Section 5.1.  (Unlike <character-string>, the
   length of a value is not limited to 255 characters.)

   Unrecognized keys are represented in presentation format as
   "keyNNNNN" where NNNNN is the numeric value of the key type without



Schwartz, et al.           Expires May 7, 2020                  [Page 9]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   leading zeros.  In presentation format, values of unrecognized keys
   should be represented in wire format, using decimal escape codes
   (e.g. \255) when necessary.

2.2.  SVCB RDATA Wire Format

   The RDATA for the SVCB RR consists of:

   o  a 2 octet field for SvcFieldPriority as an integer in network byte
      order.

   o  the uncompressed SvcDomainName, represented as a sequence of
      length-prefixed labels as in Section 3.1 of [RFC1035].

   o  the SvcFieldValue byte string, consuming the remainder of the
      record (so smaller than 65535 octets and constrained by the RDATA
      and DNS message sizes).

   AliasForm is defined by SvcFieldPriority being 0.

   When SvcFieldValue is non-empty (ServiceForm), it contains a list of
   SvcParamKey=SvcParamValue pairs with length-prefixes for the
   SvcParamValues, each of which contains:

   o  a 2 octet field containing the SvcParamKey as an integer in
      network byte order.

   o  a 2 octet field containing the length of the SvcParamValue as an
      integer between 0 and 65535 in network byte order (but constrained
      by the RDATA and DNS message sizes).

   o  an octet string of the length defined by the previous field.

   If the parser reaches the end of the RDATA while parsing a
   SvcFieldValue, the RR is invalid and MUST be discarded.

   TODO: decide if we want special handling for any SvcParamKey ranges?
   For example: range for greasing; experimental range; range-of-
   mandatory-to-use-the-RR vs range of ignore-just-param-if-unknown.

2.3.  SVCB owner names

   When querying the SVCB RR, an origin is typically translated into a
   QNAME by prefixing the port and scheme with "_", then concatenating
   them with the host name, resulting in a domain name like
   "_8004._examplescheme.api.example.com.".





Schwartz, et al.           Expires May 7, 2020                 [Page 10]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   Protocol mappings for SVCB MAY remove the port or replace it with
   other protocol-specific information, but MUST retain the scheme in
   the QNAME.  RR types other than SVCB can define additional behavior
   for translating origins to QNAMEs.  See Section 7.1 for the HTTPSSVC
   behavior.

   When a prior CNAME or SVCB record has aliased to an SVCB record, each
   RR shall be returned under its own owner name.

   Note that none of these forms alter the origin or authority for
   validation purposes.  For example, clients MUST continue to validate
   TLS certificate hostnames based on the origin host.

   As an example:

   _8443._foo.api.example.com. 7200 IN SVCB 0 svc4.example.net.
   svc4.example.net.  7200  IN SVCB 3 ( svc4.example.net. alpn="bar"
                                      port="8004" esniconfig="..." )

   would indicate that "foo://api.example.com:8443" is aliased to use
   ALPN protocol "bar" service endpoints offered at "svc4.example.net"
   on port 8004.

2.4.  SvcRecordType

   The SvcRecordType is indicated by the SvcFieldPriority, and defines
   the form of the SVCB RR.  When SvcFieldPriority is 0, the SVCB
   SvcRecordType is defined to be in AliasForm.  Otherwise, the SVCB
   SvcRecordType is defined to be in ServiceForm.

   Within an SVCB RRSet, all RRs should have the same SvcRecordType.  If
   an RRSet contains a record in AliasForm, the client MUST ignore any
   records in the set with ServiceForm.

2.5.  SVCB records: AliasForm

   When SvcRecordType is AliasForm, the SVCB record is to be treated
   similar to a CNAME alias pointing to SvcDomainName.  SVCB RRSets
   SHOULD only have a single resource record in this form.  If multiple
   are present, clients or recursive resolvers SHOULD pick one at
   random.

   The AliasForm's primary purpose is to allow aliasing at the zone
   apex, where CNAME is not allowed.  For example, if an operator of
   https://example.com wanted to point HTTPS requests to a service
   operating at svc.example.net, they would publish a record such as:

   example.com. 3600 IN SVCB 0 svc.example.net.



Schwartz, et al.           Expires May 7, 2020                 [Page 11]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   The SvcDomainName MUST point to a domain name that contains another
   SVCB record, address (AAAA and/or A) records, or both address records
   and a ServiceForm SVCB record.

   Note that the SVCB record's owner name MAY be the canonical name of a
   CNAME record, and the SvcDomainName MAY be the owner of a CNAME
   record.  Clients and recursive resolvers MUST follow CNAMEs as
   normal.

   Due to the risk of loops, clients and recursive resolvers MUST
   implement loop detection.  Chains of consecutive SVCB and CNAME
   records SHOULD be limited to (8?) prior to reaching terminal address
   records.

   As legacy clients will not know to use this record, service operators
   will likely need to retain fallback AAAA and A records alongside this
   SVCB record, although in a common case the target of the SVCB record
   might offer better performance, and therefore would be preferable for
   clients implementing this specification to use.

   Note that SVCB AliasForm RRs do not alias to RR types other than
   address records (AAAA and A), CNAMEs, and ServiceForm SVCB records.
   For example, an AliasForm SVCB record does not alias to an HTTPSSVC
   record, nor vice-versa.

2.6.  SVCB records: ServiceForm

   When SvcRecordType is the ServiceForm, the combination of
   SvcDomainName and SvcFieldValue parameters within each resource
   record associates an alternative service location with its connection
   parameters.

   Each protocol scheme that uses SVCB MUST define a protocol mapping
   that explains how SvcFieldValues are applied for connections of that
   scheme.  Appendix A defines a limited mapping between Alt-Svc
   ([AltSvc]) values and the SVCB ServiceForm.  Protocols using SVCB may
   use this Alt-Svc mapping if they also use Alt-Svc.  Unless specified
   otherwise by the protocol mapping, clients MUST ignore SvcFieldValue
   parameters that they do not recognize.

2.6.1.  Special handling of "." for SvcDomainName in ServiceForm

   For ServiceForm SVCB RRs, if SvcDomainName has the value ".", then
   the owner name of this record MUST be used as the effective
   SvcDomainName.  (The SvcDomainName of an SVCB RR in AliasForm MUST
   NOT have this value.)





Schwartz, et al.           Expires May 7, 2020                 [Page 12]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   For example, in the following example "svc2.example.net" is the
   effective SvcDomainName:

   www.example.com.  7200  IN HTTPSSVC svc.example.net.
   svc.example.net.  7200  IN CNAME    svc2.example.net.
   svc2.example.net. 7200  IN HTTPSSVC 1 . ( alpn=h2
                                       port=8002 esniconfig="..." )
   svc2.example.net. 300   IN A        192.0.2.2
   svc2.example.net. 300   IN AAAA     2001:db8::2

2.6.2.  SvcFieldPriority

   As RRs within an RRSet are explicitly unordered collections, the
   SvcFieldPriority value serves to indicate priority.  SVCB RRs with a
   smaller SvcFieldPriority value SHOULD be given preference over RRs
   with a larger SvcFieldPriority value.

   When receiving an RRSet containing multiple SVCB records with the
   same SvcFieldPriority value, clients SHOULD apply a random shuffle
   within a priority level to the records before using them, to ensure
   uniform load-balancing.

3.  Client behavior

   An SVCB-aware client resolves an origin HOST by attempting to
   determine the preferred SvcFieldValue and IP addresses for its
   service, using the following procedure:

   1.  Issue parallel AAAA/A and SVCB queries for the name HOST.  The
       answers for these may or may not include CNAME pointers before
       reaching one or more of these records.

   2.  If an SVCB record of AliasForm SvcRecordType is returned for
       HOST, clients MUST loop back to step 1 replacing HOST with
       SvcDomainName, subject to loop detection heuristics.

   3.  If one or more SVCB records of ServiceForm SvcRecordType are
       returned for HOST, clients should select the highest-priority
       option with acceptable parameters, and resolve AAAA and/or A
       records for its SvcDomainName if they are not already available.
       These are the preferred SvcFieldValue and IP addresses.  If the
       connection fails, the client MAY try to connect using values from
       a lower-priority record.  If none of the options succeed, the
       client SHOULD connect to the origin server directly.

   4.  If an SVCB record for HOST does not exist, the received AAAA and/
       or A records are the preferred IP addresses and there is no
       SvcFieldValue.



Schwartz, et al.           Expires May 7, 2020                 [Page 13]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   This procedure does not rely on any recursive or authoritative server
   to comply with this specification or have any awareness of SVCB.

   When selecting between AAAA and A records to use, clients may use an
   approach such as [HappyEyeballsV2].

   Some important optimizations are discussed in Section 5 to avoid
   additional latency in comparison to ordinary AAAA/A lookups.

3.1.  Clients using a Proxy

   Clients using a domain-oriented transport proxy like HTTP CONNECT
   ([RFC7231] Section 4.3.6) or SOCKS5 ([RFC1928]) SHOULD disable SVCB
   support if performing SVCB queries would violate the client's privacy
   intent.

   If the client can safely perform SVCB queries (e.g. via the proxy or
   an affiliated resolver), the client SHOULD follow the standard SVCB
   resolution process, selecting the highest priority option that is
   compatible with the client and the proxy.  The client SHOULD provide
   the final SvcDomainName and port (if present) to the proxy as the
   destination host and port.

   Providing the proxy with the final SvcDomainName has several
   benefits:

   o  It allows the client to use the SvcFieldValue, if present, which
      is only usable with a specific SvcDomainName.  The SvcFieldValue
      may include information that enhances performance (e.g. alpn) and
      privacy (e.g. esniconfig).

   o  It allows the origin to delegate the apex domain.

   o  It allows the proxy to select between IPv4 and IPv6 addresses for
      the server according to its configuration, and receive addresses
      based on its network geolocation.

4.  DNS Server Behavior

   When replying to an SVCB query, authoritative DNS servers SHOULD
   return A, AAAA, and SVCB records (as well as any relevant CNAME
   records) in the Additional Section for any in-bailiwick
   SvcDomainNames.

   Recursive resolvers that are aware of SVCB SHOULD ensure that the
   client can execute the procedure in Section 3 without issuing a
   second round of queries, by following this procedure while
   constructing a response to a stub resolver for an SVCB record query:



Schwartz, et al.           Expires May 7, 2020                 [Page 14]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   1.  When processing an SVCB response from an authoritative server,
       add it to the Additional section (unless it is the Answer).

   2.  If all records are in ServiceForm, resolve A and AAAA records for
       each SvcDomainName (or for the owner name if the SvcDomainName is
       "."), and include all the results in the Additional section.

   3.  Otherwise, select an AliasForm record at random, and resolve A,
       AAAA, and SVCB records for the SvcDomainName.  If the SVCB record
       does not exist, add the A and AAAA records to the Additional
       section.  Otherwise, go to step 1, subject to loop detection
       heuristics.

   All DNS servers SHOULD treat the SvcParam portion of the SVCB RR as
   opaque and SHOULD NOT try to alter their behavior based on its
   contents.

   When responding to a query that includes the DNSSEC OK bit
   ([RFC3225]), DNSSEC-capable recursive and authoritative DNS servers
   MUST accompany each RRSet in the Additional section with the same
   DNSSEC-related records that it would send when providing that RRSet
   as an Answer.

5.  Performance optimizations

   For optimal performance (i.e. minimum connection setup time), clients
   SHOULD issue address (AAAA and/or A) and SVCB queries simultaneously,
   and SHOULD implement a client-side DNS cache.  Responses in the
   Additional section of an SVCB response SHOULD be placed in cache
   before performing any followup queries.  With these optimizations in
   place, and conforming DNS servers, using SVCB does not add network
   latency to connection setup.

5.1.  Optimistic pre-connection and connection reuse

   If an address response arrives before the corresponding SVCB
   response, the client MAY initiate a connection as if the SVCB query
   returned NODATA, but MUST NOT transmit any information that could be
   altered by the SVCB response until it arrives.  For example, a TLS
   ClientHello can be altered by the "esniconfig" value of an SVCB
   response (Section 6.3).  Clients implementing this optimization
   SHOULD wait for 50 milliseconds before starting optimistic pre-
   connection, as per the guidance in [HappyEyeballsV2].

   An SVCB record is consistent with a connection if the client would
   attempt an equivalent connection when making use of that record.  If
   an SVCB record is consistent with an active or in-progress connection
   C, the client MAY prefer that record and use C as its connection.



Schwartz, et al.           Expires May 7, 2020                 [Page 15]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   For example, suppose the client receives this SVCB RRSet for a
   protocol that uses TLS over TCP:

   _1234._bar.example.com. 300 IN SVCB 1 svc1.example.net (
       esniconfig="111..." ipv6hint=2001:db8::1 port=1234 ... )
                                  SVCB 2 svc2.example.net (
       esniconfig="222..." ipv6hint=2001:db8::2 port=1234 ... )

   If the client has an in-progress TCP connection to
   "[2001:db8::2]:1234", it MAY proceed with TLS on that connection
   using "esniconfig="222..."", even though the other record in the
   RRSet has higher priority.

   If none of the SVCB records are consistent with any active or in-
   progress connection, clients must proceed as described in Step 3 of
   the procedure in Section 3.

5.2.  Preferring usable records

   A nonconforming recursive resolver might not return all the
   information required to use all the records in an SVCB response.  If
   some of the SVCB records in the response can be used without
   requiring additional DNS queries, the client MAY prefer those
   records, regardless of their priorities.

5.3.  Structuring zones for performance

   To avoid a delay for clients using a nonconforming recursive
   resolver, domain owners SHOULD use a single SVCB record whose
   SvcDomainName is in the origin hostname's CNAME chain if possible.
   This will ensure that the required address records are already
   present in the client's DNS cache as part of the responses to the
   address queries that were issued in parallel.

6.  Initial SvcParamKeys

   A few initial SvcParamKeys are defined here.  These keys are useful
   for HTTPS, and most are applicable to other protocols as well.

6.1.  "alpn"

   The "alpn" SvcParamKey defines the Application Layer Protocol (ALPN,
   as defined in {{!RFC7301}) supported by a TLS-based alternative
   service.  Its value SHOULD be an entry in the IANA registry "TLS
   Application-Layer Protocol Negotiation (ALPN) Protocol IDs".

   The presentation format and wire format of SvcParamValue is its
   registered "Identification Sequence".



Schwartz, et al.           Expires May 7, 2020                 [Page 16]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   Clients MUST ignore SVCB RRs where the "alpn" SvcParamValue is
   unknown or unsupported.

6.2.  "port"

   The "port" SvcParamKey defines the TCP or UDP port that should be
   used to contact this alternative service.

   The presentation format of the SvcParamValue is a numeric value
   between 0 and 65535 inclusive.  The wire format of the SvcParamValue
   is the corresponding 2 octet numeric value in network byte order.

6.3.  "esniconfig"

   The SvcParamKey for ESNI is "esniconfig".  Its value is defined in
   Section 8.  It is applicable to most TLS-based protocols.

   When publishing a record containing an "esniconfig" parameter, the
   publisher MUST ensure that all IP addresses of SvcDomainName
   correspond to servers that have access to the corresponding private
   key or are authoritative for the fallback domain.  (See [ESNI] for
   more details about the fallback domain.)  This yields an anonymity
   set of cardinality equal to the number of ESNI-enabled server domains
   supported by a given client-facing server.  Thus, even with SNI
   encryption, an attacker who can enumerate the set of ESNI-enabled
   domains supported by a client-facing server can guess the correct SNI
   with probability at least 1/K, where K is the size of this ESNI-
   enabled server anonymity set.  This probability may be increased via
   traffic analysis or other mechanisms.

6.4.  "ipv4hint" and "ipv6hint"

   The "ipv4hint" and "ipv6hint" keys represent IP address hints for the
   service.  If A and AAAA records for SvcDomainName are locally
   available, the client SHOULD ignore these hints.  Otherwise, clients
   SHOULD perform A and/or AAAA queries for SvcDomainName as in
   Section 3, and clients SHOULD use the IP address in those responses
   for future connections.  Clients MAY opt to terminate any connections
   using the addresses in hints and instead switch to the addresses in
   response to the SvcDomainName.  Failure to use A and/or AAAA response
   addresses may negatively impact load balancing or other geo-aware
   features and thereby degrade client performance.

   The wire format for each parameter is a sequence of IP addresses in
   network byte order.  Like an A or AAAA RRSet, the list of addresses
   represents an unordered collection, and clients SHOULD pick addresses
   to use in a random order.




Schwartz, et al.           Expires May 7, 2020                 [Page 17]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   These parameters MAY be repeated multiple times within a record.
   When receiving such a record, clients SHOULD combine the sets of
   addresses.

   When selecting between IPv4 and IPv6 addresses to use, clients may
   use an approach such as [HappyEyeballsV2].  When only "ipv4hint"
   parameters are present, IPv6-only clients may synthesize IPv6
   addresses as specified in [RFC7050] or ignore the "ipv4hint" key and
   wait for AAAA resolution (Section 3).  Recursive resolvers MUST NOT
   perform DNS64 ([RFC6147]) on parameters within an SVCB record.  For
   best performance, server operators SHOULD include "ipv6hint"
   parameters whenever they publish "ipv4hint" parameters.

   The presentation format for each parameter is a comma-separated list
   of IP addresses in standard textual format [RFC5952].

   These parameters are intended to minimize additional connection
   latency when a recursive resolver is not compliant with the
   requirements in Section 4, and SHOULD NOT be included if most clients
   are using compliant recursive resolvers.

7.  Using SVCB with HTTPS and HTTP

   Use of any protocol with SVCB requires a protocol-specific mapping
   specification.  This section specifies the mapping for HTTPS and
   HTTP.

   To enable special handling for the HTTPS and HTTP use-cases, the
   HTTPSSVC RR type is defined as an SVCB-compatible RR type, specific
   to the https and http schemes.  Clients MUST NOT perform SVCB queries
   or accept SVCB responses for https or http schemes.

   The HTTPSSVC wire format and presentation format are identical to
   SVCB, and both share the SvcParamKey registry.  SVCB semantics apply
   equally to HTTPSSVC unless specified otherwise.

   The presence of an HTTPSSVC record for an HTTP or HTTPS service also
   provides an indication that all resources are available over HTTPS,
   as discussed in Section 7.4.  This allows HTTPSSVC RRs to apply to
   pre-existing HTTP scheme URLs, while ensuring that the client uses a
   secure and authenticated HTTPS connection.

   The HTTPSSVC RR parallels the concepts introduced in the HTTP
   Alternative Services proposed standard [AltSvc].  Clients and servers
   that implement HTTPSSVC are NOT REQUIRED to implement Alt-Svc.
   However, many clients and servers will implement both, and a partial
   mapping exists between them (Appendix A).




Schwartz, et al.           Expires May 7, 2020                 [Page 18]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


7.1.  Owner names for HTTPSSVC records

   The HTTPSSVC RR extends the behavior for determining a QNAME
   specified above in Section 2.3.  In particular, if the scheme is
   "https" with port 443, or the scheme is "http" and the port is 80,
   then the client's original QNAME is equal to the origin host name.

   For origins other than https with port 443 and http with port 80, the
   port and scheme continue to be prefixed to the hostname as described
   in Section 2.3.  Following of HTTPSSVC AliasForm and CNAME aliases is
   also unchanged from SVCB.

   Note that none of these forms alter the HTTPS origin or authority.
   For example, clients MUST continue to validate TLS certificate
   hostnames based on the origin host.

7.2.  Populating Alt-Used

   When using an HTTPSSVC RR in ServiceForm, all clients SHOULD include
   the "Alt-Used" HTTP header (Section 5 of [RFC7838]).  The header's
   value (in ABNF) SHOULD be

   uri-host ":" port

   where uri-host is the final value of HOST ({client-behavior}) minus
   the trailing ".", and port is the port number in use.

7.3.  Differences from Alt-Svc

   Publishing a ServiceForm HTTPSSVC record in DNS is intended to be
   similar to transmitting the corresponding Alt-Svc field value over
   HTTPS, and receiving an HTTPSSVC record is intended to be similar to
   receiving that field value over HTTPS.  However, there are some
   differences in the intended client and server behavior.

7.3.1.  Untrusted channel

   SVCB does not require or provide any assurance of authenticity.
   (DNSSEC signing and verification, which would provide such assurance,
   are OPTIONAL.)  The DNS resolution process is treated as an untrusted
   channel that learns only the QNAME, and is prevented from mounting
   any attack beyond denial of service.

   Alt-Svc parameters that cannot be safely received in this model MUST
   NOT have a corresponding defined SvcParamKey.  For example, there is
   no SvcParamKey corresponding to the Alt-Svc "persist" parameter,
   because this parameter is not safe to accept over an untrusted
   channel.



Schwartz, et al.           Expires May 7, 2020                 [Page 19]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


7.3.2.  Caching and granularity

   There is no SvcParamKey corresponding to the Alt-Svc "ma" (max age)
   parameter.  Instead, server operators SHOULD encode the expiration
   time in the DNS TTL.

   Some DNS caching systems incorrectly extend the lifetime of DNS
   records beyond the stated TTL.  Server operators MUST NOT rely on
   HTTPSSVC records expiring on time, and MAY shorten the TTL to
   compensate.

   Sending Alt-Svc over HTTP allows the server to tailor the Alt-Svc
   Field Value specifically to the client.  When using an HTTPSSVC DNS
   record, groups of clients will necessarily receive the same Alt-Svc
   Field Value.  Therefore, HTTPSSVC is not suitable for uses that
   require single-client granularity.

   If the client has an Alt-Svc cache, and a usable Alt-Svc value is
   present in that cache, then the client MAY skip the HTTPSSVC query.

   If the client has a cached Alt-Svc entry that is expiring, the client
   MAY perform an HTTPSSVC query to refresh the entry.

7.4.  HTTP Strict Transport Security

   By publishing an HTTPSSVC record, the server operator indicates that
   all useful HTTP resources on that origin are reachable over HTTPS,
   similar to HTTP Strict Transport Security [HSTS].  When an HTTPSSVC
   record is present for an origin, all "http" scheme requests for that
   origin SHOULD logically be redirected to "https".

   Prior to making an "http" scheme request, the client SHOULD perform a
   lookup to determine if an HTTPSSVC record is available for that
   origin.  To do so, the client SHOULD construct a corresponding
   "https" URL as follows:

   1.  Replace the "http" scheme with "https".

   2.  If the "http" URL explicitly specifies port 80, specify port 443.

   3.  Do not alter any other aspect of the URL.

   This construction is equivalent to Section 8.3 of [HSTS], point 5.

   If an HTTPSSVC record is present for this "https" URL, the client
   should treat this as the equivalent of receiving an HTTP "307
   Temporary Redirect" redirect to the "https" URL.  Because HTTPSSVC is
   received over an often insecure channel (DNS), clients MUST NOT place



Schwartz, et al.           Expires May 7, 2020                 [Page 20]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   any more trust in this signal than if they had received a 307
   redirect over cleartext HTTP.

   If the HTTPSSVC query results in a SERVFAIL error, and the connection
   between the client and the recursive resolver is cryptographically
   protected (e.g. using TLS [RFC7858] or HTTPS [RFC8484]), the client
   SHOULD abandon the connection attempt and display an error message.
   A SERVFAIL error can occur if the domain is DNSSEC-signed, the
   recursive resolver is DNSSEC-validating, and an active attacker
   between the recursive resolver and the authoritative DNS server is
   attempting to prevent the upgrade to HTTPS.

   Similarly, if the client enforces DNSSEC validation on A/AAAA
   responses, it SHOULD abandon the connection attempt if the HTTPSSVC
   response fails to validate.

8.  Alt-Svc and SVCB/HTTPSSVC parameter for ESNI keys

   Both SVCB/HTTPSSVC and Alt-Svc "esniconfig" parameters are defined
   for conveying the ESNI configuration of an alternative service.  The
   value of the parameter is an ESNIConfig structure [ESNI] or the empty
   string.  ESNI-aware clients SHOULD prefer alt-values and SVCB/
   HTTPSSVC RRs with non-empty esniconfig.

   Both the SVCB SvcParamValue presentation format as well as the Alt-
   Svc parameter value is the ESNIConfig structure [ESNI] encoded in
   [base64] or the empty string.  The SVCB SvcParamValue wire format is
   the octet string containing the binary ESNIConfig structure.

   This parameter MAY also be sent in Alt-Svc HTTP response headers and
   HTTP/2 ALTSVC frames.  This parameter MUST NOT appear more than once
   in a single alt-value.

8.1.  Handling a mixture of alternatives not supporting ESNI

   The Alt-Svc specification states that "the client MAY fall back to
   using the origin" in case of connection failure (Section 2.4 of
   [AltSvc]).  This behavior is not suitable for ESNI, because fallback
   would negate the privacy benefits of ESNI.

   Accordingly, any connection attempt that uses ESNI MUST fall back
   only to another alt-value that also has the esniconfig parameter.  If
   the parameter's value is the empty string, the client SHOULD connect
   as it would in the absence of any ESNIConfig information.

   For example, suppose a server operator has two alternatives.
   Alternative A is reliably accessible but does not support ESNI.
   Alternative B supports ESNI but is not reliably accessible.  The



Schwartz, et al.           Expires May 7, 2020                 [Page 21]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   server operator could include a full esniconfig value in Alternative
   B, and mark Alternative A with esniconfig="" to indicate that
   fallback from B to A is allowed.

   Other clients and services implementing SVCB or HTTPSSVC with
   esniconfig are encouraged to take a similar approach.

9.  Interaction with other standards

   This standard is intended to reduce connection latency and improve
   user privacy.  Server operators implementing this standard SHOULD
   also implement TLS 1.3 [RFC8446] and OCSP Stapling [RFC6066], both of
   which confer substantial performance and privacy benefits when used
   in combination with SVCB records.

   To realize the greatest privacy benefits, this proposal is intended
   for use over a privacy-preserving DNS transport (like DNS over TLS
   [RFC7858] or DNS over HTTPS [RFC8484]).  However, performance
   improvements, and some modest privacy improvements, are possible
   without the use of those standards.

   Any specification for use of SVCB with a protocol MUST have an entry
   for its scheme under the SVCB RR type in the IANA DNS Underscore
   Global Scoped Entry Registry [Attrleaf].  The scheme SHOULD have an
   entry in the IANA URI Schemes Registry [RFC7595].  The scheme SHOULD
   have a defined specification for use with SVCB.

10.  Security Considerations

   SVCB/HTTPSSVC RRs are intended for distribution over untrusted
   channels, and clients are REQUIRED to verify that the alternative
   service is authoritative for the origin (Section 2.1 of [AltSvc]).
   Therefore, DNSSEC signing and validation are OPTIONAL for publishing
   and using SVCB and HTTPSSVC records.

   Clients MUST ensure that their DNS cache is partitioned for each
   local network, or flushed on network changes, to prevent a local
   adversary in one network from implanting a forged DNS record that
   allows them to track users or hinder their connections after they
   leave that network.

11.  IANA Considerations

11.1.  New registry for Service Parameters

   The "Service Binding (SVCB) Parameter Registry" defines the name
   space for parameters, including string representations and numeric




Schwartz, et al.           Expires May 7, 2020                 [Page 22]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   SvcParamKey values.  This registry is shared with other SVCB-
   compatible RR types, such as HTTPSSVC.

   ACTION: create and include a reference to this registry.

11.1.1.  Procedure

   A registration MUST include the following fields:

   o  Name: Service parameter key name

   o  SvcParamKey: Service parameter key numeric identifier (range
      0-65535)

   o  Meaning: a short description

   o  Pointer to specification text

   Values to be added to this name space require Expert Review (see
   [RFC5226], Section 4.1).  Apart from the initial contents, the name
   MUST NOT start with "key".

11.1.2.  Initial contents

   The "Service Binding (SVCB) Parameter Registry" shall initially be
   populated with the registrations below:

























Schwartz, et al.           Expires May 7, 2020                 [Page 23]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   +-------------+------------+------------------------+---------------+
   | SvcParamKey | NAME       | Meaning                | Reference     |
   +-------------+------------+------------------------+---------------+
   | 0           | key0       | Reserved               | (This         |
   |             |            |                        | document)     |
   |             |            |                        |               |
   | 1           | alpn       | ALPN for alternative   | (This         |
   |             |            | service                | document)     |
   |             |            |                        |               |
   | 2           | port       | Port for alternative   | (This         |
   |             |            | service                | document)     |
   |             |            |                        |               |
   | 3           | esniconfig | Encrypted SNI          | (This         |
   |             |            | configuration          | document)     |
   |             |            |                        |               |
   | 4           | ipv4hint   | IPv4 address hints     | (This         |
   |             |            |                        | document)     |
   |             |            |                        |               |
   | 5           | key5       | Reserved               | (This         |
   |             |            |                        | document)     |
   |             |            |                        |               |
   | 6           | ipv6hint   | IPv6 address hints     | (This         |
   |             |            |                        | document)     |
   |             |            |                        |               |
   | 65280-65534 | keyNNNNN   | Private Use            | (This         |
   |             |            |                        | document)     |
   |             |            |                        |               |
   | 65535       | key65535   | Reserved               | (This         |
   |             |            |                        | document)     |
   +-------------+------------+------------------------+---------------+

   TODO: do we also want to reserve a range for greasing?

11.2.  Registry updates

   Per [RFC6895], please add the following entry to the data type range
   of the Resource Record (RR) TYPEs registry:

   +----------+----------------------------------------+---------------+
   | TYPE     | Meaning                                | Reference     |
   +----------+----------------------------------------+---------------+
   | SVCB     | Service Location and Parameter Binding | (This         |
   |          |                                        | document)     |
   |          |                                        |               |
   | HTTPSSVC | HTTPS Service Location and Parameter   | (This         |
   |          | Binding                                | document)     |
   +----------+----------------------------------------+---------------+




Schwartz, et al.           Expires May 7, 2020                 [Page 24]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   Per [Attrleaf], please add the following entries to the DNS
   Underscore Global Scoped Entry Registry:

      +----------+------------+-------------------+-----------------+
      | RR TYPE  | _NODE NAME | Meaning           | Reference       |
      +----------+------------+-------------------+-----------------+
      | HTTPSSVC | _https     | Alt-Svc for HTTPS | (This document) |
      |          |            |                   |                 |
      | HTTPSSVC | _http      | Alt-Svc for HTTPS | (This document) |
      +----------+------------+-------------------+-----------------+

   Per [AltSvc], please add the following entry to the HTTP Alt-Svc
   Parameter Registry:

   +-------------------+-----------------------------+-----------------+
   | Alt-Svc Parameter | Meaning                     | Reference       |
   +-------------------+-----------------------------+-----------------+
   | esniconfig        | Encrypted SNI configuration | (This document) |
   +-------------------+-----------------------------+-----------------+

12.  Acknowledgments and Related Proposals

   There have been a wide range of proposed solutions over the years to
   the "CNAME at the Zone Apex" challenge proposed.  These include
   [I-D.draft-bellis-dnsop-http-record-00],
   [I-D.draft-ietf-dnsop-aname-03], and others.

   Thank you to Ian Swett, Ralf Weber, Jon Reed, Martin Thompson, Lucas
   Pardue, Ilari Liusvaara, Tim Wicinski, Tommy Pauly, Chris Wood, and
   others for their feedback and suggestions on this draft.

13.  References

13.1.  Normative References

   [AltSvc]   Nottingham, M., McManus, P., and J. Reschke, "HTTP
              Alternative Services", RFC 7838, DOI 10.17487/RFC7838,
              April 2016, <https://www.rfc-editor.org/info/rfc7838>.

   [AltSvcSNI]
              Bishop, M., "The "SNI" Alt-Svc Parameter", draft-bishop-
              httpbis-sni-altsvc-02 (work in progress), May 2018.

   [Attrleaf]
              Crocker, D., "DNS Scoped Data Through "Underscore" Naming
              of Attribute Leaves", draft-ietf-dnsop-attrleaf-16 (work
              in progress), November 2018.




Schwartz, et al.           Expires May 7, 2020                 [Page 25]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   [base64]   Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
              <https://www.rfc-editor.org/info/rfc4648>.

   [ESNI]     Rescorla, E., Oku, K., Sullivan, N., and C. Wood,
              "Encrypted Server Name Indication for TLS 1.3", draft-
              ietf-tls-esni-04 (work in progress), July 2019.

   [HappyEyeballsV2]
              Schinazi, D. and T. Pauly, "Happy Eyeballs Version 2:
              Better Connectivity Using Concurrency", RFC 8305,
              DOI 10.17487/RFC8305, December 2017,
              <https://www.rfc-editor.org/info/rfc8305>.

   [HSTS]     Hodges, J., Jackson, C., and A. Barth, "HTTP Strict
              Transport Security (HSTS)", RFC 6797,
              DOI 10.17487/RFC6797, November 2012,
              <https://www.rfc-editor.org/info/rfc6797>.

   [HTTP3]    Bishop, M., "Hypertext Transfer Protocol Version 3
              (HTTP/3)", draft-ietf-quic-http-20 (work in progress),
              April 2019.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
              November 1987, <https://www.rfc-editor.org/info/rfc1035>.

   [RFC1928]  Leech, M., Ganis, M., Lee, Y., Kuris, R., Koblas, D., and
              L. Jones, "SOCKS Protocol Version 5", RFC 1928,
              DOI 10.17487/RFC1928, March 1996,
              <https://www.rfc-editor.org/info/rfc1928>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2181]  Elz, R. and R. Bush, "Clarifications to the DNS
              Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997,
              <https://www.rfc-editor.org/info/rfc2181>.

   [RFC3225]  Conrad, D., "Indicating Resolver Support of DNSSEC",
              RFC 3225, DOI 10.17487/RFC3225, December 2001,
              <https://www.rfc-editor.org/info/rfc3225>.

   [RFC3597]  Gustafsson, A., "Handling of Unknown DNS Resource Record
              (RR) Types", RFC 3597, DOI 10.17487/RFC3597, September
              2003, <https://www.rfc-editor.org/info/rfc3597>.



Schwartz, et al.           Expires May 7, 2020                 [Page 26]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <https://www.rfc-editor.org/info/rfc5226>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <https://www.rfc-editor.org/info/rfc5234>.

   [RFC5952]  Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
              Address Text Representation", RFC 5952,
              DOI 10.17487/RFC5952, August 2010,
              <https://www.rfc-editor.org/info/rfc5952>.

   [RFC6066]  Eastlake 3rd, D., "Transport Layer Security (TLS)
              Extensions: Extension Definitions", RFC 6066,
              DOI 10.17487/RFC6066, January 2011,
              <https://www.rfc-editor.org/info/rfc6066>.

   [RFC6147]  Bagnulo, M., Sullivan, A., Matthews, P., and I. van
              Beijnum, "DNS64: DNS Extensions for Network Address
              Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
              DOI 10.17487/RFC6147, April 2011,
              <https://www.rfc-editor.org/info/rfc6147>.

   [RFC6454]  Barth, A., "The Web Origin Concept", RFC 6454,
              DOI 10.17487/RFC6454, December 2011,
              <https://www.rfc-editor.org/info/rfc6454>.

   [RFC7050]  Savolainen, T., Korhonen, J., and D. Wing, "Discovery of
              the IPv6 Prefix Used for IPv6 Address Synthesis",
              RFC 7050, DOI 10.17487/RFC7050, November 2013,
              <https://www.rfc-editor.org/info/rfc7050>.

   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              DOI 10.17487/RFC7231, June 2014,
              <https://www.rfc-editor.org/info/rfc7231>.

   [RFC7595]  Thaler, D., Ed., Hansen, T., and T. Hardie, "Guidelines
              and Registration Procedures for URI Schemes", BCP 35,
              RFC 7595, DOI 10.17487/RFC7595, June 2015,
              <https://www.rfc-editor.org/info/rfc7595>.

   [RFC7838]  Nottingham, M., McManus, P., and J. Reschke, "HTTP
              Alternative Services", RFC 7838, DOI 10.17487/RFC7838,
              April 2016, <https://www.rfc-editor.org/info/rfc7838>.



Schwartz, et al.           Expires May 7, 2020                 [Page 27]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   [RFC7858]  Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
              and P. Hoffman, "Specification for DNS over Transport
              Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
              2016, <https://www.rfc-editor.org/info/rfc7858>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC8484]  Hoffman, P. and P. McManus, "DNS Queries over HTTPS
              (DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
              <https://www.rfc-editor.org/info/rfc8484>.

13.2.  Informative References

   [DNSTerm]  Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
              Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
              January 2019, <https://www.rfc-editor.org/info/rfc8499>.

   [HTTP]     Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,
              <https://www.rfc-editor.org/info/rfc7230>.

   [I-D.draft-bellis-dnsop-http-record-00]
              Bellis, R., "A DNS Resource Record for HTTP", draft-
              bellis-dnsop-http-record-00 (work in progress), November
              2018.

   [I-D.draft-ietf-dnsop-aname-03]
              Finch, T., Hunt, E., Dijk, P., Eden, A., and W. Mekking,
              "Address-specific DNS aliases (ANAME)", draft-ietf-dnsop-
              aname-03 (work in progress), April 2019.

   [RFC2782]  Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
              specifying the location of services (DNS SRV)", RFC 2782,
              DOI 10.17487/RFC2782, February 2000,
              <https://www.rfc-editor.org/info/rfc2782>.

   [RFC6895]  Eastlake 3rd, D., "Domain Name System (DNS) IANA
              Considerations", BCP 42, RFC 6895, DOI 10.17487/RFC6895,
              April 2013, <https://www.rfc-editor.org/info/rfc6895>.





Schwartz, et al.           Expires May 7, 2020                 [Page 28]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


Appendix A.  Mapping between HTTPSSVC and Alt-Svc

   Conversion between HTTPSSVC's ServiceForm and Alt-Svc is possible.
   Note that conversion in either direction can be lossy, because some
   parameters are only defined for HTTPSSVC or Alt-Svc.

   To construct an Alt-Svc Field Value (as defined in Section 4 of
   [AltSvc]) from an HTTPSSVC record:

   o  The SvcDomainName is mapped into the uri-host portion of alt-
      authority with the trailing "." removed.  (If SvcDomainName is
      ".", the special handling described in Section 2.6.1 MUST be
      applied first.)

   o  The SvcParamValue of the "port" service parameter, or 443 if no
      such parameter is present, is written to the port portion of the
      alt-authority.

   o  The SvcParamValue of the "alpn" service parameter is mapped to the
      protocol-id.  This MUST follow the normalization and encoding
      requirements for protocol-id specified in [AltSvc] Section 3.
      This parameter is MANDATORY.

   o  The DNS TTL is mapped to the "ma" (max age) Alt-Svc parameter.

   o  For SVCB parameters with defined mappings to HTTPS Alt-Svc, each
      should be included as an Alt-Svc parameter, typically as the
      SvcParamKey name "=" a defined encoding of the SvcParamValue.

   Converting an Alt-Svc Field Value into an HTTPSSVC record follows the
   reverse of this procedure.

   Conversion between HTTPSSVC and Alt-Svc Field Value MUST ignore any
   SvcParamKeys and Alt-Svc parameters that are unrecognized or do not
   have a defined mapping.

   For example, if the operator of https://www.example.com intends to
   include an HTTP response header like

   Alt-Svc: h3="svc.example.net:8003"; ma=3600; foo=123, \
            h2="svc.example.net:8002"; ma=3600; foo=123

   they could also publish an HTTPSSVC DNS RRSet like

   www.example.com. 3600 IN HTTPSSVC 2 svc.example.net. (
                                       alpn=h3 port=8003 foo=123 )
                            HTTPSSVC 3 svc.example.net. (
                                       alpn=h2 port=8002 foo=123 )



Schwartz, et al.           Expires May 7, 2020                 [Page 29]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   Where "foo" is a hypothetical future HTTPSSVC and Alt-Svc parameter.

   This data type can also be represented as an Unknown RR as described
   in [RFC3597]:

   www.example.com. 3600 IN TYPE??? \\# TBD:WRITEME

A.1.  Multiple records and preference ordering

   Server operators MAY publish multiple ServiceForm HTTPSSVC records as
   an RRSet.  When converting a collection of alt-values into an
   HTTPSSVC RRSet, the server operator MUST set the overall TTL to a
   value no larger than the minimum of the "max age" values (following
   Section 5.2 of [RFC2181]).

   Each RR corresponds to exactly one alt-value, as described in
   Section 3 of [AltSvc].

   As discussed in Section 2.6.2, HTTPSSVC RRs with a smaller
   SvcFieldPriority value SHOULD be sorted ahead of and given preference
   over RRs with a larger SvcFieldPriority value.

   When constructing equivalent Alt-Svc headers from an RRSet:

   1.  The RRs SHOULD be ordered by increasing SvcFieldPriority, with
       shuffling for equal SvcFieldPriority values.  Clients MAY choose
       to further prioritize alt-values where address records are
       immediately available for the alt-value's SvcDomainName.

   2.  The client SHOULD concatenate the thus-transformed-and-ordered
       SvcFieldValues in the RRSet, separated by commas.  (This is
       semantically equivalent to receiving multiple Alt-Svc HTTP
       response headers, according to Section 3.2.2 of [HTTP]).

A.2.  Additional examples

   The following:

   www.example.com.  7200  IN CNAME    svc.example.net.
   example.com.      7200  IN HTTPSSVC 0 svc.example.net.
   svc.example.net.  7200  IN HTTPSSVC 2 svc3.example.net. (
       alpn=h3 port=8003 esniconfig="ABC..." )
   svc.example.net.  7200  IN HTTPSSVC 3 . (
       alpn=h2 port=8002 esniconfig="123..." )

   is equivalent to the Alt-Svc record:





Schwartz, et al.           Expires May 7, 2020                 [Page 30]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   Alt-Svc: h3="svc3.example.net:8003"; esniconfig="ABC..."; ma=7200, \
            h2="svc.example.net:8002"; esniconfig="123..."; ma=7200

   for the origins of both "https://www.example.com" and
   "https://example.com".

Appendix B.  Comparison with alternatives

   The SVCB and HTTPSSVC record types closely resemble, and are inspired
   by, some existing record types and proposals.  A complaint with all
   of the alternatives is that web clients have seemed unenthusiastic
   about implementing them.  The hope here is that by providing an
   extensible solution that solves multiple problems we will overcome
   the inertia and have a path to achieve client implementation.

B.1.  Differences from the SRV RR type

   An SRV record [RFC2782] can perform a similar function to the SVCB
   record, informing a client to look in a different location for a
   service.  However, there are several differences:

   o  SRV records are typically mandatory, whereas clients will always
      continue to function correctly without making use of Alt-Svc or
      SVCB.

   o  SRV records cannot instruct the client to switch or upgrade
      protocols, whereas Alt-Svc can signal such an upgrade (e.g. to
      HTTP/2).

   o  SRV records are not extensible, whereas SVCB and HTTPSSVC can be
      extended with new parameters.

   o  Using SRV records would not allow an HTTPS client to skip
      processing of the Alt-Svc information in a subsequent connection,
      so it does not confer a performance advantage.

B.2.  Differences from the proposed HTTP record

   Unlike [I-D.draft-bellis-dnsop-http-record-00], this approach is
   extensible to cover Alt-Svc and ESNI use-cases.  Like that proposal,
   this addresses the zone apex CNAME challenge.

   Like that proposal it remains necessary to continue to include
   address records at the zone apex for legacy clients.







Schwartz, et al.           Expires May 7, 2020                 [Page 31]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


B.3.  Differences from the proposed ANAME record

   Unlike [I-D.draft-ietf-dnsop-aname-03], this approach is extensible
   to cover Alt-Svc and ESNI use-cases.  This approach also does not
   require any changes or special handling on either authoritative or
   master servers, beyond optionally returning in-bailiwick additional
   records.

   Like that proposal, this addresses the zone apex CNAME challenge for
   clients that implement this.

   However with this SVCB proposal it remains necessary to continue to
   include address records at the zone apex for legacy clients.  If
   deployment of this standard is successful, the number of legacy
   clients will fall over time.  As the number of legacy clients
   declines, the operational effort required to serve these users
   without the benefit of SVCB indirection should fall.  Server
   operators can easily observe how much traffic reaches this legacy
   endpoint, and may remove the apex's address records if the observed
   legacy traffic has fallen to negligible levels.

B.4.  Differences from the proposed ESNI record

   Unlike [ESNI], this approach is extensible and covers the Alt-Svc
   case as well as addresses the zone apex CNAME challenge.

   By using the Alt-Svc model we also provide a way to solve the ESNI
   multi-CDN challenges in a general case.

   Unlike ESNI, SVCB allows specifying different ESNI configurations for
   different protocols and ports, rather than applying a single
   configuration to all ports on a domain.

B.5.  SNI Alt-Svc parameter

   Defining an Alt-Svc sni= parameter (such as from [AltSvcSNI]) would
   have provided some benefits to clients and servers not implementing
   ESNI, such as for specifying that "_wildcard.example.com" could be
   sent as an SNI value rather than the full name.  There is nothing
   precluding SVCB from being used with an sni= parameter if one were to
   be defined, but it is not included here to reduce scope, complexity,
   and additional potential security and tracking risks.

Appendix C.  Design Considerations and Open Issues

   This draft is intended to be a work-in-progress for discussion.  Many
   details are expected to change with subsequent refinement.  Some
   known issues or topics for discussion are listed below.



Schwartz, et al.           Expires May 7, 2020                 [Page 32]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


C.1.  Record Name

   Naming is hard.  "SVCB" and "HTTPSSVC" are proposed as placeholders
   that are easy to search for and replace when a final name is chosen.
   Other names for this record might include B, ALTSVC, HTTPS, HTTPSSRV,
   HTTPSSVC, SVCHTTPS, or something else.

C.2.  Generality

   The SVCB record was designed as a generalization of HTTPSSVC, based
   on feedback requesting a solution that applied to protocols pther
   than HTTP.  Past efforts to over-generalize have not met with broad
   success, but we hope that HTTPSSVC and SVCB have struck an acceptable
   balance between generality and focus.

C.3.  Wire Format

   Advice from experts in DNS wire format best practices would be
   greatly appreciated to refine the proposed details, overall.

C.4.  Where to include Priority

   The SvcFieldPriority could alternately be included as a pri= Alt-Svc
   attribute.  It wouldn't be applicable for Alt-Svc returned via HTTP,
   but it is also not necessarily needed by DNS servers.  It is also not
   used for AliasForm RRs.

C.5.  Whether to include Weight

   Some other similar mechanisms such as SRV have a weight in-addition
   to priority.  That is excluded here for simplicity.  It could always
   be added as an optional SVCB parameter.

Appendix D.  Change history

   o  draft-ietf-dnsop-svcb-httpssvc-01

      *  Reduce the emphasis on conversion between HTTPSSVC and Alt-Svc

      *  Make the "untrusted channel" concept more precise.

      *  Make SvcFieldPriority = 0 the definition of AliasForm, instead
         of a requirement.

   o  draft-ietf-dnsop-svcb-httpssvc-00

      *  Document an optimization for optimistic pre-connection.  (Chris
         Wood)



Schwartz, et al.           Expires May 7, 2020                 [Page 33]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


      *  Relax IP hint handling requirements.  (Eric Rescorla)

   o  draft-nygren-dnsop-svcb-httpssvc-00

      *  Generalize to an SVCB record, with special-case handling for
         Alt-Svc and HTTPS separated out to dedicated sections.

      *  Split out a separate HTTPSSVC record for the HTTPS use-case.

      *  Remove the explicit SvcRecordType=0/1 and instead make the
         AliasForm vs ServiceForm be implicit.  This was based on
         feedback recommending against subtyping RR type.

      *  Remove one optimization.

   o  draft-nygren-httpbis-httpssvc-03

      *  Change redirect type for HSTS-style behavior from 302 to 307 to
         reduce ambiguities.

   o  draft-nygren-httpbis-httpssvc-02

      *  Remove the redundant length fields from the wire format.

      *  Define a SvcDomainName of "." for SvcRecordType=1 as being the
         HTTPSSVC RRNAME.

      *  Replace "hq" with "h3".

   o  draft-nygren-httpbis-httpssvc-01

      *  Fixes of record name.  Replace references to "HTTPSVC" with
         "HTTPSSVC".

   o  draft-nygren-httpbis-httpssvc-00

      *  Initial version

Authors' Addresses

   Ben Schwartz
   Google

   Email: bemasc@google.com







Schwartz, et al.           Expires May 7, 2020                 [Page 34]


Internet-Draft        SVCB and HTTPSSVC RRs for DNS        November 2019


   Mike Bishop
   Akamai Technologies

   Email: mbishop@evequefou.be


   Erik Nygren
   Akamai Technologies

   Email: erik+ietf@nygren.org









































Schwartz, et al.           Expires May 7, 2020                 [Page 35]


Html markup produced by rfcmarkup 1.129d, available from https://tools.ietf.org/tools/rfcmarkup/