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Versions: 00 01                                                         
MASQUE                                                 A. Chernyakhovsky
Internet-Draft                                                 D. McCall
Intended status: Standards Track                             D. Schinazi
Expires: 13 January 2022                                      Google LLC
                                                            12 July 2021


                       The CONNECT-IP HTTP Method
                     draft-cms-masque-connect-ip-01

Abstract

   This document describes the CONNECT-IP HTTP method.  CONNECT-IP is
   similar to CONNECT-UDP, but allows transmitting IP packets, without
   being limited to just TCP like CONNECT or UDP like CONNECT-UDP.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Discussion of this document takes place on the Multiplexed
   Application Substrate over QUIC Encryption Working Group mailing list
   (masque@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/masque/.

   Source for this draft and an issue tracker can be found at
   https://github.com/DavidSchinazi/draft-cms-masque-connect-ip.

Status of This Memo

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

   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 13 January 2022.







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Copyright Notice

   Copyright (c) 2021 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Conventions and Definitions . . . . . . . . . . . . . . .   3
   2.  The CONNECT-IP Method . . . . . . . . . . . . . . . . . . . .   3
   3.  Transmitting IP Packets using HTTP Datagrams  . . . . . . . .   4
   4.  Forwarding of IP Packets  . . . . . . . . . . . . . . . . . .   5
   5.  Routes  . . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   6.  Capsules  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  ADDRESS_ASSIGN Capsule  . . . . . . . . . . . . . . . . .   6
     6.2.  ADDRESS_REQUEST Capsule . . . . . . . . . . . . . . . . .   6
     6.3.  ROUTE_ADVERTISEMENT Capsule . . . . . . . . . . . . . . .   7
     6.4.  ROUTE_REJECTION Capsule . . . . . . . . . . . . . . . . .   8
     6.5.  ROUTE_RESET Capsule . . . . . . . . . . . . . . . . . . .   8
     6.6.  SHUTDOWN Capsule  . . . . . . . . . . . . . . . . . . . .   9
     6.7.  ATOMIC_START Capsule  . . . . . . . . . . . . . . . . . .   9
     6.8.  ATOMIC_END Capsule  . . . . . . . . . . . . . . . . . . .  10
   7.  Extensibility Considerations  . . . . . . . . . . . . . . . .  10
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
     9.1.  HTTP Method . . . . . . . . . . . . . . . . . . . . . . .  11
     9.2.  Capsule Type Registrations  . . . . . . . . . . . . . . .  11
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     10.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  13
     A.1.  Consumer VPN  . . . . . . . . . . . . . . . . . . . . . .  13
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14








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1.  Introduction

   This document describes the CONNECT-IP HTTP method.  CONNECT-IP is
   similar to CONNECT-UDP, but allows transmitting IP packets, without
   being limited to just TCP like CONNECT or UDP like CONNECT-UDP.

   CONNECT-IP allows endpoints to set up an IP tunnel between one
   another.  This can be used to implement a consumer VPN, point-to-
   point, point-to-network, and network-to-network capabilities as
   described in [REQS].

1.1.  Conventions and Definitions

   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.

   In this document, we use the term "proxy" to refer to the HTTP server
   that responds to the CONNECT-IP request.  If there are HTTP
   intermediaries (as defined in Section 2.3 of [RFC7230]) between the
   client and the proxy, those are referred to as "intermediaries" in
   this document.

2.  The CONNECT-IP Method

   The CONNECT-IP method establishes a stream to an endpoint server that
   then permits the exchange of control data, such as IP address
   information, reachable IP ranges, and other relevant information for
   successfully transmitting IP datagrams between hosts.

   The request-target of a CONNECT-IP request is a URI [URI] which uses
   the "https" scheme and a client-specified path.  When using HTTP/2
   [H2] or later, CONNECT-IP requests use HTTP pseudo-headers with the
   following requirements:

   *  The ":method" pseudo-header field is set to "CONNECT-IP".

   *  The ":scheme" pseudo-header field is set to "https".

   *  The ":path" pseudo-header field is set to the value provided by
      the client.  That value MUST NOT be empty.

   *  The ":authority" pseudo-header field contains the host and port of
      the proxy.  The target of a CONNECT-IP request is the server
      providing the CONNECT-IP featureset, not an individual endpoint
      with which a connection is desired.



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   A CONNECT-IP request that does not conform to these restrictions is
   malformed (see [H2], Section 8.1.2.6).

   Any 2xx (Successful) response indicates that the proxy is willing to
   open an IP tunnel between it and the client.  Any response other than
   a successful response indicates that the tunnel has not yet been
   formed.

   A proxy MUST NOT send any Transfer-Encoding or Content-Length header
   fields in a 2xx (Successful) response to CONNECT-IP.  A client MUST
   treat a successful response to CONNECT-IP containing any Content-
   Length or Transfer-Encoding header fields as malformed.

   A payload within a CONNECT-IP request message has no defined
   semantics; a CONNECT-IP request with a non-empty payload is
   malformed.  Note that the CONNECT-IP stream is used to convey control
   messages, but they are not semantically part of the request or
   response themselves.

   Responses to the CONNECT-IP method are not cacheable.

   The lifetime of the tunnel is tied to the CONNECT-IP stream.  Closing
   the stream (via the FIN bit on a QUIC STREAM frame, or a QUIC
   RESET_STREAM frame) closes the associated tunnel.

3.  Transmitting IP Packets using HTTP Datagrams

   IP packets are sent using HTTP Datagrams [HTTP-DGRAM].  The HTTP
   Datagram Payload contains a full IP packet, from the IP Version field
   until the last byte of the IP Payload.  In order to use HTTP
   Datagrams, the CONNECT-IP client will first decide whether or not to
   use HTTP Datagram Contexts and then register its context ID (or lack
   thereof) using the corresponding registration capsule, see
   [HTTP-DGRAM].

   Since HTTP Datagrams require prior negotiation (for example, in
   HTTP/3 it is necessary to both send and receive the H3_DATAGRAM
   SETTINGS Parameter), clients MUST NOT send any HTTP Datagrams until
   they have established support on a given connection.  If negotiation
   of HTTP Datagrams fails (for example if an HTTP/3 SETTINGS frame was
   received without the H3_DATAGRAM SETTINGS Parameter), the client MUST
   consider its CONNECT-IP request as failed.









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4.  Forwarding of IP Packets

   Since CONNECT-IP allows the transmission of IP packets over HTTP,
   CONNECT-IP endpoints will most often forward these packets to and
   from traditional IP interfaces.  As such, CONNECT-IP endpoints act as
   IP routers.  When a CONNECT-IP endpoint receives an HTTP Datagram
   containing an IP packet, it will parse the packet's IP header,
   perform any local policy checks (e.g., source address validation),
   check their routing table to pick an outbound interface, and then use
   an implementation-specific mechanism (such as raw sockets) to send
   the IP packet on that interface.

   Conversely, when a CONNECT-IP endpoint receives an IP packet whose
   destination address does not match any local addresses, it consults
   its routing table to pick a forwarding destination, and if the table
   points to a CONNECT-IP tunnel, the endpoint performs the same
   forwarding checks before transmitting the packet inside the tunnel.

   Note that CONNECT-IP endpoints will decrement the IP Hop Count (or
   TTL) upon encapsulation but not decapsulation.  In other words, the
   Hop Count is decremented right before an IP packet is transmitted in
   an HTTP Datagram.  This prevents infinite loops in the presence of
   routing loops, and matches the choices in IPsec [IPSEC].

   Endpoints MAY implement additional filtering policies on the IP
   packets they forward.

5.  Routes

   Endpoints have the ability to advertise and reject routes using the
   ROUTE_ADVERTISEMENT (Section 6.3) and ROUTE_REJECTION (Section 6.3)
   capsule.  Note that these capsules are purely informational: receipt
   of a ROUTE_ADVERTISEMENT capsule does not require the recipient to
   start routing traffic to its peer.  Additionally, if an endpoint
   receives a ROUTE_REJECTION for a given prefix that it had previously
   received a ROUTE_ADVERTISEMENT capsule for, then the two cancel out
   and the endpoint MUST remove its state from the ROUTE_ADVERTISEMENT
   capsule instead of installing new state for the ROUTE_REJECTION
   capsule.  Conversely, the same is true of a ROUTE_ADVERTISEMENT that
   matches a previous ROUTE_REJECTION.  Routes are handled via longest-
   prefix-first preference, meaning that if a given IP prefix is covered
   by multiple route advertisement and route rejections, the one with
   the longest prefix is used.

   When processing ROUTE_ADVERTISEMENT capsules, endpoints MUST check
   their local policy before deciding whether to forward packets to
   their peer.  Since ignoring these capsules is allowed by the
   protocol, such policy decisions will not prevent interoperability.



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6.  Capsules

6.1.  ADDRESS_ASSIGN Capsule

   The ADDRESS_ASSIGN capsule allows an endpoint to inform its peer that
   it has assigned an IP address to it.  It allows assigning a prefix
   which can contain multiple addresses.  This capsule uses a Capsule
   Type of 0xfff100.  Its value uses the following format:

   ADDRESS_ASSIGN Capsule {
     IP Version (8),
     IP Address (32..128),
     IP Prefix Length (8),
   }

                  Figure 1: ADDRESS_ASSIGN Capsule Format

   IP Version:  IP Version of this address assignment.  MUST be either 4
      or 6.

   IP Address:  Assigned IP address.  If the IP Version field has value
      4, the IP Address field SHALL have a length of 32 bits.  If the IP
      Version field has value 6, the IP Address field SHALL have a
      length of 128 bits.

   IP Prefix Length:  Length of the IP Prefix assigned, in bits.  MUST
      be lesser or equal to the length of the IP Address field, in bits.

6.2.  ADDRESS_REQUEST Capsule

   The ADDRESS_REQUEST capsule allows an endpoint to request assignment
   of an IP address from its peer.  It allows the endpoint to optionally
   indicate a preference for which address it would get assigned.  This
   capsule uses a Capsule Type of 0xfff101.  Its value uses the
   following format:

   ADDRESS_REQUEST Capsule {
     IP Version (8),
     IP Address (32..128),
     IP Prefix Length (8),
   }

                  Figure 2: ADDRESS_REQUEST Capsule Format

   IP Version:  IP Version of this address request.  MUST be either 4 or
      6.

   IP Address:  Requested IP address.  If the IP Version field has value



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      4, the IP Address field SHALL have a length of 32 bits.  If the IP
      Version field has value 6, the IP Address field SHALL have a
      length of 128 bits.

   IP Prefix Length:  Length of the IP Prefix requested, in bits.  MUST
      be lesser or equal to the length of the IP Address field, in bits.

   Upon receiving the ADDRESS_REQUEST capsule, an endpoint SHOULD assign
   an IP address to its peer, and then respond with an ADDRESS_ASSIGN
   capsule to inform the peer of the assignment.

6.3.  ROUTE_ADVERTISEMENT Capsule

   The ROUTE_ADVERTISEMENT capsule allows an endpoint to communicate to
   its peer that it is willing to route traffic to a given prefix.  This
   indicates that the sender has an existing route to the prefix, and
   notifies its peer that if the receiver of the ROUTE_ADVERTISEMENT
   capsule sends IP packets for this prefix in HTTP Datagrams, the
   sender of the capsule will forward them along its preexisting route.
   This capsule uses a Capsule Type of 0xfff102.  Its value uses the
   following format:

   ROUTE_ADVERTISEMENT Capsule {
     IP Version (8),
     IP Address (32..128),
     IP Prefix Length (8),
   }

                Figure 3: ROUTE_ADVERTISEMENT Capsule Format

   IP Version:  IP Version of this route advertisement.  MUST be either
      4 or 6.

   IP Address:  IP address of the advertised route.  If the IP Version
      field has value 4, the IP Address field SHALL have a length of 32
      bits.  If the IP Version field has value 6, the IP Address field
      SHALL have a length of 128 bits.

   IP Prefix Length:  Length of the IP Prefix of the advertised route,
      in bits.  MUST be lesser or equal to the length of the IP Address
      field, in bits.

   Upon receiving the ROUTE_ADVERTISEMENT capsule, an endpoint MAY start
   routing IP packets in that prefix to its peer.







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6.4.  ROUTE_REJECTION Capsule

   The ROUTE_REJECTION capsule allows an endpoint to communicate to its
   peer that it is not willing to route traffic to a given prefix.  This
   capsule uses a Capsule Type of 0xfff103.  Its value uses the
   following format:

   ROUTE_REJECTION Capsule {
     IP Version (8),
     IP Address (32..128),
     IP Prefix Length (8),
   }

                  Figure 4: ROUTE_REJECTION Capsule Format

   IP Version:  IP Version of this route rejection.  MUST be either 4 or
      6.

   IP Address:  IP address of the rejected route.  If the IP Version
      field has value 4, the IP Address field SHALL have a length of 32
      bits.  If the IP Version field has value 6, the IP Address field
      SHALL have a length of 128 bits.

   IP Prefix Length:  Length of the IP Prefix of the advertised route,
      in bits.  MUST be lesser or equal to the length of the IP Address
      field, in bits.

   Upon receiving the ROUTE_REJECTION capsule, an endpoint MUST stop
   routing IP packets in that prefix to its peer.  Note that this
   capsule can be reordered with DATAGRAM frames, and therefore an
   endpoint that receives packets for routes it has rejected MUST NOT
   treat that as an error.

6.5.  ROUTE_RESET Capsule

   The ROUTE_RESET capsule allows an endpoint to cancel any routes it
   had previously advertised or denied.  This capsule uses a Capsule
   Type of 0xfff104.  Its value uses the following format:

   ROUTE_RESET Capsule {
   }

                    Figure 5: ROUTE_RESET Capsule Format

   Upon receiving the ROUTE_RESET capsule, an endpoint MUST stop routing
   IP packets to its peer.  Note that this capsule can be reordered with
   DATAGRAM frames, and therefore an endpoint that receives packets for
   routes it has rejected MUST NOT treat that as an error.



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   The main purpose of the ROUTE_RESET capsule is to allow endpoints to
   not have to remember the full list of routes they have shared with
   their peer.  In practice, it is expected that ROUTE_RESET capsules
   will be closely followed by ROUTE_ADVERTISEMENT capsules that will
   refill the routing table that was just cleared.

6.6.  SHUTDOWN Capsule

   The SHUTDOWN capsule allows an endpoint to communicate to its peer
   that it is about to close the CONNECT-IP stream, with a string
   explaining the reason for the shutdown.  This capsule uses a Capsule
   Type of 0xfff105.  Its value uses the following format:

   SHUTDOWN Capsule {
     Reason Phrase (..),
   }

                     Figure 6: SHUTDOWN Capsule Format

   Reason Phrase:  Additional diagnostic information for the shutdown.
      This SHOULD be a UTF-8 encoded string [UTF8], though the frame
      does not carry information, such as language tags, that would aid
      comprehension by any entity other than the one that created the
      text.

   Note that the SHUTDOWN capsule is informational, the tunnel is only
   closed when its corresponding CONNECT-IP stream is closed.  Endpoints
   MAY close the tunnel with a reason phrase by sending the SHUTDOWN
   capsule with the FIN bit set on the underlying QUIC STREAM frame that
   carried it.

6.7.  ATOMIC_START Capsule

   The ATOMIC_START capsule allows an endpoint to create an atomic set
   of capsules.  This capsule uses a Capsule Type of 0xfff106.  Its
   value uses the following format:

   ATOMIC_START Capsule {
   }

                   Figure 7: ATOMIC_START Capsule Format

   Upon receiving an ATOMIC_START capsule, an endpoint MUST buffer all
   incoming known CONNECT-IP-specific capsules (i.e., capsules defined
   in this document) until it receives an ATOMIC_END capsule.  Endpoints
   MUST NOT send two ATOMIC_START capsules without an ATOMIC_END capsule
   between them.




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   Endpoints MUST NOT buffer unknown capsules.  Endpoints MAY choose to
   immediately process IP_PACKET and SHUTDOWN capsules instead of
   buffering them.  Capsules defined in other documents are by default
   not buffered by ATOMIC_START.  Extensions that register new capsule
   types MAY specify that these capsules should be buffered by
   ATOMIC_START, and whether it is allowed to skip buffering for them.

   The purpose of this frame is to avoid timing issues where an endpoint
   installs a route before an important route rejection was received.
   Endpoints SHOULD group their initial configuration into an atomic
   block to allow their peer to mark the tunnel as operational once the
   whole block is parsed.

6.8.  ATOMIC_END Capsule

   The ATOMIC_END capsule allows an endpoint to end an atomic set of
   capsules.  This capsule uses a Capsule Type of 0xfff107.  Its value
   uses the following format:

   ATOMIC_END Capsule {
   }

                    Figure 8: ATOMIC_END Capsule Format

   Upon receiving an ATOMIC_END capsule, an endpoint MUST parse all
   previously buffered capsules, in order of receipt.  Endpoints MUST
   NOT send an ATOMIC_END capsule without a preceding ATOMIC_START
   capsule.

7.  Extensibility Considerations

   CONNECT-IP can be extended via multiple mechanisms to increase
   functionality.  There are three main ways to extend CONNECT-IP: HTTP
   headers, Capsule Types, and HTTP Datagram Registration Extension
   Data.  For example, an authentication extension could define an HTTP
   header that allows endpoints to send authentication credentials to
   their peer during the creation of the tunnel.  Alternatively, one
   could specify an extension that defines a new Capsule Type which
   allows exchanging DNS configuration between endpoints.  Additionally,
   an extension to CONNECT-IP can use multiple HTTP Datagram Contexts
   [HTTP-DGRAM] simultaneously to compress some IP packets by
   associating the compression context with an HTTP Datagram Context ID.









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8.  Security Considerations

   There are significant risks in allowing arbitrary clients to
   establish a tunnel to arbitrary servers, as that could allow bad
   actors to send traffic and have it attributed to the proxy.  Proxies
   that support CONNECT-IP SHOULD restrict its use to authenticated
   users.  The HTTP Authorization header [AUTH] MAY be used to
   authenticate clients.  More complex authentication schemes are out of
   scope for this document but can be implemented using CONNECT-IP
   extensions.

   Since CONNECT-IP endpoints can proxy IP packets send by their peer,
   they SHOULD follow the guidance in [BCP38] to help prevent denial of
   service attacks.

   In theory, endpoints could use ROUTE_ADVERTISEMENT capsules to divert
   traffic from naive endpoints.  To avoid this, receivers of
   ROUTE_ADVERTISEMENT capsules MUST check their local policy before
   acting on such capsules, see Section 5.

9.  IANA Considerations

9.1.  HTTP Method

   This document will request IANA to register "CONNECT-IP" in the HTTP
   Method Registry (IETF review) maintained at
   <https://www.iana.org/assignments/http-methods>.

     +-------------+------+------------+---------------+
     | Method Name | Safe | Idempotent |   Reference   |
     +-------------+------+------------+---------------+
     | CONNECT-IP  |  no  |     no     | This document |
     +-------------+------+------------+---------------+

9.2.  Capsule Type Registrations

   This document will request IANA to add the following values to the
   "HTTP Capsule Types" registry created by [HTTP-DGRAM]:













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+----------+---------------------+---------------------+---------------+
|   Value  |        Type         |      Description    |   Reference   |
+----------+---------------------+---------------------+---------------+
| 0xfff100 |   ADDRESS_ASSIGN    | Address Assignment  | This document |
| 0xfff101 |   ADDRESS_REQUEST   | Address Request     | This document |
| 0xfff102 | ROUTE_ADVERTISEMENT | Route Advertisement | This document |
| 0xfff103 |   ROUTE_REJECTION   | Route Rejection     | This document |
| 0xfff104 |     ROUTE_RESET     | Route Reset         | This document |
| 0xfff105 |      SHUTDOWN       | Shutdown Reason     | This document |
| 0xfff106 |    ATOMIC_START     | Atomic Start        | This document |
| 0xfff107 |     ATOMIC_END      | Atomic End          | This document |
+----------+---------------------+---------------------+---------------+

10.  References

10.1.  Normative References

   [BCP38]    Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827,
              May 2000, <https://www.rfc-editor.org/rfc/rfc2827>.

   [H2]       Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
              Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
              DOI 10.17487/RFC7540, May 2015,
              <https://www.rfc-editor.org/rfc/rfc7540>.

   [HTTP-DGRAM]
              Schinazi, D. and L. Pardue, "Using Datagrams with HTTP",
              Work in Progress, Internet-Draft, draft-ietf-masque-h3-
              datagram-03, 12 July 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-masque-
              h3-datagram-03>.

   [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/rfc/rfc2119>.

   [RFC7230]  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/rfc/rfc7230>.

   [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/rfc/rfc8174>.




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   [URI]      Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/rfc/rfc3986>.

   [UTF8]     Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
              2003, <https://www.rfc-editor.org/rfc/rfc3629>.

10.2.  Informative References

   [AUTH]     Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Authentication", RFC 7235,
              DOI 10.17487/RFC7235, June 2014,
              <https://www.rfc-editor.org/rfc/rfc7235>.

   [IPSEC]    Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <https://www.rfc-editor.org/rfc/rfc4301>.

   [REQS]     Chernyakhovsky, A., McCall, D., and D. Schinazi,
              "Requirements for a MASQUE Protocol to Proxy IP Traffic",
              Work in Progress, Internet-Draft, draft-ietf-masque-ip-
              proxy-reqs-02, 30 April 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-masque-
              ip-proxy-reqs-02>.

Appendix A.  Examples

A.1.  Consumer VPN

   In this scenario, the client will typically receive a single IP
   address that the proxy has picked from a pool of addresses it
   maintains.  The client will route all traffic through the tunnel.
   The exchange could look as follows:
















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       Client                                             Server

       ADDRESS_REQUEST          -------->
         IP Version = 4
         IP Address = 0.0.0.0
         IP Prefix Length = 0

                                <--------  ADDRESS_ASSIGN
                                             IP Version = 4
                                             IP Address = 192.0.2.42
                                             IP Prefix Length = 32

                                <--------  ROUTE_ADVERTISEMENT
                                             IP Version = 4
                                             IP Address = 0.0.0.0
                                             IP Prefix Length = 0

Acknowledgments

   The design of CONNECT-IP was inspired by discussions in the MASQUE
   working group around [REQS].  The authors would like to thank
   participants in those discussions for their feedback.

Authors' Addresses

   Alex Chernyakhovsky
   Google LLC
   1600 Amphitheatre Parkway
   Mountain View, California 94043,
   United States of America

   Email: achernya@google.com


   Dallas McCall
   Google LLC
   1600 Amphitheatre Parkway
   Mountain View, California 94043,
   United States of America

   Email: dallasmccall@google.com










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   David Schinazi
   Google LLC
   1600 Amphitheatre Parkway
   Mountain View, California 94043,
   United States of America

   Email: dschinazi.ietf@gmail.com












































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