httpbis L. Pardue
Internet-Draft October 18, 2018
Intended status: Informational
Expires: April 21, 2019
HTTP-initiated Network Tunnelling (HiNT)
draft-pardue-httpbis-http-network-tunnelling-01
Abstract
The HTTP CONNECT method allows an HTTP client to initiate, via a
proxy, a TCP-based tunnel to a single destination origin. This memo
explores options for expanding HTTP-initiated Network Tunnelling
(HiNT) to cater for diverse UDP and IP associations.
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
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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 April 21, 2019.
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Notational Conventions . . . . . . . . . . . . . . . . . . . 6
2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 6
3. Design Consideration Aspects . . . . . . . . . . . . . . . . 7
3.1. HTTP Version . . . . . . . . . . . . . . . . . . . . . . 7
3.2. HTTP Forward Proxying . . . . . . . . . . . . . . . . . . 7
3.3. Message Destination Agility . . . . . . . . . . . . . . . 7
3.4. Path MTU Discovery . . . . . . . . . . . . . . . . . . . 7
3.5. Blind forwarding vs. in-the-loop Processing . . . . . . . 8
3.6. Head-of-line Blocking . . . . . . . . . . . . . . . . . . 8
4. Candidate Solutions . . . . . . . . . . . . . . . . . . . . . 9
4.1. CONNECT Method Augmentation . . . . . . . . . . . . . . . 9
4.2. UDPASSOCIATE with HINT Frames for HTTP/2 and HTTP/QUIC . 9
4.3. HELIUM over WebSockets for all HTTP Versions . . . . . . 9
4.4. HELIUM over WebSockets for HTTP/1.1, Native Framing for
HTTP/2 or HTTP/QUIC . . . . . . . . . . . . . . . . . . . 9
5. Technical Specification for HiNT Requests . . . . . . . . . . 10
5.1. The UDPASSOCIATE Method for HTTP/1.1x . . . . . . . . . . 10
5.2. The UDPASSOCIATE Method for HTTP/2 and HTTP/QUIC . . . . 11
5.3. The IPASSOCIATE Method . . . . . . . . . . . . . . . . . 12
6. Technical Specification for HiNT Message Transfer . . . . . . 12
6.1. HiNT Message Framing . . . . . . . . . . . . . . . . . . 12
6.1.1. The HINT HTTP/2 Frame . . . . . . . . . . . . . . . . 13
6.1.2. The HINT HTTP/QUIC Frame . . . . . . . . . . . . . . 14
6.2. Light HIP HTTP/2 Framing . . . . . . . . . . . . . . . . 14
6.3. Full HIP HTTP/2 Framing . . . . . . . . . . . . . . . . . 15
6.3.1. The OHIP HTTP/2 Frame . . . . . . . . . . . . . . . . 16
6.3.2. The IHIP HTTP/2 Frame . . . . . . . . . . . . . . . . 17
6.3.3. The MHIP HTTP/2 Frame . . . . . . . . . . . . . . . . 18
7. Security Considerations . . . . . . . . . . . . . . . . . . . 20
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
8.1. UDPASSOCIATE Method Registration . . . . . . . . . . . . 20
8.2. IPASSOCIATE Method Registration . . . . . . . . . . . . . 21
8.3. The HINT HTTP/2 Frame Type . . . . . . . . . . . . . . . 21
8.4. The HINT HTTP/QUIC Frame Type . . . . . . . . . . . . . . 21
8.5. The HIP HTTP/2 Frame Type . . . . . . . . . . . . . . . . 22
8.6. The OHIP HTTP/2 Frame Type . . . . . . . . . . . . . . . 22
8.7. The IHIP HTTP/2 Frame Type . . . . . . . . . . . . . . . 22
8.8. The MHIP HTTP/2 Frame Type . . . . . . . . . . . . . . . 22
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
9.1. Normative References . . . . . . . . . . . . . . . . . . 23
9.2. Informative References . . . . . . . . . . . . . . . . . 23
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 24
Appendix B. HiNT Request Options . . . . . . . . . . . . . . . . 25
Appendix C. HiNT Message Transfer Options . . . . . . . . . . . 26
Appendix D. Changelog . . . . . . . . . . . . . . . . . . . . . 28
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D.1. Since draft-pardue-httpbis-http-network-tunnelling-00 . . 29
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction
A wide range of network tunnelling solutions already exist (e.g.
SOCKS [RFC1928], TURN [RFC5766] etc.), with various applicability.
So why consider creating another one? Several tunnelling
specifications reserve well known TCP or UDP ports that are easy to
block. Even if port usage is more agile, plain text communications
allow potential attackers to easily analyse traffic and cause
interference.
This document we consider options for HTTP-initiated Network
Tunnelling (HiNT) as a solution. The use case is a client behind a
forward proxy but other uses may be supported. Using HTTP as a
substrate for other protocols follows a trend seen elsewhere (DNS
Queries over HTTPS [DOH]). Shifting to an HTTP port, makes port
blocking less effective. However, the real advantage comes from
securing HTTP (TLS [RFC5246], QUIC [QUIC-TRANSPORT]) to provide
confidentiality, integrity and authenticity, which makes analysis and
interference harder. This also enables secure communication to a
remote proxy on the Internet (in contrast to SOCKS etc.).
A HiNT session is initiated by some HTTP mechanism. This could be a
HTTP request or some binary frame format (HTTP/2 and HTTP/QUIC only).
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Client Forward Proxy Server
+ + +
| +------------------------------------+ | |
| | TCP Connection | | |
| | | | |
| | CONNECT example.org | | |
+=========================================>| |
| | 200 OK | | +-----------------+ |
|<=========================================+ | TCP Connection | |
| | | | | | |
| | +------------------------------------------------------+ | |
| | | TLS Session | | | | | |
| | | | | | | | |
| | | GET /foo | | | | | |
+=================================================================>|
| | | 200 OK | | | | | |
|<=================================================================+
| | | | | | | | |
| | +------------------------------------------------------+ | |
| | | | | | |
| +------------------------------------+ | +-----------------+ |
+ + +
Figure 1: HTTP/1.1 CONNECT-based TLS tunnel
The CONNECT request method (see Section 4.3.6 of [RFC7231]) is
commonly used to establish a tunnelled TLS session with an origin
identified by a request-target. In HTTP/1.1, the entire client-to-
proxy HTTP connection is converted into a tunnel (Figure 1). In
HTTP/2 (see Section 8.3 of [RFC7540]) and HTTP/QUIC (see
Section 3.1.2 of [QUIC-HTTP]), a single stream gets dedicated to a
tunnel (Figure 2).
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Client Forward Proxy Server
+ + +
| +------------------------------------+ | |
| | TCP Connection or UDP Association | | |
| | +------------------------------+ | | |
| | | TLS or QUIC Security Context | | | |
| | | +------------------------+ | | | |
| | | | HTTP/2 or HTTP/QUIC | | | | |
| | | | Stream | | | | |
| | | | | | | | |
| | | | CONNECT example.org | | | | |
+=========================================>| |
| | | | 200 OK | | | | +-----------------+ |
|<=========================================+ | TCP Connection | |
| | | | | | | | | | |
| | | | +------------------------------------------------+ | |
| | | | | TLS Session | | | | | | | |
| | | | | +------------------------------------------+ | | |
| | | | | | HTTP/2 Stream | | | | | | | | |
| | | | | | | | | | | | | | |
| | | | | | GET /foo | | | | | | | | |
+=================================================================>|
| | | | | | 200 OK | | | | | | | | |
|<=================================================================+
| | | | | | | | | | | | | | |
| | | | | +------------------------------------------+ | | |
| | | | | | | | | | | | |
| | | | +------------------------------------------------+ | |
| | | | | | | | | | |
| | | +------------------------+ | | | | | |
| | | | | | | | |
| | +------------------------------+ | | | | |
| | | | | | |
| +------------------------------------+ | +-----------------+ |
+ + +
Figure 2: HTTP/2 and HTTP/QUIC CONNECT-based TLS tunnel
A proxy that supports CONNECT blindly forwards packets, in both
directions, using TCP for both client-to-proxy and proxy-to-origin
hops. The use of TCP for the latter hop is a limiting factor: other
application or transport protocols are unsupported. This document
specifically concerns itself with finding a solution that permits a
UDP-based HTTP/QUIC client behind an HTTP proxy to establish an HTTP/
QUIC session with the origin. Without such a capability, there
continues to be a dependency on origins to support TCP-based HTTP
(for a small subset of the client population).
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The document is arranged in the following order:
o Design aspects are considered in Section 3.
o Tunnel initiation options are surveyed in Appendix B.
o Messaging (post-handshake data transfer) options are surveyed in
Appendix C.
o Four candidate solutions are presented in Section 4, based on the
above options.
Candidate solutions have the purpose of stimulating discussion in the
community in order to drive toward a single solution.
2. Notational Conventions
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.
2.1. Definitions
Definitions of terms that are used in this document:
o HiNT request: a message that requests the establishment of a
network tunnel to a HiNT destination.
o HiNT response: a message that confirms the establishment of a
network tunnel.
o HiNT message: a message that allows data transfer between client,
proxy and/or destination during a HiNT session.
o HiNT client: an HTTP endpoint that sends a HiNT request to a HiNT
proxy. Also referred to as a client.
o HiNT proxy: an HTTP endpoint that services HiNT requests. It
returns a HiNT response that indicates the outcome of network
tunnel creation. Also referred to as a proxy.
o HiNT destination: the service that the HiNT client is trying to
reach via a HiNT proxy. Also referred to as a destination.
o HiNT session: a specific instance of a network tunnel.
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o Network Tunnel: describes any forms of association between client
and destination (end-to-end). A tunnel ceases to exist when both
ends of the association are closed (implicitly or explicitly).
3. Design Consideration Aspects
3.1. HTTP Version
The design should consider if all HTTP Versions need be supported.
Differences in version syntax (in particular binary framing and
streams) may provide certain design advantages.
3.2. HTTP Forward Proxying
The design considers the "forward proxying" intermediary (see
Section 2.3 of [RFC7230]) model, which is widely deployed.
HTTP clients may use a range of methods to discover the presence of
an HTTP proxy (WPAD, DHCP, manual configuration). Client
application-layer communications remain unaware of such
configuration. (In other words, handshake and data transfer
interactions with the HTTP proxy are invisible to the application
layer.)
Intermediaries may themselves have an HTTP proxy configured. A
client attempting to initiate a tunnel to a remote host may end up
traversing a proxy chain. This is a useful design characteristic and
should be considered when selecting a preferred option.
3.3. Message Destination Agility
The CONNECT method currently expresses a request-target. This is a
"fixed destination mode" where all messages travel on the same fixed
TCP path to the same destination (ignoring lower level network
elements).
The design should consider if more agile approach i.e. a "per-message
destination mode" would support new network interaction models. This
may add per-message overhead but optimisation may be possible.
3.4. Path MTU Discovery
The design should consider that endpoints may want/be required to
avoid IP fragmentation. Support for reasonable attempts at path MTU
discovery (PMTUD) should be included. Traditional PMTUD methods
(such as those described in [RFC1191] and [RFC8201] are intended for
TCP and rely on ICMP and ICMPv6 messages. [RFC2293] catalogs some of
the problems with PMTUD. Packetization Layer PMTUD (PLPMTUD)
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[RFC4821] is an extension that describes an algorithm that can
operate at the transport layer. Datagram PLPMTUD [DPLPMTUD] is a
proposed further extension that describes approaches for various UDP-
based transports.
3.5. Blind forwarding vs. in-the-loop Processing
[RFC7230] describes a tunnel as "a blind relay between two
connections without changing messages". This approach may be overly
restrictive for new interaction modes.
In the case of CONNECT for TCP-based tunnelling, the HiNT message
sent by a client (TCP/IP packet payload) is decapsulated at the proxy
and recapsulated in a new TCP/IP packet created and sent by the
proxy. The proxy performs no processing of the HiNT message.
[HELIUM] proposes an alternative model, where the proxy does (and is
expected to) modify HiNT messages.
3.6. Head-of-line Blocking
The current design of CONNECT-based tunnelling reserves either a
whole TCP connection (HTTP/1.1) or an ordered byte stream (HTTP/2 and
HTTP/QUIC) for the client-to-proxy hop. These are subject to head-
of-line (HoL) blocking. For example, where there is an end-to-end
tunnelled HTTP/2 connection, all of its streams are subject to the
blocking on the single reserved stream. It is unknown to the author
is this is perceived to be a high impact problem.
This document defines HTTP/2 and HTTP/QUIC frames (Section 6) that
are sent on HTTP/2 or QUIC streams respecitvely.
For UDP or IP-based tunnels, HoL blocking may be problematic. It is
unlikely that the application expects blocking to occur, leading to
potential issues. (QUIC is specifically designed to avoid HoL
blocking and is designed to operate on unreliable UDP, a reliable
bearer may adversely affect performance.)
Future versions of QUIC may offer partial reliability. If it were
used for the client-to-proxy hop, it could help mitigate HoL blocking
The design should consider the tension between the benefits of
tunnelling, impact of HoL, and HTTP version Section 3.1.
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4. Candidate Solutions
Strawman candidate solutions are presented in order of increasing
perceived complexity. It is hoped that wider input will help shape
the solution.
4.1. CONNECT Method Augmentation
Enhance or augment the current definitions of the CONNECT method in
HTTP/1.x, HTTP/2 and HTTP/QUIC. Data exchanges between a client and
a single destination will be conveyed over existing byte streams with
no additional framing. Client and proxy are required to assign
meaning to groups of bytes delivered on the stream, which may be
impractical.
4.2. UDPASSOCIATE with HINT Frames for HTTP/2 and HTTP/QUIC
Define a new method, UDPASSOCIATE (Section 5.1), that reserves a
stream for the carriage of newly defined HINT frames (Section 6.1).
Data exchanges between a client and a single destination will be
conveyed using these frames. This requires HTTP/2 or HTTP/QUIC
proxies, and precludes HTTP/1.x (because there is no means for
framing HiNT messages).
4.3. HELIUM over WebSockets for all HTTP Versions
Tunnelling of UDP or IP using HELIUM ([HELIUM]) over WebSockets.
Data exchanges between a client and destination(s) will be conveyed
using CBOR-encoded HIP messages. WebSockets connections between
client and proxy are established by existing means. This option
would work for all HTTP versions that support WebSockets.
4.4. HELIUM over WebSockets for HTTP/1.1, Native Framing for HTTP/2 or
HTTP/QUIC
Tunnelling of UDP or IP using HELIUM ([HELIUM]). Data exchanges
between a client and destination(s) will be conveyed using HIP
messages appropriate for the HTTP version.
For HTTP/1.x, WebSockets with CBOR-encoded HIP messages would be
used.
For HTTP/2 and HTTP/QUIC, HIP messages would be framed and exchanged
on a stream reserved by the new method, IPASSOCIATE (Section 5.3).
There are two framing options presented: light framing (Section 6.2)
that uses the CBOR-encoded format, which would allow direct reuse of
code to that used for the above WebSocket substrate; full framing
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(Section 6.3) that uses the native features of the application layer
substrate, which may have advantages.
5. Technical Specification for HiNT Requests
This section outlines the technical specifications required to
support the candidate solutions. Discussion of respective merits and
drawbacks is captured in Appendix B.
5.1. The UDPASSOCIATE Method for HTTP/1.1x
In HTTP/1.x, the UDPASSOCIATE method requests that the recipient
establish a UDP-based tunnel to the destination origin server
identified by the request-target and, if successful, thereafter
restrict its behavior to blind forwarding of UDP datagram payloads,
in both directions, until the tunnel is closed.
UDPASSOCIATE is intended only for use in requests to a proxy. An
origin server that receives a UDPASSOCIATE request for itself MAY
respond with a 2xx (Successful) status code to indicate that a
connection is established. TODO: explicitly ban this?
A client sending a UDPASSOCIATE request MUST send the authority form
of request-target (Section 5.3 of [RFC7230]); i.e., the request-
target consists of only the host name and port number of the tunnel
destination, separated by a colon. The port number is for UDP only.
UDPASSOCIATE hq.example.com:50781 HTTP/1.1
Host: hq.example.com:50781
The recipient proxy can establish a tunnel either by directly
connecting to the request-target or, if configured to use another
proxy, by forwarding the UDPASSOCIATE request to the next inbound
proxy. Any 2xx (Successful) response indicates that the sender (and
all inbound proxies) will switch to tunnel mode immediately after the
blank line that concludes the successful response's header section;
data received after that blank line is from the server identified by
the request-target. Any response other than a successful response
indicates that the tunnel has not yet been formed and that the
connection remains governed by HTTP.
TODO: how do connectionless UDP associations affirm that connection
to the remote host succeeded? Perhaps a 2xx should be formed when
the proxy believes it has sufficient capability to send or receive
packets.
A tunnel is closed when an intermediary detects that either side has
closed its connection (explicitly or implicitly). The intermediary
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MUST attempt to send any outstanding data that came from the closed
side to the other side, close both connections, and then discard any
remaining data left undelivered.
A server MUST NOT send any Transfer-Encoding or Content-Length header
fields in a 2xx (Successful) response to UDPASSOCIATE. A client MUST
ignore any Content-Length or Transfer-Encoding header fields received
in a successful response to UDPASSOCIATE.
A payload within a UDPASSOCIATE request message has no defined
semantics.
5.2. The UDPASSOCIATE Method for HTTP/2 and HTTP/QUIC
In HTTP/2 and HTTP/QUIC, the UDPASSOCIATE method requests the
establishment of a tunnel to a single remote host over a single
stream. This mechanism has a few differences from the header field
mapping described in [RFC7540], Section 8.1.2.3:
o The ":method" pseudo-header field is set to "UDPASSOCIATE"
o The ":scheme" and ":path" pseudo-header fields MUST be omitted
o The ":authority" pseudo-header field contains the host and port to
connect to (equivalent to the authority-form of the request-target
of CONNECT requests (see [RFC7230], Section 5.3)).
A UDPASSOCIATE method that does not conform to these restrictions is
malformed ([RFC7540], Section 8.1.2.6).
A proxy that supports UDPASSOCIATE can establish a tunnel to the
server identified in the ":authority" pseudo-header field. Once this
is completed (see earlier TODO), the proxy sends a HEADERS frame
containing a 2xx series status code to the client.
A successful UDPASSOCIATE request reserves the request stream for
tunnelling. After the initial HEADERS frame sent by each peer, all
subsequent frames exchanged on this stream correspond to data sent on
the UDP association. Section 6.1, Section 6.2 and Section 6.3
explore options for application-level framing and the mapping to UDP.
Some frame types MUST NOT be sent on the reserved stream (e.g.
RST_STREAM and more TBD). An endpoint that receives any of these
MUST respond with a connection error.
The UDP association can be closed (explicitly or implicitly) by
either peer. It is RECOMMENDED that peers close the association
explicitly using tunnelled application-level means (if possible).
Once this has happened, the client SHOULD close the reserved stream
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on the client-to-proxy hop. Closing the reserved stream before an
explicit close is likely to trigger an application-level implicit
close (i.e. idle timeout).
5.3. The IPASSOCIATE Method
The IPASSOCIATE method can be used by a client to request that the
recipient establish an IP-based tunnel to the destination origin
server identified by the request-target and, if successful,
thereafter restrict its behaviour to blind forwarding of IP payloads,
in both direction, until the tunnel is closed.
The IPASSOCIATE method would look and behave much like the
UDPASSOCIATE method.
TODO: expand this definition if this method is preferred or required.
Additional parameters may be required to accommodate the extra
capabilities of IP-based tunnels.
6. Technical Specification for HiNT Message Transfer
This section outlines the technical specifications required to
support the candidate solutions. Discussion of respective merits and
drawbacks is captured in Appendix C.
6.1. HiNT Message Framing
The HINT frame carries HiNT messages between client and proxy. Is
intended to be used with versions of HTTP that support binary
framing. Definitions are provided for HTTP/2 and HTTP/QUIC,
differing only in their use of padding. (The QUIC transport
([QUIC-TRANSPORT]) provides padding itself.) Frames are non-critical
extensions to their respective protocols. Endpoints that do not
support these frames will ignore them.
The payload of each HINT frame corresponds to a UDP datagram (or IP
Packet?) sent or received by a HiNT proxy. A separate HiNT request
is REQUIRED in order to initiate the tunnel with which these frames
relate.
HINT frames are subject to flow control. The size of HINT frames
should take into consideration the path MTU. Methods for path MTU
discovery are discussed in Section 3.4.
Frames MUST be associated with a non-control stream. If a frame is
received on a control stream, the recipient MUST respond with a
connection error. For HTTP/2 this is PROTOCOL_ERROR, for HTTP/QUIC
this is TBD.
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6.1.1. The HINT HTTP/2 Frame
The HINT HTTP/2 frame (type=0xTBD) defines the following flags (based
on HTTP/2 flags):
END_STREAM (0x1): When set, bit 0 indicates that this frame is the
last that the endpoint will send for the identified stream.
Setting this flag causes the stream to enter one of the "half-
closed" states or the "closed" state ([RFC7540], Section 5.1).
PADDED (0x8): When set, bit 3 indicates that the Pad Length field
and any padding that it describes are present.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Pad Length? (8)| Payload (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Padding (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: HINT HTTP/2 frame payload
The HINT HTTP/2 frame payload has the following fields:
Pad Length: An OPTIONAL 8-bit field containing the length of the
frame padding in units of octets. This field is only present if
the PADDED flag is set.
Payload: Arbitrary octets that correspond to messages sent to/from a
HiNT proxy.
Padding: Padding octets that contain no application semantic value.
Padding octets MUST be set to zero when sending. A receiver is
not obligated to verify padding but MAY treat non-zero padding as
a connection error ([RFC7540], Section 5.4.1) of type
PROTOCOL_ERROR.
HINT HTTP/2 frames are subject to flow control ([RFC7540],
Section 5.2) and can only be sent when a stream is in the "open" or
"half-closed (remote)" state. If an HINT HTTP/2 frame is received
whose stream is not in "open" or "half-closed (local)" state, the
recipient MUST respond with a stream error ([RFC7540] Section 5.4.2)
of type STREAM_CLOSED.
The HINT HTTP/2 frame is processed hop-by-hop. An intermediary MUST
NOT forward HINT HTTP/2 frames, though it can use the information
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contained in HINT HTTP/2 frames in forming new HINT HTTP/2 frames to
send to its own proxy.
6.1.2. The HINT HTTP/QUIC Frame
The HINT HTTP/QUIC frame (type=0xTBD) defines no flags.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: HINT HTTP/QUIC frame payload
The HINT HTTP/QUIC frame carries arbitrary octets that correspond to
messages sent to/from a HiNT proxy. The payload MUST be non-zero-
length. If a HINT HTTP/QUIC frame is received with with a payload
length of zero, the recipient MUST respond with a stream error
([QUIC-HTTP], Section 6) of type TBD.
The HINT HTTP/QUIC frame is processed hop-by-hop. An intermediary
MUST NOT forward HINT HTTP/QUIC frames, though it can use the
information contained in HINT HTTP/QUIC frames in forming new HINT
HTTP/QUIC frames to send to its own proxy.
6.2. Light HIP HTTP/2 Framing
The HELIUM inner protocol (HIP) [HELIUM] defines an abstract message
structure that may be carried on a variety of substrates.
The HIP HTTP/2 frame (type=0xTBD) carries CBOR-encoded HIP message.
The message type is indicated in a frame field.
The frame is a non-critical extension. Endpoints that do not support
it will ignore it.
The size of frame should take into consideration the path MTU.
Methods for path MTU discovery are discussed in Section 3.4.
Frames MUST be associated with a non-control stream. If a frame is
received on a control stream, the recipient MUST respond with a
connection error. For HTTP/2 this is PROTOCOL_ERROR.
The HIP HTTP/2 frame defines the following flags:
END_STREAM (0x1): When set, bit 0 indicates that this frame is the
last that the endpoint will send for the identified stream.
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Setting this flag causes the stream to enter one of the "half-
closed" states or the "closed" state ([RFC7540], Section 5.1).
PADDED (0x8): When set, bit 3 indicates that the Pad Length field
and any padding that it describes are present.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Pad Length? (8)| Type (8) | HIP-CBOR Message (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Padding (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: HIP HTTP/2 frame payload
The HIP HTTP/2 frame payload has the following fields:
Pad Length: An OPTIONAL 8-bit field containing the length of the
frame padding in units of octets. This field is only present if
the PADDED flag is set.
Type: An 8-bit field that identifies the HIP message type as defined
in [HELIUM].
HIP-CBOR Message: A HIP message expressed in CBOR encoding including
type, metadata (including padding), and packet or packet-prefix.
Padding: Padding octets that contain no application semantic value.
Padding octets MUST be set to zero when sending. A receiver is
not obligated to verify padding but MAY treat non-zero padding as
a connection error ([RFC7540], Section 5.4.1) of type
PROTOCOL_ERROR.
6.3. Full HIP HTTP/2 Framing
The OHIP, IHIP and MHIP frames (collectively xHIP) encode all HIP
message data directly in the HTTP/2 frame structure.
These frames are non-critical extensions, endpoints that do not
support them will ignore them.
The size of these frames should take into consideration the path MTU.
Methods for path MTU discovery are discussed in Section 3.4.2.
Frames MUST be associated with a non-control stream. If a frame is
received on a control stream, the recipient MUST respond with a
connection error. For HTTP/2 this is PROTOCOL_ERROR.
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Each xHIP frame type contains zero or more instances of the Metadata-
entry field. Fields are processed by the HIP application layer.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metadata-entry (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
A Metadata-entry field is a tuple consisting of a Key and a length-
delimited Value:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key (16) | Value Length (32) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... | Value? ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Specifically:
Key: An unsigned, 16-bit integer representing the HIP metadata key.
Value Length: An unsigned, 16-bit integer indicating the length, in
octets of the Value field.
Value: An OPTIONAL sequence of octets containing an application-
specific value.
6.3.1. The OHIP HTTP/2 Frame
The OHIP HTTP/2 frame (type=0xTBD) carries an "outbound" HIP message.
The OHIP HTTP/2 frame defines the following flags:
END_STREAM (0x1): When set, bit 0 indicates that this frame is the
last that the endpoint will send for the identified stream.
Setting this flag causes the stream to enter one of the "half-
closed" states or the "closed" state ([RFC7540], Section 5.1).
METADATA (0x2): When set, bit 1 indicates that the Metadata Entries
field and metadata that is describes are present
PADDED (0x8): When set, bit 3 indicates that the Pad Length field
and any padding that it describes are present.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Pad Length? (8)| Metadata Entries? (16) | ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metadata (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Padding (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: OHIP HTTP/2 frame payload
The OHIP HTTP/2 frame payload has the following fields:
Pad Length: An OPTIONAL 8-bit field containing the length of the
frame padding in units of octets. This field is only present if
the PADDED flag is set.
Metadata Entries: An OPTIONAL 16-bit field that indicates the number
of Metadata-entries held in the Metadata field. This field is
only present if the METADATA flag is set.
Metadata: Zero or more instances of the Metadata-entry field.
Payload: At most one packet (or prefix of a packet), in essence, a
standard IP packet starting with an IP header.
Padding: Padding octets that contain no application semantic value.
Padding octets MUST be set to zero when sending. A receiver is
not obligated to verify padding but MAY treat non-zero padding as
a connection error ([RFC7540], Section 5.4.1) of type
PROTOCOL_ERROR.
6.3.2. The IHIP HTTP/2 Frame
The IHIP HTTP/2 frame (type=0xTBD) carries an "inbound" HIP message.
The IHIP HTTP/2 frame defines the following flags:
END_STREAM (0x1): When set, bit 0 indicates that this frame is the
last that the endpoint will send for the identified stream.
Setting this flag causes the stream to enter one of the "half-
closed" states or the "closed" state ([RFC7540], Section 5.1).
METADATA (0x2): When set, bit 1 indicates that the Metadata Entries
field and metadata that is describes are present
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PADDED (0x8): When set, bit 3 indicates that the Pad Length field
and any padding that it describes are present.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Pad Length? (8)| Metadata Entries? (16) | ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Metadata (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Padding (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: IHIP HTTP/2 frame payload
The IHIP HTTP/2 frame payload has the following fields:
Pad Length: An OPTIONAL 8-bit field containing the length of the
frame padding in units of octets. This field is only present if
the PADDED flag is set.
Metadata Entries: An OPTIONAL 16-bit field that indicates the number
of Metadata-entries held in the Metadata field. This field is
only present if the METADATA flag is set.
Metadata: Zero or more instances of the Metadata-entry field.
Payload: A packet, in essence, a standard IP packet starting with an
IP header, as received by the proxy.
Padding: Padding octets that contain no application semantic value.
Padding octets MUST be set to zero when sending. A receiver is
not obligated to verify padding but MAY treat non-zero padding as
a connection error ([RFC7540], Section 5.4.1) of type
PROTOCOL_ERROR.
6.3.3. The MHIP HTTP/2 Frame
The MHIP HTTP/2 frame (type=0xTBD) carries a "meta" HIP message.
The MHIP HTTP/2 frame defines the following flags:
END_STREAM (0x1): When set, bit 0 indicates that this frame is the
last that the endpoint will send for the identified stream.
Setting this flag causes the stream to enter one of the "half-
closed" states or the "closed" state ([RFC7540], Section 5.1).
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METADATA (0x2): When set, bit 1 indicates that the Metadata Entries
field and metadata that is describes are present
ERROR (0x4): When set, bit 2 indicates that this frame includes an
Error-len field.
PADDED (0x8): When set, bit 3 indicates that the Pad Length field
and any padding that it describes are present.
PAYLOAD (0xc): When set, bit 4 indicates that the Payload field is
present
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Pad Length? (8)| Metadata Entries? (16) |Err Length? (8)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metadata (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Errors (*)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload? (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Padding (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: MHIP HTTP/2 frame payload
The MHIP HTTP/2 frame payload has the following fields:
Pad Length: An OPTIONAL 8-bit field containing the length of the
frame padding in units of octets. This field is only present if
the PADDED flag is set.
Metadata Entries: An OPTIONAL 16-bit field that indicates the number
of Metadata-entries held in the Metadata field. This field is
only present if the METADATA flag is set.
Err Length: An OPTIONAL 8-bit field containing the length of the
Errors field. This field is only present if the ERROR flag is
set.
Metadata: Zero or more instances of the Metadata-entry field.
Errors: An OPTIONAL octet array of length Err Length. Each octet of
the array represents a HIP error as described in [HELIUM].
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Payload: An OPTIONAL payload containing a prefix of the outbound
packet as sent, including any parts that were modified. This
field is only present if the PAYLOAD flag is set.
Padding: Padding octets that contain no application semantic value.
Padding octets MUST be set to zero when sending. A receiver is
not obligated to verify padding but MAY treat non-zero padding as
a connection error ([RFC7540], Section 5.4.1) of type
PROTOCOL_ERROR.
7. Security Considerations
This document is partly motivated by the desire to prevent exposure
to observers, to make detection and interference more difficult. The
effectiveness of this is dependent on the chosen solution. Where
HTTP is used only to bootstrap a HiNT session, messages will be
carried without additional HTTP traffic to mask them. A more secure
option would be to both bootstrap and carry HiNT messages inside an
HTTP session. This of course relies on secure HTTP to provide
confidentiality.
It is noted that different HiNT traffic may have different
characteristics (e.g. volumes and timing) when compared to the HTTP
context that it is operating in. Session level encryption is weak
with respect to traffic analysis. HTTP/2 provides further advice
about the use of compression ([RFC7540] Section 10.6) and padding
([RFC7540] Section 10.7) to mitigate the ability for an observer to
discriminate different forms of traffic. Additional application-
layer padding may help.
TODO: Proxy authentication might be used to establish the authority
to create a tunnel.
There are significant risks in establishing a tunnel to arbitrary
servers. Proxies that support HiNT requests SHOULD restrict a HiNT
session to a limited set of known ports or a configurable white list
of safe request targets.
This section will address more security considerations once a single
solution is chosen.
8. IANA Considerations
8.1. UDPASSOCIATE Method Registration
This section registers the "UDPASSOCIATE" method in "HTTP Method
Registry" ([RFC7230], Section 8.1).
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Method Name: UDPASSOCIATE
Safe: No
Idempotent: No
Cacheable: No
Specification document(s): Section 5.1 of this document
8.2. IPASSOCIATE Method Registration
This section registers the "IPASSOCIATE" method in "HTTP Method
Registry" ([RFC7230], Section 8.1).
Method Name: IPASSOCIATE
Safe: No
Idempotent: No
Cacheable: No
Specification document(s): Section 5.3 of this document
8.3. The HINT HTTP/2 Frame Type
This section registers the "HINT" frame type in the "HTTP/2 Frame
Type" registry ([RFC7540], Section 11.2).
Frame Type: HINT
Code: 0XTBD
Specification: Section 6.1.1 of this document
8.4. The HINT HTTP/QUIC Frame Type
This section registers the "HINT" frame type in the "HTTP/QUIC Frame
Type" registry ([QUIC-HTTP], Section 9.3).
Frame Type: HINT
Code: 0XTBD
Specification: Section 6.1.2 of this document
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8.5. The HIP HTTP/2 Frame Type
This section registers the "HIP" frame type in the "HTTP/2 Frame
Type" registry ([RFC7540], Section 11.2).
Frame Type: HIP
Code: 0XTBD
Specification: Section 6.2 of this document
8.6. The OHIP HTTP/2 Frame Type
This section registers the "OHIP" frame type in the "HTTP/2 Frame
Type" registry ([RFC7540], Section 11.2).
Frame Type: OHIP
Code: 0XTBD
Specification: Section 6.3.1 of this document
8.7. The IHIP HTTP/2 Frame Type
This section registers the "IHIP" frame type in the "HTTP/2 Frame
Type" registry ([RFC7540], Section 11.2).
Frame Type: IHIP
Code: 0XTBD
Specification: Section 6.3.2 of this document
8.8. The MHIP HTTP/2 Frame Type
This section registers the "MHIP" frame type in the "HTTP/2 Frame
Type" registry ([RFC7540], Section 11.2).
Frame Type: MHIP
Code: 0XTBD
Specification: Section 6.3.3 of this document
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9. References
9.1. Normative References
[HELIUM] Schwartz, B., "Hybrid Encapsulation Layer for IP and UDP
Messages (HELIUM)", draft-schwartz-httpbis-helium-00 (work
in progress).
[QUIC-HTTP]
Bishop, M., Ed., "Hypertext Transfer Protocol (HTTP) over
QUIC", draft-ietf-quic-http-13 (work in progress).
[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>.
[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/info/rfc7230>.
[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>.
[RFC7540] 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/info/rfc7540>.
[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>.
9.2. Informative References
[DOH] Hoffman, P. and P. McManus, "DNS Queries over HTTPS",
draft-ietf-doh-dns-over-https-10 (work in progress).
[DPLPMTUD]
Ruengeler, I., "Packetization Layer Path MTU Discovery for
Datagram Transports", draft-ietf-tsvwg-datagram-plpmtud-01
(work in progress).
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[H2-WEBSOCKETS]
McManus, P., Ed., "Bootstrapping WebSockets with HTTP/2",
draft-ietf-httpbis-h2-websockets-02 (work in progress).
[QUIC-TRANSPORT]
Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", draft-ietf-quic-
transport-13 (work in progress).
[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
DOI 10.17487/RFC1191, November 1990,
<https://www.rfc-editor.org/info/rfc1191>.
[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>.
[RFC2293] Kille, S., "Representing Tables and Subtrees in the X.500
Directory", RFC 2293, DOI 10.17487/RFC2293, March 1998,
<https://www.rfc-editor.org/info/rfc2293>.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007,
<https://www.rfc-editor.org/info/rfc4821>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using
Relays around NAT (TURN): Relay Extensions to Session
Traversal Utilities for NAT (STUN)", RFC 5766,
DOI 10.17487/RFC5766, April 2010,
<https://www.rfc-editor.org/info/rfc5766>.
[RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed.,
"Path MTU Discovery for IP version 6", STD 87, RFC 8201,
DOI 10.17487/RFC8201, July 2017,
<https://www.rfc-editor.org/info/rfc8201>.
Appendix A. Acknowledgments
The first draft of this document was written with support from BBC
Research & Development while Lucas was employed there.
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Many aspects of this document were inspired by the existing outputs
of the HTTP Working Group and the wider IETF community. Some aspects
were inspired by Mark Nottingham's previous work on HTTP/2 VPN.
The author would like to thank Richard Bradbury, Katharine Daly,
Piers O'Hanlon, and Ben Schwartz for design input and review of this
document.
Appendix B. HiNT Request Options
The following list presents options for a HiNT request in no
particular order:
1. Enhance the CONNECT method (i.e. request/response headers) that
permits negotiation of the proxy-to-destination transport
protocol.
* Pros:
+ Already widely supported for HTTP proxying use case.
+ Bootstrapping WebSockets for HTTP/2 [H2-WEBSOCKETS] has
made some headway here.
* Cons:
+ Deployability may be unrealistic. New types of tunnelling
behaviour may not meet expectations of extant endpoints.
+ CONNECT method extension may not be popular. Need to
consider if this is suited for all HTTP or specific
version.
2. Define a new method (e.g. UDPASSOCIATE Section 5.1) that is
restricted to use UDP for the proxy-to-destination transport
protocol.
* Pros:
+ Clear demarcation between the conventional TCP case.
+ Well suited for HTTP/QUIC use case.
* Cons:
+ Limited applicability (because it is UDP-only?).
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3. Define a new method (e.g. IPASSOCIATE) that permits negotiation
of the proxy-to-destination transport protocol.
* Pros:
+ Clear demarcation between the conventional TCP case.
+ Well suited for HTTP/QUIC use case.
* Cons:
+ Too complicated for most needs (?).
4. Define a substrate that is already supported by HTTP proxying
i.e. WebSocket.
* Pros:
+ Capable of functioning irrespective of HTTP version.
* Cons:
+ Multiple layers requires implementation complexity and adds
data transfer overhead.
5. Define HTTP/2 and HTTP/QUIC means of HiNT request, e.g. a new
frame or setting that is used to reserve a stream (or streams)
for special processing of HiNT messages.
* Pros:
+ Avoids coining a new method.
* Cons:
+ Excludes HTTP/1.1.
Appendix C. HiNT Message Transfer Options
The following list presents options for framing of messages within a
HiNT session in no particular order:
1. Where CONNECT is used by an HTTP/1.1 client, each TCP/IP packet
on the client-to-proxy hop maps directly to a packet (TCP/IP or
UDP/IP) on the proxy-to-destination hop.
* Pros:
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+ "Simple" option that requires no new TCP framing
definition.
* Cons:
+ Breaks the layering model
+ In practice, the endpoints are not likely to be able to do
this.
2. Where CONNECT is used by an HTTP/2 or HTTP/QUIC client, each DATA
frame on the client-to-proxy hop maps directly to a packet (TCP/
IP or UDP/IP) on the proxy-to-destination hop.
* Pros:
+ Simple option that requires no additional framing.
+ Client and proxy already handle DATA frames.
* Cons:
+ DATA frames are delivered on streams, which are treated as
an ordered byte stream. It may not be possible to treat
them individually.
3. Define framing format that uses a WebSocket substrate. For
example, the HELIUM Inner Protocol [HELIUM].
* Pros:
+ Would be supported in HTTP/1.1, HTTP/2 and HTTP/QUIC
(subject to further work).
* Cons:
+ Framing overhead which could be optimised away in HTTP/2
and HTTP/QUIC.
+ Requires WebSocket support in endpoints.
+ Breaks the layering model(?).
4. Define a new simple HTTP/2 and HTTP/QUIC extension frame for
carriage of HiNT messages. (This would likely be subject to
stream-level flow control). The frame payload would be
encapsulated by the proxy. This approach is reliant on a fixed
destination tunnel Section 3.3.
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* Pros:
+ Clear separation between stream-based and message-based
tunnels.
+ Similar to how endpoints already handle CONNECT today.
* Cons:
+ New frame may change the semantic of HTTP/2 and HTTP/QUIC.
Therefore, it may need to be negotiated by a new SETTINGS
parameter.
+ Excludes HTTP/1.1
+ Dependence on fixed destination tunnel may not support all
desired interaction modes.
5. Define a new HTTP/2 and HTTP/QUIC extension frame(s) for carriage
of HiNT messages. (This would likely be subject to stream-level
flow control). This could express HELIUM Inner Protocol [HELIUM]
messages directly and, by virtue, would support per-message
destination.
* Pros:
+ Clear separation between stream-based and message-based
tunnels.
+ Reduced overhead compared for HTTP/2 and HTTP/QUIC compared
to carriage over WebSocket substrate.
* Cons:
+ New frame may change the semantic of HTTP/2 and HTTP/QUIC.
Therefore, it may need to be negotiated by a new SETTINGS
parameter.
+ Some divergence from HTTP/1.1.
+ Differs from blind forwarding which is implemented in
CONNECT proxies today.
Appendix D. Changelog
*RFC Editor's Note:* Please remove this section prior to
publication of a final version of this document.
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D.1. Since draft-pardue-httpbis-http-network-tunnelling-00
o Author's address.
Author's Address
Lucas Pardue
Email: lucaspardue.24.7@gmail.com
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