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draft-ietf-httpbis-h2-websockets
Network Working Group P. McManus
Internet-Draft Mozilla
Intended status: Standards Track October 15, 2017
Expires: April 18, 2018
Bootstrapping WebSockets with HTTP/2
draft-mcmanus-httpbis-h2-websockets-00
Abstract
This document defines a mechanism for running the WebSocket Protocol
[RFC6455] over a single stream of an HTTP/2 connection.
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 April 18, 2018.
Copyright Notice
Copyright (c) 2017 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
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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.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. The ENABLE_CONNECT_PROTOCOL SETTINGS Parameter . . . . . . . 3
4. The Extended CONNECT Method . . . . . . . . . . . . . . . . . 3
4.1. Using Extended CONNECT To Bootstrap The WebSocket
Protocol . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Example . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Design Considerations . . . . . . . . . . . . . . . . . . . . 5
6. About Intermediaries . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
10. Normative References . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
The Hypertext Transfer Protocol (HTTP) provides compatible resource
level semantics across different versions but it does not offer
compatibility at the connection management level. Other protocols,
such as WebSockets, that rely on connection management details of
HTTP must be updated for new versions of HTTP.
The WebSocket Protocol [RFC6455] uses the HTTP/1.1 [RFC7230] Upgrade
mechanism to transition a TCP connection from HTTP into a WebSocket
connection. A different approach must be taken with HTTP/2
[RFC7540]. Due to the multiplexing nature of HTTP/2 it does not
allow connection wide header and status codes such as the Upgrade and
Connection request headers or the 101 response code. These are all
required by the [RFC6455] connection establishment process.
A server offering both HTTP/1.1 and WebSocket services can do so from
the same instance and same port although they require separate TCP
connections. Moving a server to HTTP/2 and WebSocket services
requires a separate port and protocol stack for the sole purpose of
bootstrapping WebSockets. This is a significant administrative
burden and may not even be possible in the case of large amounts of
deployed markup pointing at the old single name and port. Being able
to bootstrap WebSockets from HTTP/2 allows one server, one port, and
one TCP connection to be shared by both protocols.
This document extends the HTTP/2 CONNECT method. The extension
allows the substitution of a new protocol name to connect to rather
than the external host normally used by CONNECT. The result is a
tunnel on a single HTTP/2 stream that can carry data for WebSockets
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(or any other protocol) while the other streams on the connection
continue to carry HTTP/2 data.
Streams that have been successfully established as protocol tunnels
proceed to establish and utilize the WebSocket Protocol using the
procedure defined by [RFC6455] treating the stream as if were the
connection in that specification.
This tunneled stream will be multiplexed with other regular streams
on the connection and enjoys the normal priority, cancellation, and
flow control features of HTTP/2.
2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in BCP 14,
[RFC2119].
3. The ENABLE_CONNECT_PROTOCOL SETTINGS Parameter
This document adds a new SETTINGS Parameter to those defined by
[RFC7540] Section 6.5.2.
The new parameter is ENABLE_CONNECT_PROTOCOL (type = 0x8). The value
of the parameter MUST be 0 or 1.
Upon receipt of ENABLE_CONNECT_PROTOCOL with a value of 1 a client
MAY use the Extended CONNECT definition of this document when
creating new streams. Receipt of this parameter by a server does not
have any impact.
A sender MUST NOT send a ENABLE_CONNECT_PROTOCOL parameter with the
value of 0 after previously sending a value of 1.
The use of a SETTINGS Parameter to opt-in to an otherwise
incompatible protocol change is a use of "Extending HTTP/2" defined
by section 5.5 of [RFC7540]. If a client were to use the provisions
of the extended CONNECT method defined in this document without first
receiving a ENABLE_CONNECT_PROTOCOL parameter with the value of 1 it
would be a protocol violation.
4. The Extended CONNECT Method
The CONNECT Method of [RFC7540] Section 8.3 is modified in the
following ways:
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o A new pseudo-header :protocol MAY be included on request HEADERS
indicating the desired protocol to be spoken on the tunnel created
by CONNECT. The pseudo-header is single valued and contains a
value from the HTTP Upgrade Token Registry defined by [RFC7230].
o On requests bearing the :protocol pseudo-header, the :scheme and
:path pseudo-header fields SHOULD be included.
o On requests bearing the :protocol pseudo-header, the :authority
pseudo-header field is interpreted according to [RFC7540]
Section 8.1.2.3 instead of [RFC7540] Section 8.3. In particular
the server MUST not make a new TCP connection to the host and port
indicated by the :authority.
Upon receiving a CONNECT request bearing the :protocol pseudo-header
the server establishes a tunnel to another service of the protocol
type indicated by the pseudo-header. This service may or may not be
co-located with the server.
4.1. Using Extended CONNECT To Bootstrap The WebSocket Protocol
The pseudo-header :protocol MUST be included in the CONNECT request
and it MUST have a value of websocket to initiate a WebSocket
connection on an HTTP/2 stream.
Upon successfully establishing a protocol tunnel the client should
proceed with The WebSocket Protocol [RFC6455] using the HTTP/2 stream
from the CONNECT transaction as if it were the TCP connection in
[RFC6455]. Negotiation of WebSocket version and sub-protocols is
done unmodified within that stream.
4.2. Example
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[[ From Client ]] [[ From Server ]]
SETTINGS
ENABLE_CONNECT_PROTOCOL = 1
HEADERS + END_HEADERS
:method = CONNECT
:protocol = websocket
:scheme = wss
:path = /chat
:authority = server.example.com:443
HEADERS + END_HEADERS
:status = 200
DATA
GET /chat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Origin: http://example.com
Sec-WebSocket-Protocol: chat, superchat
Sec-WebSocket-Version: 13
DATA
HTTP/1.1 101 Plead The Fifth
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept:
s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
Sec-WebSocket-Protocol: chat
DATA
WebSocket Data
DATA + END_STREAM
WebSocket Data
DATA + END_STREAM
WebSocket Data
5. Design Considerations
A more native integration with HTTP/2 is certainly possible with
larger additions to HTTP/2. This design was selected to minimize the
solution complexity while still addressing the primary concern of not
being able to run HTTP/2 and WebSockets on the same port and address.
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6. About Intermediaries
This document does not change how WebSockets interacts with HTTP
proxies. If a client wishing to speak WebSockets connects via HTTP/2
to a HTTP proxy it should continue to use a traditional (i.e. not
with a :protocol pseudo-header) CONNECT to tunnel through that proxy
to the WebSocket server via HTTP.
The resulting version of HTTP on that tunnel determines whether
WebSockets is initiated directly or via a modified CONNECT request
described in this document.
7. Security Considerations
[RFC6455] ensures that non WebSockets clients, especially
XMLHttpRequest based clients, cannot make a WebSocket connection.
Its primary mechanism for doing that is the use of Sec- prefixed
request headers that cannot be created by XMLHttpRequest based
clients. This specification addresses that concern in two ways:
o The CONNECT method is prohibited from being used by XMLHttpRequest
o The use of a pseudo-header is something that is connection
specific and HTTP/2 does not ever allow to be created outside of
the protocol stack.
8. IANA Considerations
This document establishes a entry for the HTTP/2 Settings Registry
that was established by [RFC7540] Section 11.3
Name: ENABLE_CONNECT_PROTOCOL
Code: 0x8
Initial Value: 0
Specification: This document
9. Acknowledgments
The 2017 HTTP Workshop had a very productive discussion that helped
determine the key problem and acceptable level of solution
complexity.
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10. Normative References
[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>.
[RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol",
RFC 6455, DOI 10.17487/RFC6455, December 2011,
<https://www.rfc-editor.org/info/rfc6455>.
[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>.
Author's Address
Patrick McManus
Mozilla
Email: mcmanus@ducksong.com
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