Internet DRAFT - draft-ietf-wish-whip
draft-ietf-wish-whip
wish S. Murillo
Internet-Draft Millicast
Intended status: Standards Track A. Gouaillard
Expires: 1 October 2023 CoSMo Software
30 March 2023
WebRTC-HTTP ingestion protocol (WHIP)
draft-ietf-wish-whip-08
Abstract
This document describes a simple HTTP-based protocol that will allow
WebRTC-based ingestion of content into streaming services and/or
CDNs.
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 1 October 2023.
Copyright Notice
Copyright (c) 2023 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 Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Protocol Operation . . . . . . . . . . . . . . . . . . . . . 4
4.1. ICE and NAT support . . . . . . . . . . . . . . . . . . . 8
4.2. WebRTC constraints . . . . . . . . . . . . . . . . . . . 11
4.3. Load balancing and redirections . . . . . . . . . . . . . 12
4.4. STUN/TURN server configuration . . . . . . . . . . . . . 12
4.5. Authentication and authorization . . . . . . . . . . . . 14
4.6. Simulcast and scalable video coding . . . . . . . . . . . 14
4.7. Protocol extensions . . . . . . . . . . . . . . . . . . . 15
5. Security Considerations . . . . . . . . . . . . . . . . . . . 16
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
6.1. Link Relation Type: ice-server . . . . . . . . . . . . . 16
6.2. Registration of WHIP URN Sub-namespace and WHIP
Registry . . . . . . . . . . . . . . . . . . . . . . . . 16
6.3. URN Sub-namespace for WHIP . . . . . . . . . . . . . . . 17
6.3.1. Specification Template . . . . . . . . . . . . . . . 17
6.4. Registering WHIP Protocol Extensions URIs . . . . . . . . 19
6.4.1. Registration Procedure . . . . . . . . . . . . . . . 19
6.4.2. WHIP Protocol Extension Registration Template . . . . 20
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
8.1. Normative References . . . . . . . . . . . . . . . . . . 20
8.2. Informative References . . . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction
The IETF RTCWEB working group standardized JSEP ([RFC8829]), a
mechanism used to control the setup, management, and teardown of a
multimedia session. It also describes how to negotiate media flows
using the Offer/Answer Model with the Session Description Protocol
(SDP) [RFC3264] as well as the formats for data sent over the wire
(e.g., media types, codec parameters, and encryption). WebRTC
intentionally does not specify a signaling transport protocol at
application level.
Unfortunately, the lack of a standardized signaling mechanism in
WebRTC has been an obstacle to adoption as an ingestion protocol
within the broadcast/streaming industry, where a streamlined
production pipeline is taken for granted: plug in cables carrying raw
media to hardware encoders, then push the encoded media to any
streaming service or Content Delivery Network (CDN) ingest using an
ingestion protocol.
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While WebRTC can be integrated with standard signaling protocols like
SIP [RFC3261] or XMPP [RFC6120], they are not designed to be used in
broadcasting/streaming services, and there also is no sign of
adoption in that industry. RTSP [RFC7826], which is based on RTP, is
not compatible with the SDP offer/answer model [RFC3264].
This document proposes a simple protocol for supporting WebRTC as
media ingestion method which:
* Is easy to implement,
* Is as easy to use as popular IP-based broadcast protocols
* Is fully compliant with WebRTC and RTCWEB specs
* Allows for ingest both in traditional media platforms and in
WebRTC end-to-end platforms with the lowest possible latency.
* Lowers the requirements on both hardware encoders and broadcasting
services to support WebRTC.
* Is usable both in web browsers and in native encoders.
2. Terminology
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.
* WHIP client: WebRTC media encoder or producer that acts as a
client of the WHIP protocol by encoding and delivering the media
to a remote Media Server.
* WHIP endpoint: Ingest server receiving the initial WHIP request.
* WHIP endpoint URL: URL of the WHIP endpoint that will create the
WHIP resource.
* Media Server: WebRTC Media Server or consumer that establishes the
media session with the WHIP client and receives the media produced
by it.
* WHIP resource: Allocated resource by the WHIP endpoint for an
ongoing ingest session that the WHIP client can send requests for
altering the session (ICE operations or termination, for example).
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* WHIP resource URL: URL allocated to a specific media session by
the WHIP endpoint which can be used to perform operations such as
terminating the session or ICE restarts.
3. Overview
The WebRTC-HTTP Ingest Protocol (WHIP) uses an HTTP POST request to
perform a single-shot SDP offer/answer so an ICE/DTLS session can be
established between the encoder/media producer (WHIP client) and the
broadcasting ingestion endpoint (Media Server).
Once the ICE/DTLS session is set up, the media will flow
unidirectionally from the encoder/media producer (WHIP client) to the
broadcasting ingestion endpoint (Media Server). In order to reduce
complexity, no SDP renegotiation is supported, so no "m=" sections
can be added once the initial SDP offer/answer over HTTP is
completed.
+-------------+ +---------------+ +--------------+ +---------------+
| WHIP client | | WHIP endpoint | | Media Server | | WHIP resource |
+--+----------+ +---------+-----+ +------+-------+ +--------|------+
| | | |
| | | |
|HTTP POST (SDP Offer) | | |
+------------------------>+ | |
|201 Created (SDP answer) | | |
+<------------------------+ | |
| ICE REQUEST | |
+--------------------------------------->+ |
| ICE RESPONSE | |
|<---------------------------------------+ |
| DTLS SETUP | |
|<======================================>| |
| RTP/RTCP FLOW | |
+<-------------------------------------->+ |
| HTTP DELETE |
+---------------------------------------------------------->+
| 200 OK |
<-----------------------------------------------------------x
Figure 1: WHIP session setup and teardown
4. Protocol Operation
In order to set up an ingestion session, the WHIP client will
generate an SDP offer according to the JSEP rules and perform an HTTP
POST request to the configured WHIP endpoint URL.
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The HTTP POST request will have a content type of "application/sdp"
and contain the SDP offer as the body. The WHIP endpoint will
generate an SDP answer and return a "201 Created" response with a
content type of "application/sdp", the SDP answer as the body, and a
Location header field pointing to the newly created resource.
The SDP offer SHOULD use the "sendonly" attribute and the SDP answer
MUST use the "recvonly" attribute.
POST /whip/endpoint HTTP/1.1
Host: whip.example.com
Content-Type: application/sdp
Content-Length: 1326
v=0
o=- 5228595038118931041 2 IN IP4 127.0.0.1
s=-
t=0 0
a=group:BUNDLE 0 1
a=extmap-allow-mixed
a=msid-semantic: WMS
m=audio 9 UDP/TLS/RTP/SAVPF 111
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:EsAw
a=ice-pwd:bP+XJMM09aR8AiX1jdukzR6Y
a=ice-options:trickle
a=fingerprint:sha-256 DA:7B:57:DC:28:CE:04:4F:31:79:85:C4:31:67:EB:27:58:29:ED:77:2A:0D:24:AE:ED:AD:30:BC:BD:F1:9C:02
a=setup:actpass
a=mid:0
a=bundle-only
a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:mid
a=sendonly
a=msid:- d46fb922-d52a-4e9c-aa87-444eadc1521b
a=rtcp-mux
a=rtpmap:111 opus/48000/2
a=fmtp:111 minptime=10;useinbandfec=1
m=video 9 UDP/TLS/RTP/SAVPF 96 97
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:EsAw
a=ice-pwd:bP+XJMM09aR8AiX1jdukzR6Y
a=ice-options:trickle
a=fingerprint:sha-256 DA:7B:57:DC:28:CE:04:4F:31:79:85:C4:31:67:EB:27:58:29:ED:77:2A:0D:24:AE:ED:AD:30:BC:BD:F1:9C:02
a=setup:actpass
a=mid:1
a=bundle-only
a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:mid
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a=extmap:10 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id
a=extmap:11 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id
a=sendonly
a=msid:- d46fb922-d52a-4e9c-aa87-444eadc1521b
a=rtcp-mux
a=rtcp-rsize
a=rtpmap:96 VP8/90000
a=rtcp-fb:96 ccm fir
a=rtcp-fb:96 nack
a=rtcp-fb:96 nack pli
a=rtpmap:97 rtx/90000
a=fmtp:97 apt=96
HTTP/1.1 201 Created
ETag: "xyzzy"
Content-Type: application/sdp
Content-Length: 1400
Location: https://whip.example.com/resource/id
v=0
o=- 1657793490019 1 IN IP4 127.0.0.1
s=-
t=0 0
a=group:BUNDLE 0 1
a=extmap-allow-mixed
a=ice-lite
a=msid-semantic: WMS *
m=audio 9 UDP/TLS/RTP/SAVPF 111
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:38sdf4fdsf54
a=ice-pwd:2e13dde17c1cb009202f627fab90cbec358d766d049c9697
a=fingerprint:sha-256 F7:EB:F3:3E:AC:D2:EA:A7:C1:EC:79:D9:B3:8A:35:DA:70:86:4F:46:D9:2D:CC:D0:BC:81:9F:67:EF:34:2E:BD
a=candidate:1 1 UDP 2130706431 198.51.100.1 39132 typ host
a=setup:passive
a=mid:0
a=bundle-only
a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:mid
a=recvonly
a=rtcp-mux
a=rtcp-rsize
a=rtpmap:111 opus/48000/2
a=fmtp:111 minptime=10;useinbandfec=1
m=video 9 UDP/TLS/RTP/SAVPF 96 97
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:38sdf4fdsf54
a=ice-pwd:2e13dde17c1cb009202f627fab90cbec358d766d049c9697
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a=fingerprint:sha-256 F7:EB:F3:3E:AC:D2:EA:A7:C1:EC:79:D9:B3:8A:35:DA:70:86:4F:46:D9:2D:CC:D0:BC:81:9F:67:EF:34:2E:BD
a=candidate:1 1 UDP 2130706431 198.51.100.1 39132 typ host
a=setup:passive
a=mid:1
a=bundle-only
a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:mid
a=extmap:10 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id
a=extmap:11 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id
a=recvonly
a=rtcp-mux
a=rtcp-rsize
a=rtpmap:96 VP8/90000
a=rtcp-fb:96 ccm fir
a=rtcp-fb:96 nack
a=rtcp-fb:96 nack pli
a=rtpmap:97 rtx/90000
a=fmtp:97 apt=96
Figure 2: HTTP POST doing SDP O/A example
Once a session is setup, ICE consent freshness [RFC7675] SHALL be
used to detect non graceful disconnection and DTLS teardown for
session termination by either side.
To explicitly terminate a session, the WHIP client MUST perform an
HTTP DELETE request to the resource URL returned in the Location
header field of the initial HTTP POST. Upon receiving the HTTP
DELETE request, the WHIP resource will be removed and the resources
freed on the Media Server, terminating the ICE and DTLS sessions.
A Media Server terminating a session MUST follow the procedures in
[RFC7675] section 5.2 for immediate revocation of consent.
The WHIP endpoints MUST return an "405 Method Not Allowed" response
for any HTTP GET, HEAD or PUT requests on the endpoint URL in order
to reserve its usage for future versions of this protocol
specification.
The WHIP endpoints MUST support OPTIONS requests for Cross-Origin
Resource Sharing (CORS) as defined in [FETCH] and it SHOULD include
an "Accept-Post" header with a mime type value of "application/sdp"
on the "200 OK" response to any OPTIONS request received as per
[W3C.REC-ldp-20150226].
The WHIP resources MUST return an "405 Method Not Allowed" response
for any HTTP GET, HEAD, POST or PUT requests on the resource URL in
order to reserve its usage for future versions of this protocol
specification.
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4.1. ICE and NAT support
The initial offer by the WHIP client MAY be sent after the full ICE
gathering is complete with the full list of ICE candidates, or it MAY
only contain local candidates (or even an empty list of candidates)
as per [RFC8863].
In order to simplify the protocol, there is no support for exchanging
gathered trickle candidates from Media Server ICE candidates once the
SDP answer is sent. The WHIP Endpoint SHALL gather all the ICE
candidates for the Media Server before responding to the client
request and the SDP answer SHALL contain the full list of ICE
candidates of the Media Server. The Media Server MAY use ICE lite,
while the WHIP client MUST implement full ICE.
The WHIP client MAY perform trickle ICE or ICE restarts as per
[RFC8838] by sending an HTTP PATCH request to the WHIP resource URL
with a body containing a SDP fragment with MIME type "application/
trickle-ice-sdpfrag" as specified in [RFC8840]. When used for
trickle ICE, the body of this PATCH message will contain the new ICE
candidate; when used for ICE restarts, it will contain a new ICE
ufrag/pwd pair.
Trickle ICE and ICE restart support is RECOMMENDED for a WHIP
resource.
If the WHIP resource supports either Trickle ICE or ICE restarts, but
not both, it MUST return a "405 Not Implemented" response for the
HTTP PATCH requests that are not supported.
If the WHIP resource does not support the PATCH method for any
purpose, it MUST return a "501 Not Implemented" response, as
described in [RFC9110] section 6.6.2.
As the HTTP PATCH request sent by a WHIP client may be received out-
of-order by the WHIP resource, the WHIP resource MUST generate a
unique strong entity-tag identifying the ICE session as per [RFC9110]
section 2.3. The initial value of the entity-tag identifying the
initial ICE session MUST be returned in an ETag header field in the
"201 Created" response to the initial POST request to the WHIP
endpoint. It MUST also be returned in the "200 OK" of any PATCH
request that triggers an ICE restart. Note that including the ETag
in the original "201 Created" response is only REQUIRED if the WHIP
resource supports ICE restarts and OPTIONAL otherwise.
A WHIP client sending a PATCH request for performing trickle ICE MUST
include an "If-Match" header field with the latest known entity-tag
as per [RFC9110] section 3.1. When the PATCH request is received by
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the WHIP resource, it MUST compare the indicated entity-tag value
with the current entity-tag of the resource as per [RFC9110] section
3.1 and return a "412 Precondition Failed" response if they do not
match.
WHIP clients SHOULD NOT use entity-tag validation when matching a
specific ICE session is not required, such as for example when
initiating a DELETE request to terminate a session.
A WHIP resource receiving a PATCH request with new ICE candidates,
but which does not perform an ICE restart, MUST return a "204 No
Content" response without body. If the Media Server does not support
a candidate transport or is not able to resolve the connection
address, it MUST accept the HTTP request with the "204 No Content"
response and silently discard the candidate.
PATCH /resource/id HTTP/1.1
Host: whip.example.com
If-Match: "xyzzy"
Content-Type: application/trickle-ice-sdpfrag
Content-Length: 548
a=ice-ufrag:EsAw
a=ice-pwd:P2uYro0UCOQ4zxjKXaWCBui1
m=audio 9 RTP/AVP 0
a=mid:0
a=candidate:1387637174 1 udp 2122260223 192.0.2.1 61764 typ host generation 0 ufrag EsAw network-id 1
a=candidate:3471623853 1 udp 2122194687 198.51.100.1 61765 typ host generation 0 ufrag EsAw network-id 2
a=candidate:473322822 1 tcp 1518280447 192.0.2.1 9 typ host tcptype active generation 0 ufrag EsAw network-id 1
a=candidate:2154773085 1 tcp 1518214911 198.51.100.2 9 typ host tcptype active generation 0 ufrag EsAw network-id 2
a=end-of-candidates
HTTP/1.1 204 No Content
Figure 3: Trickle ICE request
A WHIP client sending a PATCH request for performing ICE restart MUST
contain an "If-Match" header field with a field-value "*" as per
[RFC9110] section 3.1.
If the HTTP PATCH request results in an ICE restart, the WHIP
resource SHALL return a "200 OK" with an "application/trickle-ice-
sdpfrag" body containing the new ICE username fragment and password
and OPTIONALLY a new set of ICE candidates for the WHIP client .
Also, the "200 OK" response for a successful ICE restart MUST contain
the new entity-tag corresponding to the new ICE session in an ETag
response header field and MAY contain a new set of ICE candidates for
the Media Server.
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If the ICE request cannot be satisfied by the WHIP resource, the
resource MUST return an appropriate HTTP error code and MUST NOT
terminate the session immediately. The WHIP client MAY retry
performing a new ICE restart or terminate the session by issuing an
HTTP DELETE request instead. In either case, the session MUST be
terminated if the ICE consent expires as a consequence of the failed
ICE restart as per [RFC7675] section 5.1.
PATCH /resource/id HTTP/1.1
Host: whip.example.com
If-Match: "*"
Content-Type: application/trickle-ice-sdpfrag
Content-Length: 54
a=ice-ufrag:ysXw
a=ice-pwd:vw5LmwG4y/e6dPP/zAP9Gp5k
HTTP/1.1 200 OK
ETag: "abccd"
Content-Type: application/trickle-ice-sdpfrag
Content-Length: 102
a=ice-lite
a=ice-ufrag:289b31b754eaa438
a=ice-pwd:0b66f472495ef0ccac7bda653ab6be49ea13114472a5d10a
Figure 4: ICE restart request
Because the WHIP client needs to know the entity-tag associated with
the ICE session in order to send new ICE candidates, it MUST buffer
any gathered candidates before it receives the HTTP response to the
initial POST request or the PATCH request with the new entity-tag
value. Once it knows the entity-tag value, the WHIP client SHOULD
send a single aggregated HTTP PATCH request with all the ICE
candidates it has buffered so far.
In case of unstable network conditions, the ICE restart HTTP PATCH
requests and responses might be received out of order. In order to
mitigate this scenario, when the client performs an ICE restart, it
MUST discard any previous ice username and passwords fragments and
ignore any further HTTP PATCH response received from a pending HTTP
PATCH request. WHIP clients MUST apply only the ICE information
received in the response to the last sent request. If there is a
mismatch between the ICE information at the client and at the server
(because of an out-of-order request), the STUN requests will contain
invalid ICE information and will be rejected by the server. When
this situation is detected by the WHIP Client, it SHOULD send a new
ICE restart request to the server.
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4.2. WebRTC constraints
In the specific case of media ingestion into a streaming service,
some assumptions can be made about the server-side which simplifies
the WebRTC compliance burden, as detailed in WebRTC-gateway document
[I-D.draft-ietf-rtcweb-gateways].
In order to reduce the complexity of implementing WHIP in both
clients and Media Servers, WHIP imposes the following restrictions
regarding WebRTC usage:
Both the WHIP client and the WHIP endpoint SHALL use SDP bundle
[RFC9143]. Each "m=" section MUST be part of a single BUNDLE group.
Hence, when a WHIP client sends an SDP offer, it MUST include a
"bundle-only" attribute in each bundled "m=" section. The WHIP
client and the Media Server MUST support multiplexed media associated
with the BUNDLE group as per [RFC9143] section 9. In addition, per
[RFC9143] the WHIP client and Media Server will use RTP/RTCP
multiplexing for all bundled media. The WHIP client and Media Server
SHOULD include the "rtcp-mux-only" attribute in each bundled "m="
sections as per [RFC8858].
This version of the specification only supports, at most, a single
audio and video MediaStreamTrack in a single MediaStream as defined
in [[!RFC8830]] and therefore, all "m=" sections MUST contain an
"msid" attribute with the same value. However, it would be possible
for future revisions of this spec to allow more than a single
MediaStream or MediaStreamTrack of each media kind, so in order to
ensure forward compatibility, if the number of audio and or video
tracks or number streams is not supported by the WHIP Endpoint, it
MUST reject the HTTP POST request with a "406 Not Acceptable" error
response.
Furthermore, the WHIP Endpoint SHOULD NOT reject individual "m="
sections as per [RFC8829] section 5.3.1 in case there is any error
processing the "m=" section, but reject the HTTP POST request with a
"406 Not Acceptable" error response to prevent having partially
successful WHIP sessions.
When a WHIP client sends an SDP offer, it SHOULD insert an SDP
"setup" attribute with an "actpass" attribute value, as defined in
[RFC8842]. However, if the WHIP client only implements the DTLS
client role, it MAY use an SDP "setup" attribute with an "active"
attribute value. If the WHIP endpoint does not support an SDP offer
with an SDP "setup" attribute with an "active" attribute value, it
SHOULD reject the request with a "422 Unprocessable Entity" response.
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NOTE: [RFC8842] defines that the offerer must insert an SDP "setup"
attribute with an "actpass" attribute value. However, the WHIP
client will always communicate with a Media Server that is expected
to support the DTLS server role, in which case the client might
choose to only implement support for the DTLS client role.
Trickle ICE and ICE restarts support is OPTIONAL for both the WHIP
clients and Media Servers as explained in section 4.1.
4.3. Load balancing and redirections
WHIP endpoints and Media Servers might not be colocated on the same
server, so it is possible to load balance incoming requests to
different Media Servers. WHIP clients SHALL support HTTP redirection
via the "307 Temporary Redirect" response as described in [RFC9110]
section 6.4.7. The WHIP resource URL MUST be a final one, and
redirections are not required to be supported for the PATCH and
DELETE requests sent to it.
In case of high load, the WHIP endpoints MAY return a "503 Service
Unavailable" response indicating that the server is currently unable
to handle the request due to a temporary overload or scheduled
maintenance, which will likely be alleviated after some delay. The
WHIP endpoint might send a Retry-After header field indicating the
minimum time that the user agent ought to wait before making a
follow-up request.
4.4. STUN/TURN server configuration
The WHIP endpoint MAY return STUN/TURN server configuration URLs and
credentials usable by the client in the "201 Created" response to the
HTTP POST request to the WHIP endpoint URL.
Each STUN/TURN server will be returned using the "Link" header field
[RFC8288] with a "rel"" attribute value of "ice-server". The Link
target URI is the server URL as defined in [RFC7064] and [RFC7065].
The credentials are encoded in the Link target attributes as follows:
* username: If the Link header field represents a TURN server, and
credential-type is "password", then this attribute specifies the
username to use with that TURN server.
* credential: If the "credential-type" attribute is missing or has a
"password" value, the credential attribute represents a long-term
authentication password, as described in [RFC8489], Section 10.2.
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* credential-type: If the Link header field represents a TURN
server, then this attribute specifies how the credential attribute
value should be used when that TURN server requests authorization.
The default value if the attribute is not present is "password".
Link: <stun:stun.example.net>; rel="ice-server"
Link: <turn:turn.example.net?transport=udp>; rel="ice-server";
username="user"; credential="myPassword"; credential-type="password"
Link: <turn:turn.example.net?transport=tcp>; rel="ice-server";
username="user"; credential="myPassword"; credential-type="password"
Link: <turns:turn.example.net?transport=tcp>; rel="ice-server";
username="user"; credential="myPassword"; credential-type="password"
Figure 5: Example ICE server configuration
NOTE: The naming of both the "rel" attribute value of "ice-server"
and the target attributes follows the one used on the W3C WebRTC
recommendation [W3C.REC-webrtc-20210126] RTCConfiguration dictionary
in section 4.2.1. "rel" attribute value of "ice-server" is not
prepended with the "urn:ietf:params:whip:" so it can be reused by
other specifications which may use this mechanism to configure the
usage of STUN/TURN servers.
NOTE: Depending on the ICE Agent implementation, the WHIP client may
need to call the setConfiguration method before calling the
setLocalDescription method with the local SDP offer in order to avoid
having to perform an ICE restart for applying the updated STUN/TURN
server configuration on the next ICE gathering phase.
There are some WebRTC implementations that do not support updating
the STUN/TURN server configuration after the local offer has been
created as specified in [RFC8829] section 4.1.18. In order to
support these clients, the WHIP endpoint MAY also include the STUN/
TURN server configuration on the responses to OPTIONS request sent to
the WHIP endpoint URL before the POST request is sent. However, this
method is not NOT RECOMMENDED and if supported by the underlying WHIP
Client's webrtc implementation, the WHIP Client SHOULD wait for the
information to be returned by the WHIP Endpoint on the response of
the HTTP POST request instead.
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The generation of the TURN server credentials may require performing
a request to an external provider, which can both add latency to the
OPTIONS request processing and increase the processing required to
handle that request. In order to prevent this, the WHIP Endpoint
SHOULD NOT return the STUN/TURN server configuration if the OPTIONS
request is a preflight request for CORS, that is, if The OPTIONS
request does not contain an Access-Control-Request-Method with "POST"
value and the the Access-Control-Request-Headers HTTP header does not
contain the "Link" value.
It might be also possible to configure the STUN/TURN server URLs with
long term credentials provided by either the broadcasting service or
an external TURN provider on the WHIP client, overriding the values
provided by the WHIP endpoint.
4.5. Authentication and authorization
WHIP endpoints and resources MAY require the HTTP request to be
authenticated using an HTTP Authorization header field with a Bearer
token as specified in [RFC6750] section 2.1. WHIP clients MUST
implement this authentication and authorization mechanism and send
the HTTP Authorization header field in all HTTP requests sent to
either the WHIP endpoint or resource except the preflight OPTIONS
requests for CORS.
The nature, syntax, and semantics of the bearer token, as well as how
to distribute it to the client, is outside the scope of this
document. Some examples of the kind of tokens that could be used
are, but are not limited to, JWT tokens as per [RFC6750] and
[RFC8725] or a shared secret stored on a database. The tokens are
typically made available to the end user alongside the WHIP endpoint
URL and configured on the WHIP clients (similar to the way RTMP URLs
and Stream Keys are distributed).
WHIP endpoints and resources could perform the authentication and
authorization by encoding an authentication token within the URLs for
the WHIP endpoints or resources instead. In case the WHIP client is
not configured to use a bearer token, the HTTP Authorization header
field must not be sent in any request.
4.6. Simulcast and scalable video coding
Simulcast as per [RFC8853] MAY be supported by both the Media Servers
and WHIP clients through negotiation in the SDP offer/answer.
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If the client supports simulcast and wants to enable it for
publishing, it MUST negotiate the support in the SDP offer according
to the procedures in [RFC8853] section 5.3. A server accepting a
simulcast offer MUST create an answer according to the procedures
[RFC8853] section 5.3.2.
It is possible for both Media Servers and WHIP clients to support
Scalable Video Coding (SVC). However, as there is no universal
negotiation mechanism in SDP for SVC, the encoder must consider the
negotiated codec(s), intended usage, and SVC support in available
decoders when configuring SVC.
4.7. Protocol extensions
In order to support future extensions to be defined for the WHIP
protocol, a common procedure for registering and announcing the new
extensions is defined.
Protocol extensions supported by the WHIP server MUST be advertised
to the WHIP client in the "201 Created" response to the initial HTTP
POST request sent to the WHIP endpoint. The WHIP endpoint MUST
return one "Link" header field for each extension, with the extension
"rel" type attribute and the URI for the HTTP resource that will be
available for receiving requests related to that extension.
Protocol extensions are optional for both WHIP clients and servers.
WHIP clients MUST ignore any Link attribute with an unknown "rel"
attribute value and WHIP servers MUST NOT require the usage of any of
the extensions.
Each protocol extension MUST register a unique "rel" attribute value
at IANA starting with the prefix: "urn:ietf:params:whip:ext" as
defined in Section 6.3.
For example, considering a potential extension of server-to-client
communication using server-sent events as specified in
https://html.spec.whatwg.org/multipage/server-sent-
events.html#server-sent-events, the URL for connecting to the server
side event resource for the published stream could be returned in the
initial HTTP "201 Created" response with a "Link" header field and a
"rel" attribute of "urn:ietf:params:whip:ext:example:server-sent-
events". (This document does not specify such an extension, and uses
it only as an example.)
In this theoretical case, the "201 Created" response to the HTTP POST
request would look like:
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HTTP/1.1 201 Created
Content-Type: application/sdp
Location: https://whip.example.com/resource/id
Link: <https://whip.ietf.org/publications/213786HF/sse>;
rel="urn:ietf:params:whip:ext:example:server-side-events"
5. Security Considerations
HTTPS SHALL be used in order to preserve the WebRTC security model.
6. IANA Considerations
This specification adds a new link relation type and a registry for
URN sub-namespaces for WHIP protocol extensions.
6.1. Link Relation Type: ice-server
The link relation type below has been registered by IANA per
Section 4.2 of [RFC8288].
Relation Name: ice-server
Description: For the WHIP protocol, conveys the STUN and TURN servers
that can be used by an ICE Agent to establish a connection with a
peer.
Reference: TBD
6.2. Registration of WHIP URN Sub-namespace and WHIP Registry
IANA has added an entry to the "IETF URN Sub-namespace for Registered
Protocol Parameter Identifiers" registry and created a sub-namespace
for the Registered Parameter Identifier as per [RFC3553]:
"urn:ietf:params:whip".
To manage this sub-namespace, IANA has created the "WebRTC-HTTP
ingestion protocol (WHIP) URIs" registry, which is used to manage
entries within the "urn:ietf:params:whip" namespace. The registry
description is as follows:
* Registry name: WHIP
* Specification: this document (RFC TBD)
* Repository: See Section Section 6.3
* Index value: See Section Section 6.3
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6.3. URN Sub-namespace for WHIP
WHIP Endpoint utilizes URIs to identify the supported WHIP protocol
extensions on the "rel" attribute of the Link header as defined in
Section 4.7.
This section creates and registers an IETF URN Sub-namespace for use
in the WHIP specifications and future extensions.
6.3.1. Specification Template
Namespace ID:
* The Namespace ID "whip" has been assigned.
Registration Information:
* Version: 1
* Date: TBD
Declared registrant of the namespace:
* Registering organization: The Internet Engineering Task Force.
* Designated contact: A designated expert will monitor the WHIP
public mailing list, "wish@ietf.org".
Declaration of Syntactic Structure:
* The Namespace Specific String (NSS) of all URNs that use the
"whip" Namespace ID shall have the following structure:
urn:ietf:params:whip:{type}:{name}:{other}.
* The keywords have the following meaning:
- type: The entity type. This specification only defines the
"ext" type.
- name: A required US-ASCII string that conforms to the URN
syntax requirements (see [RFC8141]) and defines a major
namespace of a WHIP protocol extension. The value MAY also be
an industry name or organization name.
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- other: Any US-ASCII string that conforms to the URN syntax
requirements (see [RFC8141]) and defines the sub-namespace
(which MAY be further broken down in namespaces delimited by
colons) as needed to uniquely identify an WHIP protocol
extension.
Relevant Ancillary Documentation:
* None
Identifier Uniqueness Considerations:
* The designated contact shall be responsible for reviewing and
enforcing uniqueness.
Identifier Persistence Considerations:
* Once a name has been allocated, it MUST NOT be reallocated for a
different purpose.
* The rules provided for assignments of values within a sub-
namespace MUST be constructed so that the meanings of values
cannot change.
* This registration mechanism is not appropriate for naming values
whose meanings may change over time.
Process of Identifier Assignment:
* Namespace with type "ext" (e.g., "urn:ietf:params:whip:ext") is
reserved for IETF-approved WHIP specifications.
Process of Identifier Resolution:
* None specified.
Rules for Lexical Equivalence:
* No special considerations; the rules for lexical equivalence
specified in [RFC8141] apply.
Conformance with URN Syntax:
* No special considerations.
Validation Mechanism:
* None specified.
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Scope:
* Global.
6.4. Registering WHIP Protocol Extensions URIs
This section defines the process for registering new WHIP protocol
extensions URIs with IANA in the "WebRTC-HTTP ingestion protocol
(WHIP) URIs" registry (see Section 6.3).
A WHIP Protocol Extension URI is used as a value in the "rel"
attribute of the Link header as defined in Section 4.7 for the
purpose of signaling the WHIP protocol extensions supported by the
WHIP Endpoints.
WHIP Protocol Extensions URIs have a "ext" type as defined in
Section 6.3.
6.4.1. Registration Procedure
The IETF has created a mailing list, "wish@ietf.org", which can be
used for public discussion of WHIP protocol extensions proposals
prior to registration. Use of the mailing list is strongly
encouraged. The IESG has appointed a designated expert [RFC8126] who
will monitor the wish@ietf.org mailing list and review registrations.
Registration of new "ext" type URI (in the namespace
"urn:ietf:params:whip:ext") belonging to a WHIP Protocol Extension
MUST be reviewed by the designated expert and published in an RFC.
An RFC is REQUIRED for the registration of new value data types that
modify existing properties. An RFC is also REQUIRED for registration
of WHIP Protocol Extensions URIs that modify WHIP Protocol Extensions
previously documented in an existing RFC.
The registration procedure begins when a completed registration
template, defined in the sections below, is sent to wish@ietf.org and
iana@iana.org. Within two weeks, the designated expert is expected
to tell IANA and the submitter of the registration whether the
registration is approved, approved with minor changes, or rejected
with cause. When a registration is rejected with cause, it can be
resubmitted if the concerns listed in the cause are addressed.
Decisions made by the designated expert can be appealed to the IESG
Applications Area Director, then to the IESG. They follow the normal
appeals procedure for IESG decisions.
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Once the registration procedure concludes successfully, IANA creates
or modifies the corresponding record in the WHIP Protocol Extension
registry. The completed registration template is discarded.
An RFC specifying one or more new WHIP Protocol Extension URIs MUST
include the completed registration templates, which MAY be expanded
with additional information. These completed templates are intended
to go in the body of the document, not in the IANA Considerations
section. The RFC SHOULD include any attributes defined.
6.4.2. WHIP Protocol Extension Registration Template
A WHIP Protocol Extension URI is defined by completing the following
template:
* URI: A unique URI for the WHIP Protocol Extension (e.g.,
"urn:ietf:params:whip:ext:example:server-sent-events").
* Reference: A formal reference to the publicly available
specification
* Name: A descriptive name of the WHIP Protocol Extension extension
(e.g., "Sender Side events").
* Description: A short phrase describing the function of the
extension
* Contact information: Contact information for the organization or
person making the registration
7. Acknowledgements
The authors wish to thank Lorenzo Miniero, Juliusz Chroboczek, Adam
Roach, Nils Ohlmeier, Christer Holmberg, Cameron Elliott, Gustavo
Garcia, Jonas Birme and everyone else in the WebRTC community that
have provided comments, feedback, text and improvement proposals on
the document and contributed early implementations of the spec.
8. References
8.1. Normative References
[FETCH] WHATWG, "Fetch - Living Standard", n.d.,
<https://fetch.spec.whatwg.org>.
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[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>.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264,
DOI 10.17487/RFC3264, June 2002,
<https://www.rfc-editor.org/rfc/rfc3264>.
[RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An
IETF URN Sub-namespace for Registered Protocol
Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June
2003, <https://www.rfc-editor.org/rfc/rfc3553>.
[RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
Framework: Bearer Token Usage", RFC 6750,
DOI 10.17487/RFC6750, October 2012,
<https://www.rfc-editor.org/rfc/rfc6750>.
[RFC7064] Nandakumar, S., Salgueiro, G., Jones, P., and M. Petit-
Huguenin, "URI Scheme for the Session Traversal Utilities
for NAT (STUN) Protocol", RFC 7064, DOI 10.17487/RFC7064,
November 2013, <https://www.rfc-editor.org/rfc/rfc7064>.
[RFC7065] Petit-Huguenin, M., Nandakumar, S., Salgueiro, G., and P.
Jones, "Traversal Using Relays around NAT (TURN) Uniform
Resource Identifiers", RFC 7065, DOI 10.17487/RFC7065,
November 2013, <https://www.rfc-editor.org/rfc/rfc7065>.
[RFC7675] Perumal, M., Wing, D., Ravindranath, R., Reddy, T., and M.
Thomson, "Session Traversal Utilities for NAT (STUN) Usage
for Consent Freshness", RFC 7675, DOI 10.17487/RFC7675,
October 2015, <https://www.rfc-editor.org/rfc/rfc7675>.
[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>.
[RFC8288] Nottingham, M., "Web Linking", RFC 8288,
DOI 10.17487/RFC8288, October 2017,
<https://www.rfc-editor.org/rfc/rfc8288>.
[RFC8489] Petit-Huguenin, M., Salgueiro, G., Rosenberg, J., Wing,
D., Mahy, R., and P. Matthews, "Session Traversal
Utilities for NAT (STUN)", RFC 8489, DOI 10.17487/RFC8489,
February 2020, <https://www.rfc-editor.org/rfc/rfc8489>.
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[RFC8725] Sheffer, Y., Hardt, D., and M. Jones, "JSON Web Token Best
Current Practices", BCP 225, RFC 8725,
DOI 10.17487/RFC8725, February 2020,
<https://www.rfc-editor.org/rfc/rfc8725>.
[RFC8829] Uberti, J., Jennings, C., and E. Rescorla, Ed.,
"JavaScript Session Establishment Protocol (JSEP)",
RFC 8829, DOI 10.17487/RFC8829, January 2021,
<https://www.rfc-editor.org/rfc/rfc8829>.
[RFC8838] Ivov, E., Uberti, J., and P. Saint-Andre, "Trickle ICE:
Incremental Provisioning of Candidates for the Interactive
Connectivity Establishment (ICE) Protocol", RFC 8838,
DOI 10.17487/RFC8838, January 2021,
<https://www.rfc-editor.org/rfc/rfc8838>.
[RFC8840] Ivov, E., Stach, T., Marocco, E., and C. Holmberg, "A
Session Initiation Protocol (SIP) Usage for Incremental
Provisioning of Candidates for the Interactive
Connectivity Establishment (Trickle ICE)", RFC 8840,
DOI 10.17487/RFC8840, January 2021,
<https://www.rfc-editor.org/rfc/rfc8840>.
[RFC8842] Holmberg, C. and R. Shpount, "Session Description Protocol
(SDP) Offer/Answer Considerations for Datagram Transport
Layer Security (DTLS) and Transport Layer Security (TLS)",
RFC 8842, DOI 10.17487/RFC8842, January 2021,
<https://www.rfc-editor.org/rfc/rfc8842>.
[RFC8853] Burman, B., Westerlund, M., Nandakumar, S., and M. Zanaty,
"Using Simulcast in Session Description Protocol (SDP) and
RTP Sessions", RFC 8853, DOI 10.17487/RFC8853, January
2021, <https://www.rfc-editor.org/rfc/rfc8853>.
[RFC8858] Holmberg, C., "Indicating Exclusive Support of RTP and RTP
Control Protocol (RTCP) Multiplexing Using the Session
Description Protocol (SDP)", RFC 8858,
DOI 10.17487/RFC8858, January 2021,
<https://www.rfc-editor.org/rfc/rfc8858>.
[RFC8863] Holmberg, C. and J. Uberti, "Interactive Connectivity
Establishment Patiently Awaiting Connectivity (ICE PAC)",
RFC 8863, DOI 10.17487/RFC8863, January 2021,
<https://www.rfc-editor.org/rfc/rfc8863>.
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[RFC9110] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/rfc/rfc9110>.
[RFC9143] Holmberg, C., Alvestrand, H., and C. Jennings,
"Negotiating Media Multiplexing Using the Session
Description Protocol (SDP)", RFC 9143,
DOI 10.17487/RFC9143, February 2022,
<https://www.rfc-editor.org/rfc/rfc9143>.
[W3C.REC-ldp-20150226]
Malhotra, A., Ed., Arwe, J., Ed., and S. Speicher, Ed.,
"Linked Data Platform 1.0", W3C REC REC-ldp-20150226, W3C
REC-ldp-20150226, 26 February 2015,
<https://www.w3.org/TR/2015/REC-ldp-20150226/>.
8.2. Informative References
[I-D.draft-ietf-rtcweb-gateways]
Alvestrand, H. T. and U. Rauschenbach, "WebRTC Gateways",
Work in Progress, Internet-Draft, draft-ietf-rtcweb-
gateways-02, 21 January 2016,
<https://datatracker.ietf.org/doc/html/draft-ietf-rtcweb-
gateways-02>.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002,
<https://www.rfc-editor.org/rfc/rfc3261>.
[RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 6120, DOI 10.17487/RFC6120,
March 2011, <https://www.rfc-editor.org/rfc/rfc6120>.
[RFC7826] Schulzrinne, H., Rao, A., Lanphier, R., Westerlund, M.,
and M. Stiemerling, Ed., "Real-Time Streaming Protocol
Version 2.0", RFC 7826, DOI 10.17487/RFC7826, December
2016, <https://www.rfc-editor.org/rfc/rfc7826>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/rfc/rfc8126>.
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[RFC8141] Saint-Andre, P. and J. Klensin, "Uniform Resource Names
(URNs)", RFC 8141, DOI 10.17487/RFC8141, April 2017,
<https://www.rfc-editor.org/rfc/rfc8141>.
[W3C.REC-webrtc-20210126]
Jennings, C., Ed., Boström, H., Ed., and J. Bruaroey, Ed.,
"WebRTC 1.0: Real-Time Communication Between Browsers",
W3C REC REC-webrtc-20210126, W3C REC-webrtc-20210126, 26
January 2021,
<https://www.w3.org/TR/2021/REC-webrtc-20210126/>.
Authors' Addresses
Sergio Garcia Murillo
Millicast
Email: sergio.garcia.murillo@cosmosoftware.io
Alexandre Gouaillard
CoSMo Software
Email: alex.gouaillard@cosmosoftware.io
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