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draft-aboba-avtcore-quic-multiplexing-00.txt
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AVTCORE Working Group B. Aboba
INTERNET-DRAFT Microsoft Corporation
Category: Informational P. Thatcher
Expires: April 24, 2018 Google
C. Perkins
University of Glasgow
23 October 2017
QUIC Multiplexing
draft-aboba-avtcore-quic-multiplexing-00.txt
Abstract
This document describes potential approaches to multiplexing of QUIC
along with RTP, RTCP, DTLS, STUN, TURN and ZRTP in WebRTC peer-to-
peer data exchange.
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 http://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 24, 2018.
Aboba, et. al Informational [Page 1]
INTERNET-DRAFT QUIC Multiplexing 23 October 2017
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
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. QUIC Header Changes . . . . . . . . . . . . . . . . . . . 4
2.2. Multiplexing Shim . . . . . . . . . . . . . . . . . . . . 5
2.3. Heuristics . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Security Considerations . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. Informative references . . . . . . . . . . . . . . . . . . 7
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
Aboba, et. al Informational [Page 2]
INTERNET-DRAFT QUIC Multiplexing 23 October 2017
1. Introduction
There are a number of ways in which communication between WebRTC
peers may utilize QUIC. One of these is transport of RTP over QUIC,
described in [I-D.rtpfolks-quic-rtp-over-quic]. Another is use of
QUIC [I-D.ietf-quic-transport] for data exchange. A Javascript API
for use of QUIC in WebRTC data exchange has been incorporated into
the ORTC API [ORTC], under development within the W3C ORTC Community
Group.
In a WebRTC scenario where ICE [RFC5245] is utilized for NAT
traversal, SRTP [RFC3711] is keyed using DTLS-SRTP [RFC5764] and QUIC
is used for data exchange, RTP/RTCP [RFC3550] STUN [RFC5389], TURN
[RFC5766], DTLS [RFC6347], ZRTP [RFC6189] and QUIC may all need to be
multiplexed over a single ICE transport.
As noted in [RFC7983] Figure 3, protocol demultiplexing currently
relies upon differentiation based on the first octet, as follows:
+----------------+
| [0..3] -+--> forward to STUN
| |
| [16..19] -+--> forward to ZRTP
| |
packet --> | [20..63] -+--> forward to DTLS
| |
| [64..79] -+--> forward to TURN Channel
| |
| [128..191] -+--> forward to RTP/RTCP
+----------------+
Figure 1: DTLS-SRTP receiver's packet demultiplexing algorithm.
As noted by Colin Perkins and Lars Eggert in [QUIC-Issue] this
creates a potential conflict with the current design of the QUIC
headers described in [I-D.ietf-quic-transport], since the first octet
of the QUIC header is either:
+-+-+-+-+-+-+-+-+
|1| Type (7) | Long header packet
+-+-+-+-+-+-+-+-+
which potentially produces values of the first octet in the range
129-134, conflicting with RTP/RTCP, or
+-+-+-+-+-+-+-+-+
|0|C|K| Type (5)| Short header packet
+-+-+-+-+-+-+-+-+
Aboba, et. al Informational [Page 3]
INTERNET-DRAFT QUIC Multiplexing 23 October 2017
which produces values for the first octet in the ranges 1-3, 33-35,
65-67 or 97-99, potentially conflicting with STUN, DTLS and TURN.
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Solutions
This section presents potential solutions to the QUIC multiplexing
problem, including changes to the QUIC headers, addition of a
multiplexing octet and use of heuristics.
2.1. QUIC Header Changes
As noted in [QUIC-Issue], one potential solution involves changes to
the QUIC headers, such as setting the top two bits of the first octet
of a QUIC packet to 1. This would imply a reduction in the size of
the type fields:
+-+-+-+-+-+-+-+-+
|1|1|1|Type (5) | Long header packet
+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+
|1|1|0|C|K|Type3| Short header packet
+-+-+-+-+-+-+-+-+
Note: [QUIC-Spin] proposes to add a spin bit to the type octet within
the QUIC header, in order to allow for RTT calculation. This would
leave 4 bits for the type field in the long header packet and 2 bits
for the type field in the short header, which would accomodate the
type field values allocated in [I-D.ietf-quic-transport].
2.1.1. Pros and Cons
The advantage to this approach is that it adds no additional overhead
on-the-wire. However it does require a reduction in the size of the
QUIC Type fields and could potentially require allocation of the
following initial octet code points for QUIC: For the Long header,
225-230 (241-246 when the spin bit is set) and for the Short header,
193-195 (209-11 with spin bit set), 209-211 (225-227 with spin bit
set) and 217-219 (233-235 with the spin bit set). Utilizing all of
these code points for QUIC would leave limited code points available
for future allocations.
Aboba, et. al Informational [Page 4]
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2.2. Multiplexing Shim
In this approach, an initial octet not allocated within [RFC7983]
would be prepended to each QUIC packet, allowing QUIC packets to be
differentiated from RTP, RTCP, DTLS, STUN, TURN and ZRTP based on the
first octet alone. As an example, an octet with decimal value 192
could be used:
+-+-+-+-+-+-+-+-+
|1|1|0|0|0|0|0|0|
+-+-+-+-+-+-+-+-+
2.2.1. Pros and Cons
Advantages of this approach include simplicity and the consumption of
only a single initial octet code point for demultiplexing of QUIC.
The disadvantage is the addition of a single octet of overhead to
every QUIC packet, which could impact performance where small
payloads are exchanged, such as in peer-to-peer gaming.
2.3. Heuristics
During the QUIC WG interim in Seattle, Martin Thomson suggested the
following heuristics for differentiation of QUIC packets from
RTP/RTCP/DTLS/STUN/TURN/ZRTP:
1. Demultiplex differently during the "QUIC handshake"
and "steady state".
2. During handshake, we only need to worry about the QUIC
Long header, which simplifies the logic.
a. Force all handshake packets to utilize the QUIC Long header.
b. The QUIC Long header (0x1XXXXXXX) (or 0x11XXXXXX with
the spin bit set) does not conflict with STUN (0x000000XX),
DTLS (0x000XXXXX), or TURN Channel (0x01XXXXXX).
c. The QUIC Long header does conflict with RTP/RTCP (0x10XXXXXX),
but those packets typically aren't sent until the QUIC
handshake is completed. Corner case: an application starts
off with audio and video keyed with DTLS-SRTP without QUIC,
then the application wishes to add QUIC data (e.g. the user
clicks on the "white-board" icon).
i. Alternative: force the RTP padding bit to 1
using a one-byte pad if there isn't already
padding (pad == 0x01). Then force QUIC to have
a type < 64 (the current max is 8).
ii. Alternative: Disallow QUIC in this case, use SCTP data
exchange instead.
3. During "steady state", we only need to worry about the QUIC
Short header.
Aboba, et. al Informational [Page 5]
INTERNET-DRAFT QUIC Multiplexing 23 October 2017
a. QUIC doesn't need the Long header after the handshake.
b. The QUIC Short header (0x0XXXXXXX or 0x01XXXXXX with
the spin bit set) does not conflict with RTP/RTCP
(0x10XXXXXX), so we only need to worry about
conflicts with STUN/TURN/DTLS/ZRTP.
c. Disallow simultaneous use of DTLS and QUIC
Short header packets.
i. Alternative: when using DTLS and QUIC at the same
time, only use the QUIC Long header. Not optimal,
but isn't really needed.
d. ICE can be demuxed using the magic cookie and checksum.
i. Alternative: STUN can only conflict with 3
QUIC packet types: Version Negotiation,
Client Initial, and Server Stateless Retry.
Out of those, none should be needed during
the steady state.
e. You shouldn't need to demultiplex QUIC with TURN channel
data or other STUN traffic. But what about consent
packets?
2.3.1. Pros and Cons
This approach has the advantage that it requires no changes to QUIC
headers, nor does it add any overhead to QUIC packets. Disadvantages
include additional complexity within the multiplexing algorithm, the
consumption of additional multiplexing code points, and potential
future difficulties in adapting the algorithm to support changes to
the QUIC protocol or additional protocols to be multiplexed.
3. Security Considerations
The solutions discussed in this document could potentially introduce
some additional security considerations beyond those detailed in
[RFC7983].
Due to the additional logic required, if mis-implemented, heuristics
have the potential to misclassify packets.
When QUIC is used for only for data exchange, the TLS-within-QUIC
exchange [I-D.ietf-quic-tls] derives keys used solely to protect the
QUIC data packets. If properly implemented, this should not affect
the transport of SRTP nor the derivation of SRTP keys via DTLS-SRTP,
but if badly implemented, both transport and key derivation could be
adversely impacted.
Aboba, et. al Informational [Page 6]
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4. IANA Considerations
This document does not require actions by IANA.
5. References
5.1. Informative References
[I-D.ietf-quic-tls]
Thomson, M. and S. Turner, "Using Transport Layer
Security (TLS) to Secure QUIC", draft-ietf-quic-tls-07
(work in progress), October 2017.
[I-D.ietf-quic-transport]
Iyengar, J. and M. Thomson, "QUIC: A UDP-Based
Multiplexed and Secure Transport", draft-ietf-quic-
transport-07 (work in progress), October 2017.
[I-D.rtpfolks-quic-rtp-over-quic]
Ott, J., Even, R., Perkins, C. and V. Singh, "RTP over
QUIC", Internet draft (work in progress), draft-rtpfolks-
quic-rtp-over-quic-01, September 1, 2017.
[ORTC] Raymond, R., Aboba, B. and J. Uberti, "Object RTC (ORTC)
API for WebRTC", W3C, http://draft.ortc.org/, October
2017.
[QUIC-Issue] Perkins, C., "QUIC header format/demultiplexing",
https://github.com/quicwg/base-drafts/issues/426, March,
2017.
[QUIC-Spin] Huitema, C., "QUIC Latency Spin Bit",
https://github.com/quicwg/base-drafts/issues/609, June,
2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI
10.17487/RFC2119, March 1997, <http://www.rfc-
editor.org/info/rfc2119>.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <http://www.rfc-editor.org/info/rfc3550>.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol
(SRTP)", RFC 3711, DOI 10.17487/RFC3711, March 2004,
Aboba, et. al Informational [Page 7]
INTERNET-DRAFT QUIC Multiplexing 23 October 2017
<http://www.rfc-editor.org/info/rfc3711>.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245, DOI
10.17487/RFC5245, April 2010, <http://www.rfc-
editor.org/info/rfc5245>.
[RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
"Session Traversal Utilities for NAT (STUN)", RFC 5389,
DOI 10.17487/RFC5389, October 2008, <http://www.rfc-
editor.org/info/rfc5389>.
[RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer
Security (DTLS) Extension to Establish Keys for the
Secure Real-time Transport Protocol (SRTP)", RFC 5764,
DOI 10.17487/RFC5764, May 2010, <http://www.rfc-
editor.org/info/rfc5764>.
[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, <http://www.rfc-
editor.org/info/rfc5766>.
[RFC6189] Zimmermann, P., Johnston, A., Ed., and J. Callas, "ZRTP:
Media Path Key Agreement for Unicast Secure RTP", RFC
6189, DOI 10.17487/RFC6189, April 2011, <http://www.rfc-
editor.org/info/rfc6189>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <http://www.rfc-editor.org/info/rfc6347>.
[RFC7983] Petit-Huguenin, M. and G. Salgueiro, "Multiplexing Scheme
Updates for Secure Real-time Transport Protocol (SRTP)
Extension for Datagram Transport Layer Security (DTLS)",
RFC 7983, September 2016.
Aboba, et. al Informational [Page 8]
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Acknowledgments
We would like to thank Martin Thomson, Roni Even and other
participants in the IETF QUIC and AVTCORE working groups for their
discussion of the QUIC multiplexing issue, and their input relating
to potential solutions.
Authors' Addresses
Bernard Aboba
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
USA
Email: [email protected]
Peter Thatcher
Google
747 6th St S
Kirkland, WA 98033
USA
Email: [email protected]
Colin Perkins
University of Glasgow
School of Computing Science
University of Glasgow
Glasgow G12 8QQ
United Kingdom
Email: [email protected]
Aboba, et. al Informational [Page 9]