Internet Engineering Task Force N. Kuhn
Internet-Draft
Intended status: Informational E. Stephan
Expires: 7 September 2022 Orange
G. Fairhurst
T. Jones
University of Aberdeen
C. Huitema
Private Octopus Inc.
6 March 2022
BDP Frame Extension
draft-kuhn-quic-bdpframe-extension-00
Abstract
This draft describes the BDP Frame extension for QUIC. It enables
the exchange of information related to the path characteristics
between the client and the server during a connection. This
information can later be exploited when a new connection is
established.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Notations and terms . . . . . . . . . . . . . . . . . . . 2
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. BDP Frame . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. BDP Frame Format . . . . . . . . . . . . . . . . . . . . 4
2.2. Extension activation . . . . . . . . . . . . . . . . . . 5
3. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
This document proposes a method to exchange values between a client
and the server in a interoperable manner:
1. For an established connection, the current RTT (current_rtt),
bottleneck bandwidth (current_bb) and current client IP
(current_client_ip) are stored as saved_rtt, saved_bb and
saved_client_ip within a BDP_FRAME;
2. The BDP_FRAME can be sent to the client and the client can also
be notified of the values of the BDP_FRAME parameters;
3. When resuming a session to the same IP address, the client is
allowed to send the BDP_FRAME;
4. The server can then utilise the parameters from the BDP_FRAME in
a later new connection to the same endpoint.
This method applies to any resumed QUIC session: both a saved_session
and a recon_session can be a 0-RTT QUIC connection or a 1-RTT QUIC
connection.
1.1. Notations and terms
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* BDP: defined below
* CWND: the congestion window used by server (maximum number of
bytes allowed in flight by the CC)
* current_bb : Current estimated bottleneck bandwidth
* saved_bb: Estimated bottleneck bandwidth preserved from a previous
connection
* RTT: Round-Trip Time
* current_rtt: Current RTT
* saved_rtt: RTT preserved from a previous connection
* client_ip : IP address of the client
* current_client_ip : Current IP address of the client
* saved_client_ip : IP address of the client preserved from a
previous connection
* remembered BDP parameters: a combination of saved_rtt and saved_bb
[RFC6349] defines the BDP as follows: "Derived from Round-Trip Time
(RTT) and network Bottleneck Bandwidth (BB), the Bandwidth-Delay
Product (BDP) determines the Send and Received Socket buffer sizes
required to achieve the maximum TCP Throughput." This document
considers the BDP estimated by a server that includes all buffering
along the network path. The estimated BDP estimated is related to
the amount of bytes in flight and the measured path RTT.
A QUIC connection could use the procedure detailed in [RFC6349] to
measure the BDP, but is permitted to choose another method [RFC9002]
. A server might be able to utilise an other information to provide
an estimate of the BDP.
Congestion controllers, such as CUBIC or RENO, could estimate the
saved_bb and current_bb values by utilizing a combination of the
cwnd/flight_size and the minimum RTT. A different method could be
used to estimate the same values when using a rate-based congestion
controller, such as BBR [I-D.cardwell-iccrg-bbr-congestion-control].
It is important to consider whether the methods could result in over-
estimating the bottleneck bandwidth, and the preserved values there
ought to be used with caution.
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1.2. Requirements Language
The keywords "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. BDP Frame
This section describes the use of a new Frame, the BDP Frame. The
BDP Frame MUST be considered by the congestion controller and its
data is not be limited by flow control limits. The server and the
client MAY send multiple BDP Frames in both 1-RTT and 0-RTT
connections.
2.1. BDP Frame Format
A BDP Frame is formatted as shown in Figure 1.
BDP Frame {
Type (i) = 0xXXX,
Lifetime (i),
Saved BB (i),
Saved RTT (i),
Saved IP length (i),
Saved IP (...)
}
Figure 1: BDP Frame Format
A BDP Frame contains the following fields:
* Lifetime (extension_lifetime): The extension_lifetime is a value
in milliseconds, encoded as a variable length integer. This
follows the design of a NewSessionTicket of TLS [RFC8446]. This
represents the validity in time of this extension.
* Saved BB (saved_bb): The saved_bb is a value in bytes, encoded as
a variable length integer. The bottleneck bandwidth estimated for
the previous connection by the server. Using the previous values
of bytes_in_flight defined in [RFC9002] can result in overshoot of
the bottleneck capacity and is not advised.
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* Saved RTT (saved_rtt): The saved_rtt is a value in milliseconds,
encoded as a variable length integer. This could be set to the
minimum RTT (min_rtt). The saved_rtt can be set to the min_rtt.
NOTE: The min_rtt defined in [RFC9002], does not track a
decreasing RTT: therefore the min_rtt reported might be larger
than the actual minimum RTT measured during the 1-RTT connection.
* Saved IP length (saved_ip_length) : The length of the IP address
in octets is set to either 4 (IPv4) or 16 (IPv6).
* Saved IP (saved_client_ip) : The saved_client_ip could be set to
the IP address of the client.
2.2. Extension activation
The client can accept the transmission of BDP Frames from the server
by using the enable_bdp transport extension.
enable_bdp (0xTBD): in the 1-RTT connection, the client indicates to
the server that it wishes to receive BDP extension Frames for
improving ingress of 0-RTT connection. The default value is 0.
Values larger than 3 are invalid, and receipt of these values MUST be
treated as a connection error of type TRANSPORT_PARAMETER_ERROR.
* 0: Default value. If the client does not send this parameter, the
server considers that the client does not support or does not wish
to activate the BDP extension.
* 1: The client indicates to the server that it wishes to receive
BDP Frame and activates the ingress optimization for the 0-RTT
connection.
* 2: The client indicates that it does not wish to receive BDP
Frames but activates ingress optimization.
* 3: The client indicates that it wishes to receive BDP Frames, but
does not activate ingress optimization.
This Transport Parameter is encoded as described in Section 18 of
[RFC9000].
3. Discussion
With the BDP Frame extension, the client has the choice of accepting
the reuse of the previous parameters or not.
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The BDP metadata parameters are measured by the server during a
previous connection. The BDP extension is protected by the mechanism
that protects the exchange of the 0-RTT transport parameters. For
version 1 of QUIC, the BDP extension is protected using the mechanism
that already protects the "initial_max_data" parameter. This is
defined in sections 4.5 to 4.7 of [RFC9001]. This provides a way for
the server to verify that the parameters proposed by the client are
the same as those that the server sent to the client during the
previous connection.
The server SHOULD NOT trust the client. Indeed, even if 0-RTT
packets containing the BDP Frame are encrypted, a client could modify
the values within the extension and encrypt the 0-RTT packet.
Authentication mechanisms might not guarantee that the values are
safe. It is not an easy operation for a client to modify
authenticated or encrypted data without this being detected by a
server. Modification could be realized by malicious clients. One
way to avoid this is for a server to also store the saved_rtt and
saved_bb parameters.
4. Acknowledgments
The authors would like to thank Gabriel Montenegro, Patrick McManus,
Ian Swett, Igor Lubashev, Robin Marx, Roland Bless and Franklin Simo
for their fruitful comments on earlier versions of this document.
5. IANA Considerations
TBD: Text is required to register the BDP Frame and the enable_bdp
transport parameter. Parameters are registered using the procedure
defined in [RFC9000].
6. Security Considerations
Security considerations are discussed in Section 3.
7. References
7.1. 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>.
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[RFC6349] Constantine, B., Forget, G., Geib, R., and R. Schrage,
"Framework for TCP Throughput Testing", RFC 6349,
DOI 10.17487/RFC6349, August 2011,
<https://www.rfc-editor.org/info/rfc6349>.
[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>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/info/rfc9000>.
[RFC9001] Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure
QUIC", RFC 9001, DOI 10.17487/RFC9001, May 2021,
<https://www.rfc-editor.org/info/rfc9001>.
[RFC9002] Iyengar, J., Ed. and I. Swett, Ed., "QUIC Loss Detection
and Congestion Control", RFC 9002, DOI 10.17487/RFC9002,
May 2021, <https://www.rfc-editor.org/info/rfc9002>.
7.2. Informative References
[I-D.cardwell-iccrg-bbr-congestion-control]
Cardwell, N., Cheng, Y., Yeganeh, S. H., Swett, I., and V.
Jacobson, "BBR Congestion Control", Work in Progress,
Internet-Draft, draft-cardwell-iccrg-bbr-congestion-
control-01, 7 November 2021,
<https://www.ietf.org/archive/id/draft-cardwell-iccrg-bbr-
congestion-control-01.txt>.
Authors' Addresses
Nicolas Kuhn
Email: nicolas.kuhn.ietf@gmail.com
Emile Stephan
Orange
Email: emile.stephan@orange.com
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Godred Fairhurst
University of Aberdeen
Department of Engineering
Fraser Noble Building
Aberdeen
Email: gorry@erg.abdn.ac.uk
Tom Jones
University of Aberdeen
Department of Engineering
Fraser Noble Building
Aberdeen
Email: tom@erg.abdn.ac.uk
Christian Huitema
Private Octopus Inc.
Email: huitema@huitema.net
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