QUIC Q. An
Internet-Draft D. Liu
Intended status: Standards Track Y. Liu
Expires: September 6, 2020 Alibaba Inc.
March 5, 2020
Key Components for Multipath QUIC Traffic Distribution
draft-an-multipath-quic-traffic-distribution-00
Abstract
This document describes several key components for Multipath QUIC
traffic distribution. The key components remain compliant with the
current Multipath Extensions for QUIC (MP-QUIC) design.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Notational Conventions . . . . . . . . . . . . . . . . . . . 2
3. Packet Scheduling . . . . . . . . . . . . . . . . . . . . . . 3
4. Stream Management . . . . . . . . . . . . . . . . . . . . . . 3
5. Congestion Control . . . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
7. Normative References . . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The QUIC connection migration feature, described in more details in
[I-D.ietf-quic-transport], enables QUIC to sustain a connection over
multiple paths, but still there is a void to specify simultaneous
usage of available paths for a single connection.
[I-D.deconinck-quic-multipath] describes how to use multiple paths
simultaneously for a single QUIC connection, but how to spread
packets over multiple paths following a traffic distribution policy,
and how to receive packets from multiple paths, are not specified.
If not standardized, implementers would still not know how to
transmit data over multipath QUIC.
There are several use scenarios about traffic distribution over
multipath QUIC. One would be stream media transmission. A typical
example is Internet live video broadcasting. It has high requirement
on data transmission speed but packet loss rate is lowly prioritized.
In this case, multipath QUIC can provide a better utilization of
multiple path bandwidth. Another use scenario is highly reliable
real-time data transmission, which is sensitive to packet loss. In
this case, redundancy data can be transmitted over multipath QUIC.
To support the requirements of these use scenarios, multipath QUIC
traffic distribution needs to be standardized.
In this document, it focuses on the description of several key
components which are necessary to support the implementation of
Multipath QUIC traffic distribution. The key components include
packet scheduling, congestion control and stream management.
2. Notational Conventions
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].
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3. Packet Scheduling
Given the established multiple QUIC paths, packet scheduling
determines which path(s) to deliver packets, how many packets are
delivered on a specific QUIC path, which packets are delivered on a
specific QUIC path.
Figure 1 illustrates the process of packet scheduling.
Path Performance
Measurement
Original | +-+-+-+
Data V +-> | | | | Path 1
+-+-+-+-+-+-+-+ | +-+-+-+
+-+-+-+-+ | Packet | | +-+
| ...| -> | Distribution| -+-> | |
+-+-+-+-+ +-+-+-+-+-+-+-+ | +-+
| +-+-+
+-> | | | Path i
+-+-+
Figure 1: Processing Flow of Data Sending Over Multipath
Since the conditions of each path are different, the different paths
need to be measured and selected, in order to pick out paths with
better performance, and distribute packets to different paths
according to path performance.
There are many traffic distribution mechanisms. Some are based on
lowest RTT, while some are based on transmission speed and packet
loss rate, which need further evaluation for MPQUIC.
In addition, in scenario where there is large performance difference
between multiple QUIC paths, how to select path(s) and how to
distribute packets need to be considered. Possible solution could be
discarding the path(s) with low performance (packet loss rate is
higher than threshold, like 5%), or only transmitting redundancy
packets on path(s) with low performance.
4. Stream Management
It is recommended to support the configuration of transmission
policies for different QUIC streams. This can be supported by multi
priority queue. Figure 2 illustrates the concept of stream
management.
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stream Multi priority queue
+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+ +----------> | |
| |----- | +-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+ |
| +-+-+-+-+-+-+-+-+
... +----------> | |
+----------> +-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+ | ...
| |----- | +-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+ +----------> | |
+-+-+-+-+-+-+-+-+
Figure 2: Multipath QUIC Stream Management
For example, high priority streams can be delivered first, and even
reinjection, while reinjection will not apply for low priority
streams.
5. Congestion Control
Congestion control is indispensable for MPQUIC. There can be two
options: decoupled congestion control, or coupled congestion control.
For decoupled congestion control, the congestion control policy of
each path is decoupled, which is beneficial for maximizing the
bandwidth utilization of each path.
6. IANA Considerations
This document makes no request of IANA.
7. Normative References
[I-D.deconinck-quic-multipath]
De Coninck, Q. and O. Bonaventure, "Multipath Extensions
for QUIC (MP-QUIC)", draft-deconinck-quic-multipath-03
(work in progress), August 2019.
[I-D.ietf-quic-transport]
Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed
and Secure Transport", draft-ietf-quic-transport-23 (work
in progress), September 2019.
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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/info/rfc2119>.
Authors' Addresses
Qing An
Alibaba Inc.
Email: anqing.aq@alibaba-inc.com
Dapeng Liu
Alibaba Inc.
Email: max.ldp@alibaba-inc.com
Yanmei Liu
Alibaba Inc.
Email: miaoji.lym@alibaba-inc.com
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