QUIC A. Menon
Internet-Draft R. Mukherjee
Intended status: Standards Track 128 Technology
Expires: July 8, 2017 January 4, 2017
Network Enhancements for QUIC
draft-abilash-quic-network-00
Abstract
QUIC aims to improve performance by multiplexing streams and various
other enhancements [I-D.ietf-quic-transport]. QUIC performs better
than existing transport protocols in most cases. However, its
performance suffers compared to HTTP under very high bandwidth when
large amounts of data needs to be downloaded [MEG2016]. This is
because QUIC is an end to end protocol and provides no means for the
intermediate network elements to contribute to QUIC improvements.
This draft proposes a change to the QUIC protocol header that will
allow session aware routers and other middleboxes to prioritize
streams in QUIC packets, divert high priority streams to low loss
paths, and adjust packet pacing on a per stream basis. This opens
the door to many possible future in-network enhancements.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3
3. QUIC Network . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Stream Header . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Stream Demultiplexing and Multiplexing . . . . . . . . . 4
3.3. Multi-Path . . . . . . . . . . . . . . . . . . . . . . . 5
3.4. Moving Streams . . . . . . . . . . . . . . . . . . . . . 5
3.5. QUIC State Machine . . . . . . . . . . . . . . . . . . . 5
3.6. Stream based Packet Pacing . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
QUIC employs stream multiplexing by interleaving frames from multiple
streams into one conversation between QUIC endpoints. These streams
are identified by a Stream ID and multiplexed on top of the same UDP
flow. These streams do not have any priority assigned to them and
all of them are treated with the same priority. A high priority
stream is affected by network conditions similar to low priority
streams. [MEG2016] shows studies where HTTP performs better than
QUIC because it opens multiple connections for each stream. When
large amounts of data are to be downloaded and when there is high
bandwidth available, QUIC underperforms compared to HTTP.
This draft proposes to make the Stream ID visible in the public
header and add a priority byte. Session aware routers and other
middleboxes can demultiplex streams at the initiator edge and
multiplex them back at the termination edge. With these enhancements
QUIC now simulates opening multiple connections similar to HTTP with
priorities in high bandwidth cases. Coupled with inherent QUIC
protocol enhancements and network participation, QUIC will be able to
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perform better than traditional transport protocols in all network
conditions.
2. Conventions and Definitions
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 RFC 2119.
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying significance described in RFC 2119.
Definition of terms that are used in this document:
o Client: The endpoint initiating a QUIC connection.
o Server: The endpoint accepting incoming QUIC connections.
o Stream: A logical, bi-directional channel of ordered bytes within
a QUIC connection.
o Stream ID: The identifier for streams within a QUIC connection.
o Connection: A conversation between two QUIC endpoints with a
single encryption context that multiplexes streams within it.
o Connection ID: The identifier for a QUIC connection.
o Initiation Edge: The first network element on the path from the
Client to the Server that supports QUIC network optimizations.
o Termination Edge: The last network element on the path from the
Client to the Server that supports QUIC network optimizations.
3. QUIC Network
Modern Enterprise WAN or SD-WAN deployments are moving towards
session/flow aware routing which provides insight into applications
for improved performance. These typical WAN deployments have edge
routers at the Client and Server side which would originate and
terminate sessions. These sessions could be based on the unique five
tuple of the packet or any other application attribute that makes it
unique. The Connection ID of the QUIC protocol is a natural
identifier to classify QUIC sessions. Each QUIC Connection will have
a unique session within these session aware routers or middleboxes.
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3.1. Stream Header
The Stream ID of the stream multiplexed into a QUIC connection with a
Connection ID must be visible in the public header. A priority byte
is added to indicate relative priority of the stream.
+--------+--------+--------+--------+--------+------------+
|Type (8)| Stream ID (8, 16, 24, or 32 bits) |Priority (8)|
| | (Variable length SLEN bytes) | |
+--------+--------+--------+--------+--------+------------+
Figure 1 QUIC Network Stream Header
o Type: Same as specified in the QUIC protocol.
o Stream ID: Same as specified in the QUIC protocol.
o Priority: Field indicating priority for each stream. It has
values from 0-255. 0 indicates lowest priority and 255 indicates
highest priority.
Stream 1 and Stream 3 will have the highest priority by default as
they are special streams to carry initial handshake and headers
respectively.
QUIC packets are always authenticated and the payload is typically
fully encrypted. The parts of the packet header which are not
encrypted are still authenticated by the receiver, so as to thwart
any packet injection or manipulation by third parties. There is no
change in this and is as defined in the QUIC protocol.
A public flag needs to be set by the Client as an indication to the
network elements to demultiplex the packets on a per stream basis.
This can be done during the initial crypto handshake (stream 1). The
client can set this flag requesting network elements to apply QUIC
optimizations. The network elements that honor these requests can
reset this flag on the return from the Server. This allows the
client to learn that it can rely on the network for QUIC related
network optimizations. Public flag 0x80 is currently unused and can
could be used for this purpose.
3.2. Stream Demultiplexing and Multiplexing
Session aware routers and middleboxes can demultiplex streams at the
Initiation Edge and multiplex them back at the Termination Edge.
Consider a QUIC connection that has 3 streams all initiated by the
Client. In Figure 2, QUIC packets with Stream IDs 5, 7, and 9 are
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sent across as 3 different flows between router 1 (Initiation Edge)
and router 2 (Termination Edge).
Stream 5
----------------------
/ \
+--------+/ Stream 7 \+--------+
Client---|Router 1|--------------------------|Router 2|---Server
+--------+\ /+--------+
\ Stream 9 /
----------------------
Initiation Edge Termination Edge
Figure 2 QUIC Sample Network
Multiplexing the connection across multiple flows during high
bandwidth and high loss network conditions when large amounts of data
are being downloaded spreads the packet losses across these different
flows. By setting the priority of these streams it is possible to
ensure that high value flows do not incur any losses.
3.3. Multi-Path
Exposing the Stream ID and its priority can help prioritize traffic
across different paths. In typical SD-WAN deployments there are
multiple paths - usually a high cost MPLS path and a lower cost
Internet path. By prioritizing streams, high value streams could be
sent over the MPLS path while lower value streams can be sent over
the Internet path.
3.4. Moving Streams
In other deployments, the Internet path can be used to send all
traffic and when there are packet losses discovered beyond acceptable
limits then the Initiation Edge can switch high value streams to the
MPLS path. SD-WAN routers provide many such enhancements that
applications supporting QUIC can avail by exposing the Stream ID.
3.5. QUIC State Machine
A QUIC state machine can be employed on a per stream basis on these
session aware routers. The state machine helps with the life cycle
of the session (creation/termination). The proposed state machine
will do the following:
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3.6. Stream based Packet Pacing
QUIC employs a packet pacing mechanism based on the inter-packet
arrival rate. However, session aware routers will have a flow per
stream. Hence the packet rate can be adjusted on a per stream basis
and not for the whole connection. For example, if there are 3
streams 5, 7, and 9. Stream 5 and 7 may have good inter-arrival rate
while stream 9 may experience some delay due to network conditions.
In this scenario, the packets can be paced differently just for
stream 9 which was affected by the network and not the other streams.
Streams 5 and 7 can continue to provide high throughput results
without affecting their latency. This can help with congestion
control techniques.
When a QUIC packet with a new Connection ID is received, it will
validate that the Stream ID of this packet is 1. Stream 1 will
have the highest priority.
Any subsequent packet with a different Stream ID will create a new
sub-session for this Connection ID and stream.
If a FIN is seen in both directions for a stream, then the session
for that stream will be removed from the router.
If a RST_STREAM is received, then the session for that stream will
be terminated in the router.
Once a stream session has been terminated, any new packets with
that Stream ID will not be forwarded and will be responded to with
a RST_STREAM packet.
A connection termination would terminate all stream sessions.
The state machine need not be limited to the above functionalities.
This can also be useful to employ per stream flow and congestion
control techniques.
4. IANA Considerations
This document makes no request of IANA.
5. Security Considerations
The security considerations for QUIC network enhancements are
believed to be the same as for QUIC.
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6. Acknowledgements
This document has benefited from input from Patrick MeLampy.
7. References
7.1. Normative References
[I-D.ietf-quic-transport]
Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed
and Secure Transport", draft-ietf-quic-transport-00 (work
in progress), November 2016.
7.2. Informative References
[MEG2016] Megyesi, P., Kramer, Z., and S. Molnar, "How quick is
QUIC", Proc. IEEE ICC 2016, Kuala Lumpur, Malaysia, May
2016.
Authors' Addresses
Abilash Menon
128 Technology
Email: amenon@128technology.com
Ritesh Mukherjee
128 Technology
Email: rmukherjee@128technology.com
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