This document is not updated

 Please refer to the documentation on GitHub.

Table of contents


Implement IETF QUIC into ATS Core.

Design Doc

The UDP core and QUIC (It explain how the UDP core works and how the UDPPacket enters the QUIC stack.)

Data Flow (draft-05 : Second Implementation)

QUIC Connection/Stream - ATS Client Session/Transaction mapping (Obsolete: Not too inaccurate, but not worth referencing)

I/O between HttpSM and QUICNetVC (Jan/24/2023: Updated, but QUICFrames are handled by Quiche now)

Packetization (Jan/24/2023: Updated, we just don't do QUIC packetization by ourselves)


Please label issues and pull-requests with "QUIC".

Branching Rules


Please use 10-Dev or master. Feature branch was merged and removed.

  • quic-latest : latest branch
  • master: draft-29 (currently)

Development Rules


Please send Pull-Requests to "quic-latest" branch until it merged into master branch


Use Catch as Unit Test Framework. The header file is under tests/include.

How to build

(Last update: Jan/24/2023)

You have two ways to enable QUIC on ATS:

  • Use Quiche library
    • This uses Quiche's QUIC implementation
  • Use an SSL library that supports QUIC (i.e. BoringSSL, or OpenSSL from quictls)
    • This uses ATS's QUIC implementation

We keep ATS's native QUIC implementation for future improvement in case we need more flexibility, but our focus is currently on using Quiche.

Build Quiche (if you want to use Quiche's QUIC implementation)

Currently ATS is compatible with Quiche 0.16.0.

Please refer to the official documents for the build step. You need to enable ffi feature at minimum. qlog is also available.

Build an SSL library (if you want to use ATS's QUIC implementation)

ATS now supports 4 variation of SSL libraries. Pick one from below and build it. 


Official BoringSSL works without patches.

These commits below work, and recent commits would probably work as well.

cbae965ca03825d517efe98cf7b8812584cab4a0 (BoringSSL API version 9)

88024df12147e56b6abd66b743ff441a0aaa09a8 (BoringSSL API version 10)

Please note that the support for BoringSSL API version 9 may be removed without notice in the future.

OpenSSL (quictls/openssl) [RECOMMENDED]

They also have branches based on OpenSSL 3.0 but we haven't fully supported it.

$ git clone --depth 1 --branch OpenSSL_1_1_1j+quic
$ cd openssl
$ ./config --prefix=/PATH/TO/THE/OPENSSL
$ make
$ make install

OpenSSL (tatsuhiro-t/OpenSSL_1_1_1g-quic-draft-32) [OBSOLETE]

This is ngtcp2 developer's customized version.

OpenSSL (akamai/master-quic-support) [INCOMPATIBLE]

This used to work, but it's incompatible now because it's based on OpenSSL master branch.

This is the branch used for .

Build ATS (10-Dev branch)

Quiche support is only available on quiche branch at the moment.

$ git clone --depth 1 --branch 10-Dev
$ cd trafficserver
$ autoreconf -if
$ ./configure --prefix=/PATH/TO/ATS --with-quiche=/PATH/TO/QUICHE --enable-debug
$ make
$ make install

Build ATS (master branch)

The master branch only supports ATS's native implementation at the moment. There is no additional requirement except that you need the SSL library you just built : Installing From Source Code

$ git clone --depth 1 --branch quic-latest
$ cd trafficserver
$ autoreconf -if
$ ./configure --prefix=/PATH/TO/ATS --with-openssl=/PATH/TO/SSL_LIBRARY --enable-debug
$ make
$ make install


Configuration files are located in the /PATH/TO/THE/ATS/etc/trafficserver/.

The detail is documented here, but below is the essential settings and only these 4 settings are available if you use Quiche.

  • records.config
# run 1 UDP thread at least
CONFIG proxy.config.udp.threads INT 1
# open server port for quic
CONFIG proxy.config.http.server_ports STRING 4433:quic
# enable debug log if you want
CONFIG proxy.config.diags.debug.enabled INT 1
CONFIG proxy.config.diags.debug.tags STRING quic
> CONFIG proxy.config.udp.threads INT 1
< CONFIG proxy.config.http.server_ports STRING 8080 8080:ipv6
> CONFIG proxy.config.http.server_ports STRING 4433:quic
< CONFIG proxy.config.diags.debug.enabled INT 0
< CONFIG proxy.config.diags.debug.tags STRING http|dns
> CONFIG proxy.config.diags.debug.enabled INT 1
> CONFIG proxy.config.diags.debug.tags STRING quic

  • ssl_multicert.config
    •  Please use absolute path to the cert and private key until Issue #2358 is fixed.
dest_ip=* ssl_cert_name=/PATH/TO/THE/CERT ssl_key_name=/PATH/TO/THE/PRIVATE/KEY/OF/CERT
  • remap.config
    • Remap request to origin server.
map /



Patches has additional patch to make debug logs readable.

QUIC specific configurations

Following docs will be moved to

Please note that current name of configurations and default values might be changed before merged in to master branch.


CONFIG proxy.config.quic.no_activity_timeout_in INT 30

   Specifies how long Traffic Server keeps QUIC connections to clients open if a transaction stalls.

How to test

Third-party tools

There is a script that builds third-party tools in the repo. It builds h2load and curl with HTTP/3 support. An HTTP/3 client under ngtcp2/example is also useful when you want to check details.


We have client implementation called "traffic_quic" for test. Not actively maintained, and compatibility with Quiche implementation is not confirmed.

// draft-17

$ traffic_quic -h
Usage: traffic_quic [--SWITCH [ARG]]
  -a, --addr              str Address
  -o, --output            str             Write to FILE instead of stdout
  -p, --port              str   4433      Port
  -P, --path              str   /         Path
  -T, --debug             str   quic|vv.. Vertical-bar-separated Debug Tags
  -c, --close             on    false     Enable connection close excercise
  -h, --help                              Print usage information
  -V, --version                           Print version string
      --run-root                          using TS_RUNROOT as sandbox

client specific configurations

traffic_quic loads records.config which is used by traffic_server.


# Enable Version Negotiation Exercise
CONFIG proxy.config.quic.client.vn_exercise_enabled INT 1

# Enable Connection Migration Exercise
CONFIG proxy.config.quic.client.cm_exercise_enabled INT 1

# Enable TLS session resumption
CONFIG proxy.config.quic.client.session_file STRING session.bin 

These configurations can be overridden by a corresponding environment variable like other configurations in records.config.

e.g. Access with version negotiation exercise

$ PROXY_CONFIG_QUIC_CLIENT_VN_EXERCISE_ENABLED=1 traffic_quic -a -p 4433 -P /en/latest/

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