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.. include:: ../../common.defs

.. _session-protocol:

Session Protocol
****************

|TS| supports some session level protocols in place of or on top of HTTP. These
can be provided by a plugin (see :ref:`developer-plugins-new-protocol-plugins`)
or be one that is supported directly by |TS|.

Session protocols are specified by explicit names:

*  ``http/0.9``
*  ``http/1.0``
*  ``http/1.1``
*  ``http/2``

The session protocols supported on a proxy port are a subset of these values.
For convenience some pseudo-values are defined in terms of these fundamental
protocols:

*  ``http`` means ``http/0.9``, ``http/1.0``, and ``http/1.1``
*  ``http2`` means ``http/2``

Each proxy port can be configured in :ts:cv:`proxy.config.http.server_ports`
to support a subset of these session protocols. For TLS enabled connections this
configuration controls which protocols are offered by NPN. Protocol sniffing is
use for non-TLS proxy ports to determine which protocol is being used by the
client. If the detected protocol is not supported for that proxy port the
connection is dropped.
