Session Protocol¶

Traffic Server supports some session level protocols in place or on top of HTTP. These can be provided by a plugin (see) or be one that is supported directly by Traffic Server. Currently the SPDY protocol is the only one current supported but it is planned to support HTTP 2 when that is finalized.

Session protocols are specified by explicit names, based on the NPN names. The core supported names are

http/0.9
http/1.0
http/1.1
http/2
spdy/1
spdy/2
spdy/3
spdy/3.1

The http/2 value is currently not functional but included for future use. spdy/1 and spdy/2 are obsolete but are include for completeness.

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

http means http/0.9, http/1.0, and http/1.1
spdy means spdy/3 and spdy/3.1.
http2 means http/2

Each proxy port can be configured in 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. For non-TLS proxy ports protocol sniffing is used 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.