# Session Protocol¶

Traffic Server supports some session level protocols in place of or on top of HTTP. These can be provided by a plugin (see New Protocol Plugins) or be one that is supported directly by Traffic Server.

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 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.