2.1.42 s-dns
This field SHOULD specify the Internet host name of the proxy if a proxy is forwarding the logging message on behalf of a client (which can be another proxy). The proxy MUST replace the value of the s-dns field that was specified by the client with its own Internet host name or with "-" if the Internet host name cannot be determined.
When a client creates a logging message, it SHOULD specify the s-dns field as "-" but MAY specify the Internet host name of the server that the client streamed the content from.
The syntax of the s-dns field is defined in [RFC3986], as follows.
-
s-dns= "-" | reg-name ;
Example:
-
wmt.adventure-works.com