How does ASP implement 301 redirect

The use of 301 redirect can be without the WWW domain name to the WWW domain name, so that the weight can be all pointed to the domain name with www, the site optimization is very helpful.

<% Dim server_name,path_infostr,query_stringstr path_infostr=lcase (Request. ServerVariables ("Path_info")) Server_name=lcase (request. ServerVariables ("SERVER_NAME")) query_stringstr=request. ServerVariables ("query_string") If query_stringstr<> "" Then query_stringstr= "?" &query_stringstr IF InStr (server_name, "www.") <1 Then response.status = "Moved Permanently" if InStr (Path_infostr, "index") >0 or InStr (PATH_INFOSTR, "default" ) >0 Then Response.AddHeader "Location", "

http://www. " &server_name Else Response.AddHeader "Location", "http://www." &server_name&path_infostr&query_stringstr End If Response.End End If%>