Which of the following represents the software that is acting on behalf of a user?
- representative agent field
- type field
- host field
- user agent
The user agent is an HTTP header inside the software that is acting on behalf of a user. For example, it might indicate the browser type and capability. The User-Agent (UA) string is intended to identify devices requesting online content, which helps with intrusion analysis.
The host field indicates the domain name of the server (for virtual hosting), and the TCP port number on which the server is listening.
– Other examples of HTTP header fields are:
– Accept – Media type(s) that is(are) acceptable for the response
– Content-Length – The length of the request body in octets (8-bit bytes)
– From – The email address of the user making the request
– Referrer – The address of the previous web page from which a link to the currently requested page was followed
– Host – The domain name of the server (for virtual hosting), and the TCP port number on which the server is listening
– Date – The date and time that the message was originated
– Authorization – Authentication credentials for HTTP authentication
Cookies are text files with information with stored information about the user. They are not HTTP header fields. There is no representative agent field in the HTTP header. There is no type field in the HTTP header. The type field is the first field in an Internet Control Message Protocol (ICMP) header, and is used to indicate the function or purpose of the communication. A control message is the function or purpose of the ICMP communication.
Common examples of Types are:
– 8 for Echo Request
– 0 for Echo Reply
– 11 for Timeout Exceeded
– 3 for Destination Unreachable
There are about sixteen formally defined Types for ICMP. The remaining fields in the ICMP header are Code, Checksum, and Rest of Header. The Code field is used to define or reference a sub-type (i.e., a more specific sub-meaning of the indicated control message). The Checksum field is used to verify that the ICMP communication was not corrupted in transit. The Rest of Header field may hold values when needed based on the Type, or is set to all zeros when unused. For example, a Type 5 Redirect will place an IP address in the Rest of Header field.