•  URL Learning - The SteelHead learns associations between a base request and a follow-on request. This feature is most effective for web applications with large amounts of static content: for example, images, style sheets, and so on. Instead of saving each object transaction, the SteelHead saves only the request URL of object transactions in a Knowledge Base and then generates related transactions from the list. This feature uses the Referer header field to generate relationships between object requests and the base HTML page that referenced them and to group embedded objects. This information is stored in an internal HTTP database. The following objects are retrieved by default: .gif, .jpg, .css, .js, .png. You can add additional object types to be retrieved.

•  Parse and Prefetch - The SteelHead includes a specialized algorithm that determines which objects are going to be requested for a given web page and prefetches them so that they are readily available when the client makes its requests. This feature complements the URL Learning feature by handling dynamically generated pages and URLs that include state information. Parse and Prefetch essentially reads a page, finds HTML tags that it recognizes as containing a prefetchable object, and sends out prefetch requests for those objects. Typically, a client would need to request the base page, parse it, and then send out requests for each of these objects. This still occurs, but with Parse and Prefetch the SteelHead has quietly perused the page before the client receives it and has already sent out the requests. This allows it to serve the objects as soon as the client requests them, rather than forcing the client to wait on a slow WAN link. For example, when an HTML page contains the tag <img src=my_picture.gif>, the SteelHead prefetches the image my_picture.gif because it parses an img tag with an attribute of src by default. The HTML tags that are prefetched by default are base/href, body/background, img/src, link/href, and script/src. You can add additional object types to be prefetched.

•  Removal of Unfetchable Objects - The SteelHead removes unfetchable objects from the URL Learning Knowledge Base.

•  Object Prefetch Table - The SteelHead stores object prefetches from HTTP GET requests for cascading style sheets, static images, and Java scripts. This helps the client-side SteelHead respond to If-Modified-Since (IMS) requests and regular requests from the client, thus cutting back on round trips across the WAN. This feature is useful for applications that use a lot of cacheable content.

•  Persistent Connections - The SteelHead uses an existing TCP connection between a client and a server to prefetch objects from the web server that it determines are about to be requested by the client. Many web browsers open multiple TCP connections to the web server when requesting embedded objects. Typically, each of these TCP connections go through a lengthy authentication dialog before the browser can request and receive objects from the web server on that connection. NTLM is a Microsoft authentication protocol which employs a challenge-response mechanism for authentication, in which clients are required to prove their identities without sending a password to a server. NTLM requires the transmission of three messages between the client (wanting to authenticate) and the server (requesting authentication).