A firewall is a machine that has access to the Internet and an organization's local area network (LAN). Firewalls are employed by many agencies and companies to protect their subnet(s) and systems from intruders and to prevent employees from leaving the LAN. Unfortunately, firewalls also stop NCSA Mosaic from retrieving documents over the Internet unless a proxy server is used. Because the proxy server is the only machine connected to the Internet, all Internet requests are handled only by the proxy server software.
A proxy server is software, running on the firewall machine, that lets authorized users make HTTP, Gopher, WAIS, and FTP requests through the firewall. The proxy server (sometimes called a proxy gateway) receives the Internet request in the form of a URL from Mosaic running behind the firewall. The proxy server retrieves the requested information and relays it back to the requesting Mosaic session. Proxy servers can also be set up to cache WWW documents so if another user requests the same document, the server will already have it stored and can return the request. The proxy server's actions are transparent to users, who should feel directly connected to the Internet.
Proxy gateways may also exercise discretion, deciding which requests to honor and which to turn down. The criteria for such decisions vary by installation, but may include server type, known or unknown URLs or machine addresses, or a user's ID.
Proxy gateway support in NCSA Mosaic for Microsoft Windows is currently implemented on a per access method basis, which means different URL access methods may send requests to different proxy servers. Typically an organization will set up one proxy server to handle all data types. However an organization may use different machines running proxy software for these request. Requests to FTP sites may go through one proxy server, for example, while requests to Gopher servers may go through another.
Mosaic will only work with Proxy gateways that support HTTP/1.0 protocol. Mosaic passes a URL to the proxy as an HTTP/1.0 GET request. The proxy then accesses the URL, and returns a copy of the file to Mosaic for display.
NOTE: News servers usually run locally and do not require proxy services. NCSA Mosaic for Windows doesn't have an entry for news servers.
Enter the name of the machine that is providing you with proxy services in each field (HTTP Proxy Server, FTP Proxy Server, WAIS Proxy Server, Gopher Proxy Server) and a port number. If the same machine provides you with services for more than one protocol, enter that name in each field. If you do not have proxy services for a listed protocol, leave the field blank.
For example, in the HTTP Proxy Server field you could enter your machine name and port number in the format machine.name:portnumber (e.g., apollo.com:8080).
If you are not sure if your organization uses proxy servers, contact your system administrator.
Many LANs run a local Web server that does not require proxy services. To improve local data access, enter your local domain name and select No proxy.
To obtain a web server that supports proxy services, see:
http://www.w3.org/hypertext/WWW/Daemon/Overview.htmlNOTE: Toggle the Proxy and No Proxy status of a listed domain by doubleclicking on the name.