Installation guide

Deployment Primer

2-9

IGURE

2-3.

FTP Proxy in Standalone Mode

FTP Proxy in Dependent Mode

You can also install IWSVA FTP on a dedicated machine between an upstream proxy

and the requesting clients. Using this setup adds other FTP features (for example, access

blocking, logging, and filtering) to supplement the existing FTP proxy.

IWSVA's FTP-proxy mode, shown in Figure 2-4, is analogous to the dependent-mode

flow of the HTTP service. Because it carries a performance penalty of an extra hop and

extra processing by the other FTP proxy server, only use this mode if your organization

does not allow the IWSVA Server to access the Internet directly.

If the other FTP proxy server uses a store-and-forward technique, the performance

penalty is more noticeable on large files because the other FTP proxy first downloads

the file and passes it on to the IWSVA FTP service. Additionally, the other FTP proxy

must have sufficient free disk space to hold all transfers in progress.

Unlike the HTTP dependent-mode service, which has the possible benefit of cached

requests, most FTP proxy servers do not cache requests.

FTP Dependent Mode also protects FTP servers from upload and download threats.