206 (Partial Content) responses is an ICAP extension that allows the
ICAP agents to optionally combine adapted and original HTTP message
content. The decision to combine is postponed until the end of the
ICAP response. Squid supports Partial Content extension by default.
Activation of the Partial Content extension is negotiated with each
ICAP service during OPTIONS exchange. Most ICAP servers should handle
negotiation correctly even if they do not support the extension, but
some might fail. To disable Partial Content support for all ICAP
services and to avoid any negotiation, set this option to "off".
Example:
icap_206_enable off