I am having problems getting an external acl to work with reply_body_max_size The steps I have taken are as follows: 1. Define the external_acl_type response_size_check_ext_acl_type # response_size_check_{pk}_acl pk external_acl_type response_size_check_ext_acl_type ttl=100 negative_ttl=100 cache=0 children=2 concurrency=20 %EXT_TAG %EXT_LOG /usr/share/bin/ext_acl_payload_check -c 20 --key=response_size_restriction 2. Create a number of acl's using this type in squid.conf, for example, then applying it to reply_body_max_size acl response_size_13_acl external response_size_check_ext_acl_type 13 http_reply_access allow response_size_13_acl !all reply_body_max_size 13 MB response_size_13_acl !all The '13' argument is to tell the external acl what the size restriction is going to be the next line tests the acl, caching the result as external acl's are 'slow' the final line, I am expecting to get the cached result and limit max_size to 13MB if 'response_size_13_acl' returns OK. This is the log from the external acl, which suggests the acl is called and it returns OK 2012-06-08 14:23:18,785 advance.policy.management.commands.ext_acl_payload_check@ext_acl_payload_check [24441:177142764] INFO: KEY IS response_size_restriction 2012-06-08 14:23:18,786 advance.policy.management.commands.ext_acl_payload_check@ext_acl_payload_check [24441:177142764] INFO: addval ['13'] 2012-06-08 14:23:18,786 advance.policy.management.commands.ext_acl_payload_check@ext_acl_payload_check [24441:177142764] INFO: VALUES - [13] 2012-06-08 14:23:18,786 advance.policy.management.commands.ext_acl_payload_check@ext_acl_payload_check [24441:177142764] INFO: Begining value checking loop 2012-06-08 14:23:18,786 advance.policy.management.commands.ext_acl_payload_check@ext_acl_payload_check [24441:177142764] INFO: Other Value type found - ie int 2012-06-08 14:23:18,787 advance.utils.management.base@base [24441:177142764] INFO: ext_acl_payload_check Response: '0 OK' I have tried other 'slow' acl's using this method and it appears to work fine, for example #TEST USER ACL acl test_user proxy_auth "/usr/blocked/users_1.txt" #testing fast/slow performance against cache for reply_body_max_size http_reply_access allow test_user !all reply_body_max_size 1 MB test_user Any thoughts would be most welcome