Blue Coat Systems Time Clock Proxy SG Manuale Utente

Chapter 2: Managing Content Policy Language

39

<Exception> Layers

<Exception>

 layers are evaluated when a proxy transaction is terminated by an exception. This could 

be caused by a bad request (for example, the request URL names a non-existent server) or by setting 
the 

deny

 or 

exception()

 properties in policy. Policy in an exception layer can be used to control how 

access logging is performed for exceptions, such as 

authentication_failed

. It can also be used to 

modify the HTTP response headers in the exception page that is sent to the client.

The syntax is:

<Exception [label]> [exception_condition][exception_properties] ...

where:

•

The 

<Exception>

 layer defines the transactions evaluated against this policy, and restricts the 

triggers and properties allowed in the rules used in the layer.

•

The optional 

 separated from the layer type by space, is a CPL User-defined Identifier. 

•

The optional 

 is a list of triggers, all of which must evaluate to true before 

the layer content is evaluated. For more information on using conditions, see Chapter 3: 
"Condition Reference". See also the following Layer Guards section.

•

The optional 

is a list of properties set if any of the rules in the layer 

match. These act as defaults, and can be overridden by property settings in specific rules in the 
layer. For more information on using properties, see Chapter 4: "Property Reference". See also the 
following Layer Guards section.

<Forward> Layers

<Forward>

 layers are evaluated when the current transaction requires an upstream connection (and 

only then: forward policy will not be evaluated for a cache hit). 

<Forward>

 layers use the 

server_url=

 

tests rather than the 

url=

 tests so that they are guaranteed to honor any policy that rewrites the URL.

The syntax is:

<Forward [label]> [forward_condition][forward_properties] ...

where:

•

The 

<Forward>

 layer defines the transactions evaluated against this policy, and restricts the 

triggers and properties allowed in the rules used in the layer.

•

The optional 

 separated from the layer type by space, is a CPL User-defined Identifier. 

•

The optional 

 is a list of triggers, all of which must evaluate to true before the 

layer content is evaluated. For more information on using conditions, see Chapter 3: "Condition 
Reference". See also the following Layer Guards section.

•

The optional 

is a list of properties set if any of the rules in the layer match. 

These act as defaults, and can be overridden by property settings in specific rules in the layer. For 
more information on using properties, see Chapter 4: "Property Reference". See also the following 
Layer Guards section.