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Manual Chapter : Configuring Content Adaptation for HTTP Requests

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  • 17.0.0

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Manual Chapter

Configuring Content Adaptation for HTTP Requests

Overview: Configuring HTTP Request Adaptation

This implementation describes how to configure the BIG-IP content adaptation feature for adapting HTTP requests. With this feature, a BIG-IP virtual server can conditionally forward HTTP requests to a pool of Internet Content Adaptation Protocol (ICAP) servers for modification, before sending the request to a web server.
In this implementation, you create a standard HTTP virtual server and pool of web servers for processing client requests. The HTTP virtual server accepts each client request in the normal way, but before load balancing the request to the pool of web servers, the virtual server forwards the HTTP request to a special internal virtual server.
The
internal virtual server
 receives the HTTP request from the standard virtual server, and load balances the request to a pool of ICAP servers for modification. After the ICAP server modifies the request, the BIG-IP system sends the request to the appropriate web server for processing.
Content adaptation configuration for modifying HTTP requests
Content adaptation configuration for modifying HTTP requests
The internal virtual server references the pool of content adaptation servers, including the load balancing method to use for those servers. The internal virtual server also references an ICAP profile, which includes specific instructions for how the BIG-IP system should wrap the HTTP request in an ICAP message for adaptation.
Optionally, the internal virtual server can reference:
  • Any persistence method that you would like the BIG-IP system to use when load balancing traffic to the ICAP pool.
  • Any health or performance monitor that you would like the BIG-IP system to use when load balancing traffic to the ICAP pool.
  • Any iRules® related to the content adaptation.

Creating a custom client-side ICAP profile

You create this ICAP profile when you want to use an ICAP server to wrap an HTTP request in an ICAP message before the BIG-IP system sends the request to a pool of web servers. The profile specifies the HTTP request-header values that the ICAP server uses for the ICAP message.
You can use macro expansion for all ICAP header values. For example, if an ICAP header value contains
${SERVER_IP}
, the BIG-IP system replaces the macro with the IP address of the ICAP server selected from the pool assigned to the internal virtual server. If an ICAP header value contains
${SERVER_PORT}
, the BIG-IP system replaces the macro with the port of the ICAP server selected from the pool assigned to the internal virtual server. For example, you can set the
URI
 value in an ICAP profile to
icap://${SERVER_IP}:${SERVER_PORT}/virusScan
.
  1. On the Main tab, click
    Local Traffic
    Profiles
    Services
    ICAP
    .
  2. Click
    Create
    .
  3. In the
    Name
     field, type a unique name for the profile.
  4. For the
    Parent Profile
     setting, retain the default value,
    icap
    .
  5. On the right side of the screen, select the
    Custom
     check box.
  6. In the
    URI
     field, type a URI in this format:
    icap://hostname:port/path
    .
    For example, using macro expansion, you can set the
    URI
     value to: 
    
                  icap://${SERVER_IP}:${SERVER_PORT}/virusScan
    .
  7. In the
    Preview Length
     field, type a length or retain the default value
    0
    .
    This value defines the amount of the HTTP request or response that the BIG-IP system offers to the ICAP server when sending the request or response to the server for adaptation. This value should not exceed the length of the preview that the ICAP server has indicated it will accept.
  8. In the
    Header From
     field, type a value for the
    From:
     ICAP header.
  9. In the
    Host
     field, type a value for the
    Host:
     ICAP header.
  10. In the
    Referer
     field, type a value for the
    Referer:
     ICAP header.
  11. In the
    User Agent
     field, type a value for the
    User-Agent:
     ICAP header.
  12. Click
    Finished
    .
After you create the ICAP profile, you can assign it to an internal virtual server so that the HTTP request that the BIG-IP system sends to an ICAP server is wrapped in an ICAP message, according to the settings you specified in the ICAP profile.

Creating a pool of ICAP servers

You perform this task to create a pool of ICAP servers that perform content adaptation on HTTP requests.
  1. On the Main tab, click
    Local Traffic
    Pools
    .
    The Pool List screen opens.
  2. Click
    Create
    .
    The New Pool screen opens.
  3. In the
    Name
     field, type a unique name for the pool.
  4. For the
    Health Monitors
     setting, from the
    Available
     list, select the
    http
     monitor and move the monitor to the
    Active
     list.
  5. From the
    Load Balancing Method
     list, select how the system distributes traffic to members of this pool.
    The default is
    Round Robin
    .
  6. For the
    Priority Group Activation
     setting, specify how to handle priority groups:
    • Select
      Disabled
       to disable priority groups. This is the default option.
    • Select
      Less than
      , and in the
      Available Members
       field type the minimum number of members that must remain available in each priority group in order for traffic to remain confined to that group.
  7. Using the
    New Members
     setting, add each resource that you want to include in the pool:
    1. (Optional) In the
      Node Name
       field, type a name for the node portion of the pool member.
    2. In the
      Address
       field, type an IP address.
    3. In the
      Service Port
       field, type a port number, or select a service name from the list.
    4. (Optional) In the
      Priority
       field, type a priority number.
    5. Click
      Add
      .
  8. Click
    Finished
    .
The pool of ICAP load balancing servers appears in the Pools list.

Creating an internal virtual server for forwarding requests to an ICAP server

A virtual server of type
internal
 provides a destination that a
standard
 type of virtual server can use when forwarding HTTP requests slated for ICAP-based content adaptation.
  1. On the Main tab, click
    Local Traffic
    Virtual Servers
    .
    The Virtual Server List screen opens.
  2. Click
    Create
    .
    The New Virtual Server screen opens.
  3. In the
    Name
     field, type a unique name for the virtual server.
  4. In the
    Description
     field, type a description of the virtual server.
    For example:
    This virtual server ensures HTTP request modification through the use of the
    service_name
     ICAP service.
    .
  5. From the
    Type
     list, select
    Internal
    .
  6. For the
    State
     setting, verify that the value is set to
    Enabled
    .
  7. From the
    Configuration
     list, select
    Advanced
    .
  8. From the
    ICAP Profile
     list, select the ICAP profile that you previously created for handling HTTP requests.
  9. From the
    Default Pool
     list, select the pool of ICAP servers that you previously created.
  10. Click
    Finished
    .
After you perform this task, a standard type of virtual server can forward HTTP requests to an internal type of virtual server. The internal virtual server then sends the request to a pool of ICAP servers, before sending the request back to the standard virtual server for forwarding to the pool of web servers.

Creating a custom Request Adapt profile

You create a Request Adapt type of profile when you want a standard HTTP virtual server to forward HTTP requests to an internal virtual server that references a pool of ICAP servers. A Request Adapt type of profile instructs the HTTP virtual server to send an HTTP request to a named internal virtual server for possible request modification.
  1. On the Main tab, click
    Local Traffic
    Profiles
    Services
    Request Adapt
    .
  2. Click
    Create
    .
  3. In the
    Name
     field, type a unique name for the profile.
  4. For the
    Parent Profile
     setting, retain the default value,
    requestadapt
    .
  5. On the right-side of the screen, clear the
    Custom
     check box.
  6. For the
    Enabled
     setting, retain the default value,
    Enabled
    .
    When you set this value to
    Enabled
    , the BIG-IP system forwards HTTP requests to the specified internal virtual server for adaptation.
  7. From the
    Internal Virtual Name
     list, select the name of the internal virtual server that you previously created for forwarding HTTP requests to the pool of iCAP servers.
  8. In the
    Preview Size
     field, type a numeric value.
    This specifies the maximum size of the preview buffer. This buffer holds a copy of the HTTP request header and the data sent to the internal virtual server, in case the adaptation server reports that no adaptation is needed. Setting the preview size to
    0
     disables buffering of the request and should only be done if the adaptation server always returns a modified HTTP request or the original HTTP request.
  9. In the
    Timeout
     field, type a numeric value, in seconds.
    If the internal virtual server does not return a result within the specified time, a timeout error occurs. To disable the timeout, use the value
    0
    .
  10. From the
    Service Down Action
     list, select an action for the BIG-IP system to take if the internal virtual server returns an error:
    • Select
      Ignore
       to instruct the BIG-IP system to ignore the error and send the unmodified HTTP request to an HTTP server in the HTTP server pool.
    • Select
      Drop
       to instruct the BIG-IP system to drop the connection.
    • Select
      Reset
       to instruct the BIG-IP system to reset the connection.
  11. Click
    Finished
    .
After you perform this task, the BIG-IP system contains a Request Adapt profile that a standard HTTP virtual server can use to forward an HTTP request to an internal virtual server for ICAP traffic.

Creating a custom HTTP profile

An HTTP profile defines the way that you want the BIG-IPsystem to manage HTTP traffic.
Other HTTP profile types (HTTP Compression and Web Acceleration) enable you to configure compression and cache settings, as required. Use of these profile types is optional.
  1. On the Main tab, click
    Local Traffic
    Profiles
    Services
    HTTP
    .
    The HTTP profile list screen opens.
  2. Click
    Create
    .
    The New HTTP Profile screen opens.
  3. In the
    Name
     field, type a unique name for the profile.
  4. From the
    Parent Profile
     list, select
    http
    .
  5. Select the
    Custom
     check box.
  6. Modify the settings, as required.
  7. Click
    Finished
    .
The custom HTTP profile now appears in the HTTP profile list screen.

Create a pool to process HTTP traffic

You can create a pool of web servers to process HTTP requests.
  1. On the Main tab, click
    Local Traffic
    Pools
    .
    The Pool List screen opens.
  2. Click
    Create
    .
    The New Pool screen opens.
  3. In the
    Name
     field, type a unique name for the pool.
  4. For the
    Health Monitors
     setting, from the
    Available
     list, select the
    http
     monitor and move the monitor to the
    Active
     list.
  5. From the
    Load Balancing Method
     list, select how the system distributes traffic to members of this pool.
    The default is
    Round Robin
    .
  6. For the
    Priority Group Activation
     setting, specify how to handle priority groups:
    • Select
      Disabled
       to disable priority groups. This is the default option.
    • Select
      Less than
      , and in the
      Available Members
       field type the minimum number of members that must remain available in each priority group in order for traffic to remain confined to that group.
  7. Using the
    New Members
     setting, add each resource that you want to include in the pool:
    1. Type an IP address in the
      Address
       field.
    2. Type
      80
       in the
      Service Port
       field, or select
      HTTP
       from the list.
    3. (Optional) Type a priority number in the
      Priority
       field.
    4. Click
      Add
      .
  8. Click
    Finished
    .

Creating an HTTP virtual server for enabling request adaptation

You perform this task to create a standard virtual server that can forward an HTTP request to an internal virtual server. The internal virtual server then sends the request to a pool of ICAP servers before the BIG-IP system sends the request to the web server.
  1. On the Main tab, click
    Local Traffic
    Virtual Servers
    .
    The Virtual Server List screen opens.
  2. Click
    Create
    .
    The New Virtual Server screen opens.
  3. In the
    Name
     field, type a unique name for the virtual server.
  4. In the
    Destination Address
     field, type the IP address that you want to use as a destination for client traffic destined for a pool of HTTP web servers.
    The supported format is address/prefix, where the prefix length is in bits. For example, an IPv4 address/prefix is
    10.0.0.1
     or
    10.0.0.0/24
    , and an IPv6 address/prefix is
    ffe1::0020/64
     or
    2001:ed8:77b5:2:10:10:100:42/64
    . When you use an IPv4 address without specifying a prefix, the BIG-IP system automatically uses a
    /32
     prefix.
    The IP address you type must be available and not in the loopback network.
  5. In the
    Service Port
     field, type
    443
     or select
    HTTPS
     from the list.
    If traffic is on a secure internal network, you can use
    80
    /
    HTTP
    .
  6. From the
    Configuration
     list, select
    Advanced
    .
  7. From the
    HTTP Profile
     list, select the name of the HTTP profile that you created previously.
  8. From the
    Request Adapt Profile
     list, select the name of the Request Adapt profile that you previously created.
  9. From the
    Source Address Translation
     list, select
    Auto Map
    .
  10. From the
    Default Pool
     list, select the name of the HTTP server pool that you previously created.
  11. Click
    Finished
    .
After you create the virtual server, the BIG-IP system can forward an HTTP request to a pool of ICAP servers before sending the request to the web server.

Implementation result

After you complete the tasks in this implementation, the BIG-IP system can perform content adaptation on HTTP requests as they pass through the BIG-IP system during normal HTTP processing. The new objects that this implementation creates are:
  • A custom ICAP profile
  • A pool of ICAP content adaptation servers
  • An internal virtual server that load balances HTTP requests to the ICAP pool
  • A custom Request Adapt profile that references the internal virtual server
  • A custom HTTP profile
  • A standard HTTP pool of web servers
  • A standard HTTP virtual server that sends HTTP requests to an internal virtual server for content adaptation and load balances HTTP requests to the web pool
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