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> Chapter 35 - WAN Optimization, Web Cache, Explicit Proxy, and WCCP > FortiGate WCCP

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FortiGate WCCP

The Web Cache Communication Protocol (WCCP) can be used to provide web caching with load balancing and fault tolerance. In a WCCP configuration, a WCCP server receives HTTP requests from user’s web browsers and redirects the requests to one or more WCCP clients. The clients either return cached content or request new content from the destination web servers before caching it and returning it to the server which in turn returns the content to the original requestor. If a WCCP configuration includes multiple WCCP clients, the WCCP server load balances traffic among the clients and can detect when a client fails and failover sessions to still operating clients. WCCP is described by the Web Cache Communication Protocol Internet draft.

The sessions that are cached by WCCP depend on the configuration of the WCCP clients. If the client is a FortiGate unit, you can configure the port numbers and protocol number of the sessions to be cached. For example, to cache HTTPS traffic on port 443 the WCCP client port must be set to 443 and protocol must be set to 6. If the WCCP client should also cache HTTPS traffic on port 993 the client ports option should include both port 443 and 993.

On a FortiGate unit, WCCP sessions are accepted by a security policy before being cached. If the security policy that accepts sessions that do not match the port and protocol settings in the WCCP clients the traffic is dropped.

WCCP is configured per-VDOM. A single VDOM can operate as a WCCP server or client (not both at the same time). FortiGate units are compatible with third-party WCCP clients and servers. If a FortiGate unit is operating as an Internet firewall for a private network, you can configure it to cache and serve some or all of the web traffic on the private network using WCCP by adding one or more WCCP clients, configuring WCCP server settings on the FortiGate unit and adding WCCP security policies that accept HTTP session from the private network.

FortiGate units support WCCPv1 and WCCPv2. A FortiGate unit in NAT/Route or transparent mode can operate as a WCCP server. To operate as a WCCP client a FortiGate unit must be in NAT/Route mode. FortiGate units communicate between WCCP servers and clients over UDP port 2048. This communication can be encapsulated in a GRE tunnel or just use layer 2 forwarding.

note icon A WCCP server can also be called a WCCP router. A WCCP client can also be called a WCCP cache engine.

WCCP service groups, service numbers, service IDs and well known services

A FortiGate unit configured as a WCCP server or client can include multiple server or client configurations. Each of these configurations is called a WCCP service group. A service group consists of one or more WCCP servers (or routers) and one or more WCCP clients working together to cache a specific type of traffic. The service group configuration includes information about the type of traffic to be cached, the addresses of the WCCP clients and servers and other information about the service.

A service group is identified with a numeric WCCP service ID (or service number) in the range 0 to 255. All of the servers and clients in the same WCCP service group must have service group configurations with the same WCCP service ID.

The value of the service ID provides some information about the type of traffic to be cached by the service group. Service IDs in the range 0 to 50 are reserved for well known services. A well known service is any service that is defined by the WCCP standard as being well known. Since the service is well known, just the service ID is required to identify the traffic to be cached.

Even though the well known service ID range is 0 to 50, at this time only one well known service has been defined. Its service ID 0, which is used for caching HTTP (web) traffic.

So to configure WCCP to cache HTTP sessions you can add a service group to the WCCP router and WCCP clients with a service ID of 0. No other information about the type of traffic to cache needs to be added to the service group.

Since service IDs 1 to 50 are reserved for well know services and since these services are not defined yet, you should not add service groups with IDs in the range 1 to 50.

note icon FortiOS does allow you to add service groups with IDs between 1 and 50. Since these service groups have not been assigned well known services, however, they will not cache any sessions. Service groups with IDs 51 to 255 allow you to set the port numbers and protocol number of the traffic to be cached. So you can use service groups with IDs 51 to 255 to cache different kinds of traffic based on port numbers and protocol number of the traffic. Service groups 1 to 50; however, do not allow you to set port numbers or protocol numbers so cannot be used to cache any traffic.

To cache traffic other than HTTP traffic you must add service groups with IDs in the range 51 to 255. These service group configurations must include the port numbers and protocol number of the traffic to be cached. It is the port and protocol number configuration in the service group that determines what traffic will be cached by WCCP.

Example WCCP server and client configuration for caching HTTP sessions (service ID = 0)

Enter the following command to add a WCCP service group to a WCCP server that caches HTTP sessions. The IP address of the server is 10.31.101.100 and the WCCP clients are on the 10.31.101.0 subnet. The service

ID of this service group is 0.

config system wccp

edit 0

set router-id 10.31.101.100

set server-list 10.31.101.0 255.255.255.0

end

Enter the following commands to configure a FortiGate unit to operate as a WCCP client and add a service group that configures the client to cache HTTP sessions. The IP address of the server is 10.31.101.100 and IP address of this WCCP clients is 10.31.101.1 subnet. The service ID of this service group is 0.

config system settings

set wccp-cache-engine enable

end

 

config system wccp

edit 0

set cache-id 10.31.101.1

set router-list 10.31.101.100

end

note icon You cannot enter the wccp-cache-engine enable command if you have already added a WCCP service group. When you enter this command an interface named w.<vdom_name> is added to the FortiGate configuration (for example w.root). All traffic redirected from a WCCP router is considered to be received at this interface of the FortiGate unit operating as a WCCP client. A default route to this interface with lowest priority is added.

Example WCCP server and client configuration for caching HTTPS sessions

Enter the following command to add a service group to a WCCP server that caches HTTPS content on port 443 and protocol 6. The IP address of the server is 10.31.101.100 and the WCCP clients are on the 10.31.101.0 subnet. The service ID of this service group is 80.

config system settings

set wccp-cache-engine enable

end

 

config system wccp

edit 80

set router-id 10.31.101.100

set server-list 10.31.101.0 255.255.255.0

set ports 443

set protocol 6

end

Enter the following commands to configure a FortiGate unit to operate as a WCCP client and add a service group that configures client to cache HTTPS sessions on port 443 and protocol 6. The IP address of the server is 10.31.101.100 and IP address of this WCCP clients is 10.31.101.1 subnet. The service ID of this service group must be 80 to match the service ID added to the server.

config system settings

set wccp-cache-engine enable

end

 

config system wccp

edit 80

set cache-id 10.31.101.1

set router-list 10.31.101.100

set ports 443

set protocol 6

end

Example WCCP server and client configuration for caching HTTP and HTTPS sessions

You could do this by configuring two WCCP service groups as described in the previous examples. Or you could use the following commands to configure one service group for both types of traffic. The example also caches HTTP sessions on port 8080.

Enter the following command to add a service group to a WCCP server that caches HTTP sessions on ports 80 and 8080 and HTTPS sessions on port 443. Both of these protocols use protocol number 6. The IP address of the server is 10.31.101.100 and the WCCP clients are on the 10.31.101.0 subnet. The service ID of this service group is 90.

config system wccp

edit 90

set router-id 10.31.101.100

set server-list 10.31.101.0 255.255.255.0

set ports 443 80 8080

set protocol 6

end

Enter the following commands to configure a FortiGate unit to operate as a WCCP client and add a service group that configures client to cache HTTP sessions on port 80 and 8080 and HTTPS sessions on port 443. The IP address of the server is 10.31.101.100 and IP address of this WCCP clients is 10.31.101.1 subnet. The service ID of this service group must be 90 to match the service ID added to the server.

config system settings

set wccp-cache-engine enable

end

config system wccp

edit 90

set cache-id 10.31.101.1

set router-list 10.31.101.100

set ports 443 80 8080

set protocol 6

end

Other WCCP service group options

In addition to using WCCP service groups to define the types of traffic to be cached by WCCP the following options are available for servers and clients.

Server configuration options

The server configuration must include the router-id, which is the WCCP server IP address. This is the IP address of the interface that the server uses to communicate with WCCP clients.

The group-address is used for multicast WCCP configurations to specify the multicast addresses of the clients.

The server-list defines the IP addresses of the WCCP clients that the server can connect to. Often the server list can be the address of the subnet that contains the WCCP clients.

The authentication option enables or disables authentication for the WCCP service group. Authentication must be enabled on all servers and clients in a service group and members of the group must have the same password.

The forward-method option specifies the protocol used for communication between the server and clients. The default forwarding method is GRE encapsulation. If required by your network you can also select to use unencapsulated layer-2 packets instead of GRE or select any to allow both. The return-method allows you to specify the communication method from the client to the server. Both GRE and layer-2 are supported.

The assignment-method determines how the server load balances sessions to the clients if there are multiple clients. Load balancing can be done using hashing or masking.

Client configuration options

The client configuration includes the cache-id which is the IP address of the FortiGate interface of the client that communicates with WCCP server. The router-list option is the list of IP addresses of the WCCP servers in the WCCP service group.

The ports option lists the port numbers of the sessions to be cached by the client and the protocol sets the protocol number of the sessions to be cached. For TCP sessions the protocol is 6.

The service-type option can be auto, dynamic or standard. Usually you would not change this setting.

The client configuration also includes options to influence load balancing including the primary-hash, priority, assignment-weight and assignment‑bucket‑format.

WCCP configuration overview

To configure WCCP you must create a service group that includes WCCP servers and clients. WCCP servers intercept sessions to be cached (for example, sessions from users browsing the web from a private network). To intercept sessions to be cached the WCCP server must include a security policy that accepts sessions to be cached and WCCP must be enabled in this security policy.

The server must have an interface configured for WCCP communication with WCCP clients. That interface sends and receives encapsulated GRE traffic to and from WCCP clients. The server must also include a WCCP service group that includes a service ID and the addresses of the WCCP clients as well as other WCCP configuration options.

To use a FortiGate unit as a WCCP client, the FortiGate unit must be set to be a WCCP client (or cache engine). You must also configure an interface on the client for WCCP communication. The client sends and receives encapsulated GRE traffic to and from the WCCP server using this interface.

The client must also include a WCCP service group with a service ID that matches a service ID on the server. The client service group also includes the IP address of the servers in the service group and specifies the port numbers and protocol number of the sessions that will be cached on the client.

When the client receives sessions from the server on its WCCP interface, it either returns cached content over the WCCP interface or connects to the destination web servers using the appropriate interface depending on the client routing configuration. Content received from web servers is then cached by the client and returned to the WCCP server over the WCCP link. The server then returns the received content to the initial requesting user web browser.

Finally you may also need to configure routing on the server and client FortiGate units and additional security policies may have to be added to the server to accept sessions not cached by WCCP.

Example caching HTTP sessions on port 80 using WCCP

In this example configuration (shown below), a FortiGate unit with host name WCCP_srv is operating as an Internet firewall for a private network is also configured as a WCCP server. The port1 interface of WCCP_srv is connected to the Internet and the port2 interface is connected to the internal network.

All HTTP traffic on port 80 that is received at the port2 interface of WCCP_srv is accepted by a port2 to port1 security policy with WCCP enabled. All other traffic received at the port2 interface is allowed to connect to the Internet by adding a general port2 to port1 security policy below the HTTP on port 80 security policy.

A WCCP service group is added to WCCP_srv with a service ID of 0 for caching HTTP traffic on port 80. The port5 interface of WCCP_srv is configured for WCCP communication.

A second FortiGate unit with host name WCCP_client is operating as a WCCP client. The port1 interface of WCCP_client is connected to port5 of WCCP_srv and is configured for WCCP communication.

WCCP_client is configured to cache HTTP traffic because it also has a WCCP service group with a service ID of 0.

WCCP_client connects to the Internet through WCCP_srv. To allow this, a port5 to port1 security policy is added to WCCP_srv.

FortiGate WCCP server and client configuration

Configuring the WCCP server (WCCP_srv)

Use the following steps to configure WCCP_srv as the WCCP server for the example network. The example steps only describe the WCCP-related configuration.

To configure WCCP_srv as a WCCP server
  1. Add a port2 to port1 security policy that accepts HTTP traffic on port 80 and is configured for WCCP:

config firewall policy

edit 0

set srtintf port1

set dstintf port2

set srcaddr all

set dstaddr all

set action accept

set schedule always

set service HTTP

set wccp enable

set nat enable

end

 

  1. Add another port2 to port1 security policy to allow all other traffic to connect to the Internet.

config firewall policy

edit 0

set srtintf port1

set dstintf port2

set srcaddr all

set dstaddr all

set action accept

set schedule always

set service ANY

set nat enable

end

 

  1. Move this policy below the WCCP policy in the port2 to port1 policy list.
  2. Enable WCCP on the port5 interface.

config system interface

edit port5

set wccp enable

end

 

  1. Add a WCCP service group with service ID 0.

config system wccp

edit 0

set router-id 10.51.101.100

set server-list 10.51.101.0 255.255.255.0

end

 

  1. Add a firewall address and security policy to allow the WCCP_client to connect to the internet.

config firewall address

edit WCCP_client_addr

set subnet 10.51.101.10

end

config firewall policy

edit 0

set srtintf port5

set dstintf port1

set srcaddr WCCP_client_addr

set dstaddr all

set action accept

set schedule always

set service ANY

set nat enable

end

Configuring the WCCP client (WCCP_client)

Use the following steps to configure WCCP_client as the WCCP client for the example network. The example steps only describe the WCCP-related configuration.

To configure WCCP_client as a WCCP client
  1. Configure WCCP_client to operate as a WCCP client.

config system settings

set wccp-cache-engine enable

end

note icon You cannot enter the wccp-cache-engine enable command if you have already added a WCCP service group. When you enter this command an interface named w.<vdom_name> is added to the FortiGate configuration (for example w.root). All traffic redirected from a WCCP router is considered to be received at this interface of the FortiGate unit operating as a WCCP client. A default route to this interface with lowest priority is added.
  1. Enable WCCP on the port1 interface.

config system interface

edit port1

set wccp enable

end

 

  1. Add a WCCP service group with service ID 0.

config system wccp

edit 0

set cache-id 10.51.101.10

set router-list 10.51.101.100

end

 

Example caching HTTP sessions on port 80 and HTTPS sessions on port 443 using WCCP

This example configuration is the same as thatdescribed in Example caching HTTP sessions on port 80 using WCCP except that WCCP now also cached HTTPS traffic on port 443. To cache HTTP and HTTPS traffic the WCCP service group must have a service ID in the range 51 to 255 and you must specify port 80 and 443 and protocol 6 in the service group configuration of the WCCP client.

Also the security policy on the WCCP_srv that accepts sessions from the internal network to be cached must accept HTTP and HTTPS sessions.

Configuring the WCCP server (WCCP_srv)

Use the following steps to configure WCCP_srv as the WCCP server for the example network. The example steps only describe the WCCP-related configuration.

To configure WCCP_srv as a WCCP server
  1. Add a port2 to port1 security policy that accepts HTTP traffic on port 80 and HTTPS traffic on port 443 and is configured for WCCP:

config firewall policy

edit 0

set srtintf port2

set dstintf port1

set srcaddr all

set dstaddr all

set action accept

set schedule always

set service HTTP HTTPS

set wccp enable

set nat enable

end

 

  1. Add another port2 to port1 security policy to allow all other traffic to connect to the Internet.

config firewall policy

edit 0

set srtintf port2

set dstintf port1

set srcaddr all

set dstaddr all

set action accept

set schedule always

set service ANY

 

set nat enable

end

 

  1. Move this policy below the WCCP policy in the port2 to port1 policy list.
  2. Enable WCCP on the port5 interface.

config system interface

edit port5

set wccp enable

end

 

  1. Add a WCCP service group with service ID 90 (can be any number between 51 and 255).

config system wccp

edit 90

set router-id 10.51.101.100

set server-list 10.51.101.0 255.255.255.0

end

 

  1. Add a firewall address and security policy to allow the WCCP_client to connect to the internet.

config firewall address

edit WCCP_client_addr

set subnet 10.51.101.10

end

config firewall policy

edit 0

set srtintf port5

set dstintf port1

set srcaddr WCCP_client_addr

set dstaddr all

set action accept

set schedule always

set service ANY

set nat enable

end

Configuring the WCCP client (WCCP_client)

Use the following steps to configure WCCP_client as the WCCP client for the example network. The example steps only describe the WCCP-related configuration.

To configure WCCP_client as a WCCP client
  1. Configure WCCP_client to operate as a WCCP client.

config system settings

set wccp-cache-engine enable

end

note icon You cannot enter the wccp-cache-engine enable command if you have already added a WCCP service group. When you enter this command an interface named w.<vdom_name> is added to the FortiGate configuration (for example w.root). All traffic redirected from a WCCP router is considered to be received at this interface of the FortiGate unit operating as a WCCP client. A default route to this interface with lowest priority is added.
  1. Enable WCCP on the port1 interface.

config system interface

edit port1

set wccp enable

end

 

  1. Add a WCCP service group with service ID 90. This service group also specifies to cache sessions on ports 80 and 443 (for HTTP and HTTPS) and protocol number 6.

config system wccp

edit 90

set cache-id 10.51.101.10

set router-list 10.51.101.100

ports 80 443

set protocol 6

end

WCCP packet flow

The following packet flow sequence assumes you have configured a FortiGate unit to be a WCCP server and one or more FortiGate units to be WCCP clients.

  1. A user’s web browser sends a request for web content.
  2. The FortiGate unit configured as a WCCP server includes a security policy that intercepts the request and forwards it to a WCCP client.

    The security policy can apply UTM features to traffic accepted by the policy.
  3. The WCCP client receives the WCCP session.
  4. The client either returns requested content to the WCCP server if it is already cached, or connects to the destination web server, receives and caches the content and then returns it to the WCCP server.
  5. The WCCP server returns the requested content to the user’s web browser.
  6. The WCCP router returns the request to the client web browser.

    The client we browser is not aware that all this is taking place and does not have to be configured to use a web proxy.

Configuring the forward and return methods and adding authentication

The WCCP forwarding method determines how intercepted traffic is transmitted from the WCCP router to the WCCP cache engine. There are two different forwarding methods:

  • GRE forwarding (the default) encapsulates the intercepted packet in an IP GRE header with a source IP address of the WCCP router and a destination IP address of the target WCCP cache engine. The results is a tunnel that allows the WCCP router to be multiple hops away from the WCCP cache server.
  • L2 forwarding rewrites the destination MAC address of the intercepted packet to match the MAC address of the target WCCP cache engine. L2 forwarding requires that the WCCP router is Layer 2 adjacent to the WCCP client.

You can use the following command on a FortiGate unit configured as a WCCP router to change the forward and return methods to L2:

config system wccp

edit 1

set forward-method L2

set return-method L2

end

You can also set the forward and return methods to any in order to match the cache server configuration.

By default the WCCP communication between the router and cache servers is unencrypted. If you are concerned about attackers sniffing the information in the WCCP stream you can use the following command to enable hash-based authentication of the WCCP traffic. You must enable authentication on the router and the cache engines and all must have the same password.

config system wccp

edit 1

set authentication enable

set password <password>

end

WCCP Messages

When the WCCP service is active on a web cache server it periodically sends a WCCP HERE I AM broadcast or unicast message to the FortiGate unit operating as a WCCP router. This message contains the following information:

  • Web cache identity (the IP address of the web cache server).
  • Service info (the service group to join).

If the information received in the previous message matches what is expected, the FortiGate unit replies with a WCCP I SEE YOU message that contains the following details:

  • Router identity (the FortiGate unit’s IP address.
  • Sent to IP (the web cache IP addresses to which the packets are addressed)

When both ends receive these two messages the connection is established, the service group is formed and the designated web cache is elected.

Troubleshooting WCCP

Two types of debug commands are available for debugging or troubleshooting a WCCP connection between a FortiGate unit operating as a WCCP router and its WCCP cache engines.

Real time debugging

The following commands can capture live WCCP messages:

diag debug en

diag debug application wccpd <debug level>

Application debugging

The following commands display information about WCCP operations:

get test wccpd <integer>

diag test application wccpd <integer>

Where <integer> is a value between 1 and 6:

  1. Display WCCP stats
  2. Display WCCP config
  3. Display WCCP cache servers
  4. Display WCCP services
  5. Display WCCP assignment
  6. Display WCCP cache status

Enter the following command to view debugging output:

diag test application wccpd 3

Sample output from a successful WCCP connection:

service-0 in vdom-root: num=1, usable=1

cache server ID:

len=44, addr=172.16.78.8, weight=4135, status=0

rcv_id=6547, usable=1, fm=1, nq=0, dev=3(k3),

to=192.168.11.55

ch_no=0, num_router=1:

192.168.11.55

Sample output from the same command from an unsuccessful WCCP connection (because of a service group password mismatch):

service-0 in vdom-root: num=0, usable=0

diag debug application wccpd -1

Sample output:

wccp_on_recv()-98: vdom-root recv: num=160, dev=3(3),

172.16.78.8->192.168.11.55

wccp2_receive_pkt()-1124: len=160, type=10, ver=0200,

length=152

wccp2_receive_pkt()-1150: found component:t=0, len=20

wccp2_receive_pkt()-1150: found component:t=1, len=24

wccp2_receive_pkt()-1150: found component:t=3, len=44

wccp2_receive_pkt()-1150: found component:t=5, len=20

wccp2_receive_pkt()-1150: found component:t=8, len=24

wccp2_check_security_info()-326: MD5 check failed