Overview of WCCP-Based Traffic Redirection

The WCCP-based traffic redirection feature allows customers to use the PacketShaper and iShared appliance at the same site and get full benefits of both appliances. The PacketShaper transparently redirects traffic to the branch office iShared appliance for optimization and reduction, and then iShared sends it back to the PacketShaper for control and further compression and/or acceleration. PacketShaper uses the Web Cache Communication Protocol (WCCP) v2 to redirect traffic to the iShared appliance via a generic routing encapsulation (GRE) tunnel.

PacketShaper is connected to the WAN router, allowing it to classify and control all WAN-bound traffic. The cache device is connected to the LAN switch so that it can communicate directly to the clients without having to go through the PacketShaper. The following diagram shows the supported redirection topology.

The diagram above illustrates the redirection process using an iShared appliance. Here are additional details about the process:

1. A client initiates a request to the server located at the data center. This request goes through the PacketShaper.
2. The PacketShaper encapsulates the packets into a GRE packet and redirects this request to the iShared appliance. Note that the packets will not be processed by the PacketShaper’s classification, monitoring, and control features before redirection.
3. One of the following happens:

• If the traffic is eligible for optimization, iShared optimizes the packets and sends them through a WDC (wide dictionary compression) tunnel to the iShared appliance at the data center. PacketShaper classifies this traffic as WDC.
• If the traffic cannot be optimized, iShared returns the packets through a GRE tunnel to the PacketShaper. The GRE packets will then be de-encapsulated, classified, controlled, and sent to their destination.
• If the file is available locally, the iShared appliance replies directly to the client. This traffic does not get classified since it doesn’t go back through the PacketShaper.

Feature Requirements

The WCCP-based traffic redirection feature has the following requirements:

• The management port (available on certain models) cannot be enabled for dedicated access, and you can enable WCCP only if the dedicated management port is disabled.
• Redirection cannot be performed in bypass or passthru modes.
• Redirection is supported on the following PacketShaper models: 1200, 1400, 1550, 1700, 2500 (with 512 MB of memory), 3500, 6500, 7500, 8500, 9500, and 10000.
• Redirection is supported on all currently shipping Windows iShared models, running version 3.2.1 or higher.
• Redirection must be configured on the PacketShaper and the iShared appliance.
• The gateway must be on the outside. (To see which side the gateway is on, use the arp show or host show <gateway-IP> CLI command.
• WCCP should be disabled on the router.
• SCPS acceleration should not be enabled on the PacketShaper.

Limitations

The WCCP-based traffic redirection feature has the following limitations:

• You can configure redirection on a single interface pair only. For example, you can configure the INSIDE and OUTSIDE ports on a lower LEM, but you cannot configure the INSIDE port on the main device and the INSIDE port on a lower LEM.
• Although you can configure an MD5 password on the PacketShaper, this type of authentication is not currently supported on the iShared appliance. Therefore, the password should not be used when pairing a PacketShaper with iShared.
• This feature does not support direct standby or watch mode.
• Topologies in which traffic between the iShared and PacketShaper bounce off of the gateway are not recommended due to a degradation in performance. An example of this type of topology is when iShared is on a different subnet from the PacketShaper and all GRE traffic goes outside to the router, then back through the PacketShaper to iShared.
• The PacketShaper will only redirect traffic destined for a different subnet.
• When using WCCPv2, only one cache device and one redirection device (PacketShaper) is supported. Load-balancing is not supported.

See also:

Notes on the WCCP-Based Traffic Redirection Feature

Configure PacketShaper for WCCP-Based Traffic Redirection

Configure a Cache Device for Redirection