Basic planning considerations

Topology considerations

Topology factors

One goal of the planning process is to map the topology of the ContentDirector components:

Location of the core application machine
Location and number of group leaders and group members

Location of core application

Content sources, such as filers or conventional servers, provide the content that ContentDirector distributes to destinations. In general, locate the core application server as close as possible to these content sources for optimal performance. This means that the core application probably should reside near the center of your network.

Planning the location of group leaders

Consider the following factors when planning the location of group leaders:

Multicast or unicast delivery channels
Size and performance of the NetCache appliance
Location of firewalls
Topological location of the CDAs
Delivery speeds between group leaders and the core application

Multicast versus unicast

ContentDirector can use either unicast or multicast transmission between transport group leaders and members, depending on whether your network is multicast-enabled. Generally, group leaders should be placed in a location where they can use a multicast channel to send content to group members. Multicasting increases performance because group leaders can distribute a single copy of the data to multiple group members simultaneously.

The default transmission mode is unicast. ContentDirector automatically switches to multicast if it detects a multicast-enabled network.

Size and performance

Consider the size and performance of the NetCache appliances. If you want a NetCache appliance to be a group leader, does it have the capacity to handle the amount of content that might need to be pushed to group members? In a unicast network for example, a C6100 can distribute content to more group members than a C1100.

Firewalls

Consider the location of firewalls. If firewalls separate the group leader from group members or the core application, additional configuration might be required to facilitate content distribution. For example, firewalls might have port restrictions that block or limit ContentDirector traffic. See Deploying ContentDirector with firewalls for more information.

Topological location and delivery speeds

Typically, group leaders should be located as close to group members as possible to minimize bandwidth requirements. However, consider the topological location of the group leader in relation to the core application and other CDAs. Will the network link provide enough bandwidth for the group leader to efficiently retrieve content from the core application? Can the group leader deliver the content to group members using the least possible bandwidth?

Determining how many group leaders to assign

Consider the following factors when determining how many CDAs to assign as group leader:

Multicast or unicast delivery channels
Estimated workload
Scheduling requirements
Reliability

Multicast versus unicast

Typically, a multicast-enabled network can have more group members per group leader than a unicast network. In multicast networks, the group leader can send a single copy of the content to all group members. In contrast, in a unicast network, the group leader must deliver a separate copy of the content to each group member.

Multicast also reduces maintenance overhead. It enables ContentDirector to auto-discover group members, and allows you to configure multiple group leader candidates on a transport group.

Estimated workload and scheduling requirements

If you plan to distribute large files across a unicast network frequently, consider the size and performance of your group leader. For example, a C6100 can distribute content to multiple group members more efficiently than a C1100.

However, you can offset performance and load issues by increasing the ratio of group leaders to group members. To achieve this, make your transport groups smaller so that fewer group members are assigned to each group leader. For example, if a unicast transport group contains 11 group members and one group leader, divide the transport group into three separate transport groups--each containing three group members and a group leader.

Reliability

For maximum reliability, designate a minimum of two potential group leaders whenever possible. For example, designate one assigned group leader and one or more candidate group leaders to every network segment.

Setting up NetCache as reverse proxy for the core application

You can set up a NetCache appliance as a reverse proxy in front of the core application server. The NetCache can serve http traffic, and cache and deliver jobs to a large number of GLs, more efficiently than the embedded web server in ContentDirector. See the NetCache Accelerator First-Time Configuration Guide and the NetCache Configuration Guide for detailed instructions.