PCMM Components
The first step in understanding how PCMM works is to look at what the various contributing components are. Figure 14-1 is a high-level illustration of the devices involved in providing PacketCable Multimedia services.
PacketCable Multimedia Components
As you can see from the diagram, seven components are used to provide PCMM services:
- Multimedia clients
- Application Server
- Application Manager
- Policy Server
- Cable modem termination system (CMTS)
- Cable modem (CM)
- Record Keeping Server (RKS)
The following sections describe these components in further detail.
PacketCable Multimedia Clients
Logically, the multimedia client is the device using a multimedia service. One example would be a software application on a personal computer providing streaming audio or video, such as Internet radio or perhaps a movie. Another example is a gaming console connected to the Internet to play against an opponent across the country. Another example is a video camera and monitor used to provide a video conferencing service. And yes, another example is an MTA used to provide telephony service.
Usually, multimedia client devices are not provided by the MSO and are located at the customer's premises, so they are untrusted devices. These devices connect to the MSO network through the cable modem. This connection could be Ethernet, USB, or wireless. The exception to this is a multimedia client embedded in the cable modem itself, such as the embedded MTA you are no doubt familiar with by now.
PacketCable multimedia clients are categorized as one of three types:
Client Type 1—Client type 1 is what most of today's multimedia clients are. These clients have no knowledge or awareness of PacketCable, DOCSIS, or even QoS. In fact, this client type is commonly referred to as QoS-unaware. These clients are generic IP networking applications such as PC applications and gaming consoles.
These devices are at the mercy of the application manager to set up quality of service resources. You'll learn more about application managers later in the chapter.
Client Type 2—Client type 2 devices are similar to the embedded MTA devices used in PacketCable telephony. These devices are aware of PacketCable, DOCSIS, and QoS but they also require an application manager to do the QoS resource allocation and part of the authorization. However, this type of client still does much of the QoS resource manipulation. This type of client is commonly referred to as Push model.
Client Type 3—The third type of multimedia client is also PacketCable QoS-aware. The difference between it and a type 2 device is that these devices do not need an application manager to set up QoS resources. These devices use the Resource Reservation Protocol (RSVP) to communicate directly with the CMTS to set up QoS. This type of client is commonly referred to as Pull model.
Currently, only client type 1 devices have been fully defined in the PCMM specifications. Consequently, they are the focus of this chapter.