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CPS
A11
CPS-SPS
Delivery
System
The DAVIC protocol specification is based on the DSM-CC specification. All U-U (User to User)
signaling from the STU to service provider takes place over RPC, and content and data download is
carried by MPEG-2 transport packets. To pass a message the STU will need to do a number of processing
including message fragmentation and protocol encapsulation. These protocols are classified into the
following information flows, namely, S1 flow for content and data delivery, S2 flow for U-U messaging
and S3 flow for U-N messaging.
4.1.1 Content Provider System (CPS)
The main function of the CPS is to provide for functionality for content providers to interact with the SPS
for loading and updating content information at the SPS using the CPS-SPS delivery system. The current
specification of DAVIC 1.0 does not deal with either CPS or CPS-SPS delivery system.
4.1.2 Service Provider System (SPS)
This system provides access for consumers to various services in the system. It comprises the 1) Content
Service Element (CSE) which provides processing for the SPS when content information is being loaded
to the server, 2) Application Service Element (ASE) which manages and processes application control
flow information, 3) Stream Service Element (SSE) which provides for processing of content information
flow at the stream level, 4) Session Control Function (SCF) which provides processing for establishing &
terminating sessions and specifies quality of service (QOS) requirements for both the application and
product entities, 5) Network Control Function (NCF) which provides for error-free transmission and
reception of content information flow to and from the server, and 6) Network Interface Function (NIF)
which handles network specific information flows and provides a non-network specific interface to the
rest of the SPS.
4.1.3 Service Consumer System (SCS)
A10
SPS
A9
SPS-SCS
Delivery
System
SCS comprises of the Set Top Unit(STU) or Set Top Box (STB) - This unit helps the human or machine
peripheral system interact with service providers. The STB comprises of the following components, 1)
Product Entity - This is responsible for accepting content information and presenting it to the peripheral
system transparently, 2) Application entity - Will handle interactive information processing for the
consumer, 3) Environment entity - Responsible for establishing and terminating the environment in which
an application will operate. QOS requirements for both consumer and product entities are a part of this
environment, 4) Connectivity entity - handles error-free transmission and reception of content to and from
STB, 5) Network interface unit - Provides a gateway for STB to communicate with the delivery system. It
is through this unit all content information flow will take place. It also provides for a non-network specific
interface.
1
2
3
4
5
A1
SCS
1. Principal
Service
interface
2. Application
Service
interface
3. Session &
Transport
Service
interface
4. Network
Service
interface
5. Physical
interface
Figure 2: DAVIC System Architecture (source: [DAVIC 95])