Specifications

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Cisco TV CDS 2.5 ISA Software Configuration Guide
OL-24788-01
Chapter 2 Network Design
CDS Workflow
Setup Server
A Streamer designated as the Setup server interfaces with the backoffice and forwards the setup
messages to the appropriate Stream Group that is assigned to the destination service group. One
Streamer in the Stream Group that is colocated with the backoffice server is assigned as the primary
Setup server. The Setup server receives the setup request from the backoffice and maps the service group.
The Setup server returns the IP address of the Control server, and the STB issues subsequent control
messages to this IP address.
Control Server
The Control server assigns requests to specific Streamers and dynamically migrates streams between
Streamers based upon changes in stream states (for example, content splice boundaries, maintenance
trickle down, or server failures). One server in the Stream Group is assigned as the primary Control
server. The Control server runs the Lightweight Stream Control Protocol (LSCP) proxy in an ISA
environment and the Real-Time Streaming Protocol (RTSP) proxy in an RTSP environment.
For each and every setup message received from the backoffice, a CCP message is generated and sent to
the Control server. In the initial setup request, the Control server receives the setup parameters but does
not choose a Play server. After a control message is received from the STB, the Control server gets
performance information (for example, server load) from the potential Play servers within the Stream
Group and sends a CCP message to the best candidate. Subsequent control messages, whether from the
STB or from the Setup server, are forwarded to the chosen Play server.
Play Server
The Play server is the Streamer that is assigned to play the stream. This Streamer acquires the content,
whether in RAM, a local disk, or a Vault, and ensures guaranteed service delivery of the stream. Every
Streamer in a Stream Group is a possible candidate to be the Play server.
Caching Node Workflow
A Cache Group is a configurable group of Caching Nodes that serve content to specified Stream Groups.
When a content request is received by a Streamer, the Streamer first checks to see if the content is stored
locally, which includes DRAM, disk cache, and Streamers in the same Stream Group. Content on the
Streamers is always the most popular content, so user requests are generally served from local storage.
Streamers send cache-fill calls to remote servers for content that is not found locally. The remote servers
can be Streamers in other Stream Groups, Caching Nodes in Cache Groups, or Vaults in Vault Groups
(Vault Groups must be enabled). The cache-fill source selected, whether another Streamer, Caching
Node, or Vault, is based on the network capacity and fill-source capacity (disk and memory), as well as
on the preference configured for that group of servers. Caching Nodes could respond to the request with
a message stating the content is not currently cached, but there are other fill sources the Caching Nodes
can contact (Caching Nodes in other Cache groups, and Vaults).
The Caching Nodes use CCP to communicate with the Vaults, and use either CCP or HTTP to
communicate with Streamers.
Note ISA environments support only CCP, while RTSP environments support only HTTP for VVI.