Specifications

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Cisco Internet Streamer CDS 2.0-2.3 Software Configuration Guide
OL-13493-04
Chapter 1 Product Overview
Content Delivery System Architecture
When content is requested by a client, the Service Router checks the client’s IP address to find the
coverage zone that contains that IP address. The Service Router then selects the Service Engine that
serves this coverage zone. If a specific IP address is in multiple coverage zones, the one with the more
specific range is selected. If no match is found in the coverage zone data and if location-based routing
is enabled on the Service Router, the Service Router looks up the best Service Engine closest to the
client. If the Service Router is unable to redirect the request, the Service Router sends an error response
to the client.
A coverage zone can be associated with one or more Service Engines. Each Service Engine can have its
own unique coverage zone, or the Service Engines can be associated with more than one coverage zone
and have over lapping coverage zones. In Figure 1-2, all Service Engines serve Coverage Zone 1, and
Service Engine 1 is specifically associated with Coverage Zone 2, a subset of Coverage Zone 1.
Figure 1-2 Coverage Zone Example
If a coverage zone is served by multiple Service Engines, all Service Engines are put in the routing table.
The metric value, entered in the Coverage Zone file, indicates the proximity of the Service Engine to the
client. When multiple Service Engines serving a coverage zone are on the same subnet and have the same
metric value, and load-based routing is not enabled, the Service Router uses round-robin routing to
redirect the client. If load-based routing is enabled, the load of the Service Engines are used to determine
the best Service Engine to redirect the client.
Routing Methods
The Service Router chooses the best Service Engine based on whether the Service Engine is participating
in the delivery service for which the origin server matches that of the requested domain and whether the
Service Engine is assigned to serve the client’s network region.
The Service Router uses four methods:
• Simplified hybrid routing (round-robin-based routing) (Releases 2.0 and 2.1)
• Load-based routing (least loaded)
• Last-resort routing (all Service Engines are overloaded)
• Location-based routing (off-net clients)
• Service aware routing
• Content-based routing
Coverage Zone 2
Coverage Zone 1
Service Engine 1
Service Engine 3
Service Engine 2
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