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
The Web Engine communicates to the upstream Service Engine for cache fill operations. This interaction
is based on HTTP. This cache fill operation is on demand and hence only occurs when the content is not
stored locally. The upstream Service Engine can be selected dynamically by means of the Hierarchical
Cache Routing Module, or can be configured statically through the Internet Streaming CDSM. The
Hierarchical Cache Router generates a list of upstream Service Engines that are alive, ready to serve the
request, and part of the delivery service. If the Web Engine is unsuccessful in locating the content on one
of these Service Engines, the content is retrieved from the origin server.
Whether the content is found locally or retrieved and stored through the cache fill operation, the Web
Engine serves the content based on the following:
• Freshness of content—The freshness of prefetched content is governed by a time-to-live (TTL)
value set for the content in the delivery service configuration. The TTL specifies the rate at which
content freshness is checked. For cached content, which is content ingested by means of the dynamic
ingest or hybrid ingest method, the freshness check is performed by the Web Engine in compliance
with RFC 2616. For expired cached content, the local copy is deleted and fresh content is ingested.
• Rate of data transfer—The rate at which the content is sent can be configured on a per-delivery
basis. By default, LAN bandwidth is used.
• Content completeness—Prefetched content is stored locally in the CDS in its entirety. For cached
content, there are two cases when the content is not complete:
– The Web Engine process halts or the Service Engine experiences a failure in the process of
caching the content. In this case, the subsequent request starts the cache fill anew.
– The content is in the process of being cached by another request. In this case, the subsequent
request is served from the cached content.
Authentication
The Web Engine supports a pass-through mode of authentication, whereby the origin server negotiates
authentication and the Web Engine passes the requests and responses between the client device and the
origin server. Content that requires authentication is not cached by the Service Engine, so all requests
for authenticated content are retrieved from the origin server.
Service Rules
Service rules can be configured that dictate how the Web Engine responds when client requests match
specific patterns. The patterns can be a domain or host name, certain header information, the request
source IP address, or a Uniform Resource Identifier (URI). Some of the possible responding actions are
to allow or block the request, generate or validate the URL signature, send an ICAP request to the policy
server, or rewrite or redirect the URL.
Windows Media Engine
The Windows Media Engine uses Windows Media Technology (WMT), a set of streaming solutions for
creating, distributing, and playing back digital media files across the Internet. WMT includes the
following applications:
• Windows Media Player—End-user application
• Windows Media Server—Server and distribution application
• Windows Media Encoder—Encodes media files for distribution
• Windows Media Codec—Compression algorithm applied to live and on-demand content
• Windows Media Rights Manager (WMRM)—Encrypts content and manages user privileges