On Demand streaming – How does it work
Category: On Demand Streaming  
Level 3’s On Demand Streaming platform is unique in the CDN streaming industry in that it supports both forward and reverse proxy caching technology. This offers the customer the advantage of selecting a mode of operation that best suits their content needs. Customers must elect which form of proxy caching they will be using, albeit most customers elect to use reverse proxy mode as the main method of CDN stream platform ingestion.
Reverse Proxy Mode
When the Level 3 platform is working in reverse proxy mode, the streaming platform will actively draw the content onto the streaming platform from a customer’s Web server when content requests are made. This offers the advantage of not having to hand over the entire asset library over to Level 3, immediate access to new content, as well as a more simplified workflow. The con against using a reverse proxy is that upon an initial request, the first user’s response time will be slower as the content does not already reside on the local media server- the content needs to be retrieved first. On subsequent end user requests for the same streaming asset, the content is already resident on the edge; therefore, there is no performance lag. For most streaming content, there is more than a 1:1 delivery relationship, hence the initial performance lag is more than outweighed by the more simplified workflow and cost savings of not having to pay for additional storage on the Level 3 platform.
When using reverse proxy mode for On Demand streaming, the content must be exposed via a customer HTTP Web server. As an alternative, customer may elect to use Level 3’s Origin Storage product for hosting media files. The Level 3 edge media server will fetch the content via an HTTP request and draw the assets onto the platform using a just-in-time methodology. The Level 3 edge server does not need to receive the entire asset in order to stream the content. Once the edge server fills its buffer up enough to start playback, it will begin to stream the file to the end user.
Reverse Proxy – High Level Workflow process for On Demand streaming
Step 1: End User Requests for Stream Asset
The customer will embed the On Demand stream link within a Web page or directly request the media asset via an external stand alone player. The end user request is directed to a Level 3 streaming media sever.
Step 2: Fetching the Asset from the Origin Server
In the event that the Level 3 streaming media server does not have the content locally, it will initiate an HTTP request to the customer’s origin Web server to get the content. Alternatively, the customer can elect to use Level 3’s Origin Storage in lieu of their own Web server.
Step 3: Stream the Asset
Once the Level 3 streaming server receives the rich media asset, it begins to play back the stream for the end user.
Forward Proxy Mode
In forward proxy mode, the customer actively pushes their entire content library to the distribution platform and is made available to the Level 3 streaming servers. The net effect is that your content is actively deployed throughout the entire network and is immediately available upon an end user request. By prepositioning content at the edge servers, the end user response is faster for the first initial request as the content is already resident. The downside of using the On Demand platform in forward proxy mode is that the entire content library consideration set must be provided to Level 3 in advance of any end user request – leading to additional storage charges.
Forward Proxy – High Level Workflow process for On Demand streaming
Step 1: Upload content
Content is uploaded to one of two Level 3 FTP staging servers. To ensure ingress availability, Level 3 provides customers with a primary and a secondary staging location. Either location may be used to transfer content to the streaming platform.
NOTE: It is not necessary to publish content to both FTP staging points.
Step 2: Replication of content
As customers FTP content to the Level 3 streaming staging servers, it is automatically replicated across the entire Level 3 streaming platform. Customers do not need to do anything to trigger content replication- this is automatically handled by the Level 3 ingest locations. Changes to the content repository are checked every five (5) minutes and replicated to the edge streaming clusters; however, depending on system load and batch cycles it may take longer for content to replicate system wide.
Step 3: Embed Level 3 streaming link
Once your streaming content is uploaded to the Level 3 customer staging location, customers need to generate the On Demand streaming links. The stream links can be directly embedded into an HTML page or the media player directly using a customer specific hostname generated by Level 3. See Creating On Demand Stream Links for more details on how to construct Level 3 streaming links.
Step 4: Directing end user to Level 3 streaming clusters
End users are directed to the Level 3 streaming platform via a customer specific hostname. This hostname is specific to a streaming media format. The streaming hostname that Level 3 provides customers is powered by Level 3’s global load balancing service called Internet Traffic Manager (ITM). The ITM service helps ensure that end users are directed to the nearest streaming cluster.
File Format Support
Level 3 supports many of the common streaming file types. The charts below illustrate the formats Level 3’s streaming service can deliver.
Windows Media
Media Playlist .asx, .wax, .m3u, .wpl, .wvx, .and wmx
Movie file (MPEG) .mpeg, .mpg, .m1v, .m2v, .mod, .mp2, .mpa, .mpe, .ifo, and .vob
Windows audio file (wav) .wav, .snd, .au, .aif, .aifc, .aiff, .wma, and .mp3
Windows Media file (asf) .asf, .wm, .wma, .wmv, and .wmd
Windows video file (avi) .avi and .wmv