CDNI Extended Design Team Meeting Virtual Meeting May 29, 2012

1. Models for adaptive-streaming-aware CDNI-Request Routing and Manifest Filesdraft-brandenburg-cdni-has-01, section 3.3 CDNI Extended Design Team Meeting Virtual Meeting May 29, 2012 Ray van Brandenburg (ray.vanbrandenburg@tno.nl)

2. Request Routing and Manifest Files – General • In a sense, Manifest Files can be considered a form of request routing • Recap, three methods for addressing chunks in a manifest • Relative URL (e.g. ‘segments/seg1.ts’) • Absolute URL with Redirection (e.g. ‘http://req_routing.cdn……’) • Absolute URL without Redirection (e.g. ‘http://surrogate2.cdn….’) • Some CDNs might prefer one method above the other • Some CDNs/CPs might NEED one method (e.g. for security, anti-deeplinking, etc.) • [Note: Should this be part of capability exchange?] • In some cases Content Provider might decide on type of URL used (e.g. in the case where the Content Provider delivers the manifest)

3. Option 3.1: “Do-Nothing” Approach - 1 • Assumes no HAS awareness in uCDN/dCDN and no additions to CDNI Interfaces • Absolute URLs with Redirection: • Work without HAS awareness • manifest directs clients to uCDNRR • uCDN RR redirects clients to dCDN RR • dCDN RR redirects clients to dCDN surrogate • Creates very significant overhead • Full Inter-CDN Request Routing process for each individual chunk • [Question: with small chunks, is it even worthwhile for a uCDN to outsource delivery to a dCDN in this case?]

4. Option 3.1: “Do-Nothing” Approach - 2 • Relative URLs: • Might or might not work depending on client implementation and dCDN capabilities • If a client uses the IP address instead of the host name as a prefix to the Relative URLs, dCDN is unable to resolve chunk request • Depends on initial manifest request process in dCDN (dCDN RR->dCDN Surrogate) to use IP addresses or hostnames • In all other cases, Relative URLs work • Suffers from brittleness • Absolute URLs without Redirection: • Does not work • Chunk URLs point to specific surrogates in uCDN • Neither uCDN or dCDN is able to adapt manifest

5. Option 3.1: “Do-Nothing” Approach - 3 Effect on CDNI Interfaces: • None • Advantages/Drawbacks: + Supports Absolute URLs with Redirection + Does not require HAS awareness and/or changes to the CDNI Interfaces - Not possible to use Absolute URLs without Redirection • - Support for Relative URLs suffers from some brittleness. Makes • assumptions on client-side implementation of the HAS client or on • structure of PATH or QUERY • - Creates significant signaling overhead in case Absolute URLs with Redirection are used (inter-CDN request redirection for each chunk)

6. Option 3.2: Manifest File rewriting by uCDN- 1 • Presents solution to request routing overhead created by the use of Absolute URLs with Redirection • Allows the uCDN to modify manifest so that the URLs in the manifest point to the RR-function of the dCDN • Requires uCDN to be aware of location of dCDN RR • Which it needs anyway for redirection and which it can query through CDNI Request Routing Interface • Two options: • Perform manifest rewriting once (for all future clients) • Perform manifest rewriting for every individual client • Allows uCDN to directly place surrogate location in the manifest file • Exposes (limited) dCDN topology information to uCDN

7. Option 3.2: Manifest File rewriting by uCDN - 2 Effect on CDNs/CDNI Interfaces: • CDNI Request Routing Interface: Allow uCDN to query dCDN for the location of its request routing function (is this covered by the existing RR interface?) Advantages/Drawbacks: + Possible to significantly decrease signalling overhead when using Absolute URLs. + Minimal changes to CDNI Interfaces (no HAS awareness) + Does not require HAS awareness in dCDN - Requires high level of HAS awareness in uCDN (for modifying manifest files)

8. Option 3.3: Two-step Manifest File rewriting - 1 • Allows for dCDN to perform further manifest rewriting • uCDN does first round of rewriting (replacing uCDN RR with dCDN RR) • dCDN does second round of rewriting (replacing dCDN RR with dCDN Surrogates) • Requires high-level of HAS awareness in both dCDN and uCDN • Probably useful to add ‘do not change manifest’ field to Metadata Interface • Allows uCDN to signal that the dCDN is not allowed to change the manifest file

9. Option 3.3: Two-step Manifest File rewriting - 2 Effect on CDNs/CDNI Interfaces: • CDNI Metadata Interface: Add necessary fields for conveying HAS specific information (e.g. the files that make up the Content Collection) to the dCDN Advantages/Drawbacks: + Allows dCDN to use Absolute URLs without Redirection without having to convey sensitive information to the uCDN • Requires high level of HAS awareness in dCDN (for modifying manifest files) • Requires adding HAS-specific information to the CDNI Metadata Interface • Complex

10. Summary