1. A Survey on Content-Oriented Networking for Efficient Content Delivery
Authors:
Jaeyoung Choi, Jinyoung Han, Eunsang Cho, Ted “Taekyoung” Kwon, and Yanghee Choi, Seoul National University
Presenters:
Prithvi Monangi ,
Amrutha Alaparthy :

2. Existing Issue
As multimedia contents become increasingly dominant and voluminous, the current Internet architecture will reveal its inefficiency in delivering time-sensitive multimedia traffic.
To address this issue, there have been studies on content oriented networking (CON) by decoupling contents from hosts at the networking level.

3. Contents discussed Content Naming Name based routing
Comparison of CON routing proposals
Evaluation of the impact of publish/subscribe paradigm and in- network caching

4. Introduction
As the bit rate of multimedia traffic increases , TCP/IP may fail to deliver time sensitive data.
Two problems with host based Internet architecture:
CPs like youtube, Hulu etc deliver HDTV streaming services
multicasting/broadcasting over IP networks (IPTV)
TCP/IP architecture fails to efficiently handle the above tasks

5. Existing Solutions
At present, multimedia is delivered to numerous users using P2P systems like BitTorrent
BitTorrent : Inefficient in networking perspective: peer can download chunks only from a small subset of peers who may be distantly located
Content-oriented applications/services, doesn’t care about hosts, but focusses on contents.

6. Existing Solutions Host oriented architecture - content delivery
This mismatch leads to application/service-specific solutions, which may be costly and/or inefficient. Two representative examples are:
Web caches and content delivery networks (CDNs) transparently redirect web clients to a nearby copy of the content file.
P2P systems enable users to search and retrieve the content file.

7. CON vs IP
CON node performs routing by content names, not by (host) locators. This means two radical changes:
• Identifying hosts is replaced by identifying contents.
• The location of a content file is independent of its name.
This makes CON location independent.

8. CON vs IP
2) publish/subscribe paradigm is the main communication model in CON, which helps us to decouple content generation and consumption in time and space….In IP, user should know which source holds the file.
3) Authenticity of contents can easily be verified by leveraging public key cryptography.
In IP networking, a host address seen by a user is irrelevant to its content name, which results in phishing attacks

9. CON Architecture
A CON architecture can be characterized by four main building blocks:
• How to name the contents
• How to locate the contents (routing)
• How to deliver/disseminate the contents
• How to cache the contents “in” the network

10. Content Naming Hierarchical Naming
Content file is often named by an identifier like web URL.
Hierarchical nature can help us mitigate the routing scalability issue since routing entries for contents might be aggregated.
components in a hierarchical name (e.g., and logo.jpg) have semantics, which prohibits persistent naming. I.e; if the ownership is changed its name becomes misleading

11. Content Naming Flat Naming
To eliminate shortcomings like persistence naming of hierarchical naming
Flat and self-certifying names are employed by defining a content identifier as a cryptographic hash of a public key.
Persistence and uniqueness are achieved.
Routing scalability decreases as there is no aggregation.
An additional resolution is needed b/w application level and human readable names.

12. Content Naming Attribute Based Naming
Identifies content with set of attribute value pairs which facilitates in network searching
Drawbacks :
An AVP may not be unique or well defined.
The semantics of AVPs may be ambiguous.
The number of possible AVPs can be huge

13. Name Based Routing Locating the content based on the name
Two types of classification:
Unstructured routing :
No structure to maintain routing tables
Routing advertisement is performed by flooding
Network prefixes in IP routing are replaced with content Identifiers
As the replication of content file increases, the level of aggregation decreases

14. Name Based Routing Structured routing :
Two structures : Implemented using either DHT or Tree
In tree arch, each router contains the routing information of all the contents published in its descendant routers
As the level of routing increases, routing burden increases - not scalable
In DHT, flatness imposes equal routing burden on routers
n(Contents) = C, each router should have log C entries
DHT might exhibit longer paths than tree sometimes

16. Multi Source Dissemination
Further issues in CON
Multi Source Dissemination
Existing internet architecture is designed with point to point connectivity
New applications require different connectivities like 1:N (one to many) and M:N (many to many)
1: N - IPTV, online streaming - uses IP multi casting framework
CON accommodates 1:N connectivity naturally with its publish- subscribe mechanism in terms of Content naming and group management

17. Multi Source Dissemination
Further issues in CON
Multi Source Dissemination
M:N Many to Many
Multiple sources disseminate different parts of the content to n recipients - Bittorrent and multi-user online gaming
Existing Internet requires application specific overlays for M:N
Example: P2P networks - Bittorrent
P2P systems are application level solutions, cannot exploit network topology information.

18. Multi Source Dissemination
Further issues in CON
Multi Source Dissemination

19. Multi Source Dissemination
Further issues in CON
Multi Source Dissemination
M:N Many to Many
CON can efficiently disseminate a content file among subscribers since CON nodes (R2 and R4) will help them download the content file also from the other overlay.
CON keeps track of individual sources of the same content allowing us to retrieve different parts of requested content in parallel
CON node dynamically decides which part to be received from which source based on traffic dynamics

20. Multi Source Dissemination
Further issues in CON
Multi Source Dissemination
M:N Many to Many
Issue: What routing info needs to be stored at each CON node for multiple sources of same content
The more sources of the same content the CON node learns of, the more selectively it may have to propagate the routing information of the sources

21. Further issues in CON In Network Caching
Generally used caching techniques: LRU - Least Recently used and LFU - Least frequently used content file replacement
Performance can be further improved by coordinating multiple CON nodes in distributed fashion
Study of distributed caching in IP networking is limited to single source dissemination and limited network topologies.
we need to reformulate the distributed caching problem in CON environments like multi source dissemination

22. In Network Caching - continued
Further issues in CON
In Network Caching - continued
Design Issue:
How to design a signalling protocol among CON nodes.
If a routing protocol is used to facilitate coordinated caching among CON nodes, then here will be no significant signaling traffic overhead
The more frequently the content information is updated, the more routing info may have to be advertised - This needs to be controlled

23. Performance Evaluation
We evaluate two things:
The effect of routing structures on resolution time to locate a content file
How much traffic load can be reduced by in network caching

24. Two-Tier architecture
Hybrid approach:
Tree can be formulated with network topology information (e.g., hop count between nodes), tree routing achieves higher throughput than DHT routing.
DHT routing is more scalable in terms of routing burden and more resilient to node/link failures due to multiple paths than tree routing.
A hybrid approach whose routing structure consists of two tiers: a DHT is the high tier, and a tree is the low tier is introduced.

25. Two-Tier architecture
Hybrid approach:
A query for a content file published in the same tree will be serviced within the tree. If a query is for a content file outside the tree structure, the DHT structure is exploited to forward the query

26. Comparisons Resolution delays:
Tree structure outperforms DHT because, the content request goes back and forth among CON nodes of DHT as the topology is constructed without any information on physical topology
Performance of two-tier architecture falls between these two
Successful resolution ratio as node failure rate increases :
Performance gain of DHT over tree because, there are multiple paths among nodes in DHT where as in tree structure, higher level node failure results in node failures

29. Network traffic load
The performance metric is the product of hop count and link bandwidth
This diminishes in CON proposals due to cache effect
Two-tier exhibits poorer performance than tree due to DHT overlay inefficiency

31. Conclusion CON vs IP Characteristics of CON - naming, routing etc
Research topics in CON environments:
M:N dissemination
In network caching

32. THANK YOU