Caching in Information Centric Network (ICN)

Presented by: Priagung Khusumanegara

Outline

Introduction Characteristics of caching in ICN

Transparent Ubiquitous Fine Granularity

Caching optimization in ICN Dimensioning Decision policy

Challenges and future research2

Introduction

One of the important features of ICN is caching Speed up content distribution Improve network resource utilization

Characteristics of caching in ICN Transparent Ubiquitous Fine granularity3

Transparent

Making its routing and caching decisions on unified content names, essentially making these names network aware.

Several Challenges: Inconsistency between caching objective

ICN should make reasonable choice of its caching objective to balance between diverse traffic types.

Cross-application competitive sharing of cache space Different types of traffic differ significantly in their population

scale, object size and object popularity. ICN have to be able to efficiently share cache resources

between different traffic types. Line rate operation of caches

The cache management quite different from traditional disk-based management.4

Ubiquitous

Topology of the cache network evolves from hierarchical trees to arbitrary graphs.

ICN more dynamics because its general cache network topology, ubiquity of in network caches and volatility of cached content.

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Traditional Caching System

Focus on Hierarchical Tree

Evolution

Information Centric Network

Focus on Arbitrary Graph

Fine Granularity

Different options for the granularity of caching: File-level

o Caching individual files as transmitted through the networko Typical size 1.5 Kb each – as proposed by CNN

Chunk-levelo Caching information chunkso An information object is split into a number of fixed-size

information chucks – as proposed by ICN

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Fine Granularity (Cont’d)

Change of cache unit raises the following issues: Change of popularity

o Different chunks of a single file can have different access frequencies. Failure of independent reference assumption

o Traditional file-based caches are based on independent reference model

o Requests for different chunks of the same file are often correlated, e.g. in sequential order

Opportunity for more efficient use of the cache spaceo It possible to retrieve different parts of the same file from different

nodes, which speeds up the retrieval rate and improves the space utilization.

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Techniques for ICN performance optimization

Focus on:– Cache dimensioning– Cache decision policy

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Cache Dimensioning

- Since ICN cache should operate at line rate, the cache size that can be installed at each caching node is thus limited.

- There are two issues that remain to be addressed: How large the cache space should be to have noticeable

performance improvement?o Preferred to configure the cache size based on the router’s

performance disparity. How to allocate the storage resource across different cache nodes?

o Degree based allocation: the cache capacity allocated to a node is proportional to its node degree.9

Cache Decision Policy

Cache decision policy– It determines which objects are to be placed at

which cache nodes.– Two kinds of cache decision policy

Explicit cache coordination decision Implicit cache coordination

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Explicit Cache Coordination

Object access pattern, cache network topology and each cache’s state as input for the calculation of the placement position of each object.

Common approaches can be classified into three categories:– Global – Path– Neighborhood

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Explicit Cache Coordination (Cont’d)

Global coordination– Involves all cache nodes – Object placement based on network distance between

cache nodes and object access frequencies at each cache node

Path coordination– Only involves the cache nodes along the path from the

request hit place to the requesting client– e.g.: en-route web caching

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Explicit Cache Coordination (Cont’d)

Neighborhood coordination– Coordination takes place among a node’s

neighborhood.– E.g.: Cooperative In-Network Caching (CINC)

13 Figure: The operation of coordination in network caching (CINC)

Implicit Cache Coordination

Each node does not need to know the state information of other cache nodes

LCE (leave copy everywhere) – Copy the object at each node along the

downloading path– Disadvantage: Degrade the performance of the

network and underutilize some of the network resources.

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Implicit Cache Coordination (Cont’d)

Leave Copy Down (LCD):– When a cache hit occurs, this scheme only caches the

object at the direct downstream node

– Avoid a large number of copies of the same object

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Figure: LCD (Leave Copy Down)

Implicit Cache Coordination (Cont’d)

Move Copy Down (MCD):– This scheme moves the object from the hit node

to its direct downstream node, and deletes the object from the hit node.

16 Figure: MCD (Move Copy Down)

Implicit Cache Coordination(Cont’d)

Copy with Probability- The requested object is copied with a given

probability p at each node along the returning path

17 Figure: Copy with Probability

Implicit Cache Coordination(Cont’d)

Random Copy One- The requested object is copied at one random

node along the returning path

18 Figure: Random Copy One

Implicit Cache Coordination(Cont’d)

Probability Cache- The requested object is copied at each node with

a probability. But, for each node, the probability varies.

19 Figure: Probability Cache

Correlation Between Cache Decisions

- WAVE adjusts the number of chunks cached at each node based on the file’s popularity

- When the number of requests for a file increases, WAVE reacts with exponential increase in the number of chucks cached for this file.

- A content router in WAVE explicitly sets the cache indication mark

- Once the chunk is cached, the cache indication mark is cleared.

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Figure: Operation of WAVE

Challenges and Future Direction

Cache object popularity– Establish the chunk- level object popularity model from prior knowledge– Measure the chunk-level object popularity directly

Correlation between requests and correlation-based cache decision

– What is the inherent correlation between different requests, – How to model this correlation, and – How to optimize the cache decision policy based on the request

correlation,

ICN friendly network topology– What kind of network topology is suitable for ICN network.

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