Hash-routing Schemes forInformation Centric Networking

Lorenzo Saino, Ioannis Psaras, George Pavlou

Communications and Information Systems GroupDepartment of Electrical and Electronics Engineering

University College Londonl.saino,i.psaras,g.pavlou@ucl.ac.uk

In-network Caching Challenges1

Cacheplacement

Contentplacement

Request-to-cache routing

1D. Kutscher and et al. ICN Research Challenges. IRTF draftdraft-kutscher-icnrg-challenges-01, July 2013.

In-network Caching Challenges1

Cacheplacement

Contentplacement

Request-to-cache routing

1D. Kutscher and et al. ICN Research Challenges. IRTF draftdraft-kutscher-icnrg-challenges-01, July 2013.

Content Placement and Request-to-cache Routing

I On-path caching with opportunistic request-to-cache routingI Very scalable but limited cache hits due to redundant caching of

contentsI Examples: LCE, ProbCache, centrality-based caching

I Off-path caching with co-ordinated request-to-cache routingI High cache hits but limited scalability due to per-content state

required for routing

I Hybrid TechniquesI Mix features of on-path and off-path techniquesI E.g. SCAN

Hash-routing

Hash-routing is a well-known Web caching technique to map contentrequests to nodes of a cache cluster using a hash function.

.

.

.

1

2

3

N

Req(C)

N = H(C)

Internet

Enterprise network

Hash-routing for Information Centric Networking

Functional entities:

I Edge nodes: Compute hash function and forward request andcontent packets to the responsible cache nodes

I Cache nodes: Store content objects for which they are responsible

Proposed routing schemes:

I Base schemes: Symmetric, Asymmetric, Multicast

I Hybrid schemes: Asymmetric-Multicast, Symmetric-Multicast

Request routing

RECEIVER SOURCE

The ingress edge node computes hash function to map the contentidentifier to the responsible cache node

Request routing

RECEIVER SOURCE

The ingress edge node forwards request to resolved cache node

Request routing

RECEIVER SOURCE

If the responsible cache node has a copy of the requested content, it servesit to receiver

Request routing

RECEIVER SOURCE

Otherwise, it forwards the request towards the original content source

Content routing - Symmetric

RECEIVER SOURCE

I Content packets follow the same path of the request

I This approach can achieve high cache hit rate but at the cost ofpossibly increasing intradomain link load

Content routing - Symmetric

RECEIVER SOURCE

I Content packets follow the same path of the request

I This approach can achieve high cache hit rate but at the cost ofpossibly increasing intradomain link load

Content routing - Symmetric

RECEIVER SOURCE

I Content packets follow the same path of the request

I This approach can achieve high cache hit rate but at the cost ofpossibly increasing intradomain link load

Content routing - Asymmetric

RECEIVER SOURCE

I Content packets are always forwarded over the shortest path

I This approach has minor impact on link load but cache nodes withsmall betweenness centrality may be underutilized

Content routing - Asymmetric

RECEIVER SOURCE

I Content packets are always forwarded over the shortest path

I This approach has minor impact on link load but cache nodes withsmall betweenness centrality may be underutilized

Content routing - Asymmetric

RECEIVER SOURCE

I Content packets are always forwarded over the shortest path

I This approach has minor impact on link load but cache nodes withsmall betweenness centrality may be underutilized

Content routing - Multicast

RECEIVER SOURCE

I Content packets are multicast to receiver and cache nodes

I This approach can achieve high cache hits and low latency, but mayincrease link load depending on network topology

Content routing - Multicast

RECEIVER SOURCE

I Content packets are multicast to receiver and cache nodes

I This approach can achieve high cache hits and low latency, but mayincrease link load depending on network topology

Content routing - Multicast

RECEIVER SOURCE

I Content packets are multicast to receiver and cache nodes

I This approach can achieve high cache hits and low latency, but mayincrease link load depending on network topology

Content routing - Symmetric-Multicast Hybrid

RECEIVER SOURCE

Edge nodes decide to forward content packets in a multicast or symmetricmanner in order to minimize the total cost of the traversed path

Content routing - Symmetric-Multicast Hybrid

RECEIVER SOURCE

Edge nodes decide to forward content packets in a multicast or symmetricmanner in order to minimize the total cost of the traversed path

Content routing - Symmetric-Multicast Hybrid

RECEIVER SOURCE

Edge nodes decide to forward content packets in a multicast or symmetricmanner in order to minimize the total cost of the traversed path

Content routing - Symmetric-Multicast Hybrid

RECEIVER SOURCE

Edge nodes decide to forward content packets in a multicast or symmetricmanner in order to minimize the total cost of the traversed path

Content routing - Asymmetric-Multicast Hybrid

RECEIVER SOURCE

Edge nodes select multicast delivery only if the marginal cost of themulticast path with respect to the source-receiver shortest path is smallerthan a predefined threshold.

Content routing - Asymmetric-Multicast Hybrid

RECEIVER SOURCE

S =

MULTICAST if C = CMCAST−CASYMM

CMAX< kMAX ∈ (0, 1)

ASYMM otherwise

Content routing - Asymmetric-Multicast Hybrid

RECEIVER SOURCE

I We use unitary link weights to calculate path costs and KMAX = 0.3

I CASYMM = 3, CMCAST = 4, CMAX = 4

I C = 0.25 < KMAX = 0.3: multicast is used

Content routing - Asymmetric-Multicast Hybrid

RECEIVER SOURCE

I We use unitary link weights to calculate path costs and KMAX = 0.3

I CASYMM = 3, CMCAST = 4, CMAX = 4

I C = 0.25 < KMAX = 0.3: multicast is used

Content routing - Asymmetric-Multicast Hybrid

RECEIVER SOURCE

I We use unitary link weights to calculate path costs and KMAX = 0.3

I CASYMM = 3, CMCAST = 5, CMAX = 4

I C = 0.5 > KMAX = 0.3: asymmetric is used

Content routing - Asymmetric-Multicast Hybrid

RECEIVER SOURCE

I We use unitary link weights to calculate path costs and KMAX = 0.3

I CASYMM = 3, CMCAST = 5, CMAX = 4

I C = 0.5 > KMAX = 0.3: asymmetric is used

Performance evaluation

I Evaluation was carried out using using our Icarus simulator. We madeall code required to reproduce this paper’s results publicly available2

I We investigate the performance of the proposed schemes in terms ofcache-hit ratio and link load and analyse their sensitivity against:

I cache to content population ratio (C): 0.04% - 5%I content popularity skewness (α): 0.6 - 1.1

I Real network topologies:I GEANT: European academic networkI GARR: Italian academic networkI WIDE: Japanese academic networkI Tiscali: pan-European commercial ISP

2http://www.ee.ucl.ac.uk/~lsaino/software/icarus/

Performance evaluationCache hits and intradomain link load vs α (GEANT, C = 0.2%)

0.6 0.7 0.8 0.9 1.0 1.1Content popularity skewness (α)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Cac

hehi

trat

io

HR SymmHR AsymmHR Hybrid AMProbCacheUbiquitousOptimal

(a) Cache hits

0.6 0.7 0.8 0.9 1.0 1.1Content popularity skewness (α)

400

500

600

700

800

900

1000

Ave

rage

link

load

(Mbp

s)

HR SymmHR MulticastHR AsymmHR Hybrid AMHR Hybrid SMProbCacheUbiquitousNo caching

(b) Link load

Performance evaluationCache hits and intradomain link load vs C (GEANT, α = 0.8)

10−3 10−2

Cache to population ratio (C)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Cac

hehi

trat

io

HR SymmHR AsymmHR Hybrid AMProbCacheUbiquitousOptimal

(c) Cache hits

10−3 10−2

Cache to population ratio (C)

550

600

650

700

750

800

850

900

950

Ave

rage

link

load

(Mbp

s)

HR SymmHR MulticastHR AsymmHR Hybrid AMHR Hybrid SMProbCacheUbiquitousNo caching

(d) Link load

Conclusions

I Hash-routing techniques are a viable solution for improving cache hitsin a scalable and incrementally deployable manner in an ICNenvironment.

I The hash-routing schemes proposed provide different trade-offsbetween intradomain link load and cache hit ratios.

I In particular, asymmetric and symmetric-multicast schemes canprovide substantial reduction in interdomain traffic (and averagelatency) at the cost of a very limited increase in intradomain traffic.