Content-based Routing for Information Centric Networks

D. ReiningerECE 544

Spring 2014

Introduction• Apart from routing protocols that use a direct identifier of

nodes, networking can take place based directly on content.• Content can be collected from the network, processed in the

network, and stored in the network• Goal is to provide a network infrastructure capable of

providing services better suited to today’s application requirements:– content distribution & mobility– more resilience to disruption and failures

• We look next at such content-based networking and data aggregation mechanisms.

Networking Evolution

• Traditional networking– Host-centric communications addressing end-points

• Information-centric networking– Data-centric communications addressing information

(e.g., data in context).– Decoupling in space – neither sender nor receiver

need to know their partner.– Decoupling in time – “answer” not necessarily directly

triggered by “question”, asynchronous communication.

Information-centric Networking• Approach

– Named Data Objects (NDOs)– in-network caching– multi-party communication through replication– decoupled senders from receivers

• Architectural questions– How do we address information?– How do we obtain information?– How do we route information?

ICN Communication ModelChart notes describe the information exchange.

Dissemination networking

• Data is request by name, using any and all means available (IP, VPN tunnels, multicast, proxies, etc).

• Anything that hears the request and has a valid copy of the data can respond.

• The returned data is signed, and optionally secured, so its integrity & association with name can be validated (data centric security)

ICN Stack

• Change of network abstraction from “named host” to “named content”• Security built-in: secures content and not the hosts• Mobility is present by design• Can handle static as well as dynamic content• Use of 2 messages: Interest and Data Objects

(1) Van Jacobson, et al, Networking Named Content, CoNEXT 2009

Universal?

• Any architecture that runs over anything is an overlay (IP is an overlay).

• IP started as a phone system overlay; today much of the phone system is an IP overlay. System theorists would say ‘IP is universal’.

• ICN has the same character: it can run over anything, including IP, and anything can run over ICN, including IP.

• And ICN has a simpler, more general relationship with lower layers than IP.

Example: Content Distribution

Example: Content Distribution

Example: Content Distribution

Example: Content Distribution

• Content goes only where there’s interest.

• It takes at most one trip across any link.

• Average latency is minimized.

• Total bandwidth is minimized.

• There’s no routing or control traffic associated with the replicas.

Example

Approaches• Content Centric Networks

– Naming: Hierarchical naming, single address– Security: Signed content– Routing: Longest prefix matching– Caching: Local or network based– Content existence knowledge: Not part of the CCN core– Producer-consumer meeting: Propagation of interests

• Network of Information – Naming: Flat naming– Security: Signed content– Routing: (1) Name resolution (2) Information transfer– Caching: Network based– Content existence knowledge: Through name resolution service– Producer-consumer meeting: Name resolution service provide locations

Approaches• Publish Subscribe Internet Routing Paradigm

– Naming: Multi-level identifiers– Security: Signed content– Routing: (1) Name resolution (2) Information transfer– Caching: Network based– Content existence knowledge: Registrations in Rendezvous system– Producer-consumer meeting: Rendezvous system provides location

• Data Oriented Networking Architecture – Naming: Flat naming– Security: Signed content– Routing: Queries are resolved to locations– Caching: Network based– Content existence knowledge: Through resolution infrastructure– Producer-consumer meeting: Resolution infrastructure provides location

Naming• Solution 1: Name the data

– Flat, not human readable identifiers• 1DB76EB8DFD6B0b92A293AADC8421830BDE73CB6

– Hierarchical, meaningful structured names• /nytimes/sport/baseball/mets/game022414/

• Solution 2: Describe the data– With a set of tags

• baseball, new york, mets– With a schema that defines attributes, values and

relations among attributes

Using Names in CCN

• The hierarchical structure is used to do ‘longest match’ lookups (similar to IP prefix lookups) which helps guarantee log(n) state scaling for globally accessible data.

• Although CCN names are longer than IP identifiers, their explicit structure allows lookups as efficient as IP’s.

(see hashing work by Rasmus Pagh and Martin Dietzfelbinger)

Routing

• Three general approaches– Name Resolution Routing (NRR)– Content-based Routing (CBR)– Name-based routing (NBR)

• Two phases– Routing of NDO requests– Routing of NDO back to the requester

Name-Based Routing• Client asks for a data object sending interest packets which

are routed toward the publisher of the name prefix using longest-prefix matching in the forwarding information base (FIB) of each node.

• The FIB is built using routing protocols of the Internet.• When a note receives multiple requests for the same NDO,

only the first is forwarded to the source.• When a copy of the data object is encountered on the path,

a data packet containing the requested object is sent on the reverse path back to the client and all nodes along the path cache a copy.

Content Centric Network (CCN)

Chart notes describe numbered steps

CCN packets

There are two CCN packet types:interest (similar to http “get”) and data(similar to http response). Both areencoded in an efficient binary XML.

CCN node model

Get /parc.com/videos/WidgetA.mpg/v3/s2

Publish-Subscribe Internet Routing Paradigm (PSIRP)

Chart notes describe numbered steps

Content-based Publish-Subscribe Routing

Content-based Pub/Sub Routing

Content-based Pub-Sub Routing

Forwarding on Bloomed link ids• The FI encodes the network links (rather than the nodes) on the path

of interest between the producer and consumers• FI is encoded in a probabilistic data structure called a Bloom filter

that routers use for selecting interfaces on which to forward an NDO.– Bloom filters encode source route-style forwarding information into packet

headers, enabling forwarding without depending on end-to-end addressing.

– Routers do not need to keep forwarding state. Forwarding decisions are simple and forwarding tables are small, potentially allowing faster, smaller, and more energy-efficient switches.

• The use of Bloom filters result in a certain number of false positives; in this case this means forwarding on some interfaces where there are no receivers.

Pub/Sub Routing using Link ID and FI

zFilter: FI Bloom Filter

See chart notes for further description

Network of Information

Name Resolution Routing• Use a Name Resolution Service (NRS) that stores the bindings

from object names to topology-based locators pointing to corresponding storage locations in the network.

• Three conceptual routing phases:– Routing the request message to the responsible NRS node where the

object name is translated into one or multiple source addresses– Routing the request message to the source address(es)– Routing the data from the source(s) to the requester.

• All phases can potentially use different routing algorithms. – A name-based routing method might be used for the first phase. – The second and third phases might use a topology-based routing like

IP. – There are multiple alternatives to loosely or tightly integrate the

phases in an ICN architecture.

Summary of characteristics of the ICN approaches

Content-Based Security• Name-content mapping verification via per-data packet

signature– Data packet is authenticated with digital signature

ICN trust establishment by associating content namespaces w/ public keys

Basic ICN forwarding

• Consumer ‘broadcasts’ an ‘interest’ over any & all available communications media:get ‘/rutgers/ECE544/Lecture06-14.pdf’

• Interest identifies a collection of data - all data items whose name has the interest as a prefix.

• Anything that hears the interest and has an element of the collection can respond with that data:HereIs ‘/rutgers/ECE544/presentation.pdf/p1’ <data>

Basic ICN transport

• Data that matches an interest ‘consumes’ it.• Interest must be re-expressed to get new data.

(Controlling the re-expression allows for traffic management and environmental adaptation.)

• Multiple (distinct) interests in same collection may be expressed (similar to TCP window).

Caching

• Storage for caching NDOs is an integral part of the ICN service.

• All nodes potentially have caches; requests for NDOs can be satisfied by any node holding a copy in the cache.

• ICN combines caching at the network edge as in P2P and other overlay networks with in-network caching (e.g., transparent web caches)

Advantages of the ICN approach

• Scalable and cost-efficient content distribution– IP traffic to quadruple from 2010 – 2015– Mobile data traffic increased 26x – Mostly attributed to media traffic that continues

to be 90% of global consumer traffic by 2015

Issues

• Scalability• Privacy (interest subscription and content

description)• Legal (caching NDOs)• Business case for deployment

References• A Survey of Information-Centric Networking, B. Ahlgren, et. al. IEEE Communications

Magazine, July 2012, http://itec.hust.edu.cn/~jwchen/courses/compnet2013/references/A%20Survey%20of%20Information-Centric%20Networking-CommMag-ADI+12.pdf

• A Survey of Information-Centric Networking Research, G. Xylomenos, et. al., Published in IEEE Communications Surveys and Tutorials

• Is Information-Centric Multi-Tree Routing Feasible? ICN Workshop 2013, M. Papalini et. al. • LIPSIN: Line Speed Publish/Subscribe Inter-Networking, Petri Jokela, et.al.• Information-Centric Networking: Seeing the Forest for the Trees, Ali Ghodsi, Scott Shenker,

et.al.• Bloom Filters

• http://billmill.org/bloomfilter-tutorial/• http://en.wikipedia.org/wiki/Bloom_filter#Examples

• A Multi-Level DHT Routing Framework with Aggregation, H. Liu et. al, http://conferences.sigcomm.org/sigcomm/2012/paper/icn/p43.pdf