Information Centric Networking and Content Addressability

Information Centric Networkingand Content Addressability

Junxiao Shi, 2013-09-12

Copyright 2013, yoursunny.com, licensed under CreativeCommons BY-NC 3.0

Why ICN?

The existing Internet

Core ideas developed in 1960s-1970s Modeled after telephony:

point-to-point conversation between two entities

IP is ‘conversational’ IP datagrams can only name communication

endpoints.

The world has changed Almost anything is available online. An ever increasing range of content can be

distributed digitally. Anyone can create, discover and consume content.

Exabytes of new content are produced yearly. Everything is connected to the Internet.

Internet is used for content distribution

IP is a poor match to its primary use today

Just as the telephone system would be a poor vehicle for the broadcast content distribution done by TV and radio.

What is ICN?

Information Centric Networking

Let the network focus on the content itself, rather than the location of the content.

Benefits of ICN

If network understands what it’s carrying, Universal caching Adaptive multipath routing Better handling of mobility, address exhaustion,

etc Secure the content rather than the pipe

Named Data Networking

NDN is one of Information Centric Networking schemes.

CCN (Content Centric Networking) is the project name at PARC.NDN (Named Data Networking) is the project name sponsored by NSF.

How NDN works?

Key idea Give each packet a unique name. Packets are routed and forwarded based on names. Essentially changing the waist of the hourglass

architecture from address-based IP to content-name based NDN.

From IP to NDN

How it works?

Applications name its data. Consumers send Interest packets, producers

respond with Data packets (ContentObjects). Interests are routed based on their names. Routers remember outstanding Interests in Pending

Interest Table (PIT). Data trace back along PIT entries. Every data packet carries a signature.

Naming

Applications give names to packets. NDN uses hierarchical names to facilitate

aggregation, management, discovery.

Receiver-driven data retrieval

All communication is initiated by consumers, ie start with an Interest packet.

Routers forward the Interest towards the producer, and remembers the incoming interface of the Interest.

The producer sends the data back. The data takes the exact reverse path of the Interest to reach the consumer.

One Interest retrieves one data.

consumer router producer

1. Interest 2. Interest

3. ContentObject4. ContentObject

Caching

Routers can now cache the data since they’re named.

consumer1

consumer2

router producercache

1.Interest 2. Interest

5. Interest

4. ContentObject3. ContentObject

6. ContentObject

Security and Privacy

Secure the content/data, not the pipe or the perimeter.

Each data packet has to carry a signature because data can come from any router or

source.

NDN and Content Addressability

Naming

NDN: hierarchical names defined by applications Names are usually not hashes.

Other ICN architectures may use hash as data name.

Fast name lookup

NDN router looks up a Name in Forwarding Information Base (FIB) to decide where to forward it.

Name could have any number of components, and a component could be arbitrarily long.

Fast name lookup could be achieved in nested hash tables.

A hash is computed over the first component, and the result is a pointer to the next hash table, which is keyed with the hash of the second component, and so on.

If a name consists of k components, then in the absence of collisions, k hash lookups would be required in the worst case to identify the longest matching prefix.

Fast name lookup – nested hash tablescomp

faces

ndn

ccnx

component faces

broadcast 12,11,10,9,8,7

keys 12,11,10,9,8,7

arizona.edu 473,7

ucla.edu

memphis.edu

10,12,11

parc.com 8,12,10

uci.edu 8,12,10

comp

faces

irl 8,12,10

apps 8,12,10

comp

faces

ping 262310

Aggregated signing

Every ContentObject must be signed. Generating signature (RSA) for every individual

block is computationally expensive. Merkle hash trees amortize the signing cost over

multiple ContentObjects.

Aggregated signing – Merkle hash trees

H0=H(block0)

H1=H(block1)

H2=H(block2)

H3=H(block3)

H4=H(H0H1) H5=H(H2H3)

H6=H(H4H5)

Aggregated signing

Sign the root hash (H6) only.

Include Merkle Path with the signature node index (eg. node 1) hash of sibling node, hash of parent’s sibling node,

and so on (eg. H0, H5 for node 1)

To verify the signature for block1, one can compute H1=H(block1), H4=H(H0H1), H6=H(H4H5), and see whether the signature is valid for H6.

H0

H1

H2

H3

H4

H5

H6

References

References

Van Jacobson et al, Networking Named Data

NDN Technical Report NDN-0001, Named Data Networking (NDN) Project

Beichuan Zhang, CSC630 Spring 2012

CCNx technical documentation, CCNx Signature Generation and Verification