1. Information Centric Networking
and Content Addressability
Junxiao Shi, 2013-09-12
Copyright 2013, yoursunny.com, licensed under CreativeCommons BY-NC 3.0

2. Why ICN?

3. The existing Internet
 Core ideas developed in 1960s-1970s
 Modeled after telephony:
point-to-point conversation between two entities

4. IP is ‘conversational’
 IP datagrams can only name communication endpoints.

5. 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.

6. Internet is used for content distribution

7. 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.

8. What is ICN?

9. Information Centric Networking
 Let the network focus on the content
itself, rather than the location of the
content.

10. 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

11. 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.

12. How NDN works?

13. 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.

14. From IP to NDN

15. 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.

16. Naming
 Applications give names to packets.
 NDN uses hierarchical names to facilitate aggregation,
management, discovery.

17. 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

18. Caching
 Routers can now cache the data since they’re named.
consumer1
consumer2
router producer
cache
1.Interest
2. Interest
5. Interest
4. ContentObject
3. ContentObject
6. ContentObject

19. 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.

20. NDN and Content Addressability

21. Naming
 NDN: hierarchical names defined by applications
 Names are usually not hashes.
 Other ICN architectures may use hash as data name.

22. 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.

23. Fast name lookup – nested hash tables
comp 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

24. 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.

25. 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)

26. 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

27. References

28. 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