Content Centric Networking in
Tactical and Emergency MANETs
Soon Y. Oh, Davide Lau, and Mario Gerla
Computer Science Department
University of California, Los Angeles
{soonoh, chiume, gerla}@cs.ucla.edu
Introduction
 Infrastructureless nature and quick deployment  a
MANET is ideally suited for emergency & tactical
operation, but
 Challenging environments
 Lossy channel and high mobility
 Limited resources
 Hard to find necessary content
 No search engine
 Scalable & efficient content search and dissemination
in MANETs  Content Centric Networking
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Content Centric Networking (CCN)
 Users are interested in WHAT content – not
WHERE it is or WHO has it
 Data is addressed by NAME OR CONTENT –
rather than by location or IP address
 No overhead in binding name to location
 Enabled by low storage prices and high speed links
Can CCN be directly applied to
MANET environment?
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WiCCN = CCN in MANETs
 Advantages
 Group based mobility/operation
 resource sharing within group
 Hierarchical data structure
 Information locality (via Cache)
Content Centric
Networking
 Challenges
 Lossy channel and resource shortage
 Data Push and Pull is required while Internet CCN is only Pull
 Must Push Critical information and operation messages
 Security and content authentication
 Critical data and wireless broadcast medium
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WiCCN protocol design goals
 Hierarchical storage/search architecture
 Topic based data vs spatial/temporal contents
 Cross-layer approach
 Scalable and resource aware
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Related Work
 TRIAD (2000)
 User-friendly, structured, with location-independent names and content
addressing (has influenced later protocols)
 Data-Oriented (and beyond) Network Architecture (DONA) (2007)
 Flat, self-certifying names instead of IP addresses and DNS
 Contents is published and registered with a tree of trusted Resolution
Handlers (RH)
 Routing on Flat Levels (ROFL) (2006)
 Semantic-free flat labels; it creates a circular namespace, e.g., DHT
 Content Centric Network (CCN) (2009)
 Network wide content caching and user-friendly, hierarchical names for
routing; Digital signature for security
 Named Data Networks (NDN) (2010)
 Future Internet Architecture
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WiCCN Network Model




Group based mobility
Hierarchical topology
Interconnection via gateways
Heterogeneous devices – different capacities
Airborne
Network
Wideband
Network
Soldier
System
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WiCCN Content Types
 Topic based content
 Data files, video and audio clips
 Data is stored at publisher (originator) or near backbone nodes and
travels anywhere in the network
 PULLED by users
 No location and time sensitivity
 Spatial/temporal content
 Situation awareness data; operational messages
 Content value is time and location sensitive
 PUSHED by publisher towards command center or proper
location
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Local Storage
Content
Repository
 Content Repository
 Intermediate nodes cache content
 Maximize the probability of sharing
Meta-Data Registry
 Meta-Data Registry
 Hash table for efficient look up
Interest Table
 It is used to forward Interest packet
 Meta-Data includes content attributes, e.g., type, time, loc, etc
 Interest Table
 Stores Interest Query packets
 To suppress duplicate Interest packets
 To relay content to requestors
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WiCCN Routing
 Content Pushing
 Spatial/temporal content
 Geo-routing to command center or other destination
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WiCCN Routing (Cont.)
 Content Pulling
 Using an Interest packet and local storages
1. Check Content Repository and send data
if it exists
2. If there is no content, check Meta-Data
Repository
3. If Meta-Data entry exist, a node relays
Interest toward data origin
4. Otherwise, Interest is passed to a
Gateway toward upper level
Content
Repository
Interest
Meta-Data Registry
Interest
5. Interest is relayed
Interest Table
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WiCCN Routing (Cont.)
 Difference to Internet CCN (due to wireless
common medium)
 Interest aggregation
 Time stagger re-broadcast Interest packets
 Upon overhearing the same Interest, cancel the re-broadcast
 Data Packet collision avoidance
 If more than one neighbors tries to transmit
 Exchange Request/Reply
 Respond with Reply before transmitting data
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Packet Collision Avoidance
REPLY
Content
Interest
REQUEST
REPLY
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Security and Authentication
 Using PKI
 A gateway has private key and members in the
domain have public keys
 A gateway adds digital signature using a private
key
 Members encrypt packets using the public key
 The private and public keys are pre-assigned
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Implementation
 Implement WiCCN on Linux OS
 A gateway and members
 The gateway floods/updates meta-data
 A node sends Interest
 Request/Reply- exchange and data transmission
 Run simple four node topology
 Compare performance with peer-to-peer protocol,
e.g., Pastry over OLSR
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Pastry Overhead




Every 3s new data generated (no real data transmitted)
A gateway floods meta-data
Pastry 378B/s average overhead
Traffic suddenly increases to maintain a P2P ring structure
 OLSR traffic in the background
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WiCCN Overhead




Every 3s new data generated (no data transmission in this experiment)
A gateway floods meta-data
Pastry 72B/s average overhead
Only Meta-Data flooding
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End-to-End Delay
 From node A to node D in the 4 node chain topology
 File size 1, 5, 10, 15, 20, 25, 100MB
 Pastry and WiCCN experience same delay in peer to peer transmissions
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End-to-End Delay (Cont.)




From node A to all nodes in the previous 4 node topology
No broadcast; each node requests data at different time
WiCCN presents significant lower delay due to content caching
In Pastry, node A transmits 3 times, but WiCCN node A transmits only once;
cached data, at an intermediate node, is transmitted
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Conclusion
 WiCCN performs better than DHT based
content sharing
 Mainly due to caching
 Future work:




Implement on smart phones
Experiment with mobility
Design cache strategies
Bigger testbed/emulator
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