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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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