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,

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 2

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? 3

WiCCN = CCN in MANETs  Advantages  Group based mobility/operation  resource sharing within group  Hierarchical data structure  Information locality (via Cache)  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 4 Content Centric Networking

WiCCN protocol design goals  Hierarchical storage/search architecture  Topic based data vs spatial/temporal contents  Cross-layer approach  Scalable and resource aware 5

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 6

WiCCN Network Model  Group based mobility  Hierarchical topology  Interconnection via gateways  Heterogeneous devices – different capacities 7

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 8

Local Storage  Content Repository  Intermediate nodes cache content  Maximize the probability of sharing  Meta-Data Registry  Hash table for efficient look up  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 9 Content Repository Meta-Data Registry Interest Table

WiCCN Routing  Content Pushing  Spatial/temporal content  Geo-routing to command center or other destination 10

WiCCN Routing (Cont.)  Content Pulling  Using an Interest packet and local storages 11 Content Repository Meta-Data Registry Interest Table Interest 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 Interest 5. Interest is relayed

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 12

Packet Collision Avoidance 13 Interest REPLY REQUEST Content

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 14

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 15

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 16

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 17

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 18

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 19

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 20

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