1 Project Status Update “Postcards from the Edge”: The Cache-and-Forward Architecture FIND Wireless BBN Sept 27, 2007 Dipankar Raychaudhuri, Sanjoy Paul, Roy Yates WINLAB, Rutgers University {ray, sanjoy, & Jim Kurose, U Mass,

2 CNF Project: Architecture Concepts Network is optimized for efficient content delivery to mobile devices  Large storage (~TB) at each network node  Single- or multi-hop wireless access with occasional disconnections  Strict hop-by-hop transport (…entire file sent via reliable link protocol)  “Post Offices” for opportunistic delivery to mobile clients  Integration of conventional routing with retrieval of cached content Receiver’s Post Office Sender’s Post Office Receiver Sender MN CNF Network Routers with Storage Reliable Link Layer

3 CNF Project: Protocol Stack Routing protocol with integrated support of address- and content-based modes of delivery (get “filename”, deliver ”filename” to “address”, etc.) Support for in-network caching of content Multi-hop wireless access with disconnections and mobility at access edge (..”postbox” concept) Core CNF_1 CNF_6 CNF_2 MN Sender Receiver MN CNF_3 CNF_4 CNF_5 CNC_1 Link Protocol Receiver’s Post Office Sender’s Post Office Link Protocol

4 CNF Project: Simulation Results – Network Topology and Simulation Parameters GT-ITM’s transit-stub model Transit-transit links  10000Mbps bandwidth  Uniform (20,23)msec delay Transit-stub links  155Mbps bandwidth  Uniform (20,23)msec delay Stub-stub links  1000Mbps bandwidth  Uniform (2,11)msec delay 15 source-destination pairs ON State: Exponentially distributed with mean 100sec OFF State: Exponentially distributed with 3600sec An ON state is always followed by an OFF state (vice versa) Initial state of the source is ON During ON State: Fixed file size (50MB), Poisson arrivals S S D D S S D D

5 CNF Project: Simulation Results (1) – CNF vs. TCP Delay vs. Traffic Type & File Size TCP outperforms CNF for “always on” traffic and at low arrival rate Advantage of TCP over CNF reduces for ON-OFF traffic Advantage of TCP over CNF for “always on” traffic is higher at smaller file size Advantage of TCP over CNF for ON- OFF traffic is lower at smaller file size In-network storage in CNF serves to smooth traffic bursts However, this must be balanced against loss of pipeline gain Overall, CNF performs well relative to TCP except at low loads

6 CNF Project: Simulation Results (2) –Delay Histograms for Alternative Content Routing/Caching Strategies “Content Broadcast” scheme has more “low delay” file transfers compared to “Caching and Capture” When nodes exchange “content caching” information with neighbors Average Delay in locating content reduces and the reduction is more when caching is limited to fewer nodes ExperimentsAverage DelayImprovement Caching only, h= % Broadcast, h= Caching only, h= % Broadcast, h= Caching only, h=max % Broadcast, h=Max0.6590

7 CNF Project: Status & Next Steps Basic protocol architecture done, some details being worked on  Link layer protocol  Name resolution and file name resolution services  Caching service protocol  Routing algorithms System level simulation studies to be completed this year (12/07)  More results on caching and integrated routing protocol  Addition of wireless multi-hop scenarios to network model Started work on prototype implementation of CNF protocol on ORBIT/PlanetLab/VINI  Using BBN’s DTN code base as starting point  Staged implementation and evaluation of protocol modules  Proof-of-concept service demos by the end of year 2 (8/08)