Design of Link and Routing Protocols for Cache-and- Forward Networks Shweta Jain, Ayesha Saleem, Hongbo Liu, Yanyong Zhang, Dipankar Raychaudhuri
Introduction Future Internet usage is expected to involve an increasing proportion of content delivery to mobile end users. End to end connection model of TCP/IP is unsuitable for mobile and wireless Internet access. TCP file transfer rate limited by the wireless bottleneck link There is a research drive toward clean-slate protocol solutions under research programs (FIND and GENI in USA, FP7 Future Networks and FIRE in Europe). Cache and Forward A clean slate network architecture optimized for mobile content delivery.
Cache and Forward Router Because storage is cheap and getting cheaper Buffer to store content in transit Buffer ~ 0MB Hold to store content when router decides not to forward due to disconnection, link qualities, congestion etc Hold~ 1GB Cache for in-network storage Cache ~ 1TB Potentially a distributed data center! In an ideal world we replace all routers with CNF routers. In real world incremental replacement is feasible.
CNF Network Features Content Management, Content Naming, Content Reliable Link Layer Multi-hop Wireless Access network Discovery, Cache replacement In Network Storage Hop by Hop Transport Media File ~MB-1GB Movie 1.mpg Multicast Movie 1.mpg Media Server Mobile End-User
CNF TP CNF NP CNF LL CNF Protocol Stack CNRS Protocol 802.11 / 802.3 Routing Protocol Physical Layer (RF) Cache mgmt Protoco l Control Plane Search content by name Routing Cache management Data Plane Services Content Pull Get(M) Content Push Unicast Send(M,D) Content Push Multicast Send(M,[D1,D2 Dn]) Reliable Link protocol Hop by hop transport
Forward the content one hop at a time instead of packet by packet and end to end streaming CNF Transport End to end Acknowledgement Failure Case Incomplete file S ACK A ACK B ACK D Query satisfied Offered load at an = intermediate router file_size * No. of files * No. of senders/time
NACK 00000000 (Batch 0) Reliable Link Layer Sender Receiver Offered Load = λ Fragment * file size large * number files into of sources * average hop length batches of smaller packets. Transmit each batch to the next hop Exchange ACKs, NACKs and retransmit to achieve reliability Control (Batch 0) (Batch 0) Control (Batch 0) NACK 111011 Average file delays for varying offered load (Batch 0) (Batch 0) 1.TCP at the transport layer and IEEE 802.11 MAC. Control NACK (Batch 0) 11111111 2.UDP at the transport layer, CNF Link layer and IEEE Control 802.11 without RTS/CTS (Batch and 0) ACK. (Batch 1) NACK 00000000 (Batch (Batch 1) 1)
Storage and Mobility aware Routing Metric Maintain long and short term routing costs o Short term (S): instantaneous view of the cost to reach a destination o Long term (L): Historical perspective of the cost to reach the same destination along the same route o Ratio S/L: Indicator of fluctuation in link rate due to mobility as well as other channel conditions. o Collect and maintain multiple such routes Maintain view of current available storage at routers o Indicates queue build up and therefore contention Costs and at the storage MAC values layer, are broken links and congestion essentially providing link conditions averaged over route update time. COST Expected Transmission Time based upon physical data rate, queuing delay, congestion Expected Transmission count reflects number of transmissions necessary for successful data reception Load, energy, traffic priority
DS Next Long Shor Min T Hop t t Storag Cost e 40 40 D A 85 85 40 40 Cost 130 1G 1G 0M 1G D G 40 85 85 40 130 1G Short term route cost is high, store the data 0M Route improved, commence data S transfer DS T Next Hop Long Shor t Min Storag Cost e 1 D F 75 Cost 1 1G G D B 30 75 30 120 1G 0M Routing in CNF 0M G 1 0M G A B 0 C DS Next Long Shor Min T Hop t Storag Cost e D C 65 Cost 1 1G 0M D F 65 1 1G 1 G E 0 0 Cache And Forward (CNF) Network Architecture and Design 1 G F 1 G D
Routing Results 1) CNF TP over OLSR enhanced with the storage aware metric 2) CNF TP over OLSR with hop count metric Traffic model and parameters 3) FTP over Random OLSR source destination pairs start 500 file transfers in the first 180 seconds. Therefore, on average each node transmits 20 files. The simulation runs for 750 seconds. MAC and channel parameters: Adaptive Auto-rate 802.11 MAC protocol with supported rates 1Mbps, 2Mbps, 5.5Mbps, 6Mbps and 11Mbps Rate adaptation, collision and capture effects are implemented based upon received SINR. Two Ray Ground channel model with path loss
Summary and Future Directions CNF architecture is optimized for content delivery in the future Internet usage scenario. We promote CNF as a service for content delivery which co-exists with other protocols that carry real time traffic. We are working on completing the CNF protocol stack and porting it on the Orbit testbed.