Paper Group: 12 Data Transport in Challenged Networks Above papers are original works of respective authors, referenced here for academic purposes only Papers Discussed: - Delay-Tolerant Network Architecture for Challenged Internets (ACM SIGCOMM 2003) - Interplanetary Internet: Communications infrastructure for Mars exploration (53 rd International Astronautical Congress) Chetan Hiremath CSE525 – Advanced Networking, Winter 2004 Oregon Graduate Institute

Paper Group Objectives Issues with communication nodes deployed in mobile and extreme environments Propose Delay Tolerant Network Architecture (DTN), that – Allow interoperability between “challenged” networks and Internet –Provide key services such as in-network data storage, retransmission interoperable naming, authentication and COS Interplanetary Internet: An example of DTN

“Challenged Networks” Terrestrial Mobile Networks –Networks become unexpectedly ‘partitioned’ Exotic Media Networks –High latencies with predictable interruptions Military Ad-Hoc Networks –Strong authentication and Class of Service required Sensor/Actuator Networks –Have limited CPU, memory and power resources

Characteristics of Challenged Internets Path and Link Characteristics –High latency, low data rate –Disconnection –Long queuing times Network Architectures –Interoperability considerations –Security End System Characteristics –Limited longevity –Low duty cycle operation –Limited resources

Tailor Internet Protocols for Challenged Networks ? Performance Enhancement Proxies –Violates fate sharing principle; connection state should be maintained by end stations only –Suggested for performance improvement applications only Protocol Boosters –Limits performance scalability under failure conditions Proxies –Too specific; not scalable Electronic Mail –Lack of dynamic routing Preset mail relays, acknowledgement, etc

Delay Tolerant Message based Overlay Architecture Region A (Internet) Region B Region D Region C (Intranet) {A, user} {A, R1} {A, R2} {B, R3} {B, R4} {C, R5} {D, R5} {B, R2} {C, R4} {D, Space}

Delay Tolerant Network Features Regions and Gateways Name Tuples Postal Class of Service Path Selection and Scheduling Custody Transfer and Reliability Time Synchronization Security Congestion and Flow Control Convergence Layers and Retransmission

Structure of DTN Gateway Scheduling and Message Forwarding RPC Server DTN Library + RPC DTN App Internet Convergence Layer Sensor Net Convergence Layer Other Convergence Layer Database Manager TCPUDPSCTP IP Other File Store SocketsSensor Net API Sensor Network Stack (TBD) Other Transport Or Raw Protocols (TBD) File Store DTN (Bundle) Gateway Serial Port

Interplanetary Internet Concept Use Internet and related protocols to form low delay, low noise local internets on Earth and other planets Specialized deep space backbone network of long-haul wireless links; interconnecting local internets –Characterized by intermittent connectivity, huge propagation delay and noisy data channels This “network of internets” employs a overlay concept called “bundling” to tie together this set of heterogeneous internets

Bundling Operates in “store and forward” mode –Messages are held at routers until forward path is established Avoids need for sender to store data until an ACK is received –Operate in custodial mode –Messages can be differentiated for priority based message transfers Store and forward model increases per hop error control for high error rate links –Good for deep space wireless backbones

Categories of Interoperability Data Handling Interfaces –Space vehicle communicates to orbiter via space link Long haul data links –Connect spacecraft with its ground system End-to-end data paths –Data flow between ground and space Mission management services Describe, sharing and archiving scientific information

Current Space Protocol Stack Space Wireless Frequency and Modulation Space Channel Coding Space Link Space Networking Space End-to-End Security Space End-to-End Reliability Space File Transfer Space Applications Defined by CCSDS – Consultative Committee for Space Data Systems Network layer allows abbreviated form of IP, as part of Space Communication Protocol Standards (SCPS) IPSec can be employed for end-to-end security SCPS extensions and TCP provide end-to-end reliability FTP, SCPS extensions and CFDP provide file transfer mechanisms

Mars Communication Protocol Stack CCSDS File Delivery Protocol (CFDP) TCP, UDPCCSDS TCP Tranquility IPSECCCSDS End-to-End Security CCSDS Path, Network or IPIP Local Terrestrial Link CCSDS Long Haul Link and Coding CCSDS proximity link and coding CCSDS Link Security CCSDS S, X or Ka bandLocal WiredCCSDS UHF UHF Wireless

CCSDS Long Haul Link CCSDS Proximity Link SONETE’net Convergence Layer Current “bundling” architecture Bundle API End-to-End Applications Bundle FTP, CDFP, Bundle NTP, etc Routing Custody Transfer End-to-end Reliability Authentication Encryption Other Services Licklider Transmission Protocol (LTP) TCP IP UDP Support for real end-to-end applications, not only file transfer Modular architecture allows ease of evolution for individual layers Increased flexible custodial transfer capability than CFDP

Advantages of DTN Design embraces notion of message switching, in-network storage and retransmissions for challenged networks Leverages trends of content based naming, administrative regions from Internet Prototype DTN implementation provides validation of architecture and proof of concept.

Concerns / Disadvantages of DTN Proposes change to basic service model and system interfaces –Existing applications may not interoperate –Increases barrier to acceptance Diverging set of choices, relative to widely used Internet –Messages versus packets –Hop-to-hop reliability and security, as opposed to end-to-end

Avenues for future work Definition of standards based stack for sensor networks allow interoperability Study application behavior transitioning from typical network to DTN based model

Questions ?