Paper Group: 12 Data Transport in Challenged Networks

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Paper Group 12Data Transport in Challenged
Networks
Chetan Hiremath CSE525 Advanced Networking,
Winter 2004 Oregon Graduate Institute
Papers Discussed- Delay-Tolerant Network
Architecture for Challenged Internets (ACM
SIGCOMM 2003)- Interplanetary Internet
Communications infrastructure for Mars
exploration (53rd International Astronautical
Congress)

• Above papers are original works of respective
  authors, referenced here for academic purposes
  only

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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

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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

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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

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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

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

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Structure of DTN Gateway
DTN (Bundle) Gateway
DTN App
Scheduling and Message Forwarding
RPC Server
DTN Library RPC
Internet Convergence Layer
Sensor Net Convergence Layer
Other Convergence Layer
Database Manager

Sockets
Sensor Net API
TCP
UDP
SCTP
File Store
File Store
Sensor Network Stack (TBD)
Other Transport Or Raw Protocols (TBD)
IP
802.11
802.3
Other
Serial Port
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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

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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

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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

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Current Space Protocol Stack

• 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

Space Applications
Space File Transfer
Space End-to-End Reliability
Space End-to-End Security
Space Networking
Space Link
Space Channel Coding
Space Wireless Frequency and Modulation
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Mars Communication Protocol Stack
CCSDS File Delivery Protocol (CFDP)
TCP, UDP
CCSDS TCP Tranquility
IPSEC
CCSDS End-to-End Security
CCSDS Path, Network or IP
IP
Local Terrestrial Link
CCSDS Long Haul Link and Coding
CCSDS proximity link and coding
CCSDS Link Security
CCSDS S, X or Ka band
Local Wired
CCSDS UHF
UHF Wireless
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Current bundling architecture

• 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

End-to-End Applications Bundle FTP, CDFP, Bundle
NTP, etc
Bundle API
Custody Transfer
End-to-end Reliability
Other Services
Routing
Authentication
Encryption
Convergence Layer
TCP
UDP
Licklider Transmission Protocol (LTP)
IP
CCSDS Long Haul Link
CCSDS Proximity Link
SONET
Enet
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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.

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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

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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

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Questions ?