embedded transport agents for near earth communications june 8 2004
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Embedded Transport Agents for Near-Earth Communications June 8, 2004. Timothy J. Salo Architecture Technology Corporation 952-829-5864, x133 [email protected] Contents. Objective Benefits TCP Control Plane Resilient Connections Interoperability Potential Applications Current Status.

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embedded transport agents for near earth communications june 8 2004

Embedded Transport Agents forNear-Earth CommunicationsJune 8, 2004

Timothy J. Salo

Architecture Technology Corporation

952-829-5864, x133

[email protected]

contents
Contents
  • Objective
  • Benefits
  • TCP Control Plane
  • Resilient Connections
  • Interoperability
  • Potential Applications
  • Current Status
objective
Objective
  • Enhance TCP behavior for near-Earth space communications
    • Create a general, extensible TCP control plane facility (“embedded TCP agents”)
      • User-space, transport-layer tuning/control application
      • Agent-to-agent, reliable transport protocol
      • TCP in-band, secondary data channel (SDC)
      • TCP instrumentation
objectives
Objectives
  • Enhance TCP behavior for near-Earth space communications
    • Maintain TCP sessions across connectivity loss (“resilient TCP connections”)
    • Retain interoperability with Internet-standard TCP
    • Benefit SCPS-TP
    • Demonstrate feasibility of Embedded TCP Agent concept
benefits
Benefits
  • Embedded TCP Agent Architecture
    • Embeds greater intelligence into TCP stack
    • Dynamically adapts or tunes TCP’s behavior to current or projected conditions
    • Minimizes changes to TCP protocol
    • Hosts TCP intelligence in user-space
    • Enables rapid integration of cutting-edge research results into TCP implementations
benefits1
Benefits
  • Resilient TCP Connections
    • Maintain TCP connections in face of episodic or intermittent connectivity
      • e.g., LEO satellites
      • Extend/clarify RFC 1122, SCPS-TP behaviors
    • Hide intermittent connectivity from applications
      • obviate need to modify applications to handle temporary communications interruptions
    • Provide benefit of resilient TCP connections to all TCP users
benefits2
Benefits
  • Interoperability with unmodified TCP implementations
    • Enables a single, enhanced TCP implementation to interoperate with:
      • both enhanced and unmodified partners
      • both terrestrial and near-Earth space partners
benefits3
Benefits
  • Compatibility with SCPS-TP
    • Embedded transport agent concept and implementation could easily be ported to SCPS-TP
    • Resilient TCP connection extends SCPS-TP link-outage behaviors
      • Can easily be integrated into SCPS-TP specification, implementations
tcp control plane
TCP Control Plane
  • Provides an end-to-end control plane that will intelligently and dynamically modify the behavior of TCP
    • User-space “Embedded TCP Agents”
    • Agent-to-agent data stream
      • TCP-like transport protocol
    • TCP in-band, secondary data channel
      • Uses TCP options
    • TCP instrumentation
tcp control plane1
TCP Control Plane

Embedded TCP Agents

EmbeddedTCPAgent

Appl

Appl

User Space

Agent

Application Data Flow

Agent-to-Agent Control Flow

TCP

TCP

Kernel

TCP-to-TCP Control Flow

IP, etc.

IP, etc.

resilient connections
Resilient Connections

Resilient TCP connections will

  • Maintain TCP connections across connectivity losses
    • Proactive response in anticipation of planned connectivity loss
    • Reactive response when (presumably temporary) connectivity loss detected
resilient connections1

TCP Session Suspended

TCP Session Suspended

TCP Session Suspended

TCP Session Activethrough GroundStation C

TCP Session Activethrough GroundStation C

TCP Session Activethrough GroundStation B

TCP Session Activethrough GroundStation B

TCP Session Active through Ground Station A

TCP Session Active through Ground Station A

Resilient Connections
  • Resilient TCP connections will maintain TCP connections across connectivity losses

Ground Station B

Ground Station C

Ground Station A

Note: Mobile IPnot shown

Researcher

resilient connections2
Resilient Connections

Resilient TCP connections should:

  • Manage congestion window appropriately
  • Free resources eventually
  • Provide configuration controls
interoperability
Interoperability
  • Enhanced versions of TCP will maintain strict interoperability with existing TCP implementations
    • Use of new capabilities will be negotiated at run time between end points (TCP options)
    • Agent-to-agent communication will use TCP options
      • Minimize interaction with NATs, firewalls
    • An enhanced TCP will interoperate with an unmodified TCP
interoperability1
Interoperability
  • Enhanced versions of TCP will maintain current end-to-end behaviors
    • No network infrastructure upgrades required
    • Avoid requirement of a proxy/gateway
    • Coexist with end-to-end encryption (IPSec)
    • Maintain end-to-end TCP semantics
      • End-to-end acknowledgements
potential applications
Potential Applications
  • Provide robust Internet-access-to-space service for investigators
    • Optimized performance provided by Embedded TCP Agents
    • Uninterrupted, end-to-end transport-layer communications provided by Persistent TCP Connections
  • Automate satellite operations
  • Enhance tactical or mobile communications
    • Future Combat Systems (FCS)
current status
Current Status
  • Funded by NASA/GRC under a Phase I SBIR contract
    • Draft protocol specification completed
    • Developing proof-of concept implementation
      • Using Alpine and Alpine4Linux user-space port of BSD TCP stack
    • Developing ns-2 model
  • NASA COTR: Rich Slywczak
current status1
Current Status
  • Creating proof-of-concept demonstration
    • Demonstrate secondary data channel

Appl

Appl

Agent

Agent

TCP User Data

User Space

TCP/IP (alpine4linux)

TCP/IP (alpine4linux)

Secondary User Data

(TCP Options)

kernel

kernel

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