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

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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

    • [email protected]

    • (216) 433-3493


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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