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An Integrated Prototyping and SimulationArchitecture for Space Specific ProtocolDevelopments and Verifications
An Integrated Prototyping and SimulationArchitecture for Space Specific Protocol Developmentsand Verifications
Marc Emmelmann, [email protected]
Fraunhofer Institute forOpen Communication Systems
NASA 3nd Internet Space Workshop
Cleveland, OH, USA
June 4—6, 2003
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
Outline
Introduction - Project Framework- System Design with Reduced Development Costs
System Architecture - Integrated Development Flow (Overview)- Simulation on Network Level- Protocol Prototyping and Verification
Use Cases - ATM-Sat MAC Protocol Development- ATM connectivity between ISS Columbus and Earth
Summary & Outlook
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
IntroductionProject Framework
ATM-Sat Project - System Design and Study of an ATM-based LEOSatellite System for Multimedia Applications
- Financed by German Ministry for Education andResearch (BMBF)
ATM-Sat Partners - German Aerospace Agency (DLR), and- Tesat Spacecom (formerly BOSCH SatCom)
Project Constraints - None: ATM-Sat mere research project- Commercial aspects discussed: reduce development
costs while still designing failure save systems
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
IntroductionSystem Design with Reduced DevelopmentCosts
Possible Solution - Usage of commercial of the shelf equipmentfor development and simulation
- Standard operation systems as target systems- Design re-usable components
Integrated Dev. Approach - Idea by Fraunhofer FOKUS- Supported by TU Berlin (Research Group for Open
Communication Systems, OKS)
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
System ArchitectureIntegrated Development Flow (Overview)
satellite channelemulationterminalcontrol stationSDLCoptical splittingboxATMethernet (satellite channel)ethernet (management)TDLCTDLCTDLCterminalterminalPC
System Specification
Orbit description or meredelay information
Delay and elevationangle
Exchange of protocoldescriptions / algorithms
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
System ArchitectureSimulation on Network Level
- Focus on the entire communication network(large scale network simulation)
- Performance evaluation and dimensioning ofenvisioned system
- Analysis of interaction with other network types
- New protocols and algorithms “encapsulated” inprocesses and programmed in C
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
System ArchitectureProtocol Prototyping and VerificationKey Features: Std. COTS components
Focus on target systemFreeBSD 5 current-version
Core Units:
` Sat. channel emulator Configurable via SNMPAdds variable delayPacket corruptions
Protocol Dev. Entity “External VSAT System”Netgraph used for devel.
Control Station Time synchronization (NTP)Initializes SCE & PDE
satellite channel emulation
terminal
control station PDE
optical splitting box
ATM
ethernet (satellite channel)
ethernet (management)
PDE
PDE
PDE
terminal
terminal
PC
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
Use CasesATM-Sat MAC Protocol Development
Development Steps - Specification (SDL based)- Simulation (with Opnet)- Implementation (using the Prototyping and Simulation
Architecture)
Most complex scenario which incorporates all aspect of the integrated design anddevelopment work flow and all possible functionalities of the Prototyping and SimulationEnvironment.
Opnet Simulation - Conducted by DLR- Focus on large scale networks and scheduling
Target System MAC - Implemented by Fraunhofer FOKUS- Focus on performance- Used for demonstrations
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
controlstation
terminal
terminal
ISL
SDLC
SDLC
TDLC
TDLC
Use CasesATM-Sat MAC Protocol Development
two terminal in differentfootprints
satellite
satellite channel
application terminal satellite channelemulation
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
DemonstratorDLC System
DLC layer node with threeSAPs (ng_dlc)
convergence layer for ethernetencapsulation (ng_SATtrans)
multiplexer for ATMconnections between DLCsystem and terminal system(ng_mux)
ATM cells from separate PVCfor UNI messages are directlyforwarded to the DLC layer
ng_dlc
(PHY SAP)
(ATM SAP)
(UNI SAP)
DLC
ng_ether
ng_SATtrans
ether_if
to/from satellitechannel system
ng_mux
ng_atm
atm cells
ctrl cells
atm_if
to/from satellitectrl/terminal system
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
Use CasesISS Columbus ATM connectivity
ng_ether
ng_SATtrans
ether_if
ng_ether
ng_SATtrans
ether_if
to/from DLCsystem
userkernelng_socketng_ccatmng_uning_sscfung_sscopng_atmf/hatmilmidTCP/IPsocketApplicationng_clipng_lane
Loc
al M
anag
eent
DLC system
ng_atm
f/hatm
to/from userterminal
ng_atm
f/hatm
User Terminal
Channel Emulation: Delay, BER, Shadowing
Satellite Channel EmulatorDLC System
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
Interaction between Opnet and theProtocol Development Entity
Opnet - Encapsulates algorithms and protocolsin “Process-Nodes”
- Input combination of FSMs (graphical input) and C
PDE - Applies Netgraph concept of FreeBSD 5.0 current‡ encapsulation of algorithms / protocols
- Encapsulation is by nature split into two files:File a) Source code of algorithm / protocolFile b) Hookup with Netgraph system
Code Sharing - Currently by hand, restricted to some algorithms- Common code basis seems to be possible,- Requires “remapping” function calls
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
Summary & Outlook
Integrated Simulation - Evaluation and dimensioning of entire network& Prototyping System - Protocol development wrt. target system
- Already fully integrated environment fordevelopment, testing, and demonstration oftarget system protocols
- Partial code exchange between Opnet and PDEdone, common code basis seems feasible
Future Work - Common code basis- Determine how performatory target system code
is in the simulator- Determines on follow-up projects
Further Information - [email protected] http://www.fokus.fraunhofer.de/cats/satellite
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
Acronyms
ATM Asynchronous Transfer ModeCOTS Commercial Of-The-ShelfCS Control StationDLC Data Link ControlISL Inter-Satellite-LinkMAC Medium Access ControlPDE Protocol Development and Prototyping EntityPVC Private Virtual ChannelSCE Satellite Channel EmulatorSDLC Satellite DLCTDLC Terminal DLCISS International Space StationNTP Network Timing ProtocolSAP Service Access PointVSAT Very Small Aperture
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
References & Further Reading
- http://www.fokus.fraunhofer.de/cats/satellite
- J. Bostic, “Report on OPNET simulations,” German Aerospace Agency (DLR),Oberpfaffenhofen, Germany, Tech. Rep. DLR-IB, IB 554-01/02.
- Marc Emmelmann, “Effects of advertised receive buffer size and timer granularity onTCP performance over erroneous links in LEO satellite networks,” in Proc. IEEEGlobecom ’02, Taipei, Taiwan, Nov. 17-21, 2002.
- http://www.opnet.com- http://www.stk.com- http://spacesensors.dlr.de/SE/bird- http://www.freebsd.org- http://www.daemonnews.org/200003/netgraph.html
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
Supportive Slides
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
Simulation EnvironmentSimulation Workflow
Definition of satellite network - Orbit altitude- Orbit type
Definition of communication - Bandwidthnetwork aspects - Bit Error Rates
- Internet ProtocolSuite
AER DataSatellite
PathDescription
*.c and *.h Files for pipeline stages
Parser Programs
p2p-link w/variable delay
STK
Opnet
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
Satellite System ArchitectureSystem Parameters
LEO satellite network
70 ... 100 satellites
one satellite connected to 4neighbors via optical ISLs(inter- and intra-orbit)
ISLs existing all the time
dynamic bandwidth allocation
2400 ... 300000 user persatellite depending onthe allocated bandwidth
Uplink bitratefixed and portable terminals:up to 2048 kbit/smobile terminals:up to 384 kbit/s in steps of 16 kbit/sDownlink bitrateup to 32786 kbit/sin steps of 16 kbit/sModulation schemeQPSKAccess schemeuplink: MF-TDMAdownlink: TDMSpotbeam diameter50 km – 500 kmSatellite switch capacity5 Gbit/s - 10 Gbit/sISL capacity7 Gbit/s - 10 Gbit/sDownlink data rate per carrier32 Mbit/sMaximum number of downlinkchannels per carrier32Mbit/s / 16kbit/s = 2000
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
Satellite System ArchitectureProtocol Architecture
standard ATM is used
modified ATM signalingis used due to limitedonboard processingpower and unnecessaryprotocol functions
DLC layer with amanagement interfaceto upper layer isimplemented
Radio PHYRadio DLCATMS-AALAAL-XAAL-5M-UNISNMPILMICall ControlLMEApplicationRadio PHYRadio DLCATMS-AALAAL-5M-UNISNMPILMILMES-MIBCall Control andResource ManagementSatellite terminalSatellitecontrolplaneuserplanemgmt.planecontrolplaneuserplanemgmt.plane
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
DemonstratorUser Terminal
FreeBSD netgraph subsystem usedfor entire ATM signaling stack
applications can access ATMdirectly or via usual TCP/IP
IP realised via CLIP andATM Forum LAN emulation
local management interface(UNI <-> DLC) implementedvia a PVC between the systems
of-the-shelf IP and native ATMapplications can be demonstrated
userkernelng_socketng_ccatmng_uning_sscfung_sscopng_atmf/hatmilmidTCP/IPsocketApplicationng_clipng_lane
Loc
al M
anag
eent
DLC system
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
DemonstratorControl Stationconsole server for the DLC systems and the ATM switch
signaling VCs are forwarded as PVCs to the control stationpreforming the signaling
call control daemon is built around an SNMP daemon
management station for the complete demonstrator
can run many tracing tools for measurements
diskless boot support for DLC systems
DLC1VCI=5VCI=16DLC2VCI=5VCI=16UNI-Nstack 1UNI-Nstack 240424143ilmiatmroutecc (call control)control stationSNMP/LANemulation
Page [email protected] NASA 3nd Internet Space Workshop, Cleveland, OH, USA, June 4—6, 2003
DemonstratorManagement (Internal Structure)
NetgraphModule
NetgraphModule …
SNMPModule
SNMPModule …
SNMPBase
SNMPDaemon
System (Wlink)SNMPPart
HTTPPart
Translator HTTPModule
CGI-Scripts
Apache
WebBrower
NetgraphHook
SNMPHTTPText/plain
HTTPText/html
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DemonstratorManagement (Graphical User Interface)
Compatible with almost allbrowsers with frame support
For simplicity, only minimumset of HTML features used
Working Page divided in twozones: top part for navigationand status reports, bottompart for setting parameters
Optional additional reportingwindows and periodic refresh