Download - Internet and Satellite 1/9/2003
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Internet and Satellite1/9/2003
JSAT Co./WIDE ProjectJun TAKEI
Agenda
Day1– Satellite communication fundamentals– The history of satellite communications and
internetDay2– Satellite internet technology– Future and expected satellite internet
technology
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Satellite Internet Technology
Network Topology
Bi-directional link– Satellite link as a both way communication link– Topology A: VSAT style topology
Unidirectional link– Satellite link as a unidirectional communication link– Topology B: network connection
• IP connectivity to a network
– Topology C: host connection• IP connectivity to a host
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Topology A: Bi-directional LinkVSAT Style Topology
Both way communication via satellite
The Internet
Topology B: Unidirectional LinkNetwork Connection
Satellite receiver work as a router.Connect a network or host.
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Topology C-1:unidirectional LinkHost Connection
Route IP traffic by IP address assignment.
Topology C-2:Host Connection
Route IP traffic by proxy server.
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Topology Summary
Topology A (bi-direction).– No routing capability restriction.– Use satellite link as a vent pipe.
Topology B (UDL network connection).– Need dynamic routing capability.
Topology C (UDL host connection).– Dynamic routing capability is not required.– Subsets of topology B.
Topology and the Technology
Topology A (bi-direction)– VSAT, DVB-RCS
Topology B (UDL network connection)– UDLR, RFC3077
Topology C (UDL host connection)– DirecPC, SLCP
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UDLR - RFC3077
IETF UDLR-WG.– Established 1997.– First RFC, RFC3077 released in 2000.– Aim.
• To provide dynamic routing capability mechanism on UDL network without any existing routing protocol modification.
RFC3077
“A link-layer tunneling mechanism for unidirectional links.”Current existing dynamic routing protocol assume bi-directional communication capability on each network interface.
Router RouterBDL BDL UDL
UDL
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RFC3077 (Cont.)
Routing program expect a response of a routing message should be returned from the same network interface.
RouterUDL
UDL
Link Layer Tunneling Mechanism
Hide unidirectional link from kernel level.Use GRE (generic routing encapsulation).Why GRE?– GRE designed for carry routing information.– Layer 2(link layer) encapsulation.
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LLTM
Definition.– Feed: A router which has a send only interface.– Receiver: A router which has a receive only
interface.
BDL
UDL
Feed ReceiverIPLL
TCPENCAPDECAP
LLTM (Cont.)
By employing LLTM, routing protocol can communicate on UDL.Every unicast routing protocol works fine.– RIP, OSPF, IS-IS, etc.
Multicast protocol.– Yes and no.– Reverse path forwarding mechanism.In any case, some tips needed.
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IETF UDLR-WG
Preparing next RFC.– Informational RFC.– To help UDLR operation.– Clarify issue of IP multicast operation.
Future work.– Ipv6.– Interoperability test.– Etc.
Host Connection Model
How to route return traffic to a node via satellite link?
1. Application layer: proxy server2. IP address assignment: IP routing
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Host Connection Model 1
Route return traffic by proxy server.
Host Connection Model 1:Application GW
Proxy gateway technology.Proxy server forward return traffic via satellite link.Needs software configuration on client node.Not all application program can be supported.Scalable issue.DirecPC.
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Host Connection Model 2Assign IP address on UDL if and forward the traffic via satellite.
Host Connection Model 2:SLCP
Satellite link configuration protocolUDL interface has own IP address and the return traffic forwarded to its IP address.Client node send IP packet which source IP address is UDL if’s.Need modification in IP stack– Similar concept of LLTM
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TCPSAT
IETF TCP over satellite (TCPSAT)-WG.1997-2000 Feb.RFCs.– RFC2488 enhancing TCP over satellite channel
using standard mechanism, Jan 1999.– RFC2760 ongoing TCP research related to
satellite, Feb 2000.
TCPSAT (Cont.)
Scope of WG.– Transport layer issues affecting TCP over
satellite links.– Existing TCP option.– Compliant implementations which have some
known improved performance over sat. Links.– Recommendation of well understood protocol
changes.– Etc.
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DVB
DVB.– Digital video broadcasting project.– Getting world standard in MPEG transmission.
DVB standard.– More detail specification on MPEG system.
DVB family.– DVB-S: satellite.– DVB-C: cable.– DVB-T: terrestrial.
DVB-RCS
New VSAT style communication platform.Low cost terminal and also hub system.Hub to terminal.– Forward link: about 30mbps.
Terminal to hub.– Return link: upto 2mbps.
Typical antenna size.– 60cm-90cm.
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DVB-RCS (Cont.)
Terminal equipment size– First generation
• 2u full thick pizza box
– Second generation• 1u think pizza box
– Third generation• Lunch box
DVB-RCS Hub System
2 rack redundant hub system.ESA is doing interoperability test.
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Future Satellite Communication
What is Next?
Key Technology
On board possessing.– Switch packets on the satellite.– Switch in the sky.– Router in the sky.
Multi-beam spot beam antenna.– Route traffic from a beam to another beam.
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On Board Processor
Experimental satellite test.– ACTS program by NASA.
• ATM cell switch.• Why ATM?
• Fixed length packet.• Easy to synclines.• Too large overhead!!
OBP on Commercial Satellite
EUTELSAT HotBird– MPEG packet multiplex capability– Uplink
• MPEG SCPC carrier
– Downlink• MPEG MCPC carrier• Small terminal can transmit the traffic• DVB-S small receive dish(50cm)
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IP Router in the Sky
NASA planning to launch Cisco router on orbit.C3651 mobile routing test bed.Space proven module.– Launched by small
satellite project.– Cots.
What Should We Do?Research Topics
IPv6 on DVB-RCSIPv6 on UDLRNetwork modeling with OBP satelliteContents distribution via satellite IP network.New cording mechanism.SecurityEtc.
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Enjoy real satellite Interneton AI3 !