Internetworking Over SpaceWire: A Link-Layer Layer Broadcast Service for Network Stack Support Robert Klar, Sandra G. Dykes, Allison Roberts, Chris Mangels, Buddy Walls, Mark A. Johnson, Kristian Persson Southwest Research Institute
Standard Network Stack On-Board? Standard Network Stack Application SNMP, Web (HTTP), SSH, FTP, SCPS-FP Transport TCP, UDP, SCPS-TP Network IPv, IPv6, SCPS-NP Data Link SpaceWIre, Ethernet, FireWire, HDLC, WiFi, Advantages Software reuse; mature APIs and implementations. Simpler application code. Rapid development. Lower cost. Interoperability. Disadvantages Platform-Specific Integrated Application & Network Data Link Physical Physical Protocol assumptions may not hold (e.g., TCP assumes delay is related to congestion, IP assumes end-to-end connectivity, ). Performance may not be optimal Space Internetworking Workshop, September 2006 Slide 2
SpaceWire Overview Switched N designed for high speed on-board data handling. Low power, low cost. Scalable Scientific Instrument Scientific Instrument 2 to 00 Mbps, low latency. Backplane or Cables. Command Computer Telemetry System Based on IEEE 155 and LVDS. Onboard Switched Local Area Network (N) Wormhole routing ESA Specification ECSS-E-50-12A Space Internetworking Workshop, September 2006 Slide
SpaceWire Path Addressing Header contains output port of each hop (0.. 2) SpaceWire s apply header deletion Example: N1 sends to N6 <><2><><cargo><EOP> Region 1 R 109 Region 2 165 R1 R2 R N1 1 N2 2 N N 129 N5 10 N6 11 N7 1 N8 2 N9 Space Internetworking Workshop, September 2006 Slide
SpaceWire Logical Addressing Header contains logical address of destination (2.. 25) Path determined by router forwarding tables. Example: N1 sends to N6 <11><cargo><EOP> Region 1 11 11 2 2 R 11 11 R1 11 11 R2 109 165 Region 2 R N1 1 N2 2 N N 129 N5 10 N6 11 N7 1 N8 2 N9 Space Internetworking Workshop, September 2006 Slide 5
SpaceWire Regional Logical Addressing Regional addressing used for larger networks. Logical addresses may be reused in different regions. s configured as gateways between regions. Example: N1 sends to N9 <165><><cargo><EOP> Region 1 165 165 R Header Deletion Applied 165 165 R1 R2 109 165 Region 2 R N1 1 N2 2 N N 129 N5 10 N6 11 N7 1 N8 2 N9 Space Internetworking Workshop, September 2006 Slide 6
IP, etc. Over SpaceWire Application Interest in on-board IP / SCPS-NP, esp. for rapid development programs. Transport Network: IP, SCPS-NP Need to level the playing field with Ethernet by providing full support for network protocols and standard network management. Data Link: SpaceWire SpaceWire is missing 2 key elements: Physical Encapsulation service Address Resolution Protocol (ARP) Space Internetworking Workshop, September 2006 Slide 7
Encapsulation Service SpaceWire cargo Type Virtual Channel ID SpaceWire Header Encapsulation Header Data ARP 1 IPv 2 IPv6 1 byte Virtual Channel ID CCSDS SCPS-NP CCSDS Source Packet 5 Broadcast 25 1 byte Encapsulation header (Virtual Channel ID). Identifies network protocol or software module on destination. Enables SpaceWire to support multiple network types. Lightweight but sufficient. SpaceWire Virtual Channel ID: 8 bits Ethernet Type field: 16 bits Space Internetworking Workshop, September 2006 Slide 8
SpaceWire Address Resolution IP Address SpaceWire Address 192.168.0.1 1 192.168.0.2 129 192.168.0. 5 No ARP defined for SpaceWire Manual configuration of address resolution tables: Assign SpaceWire and IP addresses. Install table on each node. Tables are static. Changing network topology requires new tables. SpaceWire cannot use standard ARP (RFC 826) Logical addresses not unique. No link-layer broadcast for full network. Solution: Develop these and use standard ARP Unique SpaceWire Address = Region + Node Logical Address Space Internetworking Workshop, September 2006 Slide 9
Broadcast Service Features Guarantees loop-free broadcast Link-layer implementation, no modification to the network layer (e.g. IP, SCPS-NP) Host implementation; no modification to Spacewire routers. Driver software implementation, no modification to Spacewire interface hardware. Adheres to SpaceWire standard. Space Internetworking Workshop, September 2006 Slide 10
Broadcast Service Introducing Concept of a SpaceWire Subnet Set of nodes attached to one routing switch 1 Broadcast Server B SUBNET A 5 6 A SUBNET C 5 6 C N1 1 N2 2 N N N5 5 N6 6 S A S C Space Internetworking Workshop, September 2006 Slide 11
Broadcast Service Protocol Messages Type 0: Subnet Broadcast 1 byte 2 25 0 SpaceWire header: Address Encapsulation header: Protocol 25 = Broadcast Broadcast header: Type 0 Broadcast Message Payload Space Internetworking Workshop, September 2006 Slide 12
Broadcast Service Protocol Messages Type 0: Subnet Broadcast 1 byte 2 25 0 1 SpaceWire header: Address Encapsulation header: Protocol 25 = Broadcast Broadcast header: Type 0 Encapsulation header: Protocol 1 = ARP Broadcast Message Payload ARP Message Space Internetworking Workshop, September 2006 Slide 1
Broadcast Service Protocol Messages Type 1: Server Broadcast 1 byte 5 25 1 SpaceWire header: Logical Address Encapsulation header: Protocol 25 = Broadcast Broadcast header: Type 1 Broadcast Message Payload Space Internetworking Workshop, September 2006 Slide 1
Broadcast Service Protocol Operation Node sends Subnet Broadcast Sends Type 0 message to all other ports on local router using path addressing. Neighbor s configured to discard 25 Broadcast Server sends Server Broadcast On receipt of Type 0 message, extracts the broadcast payload, encapsulates in Type 1 message and sends to all other Broadcast Servers. Remote Server sends Subnet Broadcast On receipt of Type 1 message, extracts the broadcast payload, encapsulates in Type 0 message and sends to all other ports on local router. Space Internetworking Workshop, September 2006 Slide 15
Broadcast Service Node N sends Subnet Broadcast (Type 0) B SUBNET A 5 6 A SUBNET C 5 6 C N1 1 N2 2 N N N5 5 N6 6 S A S C Space Internetworking Workshop, September 2006 Slide 16
Broadcast Service Broadcast Server sends Server Broadcast (Type 1) Type 1 Message Sent as Unicast to B All Servers SUBNET A 5 6 A SUBNET C 5 6 C N1 1 N2 2 N N N5 5 N6 6 S A S C Space Internetworking Workshop, September 2006 Slide 17
Broadcast Service Remote Server sends Subnet Broadcast (Type 0) B SUBNET A 5 6 A SUBNET C 5 6 C N1 1 N2 2 N N N5 5 N6 6 S A S C Space Internetworking Workshop, September 2006 Slide 18
Test Network SwRI SpaceWire Link Interface Module (SLIM) Single Channel, full-duplex SpaceWire Link Interface Fully Compliant CompactPCI target interface U cpci form-factor Star Dundee s (8 port) Links SpaceWire-PCI R1 SUBNET R2 SUBNET N1 SLIM N2 SLIM N Links N SLIM Space Internetworking Workshop, September 2006 Slide 19
Summary Scientific Instrument Scientific Instrument By adding missing elements, standard network stacks can be supported with SpaceWire Encapsulation Service Address Resolution Protocol (ARP) Flight Computer Telemetry System Spacecraft Onboard N Internet Standard ARP is possible if Broadcast Service supported Supports multiple network layer protocols (IPv, IPv6, SCPS-NP). Next step: Implement Broadcast and Encapsulation Service in device drivers for SwRI SLIM and COTS interface boards, and test IP and SCPS-NP applications on multi-router SpaceWire test network (SCPS-FP, DHCP, SNMP, HTTP, FTP, etc.). Space Internetworking Workshop, September 2006 Slide 20