Backbones in SpaceInter-Domain Routing with big satellite constellations

August 2017 Tobias Klenze

Launch Vehicle Cost to LEO per kg

Space Shuttle $60,000

ULA Atlas V $8,132

SpaceX Falcon 9 $2,719

SpaceX Falcon Heavy(expected to fly 2017) $1,406

Reusability will bring even more drastic reductions in cost

Rapidly decreasing cost to orbit

Satellite Manufacturing

• GEO satellite: $100-500M (3,000kg, each is unique)

• LEO Globestar satellite: $8M (550kg, 48 built)

• LEO Iridium satellite: $5M (689kg, 98 built)

• LEO satellite internet: ? (300kg, >1000 to be built)

Mass production will make satellites much cheaper

Planned Satellite Constellations

SpaceX (+Google) OneWeb (+Virgin) Boeing (+Apple)

# of Satellites

4,425 by 2024 (+7,500 later)

648by 2019

1,396by 2023 (?)

Bandwidth per Satellite 20 GBit/s 6 GBit/s ?

Orbit Circular LEO ~1200km

Frequencies 12-40 GHz (40-75 GHz) 12–18 GHz 40-75 GHz

Not just connecting end hosts, but backbone of the Internet

Misconception: Sat Internet is Slow

• Past satellite Internet was based on GEO satellites with >250ms RTT.

• New, proposed satellites in LEO, 25-35ms RTT.

• 1.4x faster speed of light in vacuum vs optic fibre.

• Directer & faster for intercontinental flows.

Samsung: Mobile Internet from the Heavens https://arxiv.org/ftp/arxiv/papers/1508/1508.02383.pdf

Samsung: Mobile Internet from the Heavens https://arxiv.org/ftp/arxiv/papers/1508/1508.02383.pdf

Samsung: Mobile Internet from the Heavens https://arxiv.org/ftp/arxiv/papers/1508/1508.02383.pdf

Inter-AS routing is crucial

Routing via Satellite Constellation

• Highly dynamic topology

• Each Satellite only visible for a few minutes

• Spotty connectivity (dead satellites may not serviced or replaced rapidly; terrestrial & space weather)

• Fluctuations in capacity and latency (depending on precise location of satellites)

• Highly predictable!

Proposal: Hop Annotations in SCION

• Lightweight SCION extension of beacons (PCBs)

• Annotations of expected future fluctuations. Examples:

• "Link will be down at time x until y due to bad weather."

• "Latency will be increased by 100ms from time x to y."

Proposal: Hop Annotations in SCIONAllows for proactive routing, rather than reacting to rapid and frequent link changes. Examples:

• Everyone: "Use cable uplink during satellite downtime."

• High availability users: "Increase SIBRA bandwidth reservation via cable uplink from time x to y"

• Low latency users: "Route Skype call via cable uplink during high latency"

Hypotheses• Satellite Internet constellations are coming

• Using them as a backbone is attractive

• Rapidly changing topology is a challenge for existing Inter-AS routing

• Predicability makes it possible to solve this problem

• SCION can be part of the solution

Research Questions• Is there actually a problem? Perhaps multipath in

vanilla SCION is enough to handle connectivity interruptions.

• If not: Could hop annotations solve this problem?

• Are there other benefits to using SCION specific to satellite routing?

• Where in the topology of SCION do satellite ASes fit in? What happens to Isolation?

Topology

Satellite AS

Terrestrial AS

Problem: Non-blue ASes are excluded!

Topology

Satellite AS

Terrestrial AS

Topology

Satellite AS

Terrestrial AS

Problem: Loss of Isolation

Literature

• Lots and lots of literature on Intra-AS satellite routing

• Some literature on Inter-AS satellite routing

• Takes into account changed internal and external metrics for terrestrial vs satellite ASes.