Astrolabe: BGP Geospatial Encoding

Astrolabe is a protocol for encoding geospatial data in BGP communities. It's designed to enhance routing decisions and network diagnostics without compromising the existing BGP infrastructure.

Technical Specifications

• Uses standard 32-bit BGP communities (AS:NNNNNNNNNN format)
• Encodes latitude, longitude, and altitude
• Precision: ~1 meter for all dimensions
• Range:
  • Latitude: -90° to 90°
  • Longitude: -180° to 180°
  • Altitude: -8,388,607 to 8,388,607 meters

Encoding Scheme

ASN:GeospatialValue

Latitude:  600,000,000 to 633,554,431
Longitude: 900,000,000 to 967,108,863
Altitude:  681,611,393 to 698,388,607

Total BGP community space usage: 2.734%

Implementation

const LAT_SCALE: f64 = (1 << 25) as f64 - 1.0;
const LON_SCALE: f64 = (1 << 26) as f64 - 1.0;
const ALT_BASE: i32 = 690_000_000;
const ALT_MAX: i32 = 8_388_607;

pub fn encode_latitude(lat: f64) -> u32 {
    let lat = lat.clamp(-90.0, 90.0);
    let lat_normalized = ((lat + 90.0) * LAT_SCALE / 180.0).round() as u32;
    600_000_000 + lat_normalized
}

pub fn decode_latitude(lat_community: u32) -> f64 {
    let lat_normalized = (lat_community.saturating_sub(600_000_000)) as f64;
    ((lat_normalized * 180.0 / LAT_SCALE) - 90.0).clamp(-90.0, 90.0)
}

// Similar functions for longitude and altitude

Security Considerations

• Data Exposure: Geolocation data is sensitive. Use only on necessary prefixes.
• Unauthorized Updates: Implement strict update policies to prevent malicious alterations.
• Precision vs. Privacy: Consider using reduced precision for sensitive locations.
• Validation: Always validate incoming Astrolabe data. Reject out-of-range or nonsensical values.
• Spoofing: Astrolabe data should not be trusted implicitly. Cross-verify with other data sources when critical.

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