SpeedDrain
Optical Fiber Physics · RTT Bounds · Haversine Geodesic · Routing Overhead

Global Ping Latency & RTT Simulator

Model physical packet propagation delay through undersea fiber cables and compare theoretical light-speed limits against empirical inter-region round-trip times.

us-east-1 (N. Virginia)
eu-west-2 (London)
Common Routes:
Physical Fiber Lower Bound (RTT)72.0 ms

Theoretical vacuum limit in silica glass (no routers, zero buffer)

Expected Real-World Ping (RTT)~93.2 ms

Includes fiber detours, 12 routing hops & switching

Fiber Cable Distance7,353 km

Straight-line: 5,570 km (3,461 mi)

Latency Delay Component Breakdown

Total: 93.2 ms
Fiber Propagation (72.0 ms / 77%)
Router Switching (19.2 ms / 21%)
Queueing Jitter (2.0 ms / 2%)

Simulation Tuning & Physics Parameters

Fused silica glass is typically 1.4682. Speed: ~204,190 km/s.
Subsea & terrestrial cables detour along coastlines and highways.
Edge, transit, BGP peering, and data center core routers.
Simulates bufferbloat, peak internet hours and packet queuing.

Network Physics: What Determines Packet Latency?

01.The Speed of Light in Glass Fiber (c / n)

In a true vacuum, light travels at approximately 299,792 km/s (~3.33 microseconds per kilometer).

However, modern telecom cables use single-mode fused silica optical glass, which has a refractive index (n) of roughly 1.4682. Photons traveling through glass undergo continuous refraction, slowing their effective speed:

v = c / n = 299,792 km/s / 1.4682 ≈ 204,190 km/s (or ~4.9 μs/km)

Because round-trip time (RTT) requires sending the packet and awaiting the acknowledgement, the absolute physical minimum RTT is ~9.8 milliseconds per 1,000 km of fiber.

02.Why Cables Don't Travel in Straight Lines (The Detour Factor)

When measuring the straight-line distance on a globe (the Great-Circle geodesic), London to New York is approximately 5,570 km.

In reality, transatlantic fiber cables (such as MAREA, Dunant, or Grace Hopper) must:

  • Navigate deep ocean trenches, fishing shipping lanes, and fault lines.
  • Land at coastal cable stations (e.g. Bude, UK or Virginia Beach, USA).
  • Traverse terrestrial conduits following railway and highway easements to reach urban colocation facilities.

This routing overhead introduces a 1.25× to 1.4× distance multiplier over the theoretical straight line.

03.Four Pillars of Packet Delay: d = d_prop + d_trans + d_proc + d_queue

Network latency experienced by end applications comprises four distinct components:

  1. Propagation Delay (d_prop): Time taken for light to traverse the physical medium. Bound by physics and cable distance.
  2. Transmission / Serialization (d_trans): Time to push bits onto the wire, determined by link bandwidth (PacketSize / DataRate).
  3. Processing Delay (d_proc): Router ASIC table lookups, header checksums, and NAT translation (usually 10–100 microseconds per modern BGP router).
  4. Queuing Delay (d_queue): Time packets sit in hardware buffer pools awaiting transmission during congestion (the primary cause of jitter and bufferbloat).

04.Hollow-Core Fiber & Low Earth Orbit (LEO) Satellites

Cutting-edge advancements are breaking traditional glass fiber limits:

  • Hollow-Core Fiber (HCF): Light travels through an air cavity inside a microstructured glass capillary rather than solid silica. Since air has a refractive index close to 1.0003, speed jumps from ~204,000 km/s to ~299,700 km/s—slashing physical propagation delay by nearly 33%! High-frequency trading firms heavily invest in HCF for routes like Chicago–New York.
  • LEO Laser Crosslinks (e.g. Starlink): Radio and laser beams traveling through space at 300,000 km/s can actually beat undersea cables over ultra-long transoceanic journeys (e.g., London to Singapore) despite altitude overhead, thanks to higher vacuum speed and fewer terrestrial doglegs.