7 ms·

> "So even though it's only one hop from an L2 perspective, the light is being decoded, error corrected, and re-transmitted many times along the way to hong kon

> "So even though it's only one hop from an L2 perspective, the light is being decoded, error corrected, and re-transmitted many times along the way to hong kong from SF." This is not right. Submarine cable along the ocean floor is strictly Layer 1 ,there is no L2 down there. Also nothing is being decoded and retransmitted along that path. Signal regeneration only happens at the terminal stations. There's no repeaters along the ocean floor. The signal undergoes no conversion from optical to electrical, its optical the whole time it's under water. Submarine cables use an optical amplifier. Basically the fiber itself is doped with erbium creating an EDFA - erbium doped fiber amplifier. See: https://www.rp-photonics.com/fiber_amplifiers.html https://www.rp-photonics.com/fiber_amplifiers.html

detaro 9y ago
> Submarine cable along the ocean floor is strictly Layer 1 ,there is no L2 down there. Isn't that what "only one hop from a L2 perspective" would mean?
- bogomipz 9y ago
  I understood perhaps mistakenly the OP's comment to mean each "repeater" point was an L2 hop. But my main point was that the undersea spans are not in fact "repeatered" and there is no conversion of signal once it leaves land.
  - hueving 9y ago
    Yes, you are mistaken. "only one hop" was actually intended to mean only one hop.
    - bogomipz 9y ago
      Well there's no such things as a "hop" at Layer 2. And as others also pointed out its an optical amplifier, there is no "decoded, error corrected, and re-transmitted" being done along the path of the submarine cable.
      - hueving 9y ago
        >Well there's no such things as a "hop" at Layer 2. Only if you're being obtuse and don't actually work in networking. A hop in L2 is a device that does L2 forwarding and participates in L2 protocols like STP. >And as others also pointed out its an optical amplifier, there is no "decoded, error corrected, and re-transmitted" being done along the path of the submarine cable. This is only true for newer stuff. Look up OEO fiber repeaters. Those cables are still in use.

detaro 9y ago

> Submarine cable along the ocean floor is strictly Layer 1 ,there is no L2 down there. Isn't that what "only one hop from a L2 perspective" would mean?

bogomipz 9y ago
I understood perhaps mistakenly the OP's comment to mean each "repeater" point was an L2 hop. But my main point was that the undersea spans are not in fact "repeatered" and there is no conversion of signal once it leaves land.
- hueving 9y ago
  Yes, you are mistaken. "only one hop" was actually intended to mean only one hop.
  - bogomipz 9y ago
    Well there's no such things as a "hop" at Layer 2. And as others also pointed out its an optical amplifier, there is no "decoded, error corrected, and re-transmitted" being done along the path of the submarine cable.
    - hueving 9y ago
      >Well there's no such things as a "hop" at Layer 2. Only if you're being obtuse and don't actually work in networking. A hop in L2 is a device that does L2 forwarding and participates in L2 protocols like STP. >And as others also pointed out its an optical amplifier, there is no "decoded, error corrected, and re-transmitted" being done along the path of the submarine cable. This is only true for newer stuff. Look up OEO fiber repeaters. Those cables are still in use.