Reliable-Message-Delivery

Reliable message delivery

First, a look at what can go wrong:

• bit errors from electrical interference along the link
• a fiber is accidentally cut
• switch machine crash or runs out of bufffer space
• bugs in the network software

But the important thing to remember is there are three main error classes:

• bit errors: usually bursts of consecutive bits get flipped, perhaps from a lightning strike or power surge.
  • $1 / 10^6$ bits on a copper cable
  • $1 / 10^{12}$ bits on optical fiber
  • pretty easily detected, sometimes even correctable.
• packet loss: e.g. from a congested node (see resource-sharing). or perhaps an uncorrectable bit error.
• link/node error: physical link is cut or computer crashes, even network misconfiguration. this type of error can have dramatic effects, but it's also possibly to route around failed node/links