StartPingCheck

Message Layout

{
        StartPingCheck High 1 NotTrusted Unencoded
        {
                PingID Single
                {       PingID  U8      }
                {       OldestUnacked   U32     }
        }
}

Usage and Notes

• Used to measure circuit ping times.
• PingID is increased by 1 each time StartPingCheck is sent by the source.
  • After 255, PingID rolls over to 0.
  • The recipient is expected to respond with CompletePingCheck and return this PingID back to the source.
• OldestUnacked is simply the sequence number (see Packet Layout) of the most recent message sent by the source (excluding this packet), regardless of whether that message was sent reliably.
  • It is stored as little-endian.

For example, the following packet (hex data) is the 88th ping, with the last unacked message being sequence number 1364.

00 00 00 05 55 00 01 58 54 05 00 00