[Ippm-ioam-ix-dt] IOAM Flag Draft: Loopback on the Reverse Path

[Tal Mizrahi <[e-mail]>]

Hi,

This is a short summary of the open issue we have about loopback on
the reverse path.
The loopback flag indicates to transit IOAM nodes that they need to
loop back the packet. When an IOAM packet is looped back we want it to
be forwarded back to the encapsulating node so that (1) no data fields
will be pushed along the reverse path, and (2) the encapsulating node
will know that this is a looped back packet and terminate it.

We have discussed five possible options of how to indicate that a
looped back packet is in transit on the reverse path:
- Flag: A dedicated flag (new flag) that indicates that a packet is looped back.
- IOAM type: A dedicated IOAM type that indicates this.
- RemainingLen: An IOAM transit node that loops back the packet clears
the RemainingLen field. This will not work for the pre-allocated trace
option.
- Exporting format: A packet on the reverse path is sent with an
exporting format (e.g., using the IOAM raw exporting format).
- E2E option: A packet that is intended for loopback includes an E2E
option that includes the ID of the encapsulating node, and an
indication about whether the packet is on the reverse path.

Thoughts/preferences?

Cheers,
Tal.