INT identification after L4 headers

[jklr]

The spec currently suggests two ways to indicate the existence of INT after TCP/UDP/ICMP.

• DSCP
• Destination L4 port

Each has certain drawbacks, for example DSCP approach limits the available DSCP code points from 64 to 32. Changing the destination port will change ECMP behavior and complicate ACL.

Another options are

• IPv4 Option Header
• 8B Probe Marker, similar to that of Dataplane Probe

We can discuss pros/cons of the overall approaches in the following meetings and include in the spec.