Referring to item 5.3, we think that the timestamp value need not be set to "Reserved".
This is because we can just use the timestamp and the current time to determine that the PMTU has expired. For example, before sending out a packet, the timer-based procedure should check whether the PMTU to be used has expired based on the cached timestamp and current time. If it has expired indeed, then there are no packets should be sent out using this PMTU. The PMTU value should be reset to the MTU value of the first hop and the PMTU discovery should be restarted.
We think the "Reserved" value can be removed to make the process of detemining the stale PMTUs less complicated.
We welcome suggestions and comments.
Computer Science School
USM 11800
Pulau Penang
Malaysia
