> The thing is, we know that the router that's in a position to truncate the packet can probably get a packet to the destination (otherwise, it wouldn't have th

> The thing is, we know that the router that's in a position to truncate the packet can probably get a packet to the destination (otherwise, it wouldn't have this packet). We don't have anything to indicate that it can get a packet to the source; and it turns out that often it can't. Another point to add to this is that many routers will rate limit control plane traffic (ICMP, BGP etc), or prioritize data plane traffic ahead of it, so the ICMP too large message is more likely to be lost than a hypothetical in-band indication. It's the same reason you sometimes see packet loss in the middle of a traceroute, but not the end.