Understand, the following two steps are involved with a Traceroute:
1- Manipulating the TTL in the IP header to find the routers in the path to the destination.
>> The source initiating the trace will generate three ICMP echos towards the destination, starting with a TTL=1.
>> Each router in the path decrements the IP TTL by 1 upon receipt of the packet.
>> If a router in the path decrements the received packet’s TTL to 0, that router will discard the packet and generate an ICMP ‘time-exceeded’ message to indicate to the source that the packet expired in transit.
>> Every time the source gets a ‘time-exceeded’ it will generate three new echos with the previous TTL incremented by 1.
>> This cycle continues until the router receiving the ICMP packets matches the destination IP specified to one of its own.
2- Getting some form of response from the destination to know if it was reached.
>> When the three echos reach the destination, the reply will depend on the packet type used by the traceroute application of the source.
>> If UDP was used (like from a cisco router), the three echos sent to the destination would be sent to incremented unused UDP Ports starting at UDP port 33434 for the first hop. When the final destination receives three packets sent to an
unused local UDP port, the destination will respond with three ICMP port-unreachable message. Once the source receives the ICMP port-unreachable, it knows the destination was reached.
>> If ICMP was used (like windows pc), the process is the same as before, but the destination will reply with an ICMP echo-reply.

I believe the post is clear. The command rate-limit the response of the ICMP unreachables per time interval. The bigger the rate-limit value per packet the less ICMP unreachables will be sent, as the router will wait for the timer to reach zero before responding to the next. The lower the rate-limit value per packet, the more unreachable responses will be sent as less time is spend waiting.

For additional reading, I would recommend the services chapter in Routing-Bits Handbook RS.

HTH :)

Quick question: Will i be notified somehow about updates to the book, or do i need to keep an eye on the site?

Thanks again!