too low the packet is not processed any further with respect to providing a routing response an icmp error u201c ttl expired u201d message is formulated for the packet by block 524 the source and destination network node addressing specifications of the received packet are extracted and reversed and the packet conveying the icmp message is provided to the exit packet processing leg as will be described with reference to fig5 c the packet is placed on an output port queue 528 lowest priority of the external output port 530 corresponding to the input port 502 via which the packet was received if the decision block 520 does not find a low packet ttl value the packet is forwarded on the packet is typically but not necessarily subjected to a packet acceptance rate control block 536 the packet is further processed through various other entry packet processing blocks for example to check the integrity of the packet header to remove a number of bytes etc which will be omitted from being shown for brevity of the description of the exemplary embodiment presented herein a person skilled in the art would specify the correct sequence of entry packet processing blocks necessary to support the services provided each such block typically performs a combination of accepting the packet modifying the packet header dropping the packet with or without associated processing such as sending a message back etc the packet is classified by classifier block 564 in accordance with the packet 39 s priority for preferential processing and stored in a priority queue 566.