Which of these would not be a valid internet control message protocol (icmp) error message:
a) network unreachable
b) host unreacheable
c) router delay
d) destination network unknown

(c) Router Delay

Explanation:

The network layer of the TCP/IP provides a mechanism or tool for troubleshooting and error messaging called Internet Control Message Protocol (ICMP). Network layer devices such as routers may use this tool to communicate errors especially if there is an issue delivering data packets.

Some of these error messages are;

i. Source Route Failed

ii. Source Host Isolated

iii. Network Unreachable

iv. Host Unreachable

v. Destination Network Unknown

vi. Destination Host unknown

Note:

Router delay is not one of the error messages identified by the ICMP.