Network Applications and Network Applications Lab
Chapter Four Notes
Other Chapter Notes:
– Internet Control Message Protocol: Method of reporting error
conditions and issuing and responding to simple requests.
do you need ICMP?
a simple means of communicating between hosts or a router and a
host to alert them to some kind of problem.
does ICMP fit in?
is in the same laver as IP.
is encapsulated in the IP datagram after the IP header.
no port numbers like in TCP and UDP
is in the internet layer, TCP and UDP are in the transport layer.
more ICMP information, go to www.iana.org/assignments/icmp-parameters.
gives no promise of the delivery of the message.
every operating system will respond to ICMP requests, requires no
listening ports or services.
uses ICMP for simple replies and requests and uses it to inform
another host of some kind of error condition.
also use ICMP to tell host of some kind of problem.
tell a host the destination host is unreachable.
step in reconnaissance attempts to discover the live hosts in a
can then send an attack to a live host
mapping is not done, then an attack can get very noisy and will not
be very productive.
of the most common methods of mapping is to issue ICMP echo
host then responds to an ICMP request with an ICMP echo reply that
it is alive.
network administrators block ICMP echo requests.
usually does not issue alerts for individual ICMP echo requests.
requests from the same host would cause there to be an alert.
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