This function is to process the echo request.
The data received in the echo message must be returned in the echo reply message.
This function is to initialize the ICMP parameters
Operations Manager uses
a high-performance, asynchronous ICMP poller.
The ICMP poller performs at
a consistent rate that is independent of poll response times.
Operations Manager achieves this using two asynchronous threads:
one that sends polls and one that receives polls. Because the send and receive threads
operate asynchronously, slow response times or excessive timeouts do not affect the polling rate.
static struct stru_802_11_Phy_Parameters_HT a
This function is used to generate echo request
This function is to check the gateway state
The ICMP router discovery messages are called "Router Advertisements" and "Router Solicitations". Each router periodically multicasts a Router Advertisement from each of its multicast interfaces, announcing the IP address(es) of that interface. Hosts discover the addresses of their neighboring routers simply by listening for advertisements. When a host attached to a multicast link starts up, it may multicast a Router Solicitation to ask for immediate advertisements, rather than waiting for the next periodic ones to arrive; if (and only if) no advertisements are forthcoming, the host may retransmit the solicitation a small number of times, but then must desist from sending any more solicitations. Any routers that subsequently start up, or that were not discovered because of packet loss or temporary link partitioning, are eventually discovered by reception of their periodic (unsolicited) advertisements. (Links that suffer high packet loss rates or frequent partitioning are accommodated by increasing the rate of advertisements, rather than increasing the number of solicitations that hosts are permitted to send.)
The router discovery messages
do not constitute
a routing protocol:
they enable hosts to discover the existence of neighboring routers,
but not which router is best to reach
a particular destination. If
ahost chooses
a poor first-hop router
for a particular destination, it
should receive an ICMP Redirect from that router, identifying
abetter one.
A Router Advertisement includes
a "preference level" for eachadvertised router address. When
a host must choose
a default router
address (i.e., when,
for a particular destination, the host has not
been redirected or configured to use
a specific router address), it
is expected to choose from those router addresses that have the
highest preference level.
A Router Advertisement also includes
a "lifetime" field, specifying
the maximum length of time that the advertised addresses are to be
considered as valid router addresses by hosts, in the absence of
further advertisements. This is used to ensure that hosts eventually
forget about routers that fail, become unreachable, or stop acting as
routers.
The default advertising rate is once every 7 to 10 minutes, and the
default lifetime is 30 minutes.
If, according to the information in the gateway's routing tables,
the network specified in the internet destination field of a
datagram is unreachable, e.g., the distance to the network is
infinity, the gateway sends a destination unreachable message to
the internet source host of the datagram. In addition, in some
networks, the gateway may be able to determine if the internet
destination host is unreachable. Gateways in these networks may
send destination unreachable messages to the source host when the
destination host is unreachable.
If, in the destination host, the IP module cannot deliver the
datagram because the indicated protocol module or process port is
not active, the destination host may send a destination
unreachable message to the source host.
Another case is when a datagram must be fragmented to be forwarded
by a gateway yet the Don't Fragment flag is on. In this case the
gateway must discard the datagram and
return a destination
unreachable message.
Definition at line 39 of file ICMP.c.
1.9.5 
