Are ICMP packets important?

[Chuck Hallenbeck]

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Hi gang,

Now that I have a cable modem connection, I have implemented a
firewall and have been tinkering with it. I have been unable to
ping any hosts on the net, and have disected my firewall up one
side and down the other looking for the problem. Ping uses ICMP
packets.

Finally, out of either desperation or inspiration, not sure
which, I called my ISP and mentioned that I am unable to ping
anyone on other systems. He said that they have "disabled ICMP
packets" due to security concerns. Since ping is the only thing I
know about that uses ICMP, I decided I would not press the point
until something else came along.

Does anyone know what else I ought to be on the lookout for?

What about audio streams that persist over long periods of time?
I occasionally lose a connection to a realaudio stream with the
message "the server has timed out", and this seems sometimes to
happen right in the middle of playing something, not after a
lengthy silence. No more silences with cable modem. Is it
possible that a remote host might be trying to ping me to see if
I am alive, and my inability to send or receive ICMP packets
makes me appear absent?

If anyone has any light to shed on this issue of what trouble I
might expect with my ICMP packets blocked, I would appreciate
hearing about it.

Thanks,
Chuck


- -- 
The Moon is Waning Gibbous (70% of Full)
In a world without Fences or Walls no one needs Windows or Gates.
My home page is now at http://www.mhcable.com/~chuckh
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