Pingable IPs on backbones?

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1

I just had one of those "duh" experiences today, and it made me think a
bit...

At my job at <vijay> a promising local ISP </vijay>, I was turning up a
customer, who decided to test his connectivity by trying to ping and trace
to www.sprint.net and www.uu.net. As it turns out, both servers are behind
firewalls, that block ICMP and UDP, so you can't ping or trace to either
server. But then my customer asked me, "OK, can you give me a hostname in
UU's netspace that I CAN ping?" It took some thought and experimentation
to find one (mail.uu.net and ns1.sprint.net, in case anyone wants to
know).

What this brought to mind was this question: would it be worth my time to
compile a list of pingable and traceable IPs that live on the major
backbones for connectivity testing and troubleshooting? I do wind up
seeing a lot of cloobies trying to ping a site, and assuming it's down
because IMCP-blocked.

Thoughts?

-C

2

What I've been wondering is why is ICMP seen as such an inherent evil that
it should be completely blocked? There are so many ways to pound on host
tcp stacks, the days that "ping -f" was an actual problem seem far gone.
This ICMP-envy seen on some networks takes away a useful tool and leads to
paranoid misconfiguration (like blocking pmtu-discovery combined with tcp
don't fragment flags, *cough*) makes me wonder, is it still really any use
at all to block icmp echo-requests? If so, would using CAR on it be
prohibitively expensive? Or is this all just a brick wall to run in to,
sort of like the smurf-reflector issues?

Cheers,
Pi