Subject: (ngtrans) oops, forgot to attach trace (another 6to4 question/comment)

From: Paul Francis <[email-masked]>
Date: Tue, 08 Aug 2000 16:58:13 -0700

PF

From Vern:
----------------------------------------------------------

I took an hour-long trace on one of the two UCB
Internet links.  It totalled
167,779 ICMPs (clearly, no smurf attacks!).  These
broke down as follows:

        54,430 echo request
        46,896 echo reply
        32,689 unreachable
                23,646 unreachable port (a wide
variety of ports)
                 5,434 unreachable host
                 3,390 administratively prohibited
                   108 unreachable net
                    55 prohibited access
                        (old flavor of admin
prohibited, I believe)
                    43 need fragmentation
                        (huh, not much useful MTU
discovery, eh?)
                    12 unreachable protocol
                     1 another flavor of
prohibited access
        29,428 time exceeded (about 75% of these
are Skitter)
         3,605 source quench (!)
           564 timestamp request
           136 timestamp reply
             8 redirect (!)

Of the unreachables potentially returned by
backbone routers (host, net),
93% returned just 8 bytes beyond the IP header
(assuming no IP options);
3% returned 58 bytes beyond; 1.25% returned 44
bytes beyond; 0.6% returned
528 bytes beyond; and the remaining 1.7% returned
sundry values around 40
bytes beyond (probably they could've returned a
bit more if the original
packet had been longer).

So, you can only rely on 8 bytes beyond the IP
header :-(.

                Vern