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Re: Smallest Transit MTU

  • From: Sabri Berisha
  • Date: Wed Jan 05 11:40:21 2005

On Wed, Dec 29, 2004 at 05:04:11PM -0500, Joe Abley wrote:
> 
> 
> On 29 Dec 2004, at 16:33, Tony Rall wrote:
> 
> >But that only affects tcp traffic - it does nothing to help other
> >protocols.
> 
> Are there any common examples of the DF bit being set on non-TCP 
> packets?

[root@bofh sabri]# host -t ns verisign.com 192.5.6.30
Using domain server 192.5.6.30:

verisign.com name server bay-w1-inf5.verisign.net

[root@bofh root]# tcpdump -Xn host 192.5.6.30            
tcpdump: listening on fxp0
17:37:53.124955 217.69.153.39.55058 > 192.5.6.30.53:  58565+ NS? verisign.com. (30)
0x0000   4500 003a 5f10 0000 4011 e312 d945 9927        E..:_...@....E.'
0x0010   c005 061e d712 0035 0026 8ac9 e4c5 0100        .......5.&......
0x0020   0001 0000 0000 0000 0876 6572 6973 6967        .........verisig
0x0030   6e03 636f 6d00 0002 0001                       n.com.....
17:37:53.216656 192.5.6.30.53 > 217.69.153.39.55058:  58565- 3/0/3 NS[|domain] (DF)
0x0000   4500 00ca 0000 4000 3111 1093 c005 061e        E.....@.1.......
0x0010   d945 9927 0035 d712 00b6 1b79 e4c5 8100        .E.'.5.....y....
0x0020   0001 0003 0000 0003 0876 6572 6973 6967        .........verisig
0x0030   6e03 636f 6d00 0002 0001 c00c 0002 0001        n.com...........
0x0040   0002 a300 001a 0b62 6179 2d77 312d 696e        .......bay-w1-in
0x0050   6635                                           f5

Here you go. A root-nameserver setting the DF-bit on its replies :)

-- 
Sabri Berisha, SAB666-RIPE              - I route, therefore you are
http://www.cluecentral.net              - http://www.virt-ix.net

http://www.bash.org/?78486




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