packet lengths


Tait Cyrus (hi!cyrus@hc.dspo.gov)
15 Apr 88 17:15:33 GMT


I have been comparing the lengths of packets specified in IP headers
against actual packet lengths. What I am seeing, ignoring IP packets
smaller than the minimum packet size, is that a fair number of machines
send out packets that are 1-3 bytes longer than is specified by the
IP length. Although this does not hurt anything, I am wondering
why this is. Is it because some machines short/long/quad align the
end of the packet before sending?

Also, this phenomenon appears to be protocol dependent. For example,
I saw several 4.3 machines doing this when sending out timed packets
and routed packet, but not with other packets. I've seen our IP/TCP
Imagen sending out UDP packets doing this.

Although this does not hurt anything, I am just curious as to the reason
why.

--
    @__________@    W. Tait Cyrus   (505) 277-0806
   /|	      /|    University of New Mexico
  / |	     / |    Dept of Electrical & Computer Engineering
 @__|_______@  |       Parallel	Processing Research Group (PPRG)
 |  |	    |  |       UNM/LANL	Hypercube Project
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 @/_________@/	      cyrus@hc.dspo.gov



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