Re: proposal: rename DLT_PRISM_HEADER

[David Young <dyoung () ojctech com>]

On Mon, Dec 16, 2002 at 04:59:21PM -0800, Guy Harris wrote:
> On Mon, Dec 16, 2002 at 06:56:24PM -0600, David Young wrote:
> > BTW, I keep thinking of reasons to adopt length-type-value tuples for
> > the radio header. There are three, so far.  First, records such as RSSI
> > are meaningless for transmitted frames, so they may as well be omitted.
> > Second, certain records are not supported by certain hardware.  Third,
> > the radio header is likely to change fast: one may desire to adopt a
> > new device driver without breaking compatibility with your tcpdump.
> > With LTVs, your tcpdump may skip records whose type it does not know.
>
> That might require some central registry for values for the T part of
> the TLV.

  Won't Solomon will keep that? =)

> Note that there should still be a field at the beginning of the header
> giving the length of the header, so that, in order to find the 802.11
> header, one doesn't need a loop - machine code for most processors
> running libpcap-based applications can do loops, but BPF code can't.

  Right. Also, since variable-length headers are difficult for
  libpcap/tcpdump to deal with, implementations should probably
  return radio headers with a suitably large, standard length until
  variable-length headers are supported. A "null" LTV should fill unused
  space in the radio header.

Dave

-- 
David Young             OJC Technologies
dyoung () ojctech com      Engineering from the Right Brain
                        Urbana, IL * (217) 278-3933
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