Re: TCP Option 20 processed incorrectly?

[Guy Harris <guy () alum mit edu>]

On Jul 6, 2011, at 10:38 AM, Scott, Keith L. wrote:

> The tcp.h file defines option 20 as 'Enhanced AUTH option' when I think it
> should be 'SCPS Capabilities'.  I'd like to prepare and present a patch that
> processes at least the initial option 20 correctly.  Does anyone know why 20
> was chosen for Advanced Auth

The checkin comment (in Git, but this was done before tcpdump switched to Git) for the change to tcp.h was:

        commit 95f66c8c622d57b50443c4d40be8b00a7de0aa94
        Author: hannes <hannes>
        Date:   Tue Nov 29 09:07:47 2005 +0000
    
            add basic support for keyed authentication TCP option

Hannes, was that based on some Internet-Draft?  According to

        http://www.iana.org/assignments/tcp-parameters/tcp-parameters.xml

option 20 is, in fact, "SCPS Capabilities", which is presumably for the CCSDS Space Communications Protocol 
Specification - Transport Protocol:

        http://public.ccsds.org/publications/archive/714x0b2.pdf

which is, apparently, "A set of TCP options and sender-side modifications to improve TCP performance in stressed 
environments including long delays, high bit error rates, and significant asymmetries." - "The SCPS-TP options are TCP 
options registered with the Internet Assigned Numbers Authority (IANA) and hence SCPS-TP is compatible with other 
well-behaved TCP implementations.":

        https://secure.wikimedia.org/wikipedia/en/wiki/Space_Communications_Protocol_Specifications
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