On Friday, 10/19/2007 at 02:59 EDT, "Ponte, Doug" 
<[EMAIL PROTECTED]> wrote:

> I don't know the details of your trace, but this looks similar to an 
incident 
> that occured here recently. This may be a shot in the dark, but it's 
worth a 
> try.  Make a small change to your PROFILE TCPIP to include a parmameter 
called 
> 'OVERRIDEPRECEDENCE' under the ASSORTEDPARMS section like so:
> 
> ASSORTEDPARMS
> PROXYARP RESTRICTLOWPORTS OVERRIDEPRECEDENCE
> ENDASSORTEDPARMS
> 
> In our client's problem, FTP started giving OPEN TIMEOUTs to z/OS FTPD 
IP 
> addresses *only*...other FTP sessions opened just fine it seemed. 
Nothing 
> changed, yada yada...same thing customers always told me when I was at 
IBM :) 
> Though, I still suspect that something in z/OS TCPIP was altered that 
> indirectly affected the precidence values. E.g expecting an 'immediate', 
a '1' 
> whatever they use.

If you have DiffServ (Differentiated Services, RFC 2475)-enabled equipment 
(i.e. traffic shapers), they will use the precendence fields in a way 
contrary to the TCP standard (RFC 793).  [Great - two RFCs that conflict!]

Think of OverridePrecedence as implementing RFC 2873, which relaxes the 
rules in RFC 793.

Chucky says OverridePrecedence should be the next "unchangeable default". 
:-)

Alan Altmark
z/VM Development
IBM Endicott

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