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From: Doug Rabson <dfr@nlsystems.com>
To: Alexander Nedotsukov <bland@FreeBSD.org>
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cc: freebsd-firewire@FreeBSD.org
Subject: Re: max MTU for fwip device.
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On Tue, 2004-08-10 at 11:33, Alexander Nedotsukov wrote:
> >>>Interesting. The specification for IPv6 on firewire is clearer:
> >>>
> >>>  The default MTU size for IPv6 packets on an IEEE1394 network is 1500
> >>>  octets.  This size may be reduced by a Router Advertisement [DISC]
> >>>  containing an MTU option which specifies a smaller MTU, or by manual
> >>>  configuration of each node.  If a Router Advertisement received on an
> >>>  IEEE1394 interface has an MTU option specifying an MTU larger than
> >>>  1500, or larger than a manually configured value, that MTU option may
> >>>  be logged to system management but MUST be otherwise ignored.  The
> >>>  mechanism to extend MTU size between particular two nodes is for
> >>>  further study.
> >>> 
> >>>
> >>>      
> >>>
> >>Mmm. I still do not see any prohibition of MTU size > 1500. What I see 
> >>here is definition of automatic MTU adjustment. It's stated that ATM MTU 
> >>size may be only reduced by such mechanism. Am I right?
> >>So manual configuration of interface for MTU size > 1500 violates nothing.
> >>    
> >>
> >
> >Of course - I certainly don't want to stop people from configuring an
> >MTU size > 1500. I just think that for the compiled in default, we
> >should go with the spec for now.
> >
> >  
> >
> I do not object default MTU either. But the problem is we have hardcoded 
> 1500 limit in SIOCSIFMTU  ioctl handler ATM. Check sys/net/if_fwsubr.c ;-)

Oops - I'll fix that when I get a chance. I've been side-tracked
recently trying to finish off the TLS stuff.