Date: Tue, 10 Aug 2004 19:33:15 +0900 From: Alexander Nedotsukov <bland@FreeBSD.org> To: Doug Rabson <dfr@nlsystems.com> Cc: freebsd-firewire@FreeBSD.org Subject: Re: max MTU for fwip device. Message-ID: <4118A46B.9030901@FreeBSD.org> In-Reply-To: <1092133653.13089.0.camel@builder02.qubesoft.com> References: <4116EA33.8040405@FreeBSD.org> <200408090859.34574.dfr@nlsystems.com> <411843FD.4090201@FreeBSD.org> <200408100851.32087.dfr@nlsystems.com> <41189199.5020201@FreeBSD.org> <1092133653.13089.0.camel@builder02.qubesoft.com>
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>>>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 ;-)
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