Date: Mon, 31 May 1999 16:13:37 +0200 (MET DST) From: John K <john@volvo.se> To: slava <sl@zeus.dnt.md> Cc: freebsd-questions@freebsd.org Subject: Re: [off-topic] DF bit and IP Message-ID: <Pine.BSD/.3.91.990531160115.20110B-100000@nike.volvo.se> In-Reply-To: <Pine.BSF.4.05.9905311019300.61220-100000@zeus.dnt.md>
next in thread | previous in thread | raw e-mail | index | archive | help
Hi,=20 A dont fragment bit should be set only when the application "at the other= =20 end" isn=B4t able to puzzle the packets together, so AFAIK , setting DF=20 bits is an application specific matter. Also, you shouldn=B4t write a=20 program that cannot=20 defragment packets, as it behaves wired on routed network with differnet=20 MTU=B4s (eg, T/R-> Eth-> T/R ) I dont think TCP=B4s will be resent if there isn=B4t even an ICMP answer. When a packet is to be sent out on a router interface with a smaller MTU than the inbound interface, it is dropped by default and an ICMP packet is= =20 sent back. (like in the example above, if a DF bit would have been set.) hope this helped some,=20 br John On Mon, 31 May 1999, slava wrote: >=20 > Hi >=20 > Does TCP always gets encapsulated in an IP header with DF bit set? > I know this is needed for path MTU discovery to make tcp more efficient > but is this implemented on all OSes? >=20 > What if something in the way is blocking the icmp packet-too-big type > to the initiator of a TCP connection and it never finds out about a small > MTU in the path? Will it retry with a smaller MTU itself? >=20 > thanks > slava >=20 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?Pine.BSD/.3.91.990531160115.20110B-100000>