Hesham, This is what you have said below that I have put inside double quotes:
"Instead, clearing the L flag means that the host should not assume that an address derived from this prefix is on-link." My response to this statement is below. I have snipped text from RFC 4861 below (within square brackets) [Note, however, that a Prefix Information option Narten, et al. Standards Track [Page 54] RFC 4861 Neighbor Discovery in IPv6 September 2007 with the on-link flag set to zero conveys no information concerning on-link determination and MUST NOT be interpreted to mean that addresses covered by the prefix are off-link.] The text from RFC is saying the receiver of such an RA cannot assume addresses covered by the prefix are off-link while your statement above says cannot assume on-link. Now, if I go by this text in the RFC, I as a host WILL NOT send traffic to the default router because I cannot assume off-link. Hemant -----Original Message----- From: Hesham Soliman [mailto:[EMAIL PROTECTED] Sent: Wednesday, December 05, 2007 8:21 PM To: Hemant Singh (shemant); 'Erik Nordmark' Cc: ipv6@ietf.org; 'Suresh Krishnan' Subject: RE: Off-link and on-link > I know how to configure off-link on a router. I was asking the > community. At least the people we pinged in the past in the community > didn't know how or didn't reply including Hesham. > > How off-link is configured is described in section 2.1, and > 2.2.1 of our > draft. Your explanation below for the section 2.1 is fine. As for the > off-link suggestion you make below for AdvOnLinkFlag=False, > folks might > not agree with you on just setting L-bit in RA to be clear > and off-link > is signaled. Here is one reason why. Snipped below is text > from section > 2.3 on our draft. > > [An on-link bit of clear indicates nothing regarding on-link > determination. In section 6.3.4 of draft-ietf-ipv6-rfc2461bis-11 > (Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor > Discovery for IP Version 6 (IPv6)," March 2007.) [NDbis]": > > "...a Prefix Information Option with on-link flag set to > zero conveys no > information concerning on-link determination and MUST NOT be > interpreted > to mean that addresses covered by the prefix are > off-link.... Prefixes > with the on-link flag set to zero would normally have the autonomous > flag set and be used by [ADDRCONF]."] > > Did we miss anything in the interpretation of the text above from RFC > 4861. This text is not clear. => I tried to explain it in the meeting and on the list but clearly my explanation is not getting through. Let me have another shot. There is no flag in 4861 that says that an entire prefix is off-link. Instead, clearing the L flag means that the host should not assume that an address derived from this prefix is on-link. So what's the consequence of this? The consequence is that the host should send all packets to the default router. The same consequence as if the flag says the prefix is off-link. So if all you want to do is make sure that a host avoids address resolution and sends packets straight to the default router then make sure the L flag is clear. In the absence of the PIO, the default behaviour is to send packets to the default router. If none of this is clear please read Bernie's earlier response. I don't know how to make it any clearer. Hesham > > Thanks. > > Hemant > > -----Original Message----- > From: Erik Nordmark [mailto:[EMAIL PROTECTED] > Sent: Wednesday, December 05, 2007 1:46 PM > To: Hemant Singh (shemant) > Cc: Suresh Krishnan; ipv6@ietf.org > Subject: Re: Off-link and on-link > > Hemant Singh (shemant) wrote: > > Good question, Erik. To the best of my knowledge such an > RFC does not > > exist - at least describing total details of an > aggregation router - > > like unicast, mcast, and anycast data forwarding rules etc. The > > closest I have found in IETF is what IETF calls as > multi-link router. > > FWIW I don't find "multi-link router" in any RFC. My point was that > using this undefined term doesn't help clarify things. It would have > been better to talk about a router which has been configured to never > send any redirects. > > > Now the question I asked in my presentation. I have to > configure this > > aggregation router to signal off-link. How do I do that? > > By not to configuring it to enable the L flag for any prefix that the > router advertized. Abstractly (per RFC 4861) this is done by setting > AdvOnLinkFlag=False. > > If you have a question on how to do that for a particular product you > should ask the vendor of that product. If you are using OpenSolaris I > can help. > > > As I said in the presentation, let's forget the > aggregation router. > > The host implementation bug we found is reproduced in an > Ethernet LAN > > network too. An RA from the router was sent where RA was > NOT signaling > > > on-link and the host still behaved as on-link for traffic > forwarding. > > That is clearly a bug in the host implementation. > Have you contacted the host vendor? > > > The RA we used was an RA that did not send any PIO (Prefix > Information > > > Option). BTW, such a case (RA with no PIO) is not even > covered by the > > definition of on- and off-link in section 2.1 of RFC 4861, > especially > > since section 2.1 goes to so much copious details to > describe on-link. > > It does cover it. If no information is know about an address > (which is > this case - no prefix options with L=1 and no redirects) > then the host > will send to a default router. > > Erik > > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > ipv6@ietf.org > Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- > -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
