Resend: [dhcwg] question about NoPrefixAvail in DHCPv6 advertisement
JINMEI Tatuya / 神明達哉 <jinmei@isl.rdc.toshiba.co.jp> Sat, 19 March 2005 11:32 UTC
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Date: Sat, 19 Mar 2005 20:29:04 +0900
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From: JINMEI Tatuya / 神明達哉 <jinmei@isl.rdc.toshiba.co.jp>
To: dhcwg@ietf.org
Subject: Resend: [dhcwg] question about NoPrefixAvail in DHCPv6 advertisement
References: <y7vk6zf6vct.wl@ocean.jinmei.org>
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I happen to recall the attached message has not had any responses...could someone answer the question, please? Thanks, JINMEI, Tatuya Communication Platform Lab. Corporate R&D Center, Toshiba Corp. jinmei@isl.rdc.toshiba.co.jp
--- Begin Message ---Hello, I have a question about the following part of RFC3633 (Prefix Options for DHCPv6): 11.2. Delegating router behavior [...] If the delegating router will not assign any prefixes to any IA_PDs in a subsequent Request from the requesting router, the delegating router MUST send an Advertise message to the requesting router that includes the IA_PD with no prefixes in the IA_PD and a Status Code option in the IA_PD containing status code NoPrefixAvail and a status message for the user, a Server Identifier option with the delegating router's DUID and a Client Identifier option with the requesting router's DUID. Why should the delegating router include the IA_PD option(s) as well as the status code option (for NoPrefixAvail)? According to the condition that "the router will not assign *any prefixes* to *any IA_PDs*", it should be enough to include the status code only. In fact, in the similar condition of RFC3315 a DHCPv6 server just include a status code option with NoAddrsAvail: If the server will not assign any addresses to any IAs in a subsequent Request from the client, the server MUST send an Advertise message to the client that includes only a Status Code option with code NoAddrsAvail and a status message for the user, a Server Identifier option with the server's DUID, and a Client Identifier option with the client's DUID. I don't see any fundamental differences between the two cases. Moreover, the description for the counterpart at the requesting router seems to not be consistent very much with the above description for the delegating router. In section 11.1, RFC3633 says: The requesting router MUST ignore any Advertise message that includes a Status Code option containing the value NoPrefixAvail, with the exception that the requesting router MAY display the associated status message to the user. It seems to me that this description does not assume the IA_PD option containing a Status Code option (with NoPrefixAvail). Rather, the intention seems to be an advertisement only containing a status code option. To be more concrete, consider the following example. 1. the requesting router sends a DHCPv6 solicit message that includes two IA_PD options: solicit: IA_PD (IAID=1, T1, T2), IA_PD(IAID=2, T1, T2) 2. unfortunately, the delegating router cannot assign any prefix to any IA_PDs specified by the requesting router. According to section 11.2, the delegating router sends a DHCPv6 advertisement like this: advertisement: IA_PD (IAID=1, T1, T2, StatusCode(NoPrefixAvail)), IA_PD (IAID=2, T1, T2, StatusCode(NoPrefixAvail)) 3. the delegating router receives the advertisement. The intention of section 11.1 is probably that the delegating router must ignore the advertisement. The intention looks sane, but the description of the specification is not very clear. It says: The requesting router MUST ignore any Advertise message that includes a Status Code option containing the value NoPrefixAvail, so, can the requesting router ignore the advertisement by simply seeing the first StatusCode with NoPrefixAvail containing in the first IA_PD? Or, is the requesting router expected to parse the entire advertisement and to make the decision to ignore the advertisement only after confirming all the IA_PD options contain StatusCode with NoPrefixAvail? What should the requesting router do if the first IA_PD contains NoPrefixAvail but the second one does not? I personally think the behavior described in RFC3633 is not the best one, and should be revised to be consistent with RFC3315. It should probably be too late, however, and if so, I believe we should at least clarify the point and make a separate internet draft clarifying this point (which will hopefully be merged to the PD specification when it is ready for becoming a DS). Otherwise, this might be a serious interoperability issue. JINMEI, Tatuya Communication Platform Lab. Corporate R&D Center, Toshiba Corp. jinmei@isl.rdc.toshiba.co.jp _______________________________________________ dhcwg mailing list dhcwg@ietf.org https://www1.ietf.org/mailman/listinfo/dhcwg--- End Message ---
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