Hi all, I agree with Ian.
Actually, the document should use a similar wording in both the section mentioned in the errata report and the one in of 6.3. I’m afraid editorial changes are also needed for 6.3 to avoid any confusion. (1) 5.3: OLD: However, as not all service providers will be able to increase their link MTU, the B4 element MUST perform fragmentation and reassembly if the outgoing link MTU cannot accommodate the extra IPv6 header. The original IPv4 packet is not oversized. The packet is oversized after the IPv6 encapsulation. The inner IPv4 packet MUST NOT be fragmented. Fragmentation MUST happen after the encapsulation of the ^^^^^^ IPv6 packet. Reassembly MUST happen before the decapsulation of the ^^^^^^^^^^ IPv4 packet. A detailed procedure has been specified in [RFC2473] ^^^^^^^^^^^^ Section 7.2. NEW: However, as not all service providers will be able to increase their link MTU, the B4 element MUST perform fragmentation and reassembly if the outgoing link MTU cannot accommodate the extra IPv6 header. The original IPv4 packet is not oversized. The packet is oversized after the IPv6 encapsulation. The inner IPv4 packet MUST NOT be fragmented. Fragmentation MUST happen after the IPv6 encapsulation. ^^^^ Reassembly MUST happen before the decapsulation of the of the IPv6 header. A detailed procedure has been specified in [RFC2473] ^^^^^^^^^^^^^^^^^^ Section 7.2. (2) 6.3 OLD: As noted previously, fragmentation and reassembly need to be taken care of by the tunnel endpoints. As such, the AFTR MUST perform fragmentation and reassembly if the underlying link MTU cannot accommodate the encapsulation overhead. Fragmentation MUST happen after the encapsulation on the IPv6 packet. Reassembly MUST happen ^^^^^^^^^^^^^^^^^^ before the decapsulation of the IPv6 header. A detailed procedure has been specified in [RFC2473] Section 7.2<https://datatracker.ietf.org/doc/html/rfc2473#section-7.2>. NEW: As noted previously, fragmentation and reassembly need to be taken care of by the tunnel endpoints. As such, the AFTR MUST perform fragmentation and reassembly if the underlying link MTU cannot accommodate the encapsulation overhead. Fragmentation MUST happen after the IPv6 encapsulation. Reassembly MUST happen^ ^^^^ before the decapsulation of the IPv6 header. A detailed procedure has been specified in [RFC2473] Section 7.2<https://datatracker.ietf.org/doc/html/rfc2473#section-7.2>. Cheers, Med De : Int-area [mailto:int-area-boun...@ietf.org] De la part de ianfar...@gmx.com Envoyé : lundi 10 mai 2021 16:40 À : Eric Vyncke (evyncke) <evyncke=40cisco....@dmarc.ietf.org> Cc : softwi...@ietf.org; int-area@ietf.org Objet : Re: [Int-area] [Softwires] Errata on RFC 6333, "Dual-Stack Lite Broadband Deployments Following IPv4 Exhaustion" Hi Éric, My reading of the current RFC6333 text is that it is trying to highlight the importance of not fragmenting the IPv4 packet before encapsulation as this will break things. This, combined with ‘… after the encapsulation of the IPv6 packet.’ which should certainly be ‘… of the IPv4 packet.’ Is where the confusion is from. So, as a minimum, the errata is correct regarding the encapsulated IP version. Beyond that, I don’t find the remaining text to conflict with RFC2743 section 7.2. The text is only covering how to deal with packets that you will encapsulate and forward (DF=0) - case (b) in the RFC2473 text. Case (a) - DF=1 for received packet, so drop and send ICMP error isn’t discussed as these packets will not be encapsulated and need to be fragmented. I do agree that this is open to misreading. How about the following wording to preserve (what I think is) the authors intention: However, as not all service providers will be able to increase their link MTU, the B4 element MUST perform fragmentation and reassembly if the outgoing link MTU cannot accommodate the extra IPv6 header. The original IPv4 packet is not oversized. The packet is oversized after the IPv6 encapsulation. The inner IPv4 packet MUST NOT be fragmented. For packets forwarded by the B4 element, fragmentation MUST happen after the encapsulation of the IPv4 packet. Reassembly MUST happen before the decapsulation of the IPv4 packet. A detailed procedure has been specified in [RFC2473] Section 7.2. From Mikael’s comment: "RFC2473 7.2 says to use the DF bit and decide whether to inner fragment or drop+send ICMP error." I can’t find anything in the Section 7.2 text that would result in inner fragmentation. Thanks, Ian _________________________________________________________________________________________________________________________ Ce message et ses pieces jointes peuvent contenir des informations confidentielles ou privilegiees et ne doivent donc pas etre diffuses, exploites ou copies sans autorisation. Si vous avez recu ce message par erreur, veuillez le signaler a l'expediteur et le detruire ainsi que les pieces jointes. Les messages electroniques etant susceptibles d'alteration, Orange decline toute responsabilite si ce message a ete altere, deforme ou falsifie. Merci. This message and its attachments may contain confidential or privileged information that may be protected by law; they should not be distributed, used or copied without authorisation. If you have received this email in error, please notify the sender and delete this message and its attachments. 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