Mark, Here's some feedback about the aforementioned I-D:
** Technical: ** Section 1: > In order to avoid PMTUD [RFC 1191] in IPv6 an application must not > only force packets to be fragmented at the network MTU it must also s/network MTU/minimum IPv6 MTU/ (note that there are other instances of this throughout the document... all should be fixed) Section 1: > otherwise PTB ICMPv6 may be sent if the packet goes through a IPv6 to > IPv4 translating router [RFC 2460]. Are there any existing devices that exploit this feature? NAT64? Others? Section 2: > 2. Extend IPV6_USE_MIN_MTU > > > If IPV6_USE_MIN_MTU is set to 1 then a Fragment header MUST be added > to both multicast and unicast packets. > > If IPV6_USE_MIN_MTU is set to -1 then a Fragment header MUST be added > to multicast packets. I might be missing something, but: the current semantics of the IPV6_USE_MIN_MTU are that you force the *PMTU* to be 1280, rather than force the *inclusion* of a fragment header. Right now, if an app sets IPV6_USE_MIN_MTU, but the packet it sends equal to or smaller than 1280, a fragment header would *not* be added. However, with the new semantics you're specifying, it would. Section 6: At the risk of sounding my own horn, draft-gont-6man-predictable-fragment-id may be your friend here. Additionally, you may note that when a fragment header is included, but the packet does not actually get fragmented into multiple pieces, draft-gont-6man-ipv6-atomic-fragments eliminates the fragmentation-related security issues. ** Editorial ** Abstract: Expand it mentioning at least some scenario where you'd need this. (trivial: the DNS/UDP scenario). Section 1: > There appears to be 3 viable alternatives. 1) extend IPV6_USE_MIN_MTU > to force the inclusion of a Fragment header. 2) extend IPV6_DONTFRAG > to signal that a Fragment header needs to be included. 3) add a new > socket option like IPV6_DOFRAG. Have the document focus on only one of them (IMHO, option 3), and simply put any discussion of "alternative approaches" in an appendix. ** Nits ** Section 1: > The Advanced Sockets API for IPv6 [RFC 3542] provides mechanisms to > force fragmentation of packet greater than the network MTU > (IPV6_USE_MIN_MTU). s/of packet/of a packet/ Thanks, -- Fernando Gont SI6 Networks e-mail: [email protected] PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492 -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
