Florian, On 01/05/2012 06:40 AM, Florian Weimer wrote: >>> Do we really know that adding a fragment header to all outgoing packets >>> does not cause them to be rejected? >> >> Are you arguing that IPv6 fragmentation does no work at all, or what? > > I fear that it might work as well as in IPv4, that is, you can only get > there with some effort, and for some nodes, it will never work.
But that's an entirely different question. If you're thinking about e.g. banning all fragmentation from IPv6, that's certainly completely unrelated to the two I-D's that I've published on the subject... >>> Could this be deployed at large DNS servers in a risk-free fashion, >>> for instance? >> >> What's the specific question you're asking, and what is your concern, >> specifically? > > If DNS servers started sending either atomic fragments or fragmented > responses today (i.e., all generated packets carry an IPv6 extension > header), would these servers become unreachable for some clients? > (I think we have to assume the answer is "yes".) Because some clients ignore atomic fragments, because fragments would be dropped in the path to the client, or what? Note: I'm interested on the topic, but this one has to do more with Mark Andrews' proposal than with mine. -- Mine is about how to improve the state of affairs of IPv6 fragmentation. Mark's is about increasing its use. > IPv4 is different in this regard because clients can opt out from > fragmented responses by requesting 512 byte responses (even if it's > technically a DNS protocol violation). This is just not possible with > IPv6---unless the server keeps per-client state, which is a non-starter > for large DNS server deployments. Strictly speaking, that's not correct. Requesting 512-byte responses does not necessarily avoid fragmentation. The IPv4 MTU is 68 bytes, not 576. For instance, OpenBSD's imposes a lower limit of 296 (rather than 576 or the like) because such low-MTU technologies exist. Thanks, -- Fernando Gont e-mail: ferna...@gont.com.ar || fg...@si6networks.com PGP Fingerprint: 7809 84F5 322E 45C7 F1C9 3945 96EE A9EF D076 FFF1 -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
