+1 for Fernando's comments
2013/6/29 Fernando Gont <[email protected]> > Folks, > > I wanted to comment on some met-issues regarding the deprecation of the > IPv6 fragmentation function. > > ** On the motivation of deprecating the fragmentation function ** > > So far (and without having read Ron's recent I-D -- shame on me), it > looks like the main two reasons for deprecating the fragmentation > function are: > > 1) The inability of middle-boxes to parse past the first XXX bytes of a > packet > > 2) Unavailability of the connection-id (five-tuple) in the non-first > fragments. > > Regarding "1)", I believe that deprecating fragmentation is not really > the right solution. If anything, one could require the entire header > chain to be within the first XXX bytes of a packet (as a former version > of draft-ietf-6man-oversized-header-chain did). Besides, if we're going > to deprecate the fragmentation function because of this, then we should > also deprecate all extension headers, because they might lead to the > same issue. > > Regarding "2)", IPv4 doesn't have the connection-id in the non-first > fragments, either. So whatever middle-boxes are doing, they should/could > do it in the same way as they currently do for IPv4. > > > ** On the impact on applications ** > > It has been stated that fragmentation is uncommon. However, multiple > uses for IPv6 fragmentation have been mentioned -- from NFS, to tunnels > or the recent data posted by Mark Andrews. I think such use cases should > really be considered. > > That aside, if the IPv6 fragmentation function is removed, it also means > that UDP can only be used for applications that send datagrams > smaller than 1280 bytes (assuming no Path-MTUD for UDP). I haven't done > a survey myself, but I wonder to what extent one can really conclude > there's no need for that (e.g., I'm told that in the stock market sector > they employ multicast... which might mean that they need to send such > "large" UDP datagrams). > > > ** Therefore.... ** > > Considering the above, I guess I'm in the camp of "avoid fragmentation > where possible". However, I don't think I'd go as far as deprecating it. > > Just my two cents. > > Cheers, > -- > 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 > -------------------------------------------------------------------- >
-------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
