Re: Meta-issues: On the deprecation of the fragmentation function

[Antonios Atlasis <[e-mail]>]

+1 for Fernando's comments


2013/6/29 Fernando Gont <[e-mail]>

> 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: [e-mail]
> PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492
>
>
>
>
> --------------------------------------------------------------------
> IETF IPv6 working group mailing list
> [e-mail]
> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
> --------------------------------------------------------------------
>