"George, Wes E [NTK]" <wesley.e.geo...@sprint.com> writes: > [WEG] now it's my turn to be confused by your comment, Brian. I missed this > detail of interpretation when reviewing the draft for > LC, and I apologize, but I think it's pretty important... > >From the 3697bis draft: > "There is no way to verify whether a flow label has been modified en > route or whether it belongs to a uniform distribution. Therefore, no > Internet-wide mechanism can depend mathematically on immutable and > uniformly distributed flow labels; they have a "best effort" quality." > But it goes on to say: > " This specification defines the flow label as immutable once it has > been set to a non-zero value. However, implementers are advised that > forwarding nodes, especially those acting as domain border devices, > might nevertheless be configured to change the flow label value in > packets. This is undetectable."
> My interpretation of the above is that it functionally renders the > flow label mutable. I think we are getting too hung up on definitions. Is the UDP port number mutable? Is the TCP sequence number immutable? There are ways of modifying them that are undetecable. Does that make them mutable? The intention is that the Flow Label not get modified. Doing so can impact its usefulness. This is true of most fields in packets. If random actors start tweaking various fields in a packet, that tends to not be helpful (or worse). I do think the document needs to say something about covert channels and border routers zeroing out the field (and not just stick its head in the sand and try to have it both ways, which the wording Wes quoted effectively does). But that doesn't mean we are declaring that the field is "mutable", implying that anyone can start doing with it what they want. Thomas -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
