On 8/12/2016 10:54 AM, Tom Herbert wrote: > On Fri, Aug 12, 2016 at 10:21 AM, Joe Touch <[email protected]> wrote: >> >> On 8/11/2016 4:59 PM, Jesse Gross wrote: >> >> The most common example given in this area is the use of IP options. At the >> time that routing was moving to hardware implementations, options were not >> widely used and so were not implemented. However, imagine that options were >> in common use – do you think that router vendors would have decided that IP >> was too difficult to implement and abandoned that market? Or would we now be >> accepting that this is a common element of protocols? >> >> >> A good example from history here are TCP options. In the beginning, they >> were considered only a complexity overhead. >> >> Another example is IPsec. >> >> Both, are examples of TLV options (TCP within the TCP header; IPsec as a >> 'next layer' protocol). >> >> Both are widely supported in hardware. >> >> That's not to suggest that we should focus on TLV solutions, but it goes to >> prove that even TLV-format options do not prevent widespread hardware >> support. >> > Joe, > > I don't know sure that parsing of TCP options is really all that > widespread, In hardware at the endsystems, it is.
> but I do know that the inability of middleboxes to > properly implement support for both IP options and IPv6 extension > headers have pretty much made those non-starters for widespread > deployment. IPsec is a counterexample. For many years, the network device community pushed back on options because it undercuts their profit model (build for the 80% case and toss the rest to software slow-path). The tide there is turning; even the OPS groups are starting to admit that we can't simply deprecate IP options, but we can do things to encourage their more widespread support (e.g., limit the chain, etc.). Middleboxes ignore or misimplement options by design; they''re never useful as a constraint for protocol design. Joe _______________________________________________ nvo3 mailing list [email protected] https://www.ietf.org/mailman/listinfo/nvo3
