RE: HBH Obsolete? (was Review of draft-ietf-6man-hbh-header-handling-01)

Hi Mike,

Thanks for this analysis.

Although Router Alert begins with 00, it really should be on the first list. Think about what would happen if:

- You implemented RSVP-TE over IPv6
- One router the path does not recognize the Router Alert Option

For this reason and others, when people implement RSVP-TE over IPv6, they should not rely on the Router Alert HBH Option.

                                                                                           Ron

> -----Original Message-----
> From: ipv6 [mailto:ipv6-bounces@ietf.org] On Behalf Of C. M. Heard
> Sent: Friday, March 25, 2016 12:56 AM
> To: ipv6 <ipv6@ietf.org>
> Subject: Re: HBH Obsolete? (was Review of draft-ietf-6man-hbh-header-
> handling-01)
> 
> On 3/24/16,  Ronald Bonica wrote:
> > If we continue down the path of RFC 7045, we break the semantics of
> >the first two bits of the Option Type. If we are to do that, we should
> >probably repurpose draft-ietf-6man-hbh-header-handling-01 to:
> > 	- document the decision
> > 	- deprecate the semantics of the first two bits of the option type
> > 	  (because we broke them)
> > 	- explain how this deprecation limits the applicability of HBH.
> > 	  (i.e., HBH cannot support applications that absolutely require the
> >	   01/10/11 semantic)
> > 	- figure out if we have broken any existing HBH options that start
> > 	  with 01/10/11
> 
> I advocate doing this, rather than deprecating the entire HBH mechanism.
> 
> Of the eight non-trivial defined HBH options, only four demand actions other
> than ignore if unrecognized:
> 
> opt		act	chg	bin		Descr
> 	Reference	Status
> 0x63		01	1	00011	RPL Option	 	[RFC6553]
> 	PS
> 0x6D	01	1	01101	MPL Option	 	[RFC7731]	PS
> 0xC2	11	0	00010	Jumbo Payload	[RFC2675]	PS
> 0xEE	11	1	01110	IP_DFF	 	 	[RFC6971]
> 	Experimental
> 
> Indeed, the question arises whether allowing a router to ignore these
> options beaks them, or not.  Clearly so for Jumbo Payload, but it's unclear to
> me why RPL, MPL, and DFF need to be specified as other than ignore if
> unrecognized.  If they work only in a controlled forwarding domain, would
> not one expect all routers in such a domain to recognize them and act upon
> them?  Would they not still work if routers in the general internet ignored
> them?
> 
> The remaining four non-trivial HBH options are
> 
> opt		act	chg	bin		Descr		Reference
> 	Status
> 0x05		00	0	00101	Router Alert	[RFC2711]	PS
> 0x07		00	0	00111	CALIPSO		[RFC5570]
> 	Informational
> 0x08		00	0	01000	SMF_DPD	[RFC6621]
> 	Experimental
> 0x26		00	1	00110	Quick-Start	[RFC4782]
> 	Experimental
> 
> These are compatible with the RFC 7045 treatment.  CALIPSO, at least, seems
> to be of practical importance.
> 
> Mike Heard
> 
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