Re: [mpls] [nvo3] Encapsulation considerations

Hi Erik,

> -----Original Message-----
> From: Erik Nordmark [mailto:nordmark@acm.org]
> Sent: Thursday, April 09, 2015 8:05 AM
> To: Xuxiaohu; nvo3@ietf.org
> Subject: Re: [nvo3] Encapsulation considerations
> 
> On 4/7/15 7:15 PM, Xuxiaohu wrote:
> > Hi Erik,
> >
> > As it has said in the draft : "... We later expanded the scope somewhat to
> consider how the encapsulations would play with MPLS "transport", which is
> important because SFC and BIER seem to target being dependent of the
> underlying "transport"...", it would be necessary to consider the first nibble
> issue for those encapsulations which may be transported over MPLS. More
> specifically, for those encapsulations which may be directly encapsulated further
> with an MPLS header, they must not start with the value 4 (IPv4) or the value 6
> (IPv6) in the first nibble. Otherwise, they would be mistakenly interpreted as IP
> payloads by transit LSRs and therefore be subjected to ECMP and potential
> packet misordering.
> 
> Xiaohu,
> Good point.
> 
> But I couldn't tell from the emails on the BIER list whether the constraints on the
> first nibble value is a strict requirement in all cases, or whether it is conditional
> on something (and if so, what is the condition).

The conditions that I have thought of include: 1) the encapsulation is sensitive to packet misordering; 2) the encapsulation may be transported over an MPLS PSN; 3) LSRs within that MPLS PSN may use the contents of the MPLS payload to select the ECMP path.

Best regards,
Xiaohu 

> Once I know that answer we can definitely add some text pointing out the issue.
> 
> Thanks,
>     Erik
> 
> >
> > Best regards,
> > Xiaohu
> >
> >> -----Original Message-----
> >> From: Erik Nordmark [mailto:nordmark@sonic.net]
> >> Sent: 2015年3月26日 5:01
> >> To: nvo3@ietf.org
> >> Subject: [nvo3] Encapsulation considerations
> >>
> >>
> >> I presented part of this at the most recent NVO3 interim meeting.The
> >> full
> > 12
> >> areas of considerations where presented at RTGWG earlier this week.
> >>    The draft is
> >>      http://datatracker.ietf.org/doc/draft-rtg-dt-encap/
> >>    and the slides are at
> >>     http://www.ietf.org/proceedings/92/slides/slides-92-rtgwg-8.pdf
> >>
> >> There is probably additional things in there to consider for NVO3,
> >> and
> > advice
> >> that can be reused to make it easier to move NVO3 forward.
> >>
> >> Regards,
> >>      Erik
> >>
> >>
> >>
> >
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