RE: RtgDir review: draft-ietf-l2vpn-vpls-ldp-mac-opt-11.txt

["Adrian Farrel" <[e-mail]>]

Hi Don,

[snip]

> > a) Some clear text/statement of when the new optimised MAC flush
> mechanism should be used instead of the existing RFC4627 mechanism (e.g.
> when is a full RFC4627 MAC flush "bad").
> [Don] OK I'll ask Adrian if he would like this highlighted.

I think that would be valuable to include (and am embarrassed to have not picked
up on it myself). Essentially, you are introducing an option: new flush
mechanism or old flush mechanism. You should help implementers decide which to
use. Might be as simple as "always" or might be some other issues.

[snip]

> > 1) The first paragraph of section 3 states:
> >
> >   When the MTU-s switches over to the backup PW, the requirement is to
> >   flush the MAC addresses learned in the corresponding Virtual Switch
> >   Instance (VSI) in peer PE devices participating in the full mesh, to
> >   avoid black holing of frames to those addresses.  This is
> >   accomplished by sending an LDP Address Withdraw Message from the PE
> >   that is no longer connected to the MTU-s with the primary PW, with
> >   the list of MAC addresses to be removed to all other PEs over the
> >   corresponding LDP sessions [RFC4762].
> >
> > Comparing this against Figure 1, my understanding is that the "PE that is no
> longer connected to the MTU-s with the primary PW" is PE1-rs. However section
> 3.1.1 states:
> >
> >   [RFC4762] specifies that on failure of the primary PW, it is the
> >   PE3-rs (Figure 1) that initiates MAC flush towards the core.
> >
> > Which contradicts the first paragraph of section 3?
> [Don] I see your point here, is what is being described.
> 1) PE-rs dual homing Aware
> - Control of dual homing by the PE-RS <- This is 3.1.1
> - Control of dual homing by the MTUs <-This is 3.
> 2) PE-Rs dual homing unaware.
> 
> [Don] It is up to you Ads & WG chairs to say if this should be highlighted,  I
think it
> covers the cases and I can try make it clearer as above if that helps.

My general rule of thumb is that if a reasonably smart reader has questions
arising from the text, clarifying the text is worthwhile. Maybe that some
pointers as highlighted would cover the case.

[snip]

Thanks,
Adrian