Hi Eduard,
I don't think an Ethernet A-D per ES route with a zero ESI is better to use,
Because each single-homed CE is an individual ES,
that's why MAC mobility happens between two zero ESIs (for different
single-homed ethernet segments)
but not happens between the same ESI (local and remote).
And I think such Ethernet A-D per ES route can't achieve the expected
"mass-withdraw" behavior actually,
Because it may not influence the installing of the RT-2 routes whose ESI are
zero.
If we want to use such Ethernet A-D per ES route to achieve mass-withdraw
behavior,
I think it will be difficult for us to decide when to trigger the mass-withdraw
too.
Please see section 9.2.2 of RFC7432:
"9.2.2. Route Resolution
If the Ethernet Segment Identifier field in a received MAC/IP
Advertisement route is set to the reserved ESI value of 0 or MAX-ESI,
then if the receiving PE decides to install forwarding state for the
associated MAC address, it MUST be based on the MAC/IP Advertisement
route alone."
Regards,
Yubao
On Wed, 8 Dec 2021 09:28:27 +0000
Vasilenko Eduard <vasilenko.edu...@huawei.com> wrote:
> Hi Yuya,
> Thanks.
> Your explanation looks reasonable because section 8.2:
> " If no other PE had advertised an Ethernet A-D route for the same segment,
> then the PE that received the withdrawal simply invalidates the MAC entries
> for that segment."
> Does not say "MUST" or "SHOULD".
> But the word "may" in this sentence was better to use.
> OK. I understood. It is an optional feature that was not claimed optional
> plainly.
> Eduard
> -----Original Message-----
> From: BESS [mailto:bess-boun...@ietf.org] On Behalf Of Yuya KAWAKAMI
> Sent: Wednesday, December 8, 2021 3:58 AM
> To: Vasilenko Eduard <vasilenko.eduard=40huawei....@dmarc.ietf.org>;
> bess@ietf.org
> Subject: Re: [bess] Contradiction for the RFC 7432 definition of the fast
> convergence (withdrawal) for single-homed CEs
>
> Hi Eduard,
>
> As my understanding, these statements are not contradictory because mass
> withdrawal is an optional functionality.
> Section 8.3 says when PEs are operating All-Active redundancy mode, Ethernet
> A-D per Ethernet Segment Route must be advertised for split horizon.
> This would be reason why section 8.2.1 says "not needed" in case of
> single-homed scenarios.
>
> I understand these sentences as:
> - Implementations can use Ethernet A-D per ES routes to achieve mass
> withdrawal for single-homed CE (optional)
> - If Implementations want to achieve mass withdrawal, Ethernet A-D per ES
> routes should be used
>
> The implementation I'm using does not support mass withdrawal for
> single-homed CE.
>
> If there is any misunderstanding, I would appreciate it if you could point it
> out.
>
> Thanks,
> Yuya
>
> On 2021/12/08 4:24, Vasilenko Eduard wrote:
> > Hi EVPN guru,
> >
> > It looks like RFC 7432 section 8.2.1 (Constructing Ethernet A-D per
> > Ethernet Segment Route) has an error:
> > "The Ethernet A-D route is not needed when the Segment Identifier is set to
> > 0 (e.g., single-homed scenarios)."
> >
> > Because without "per ES route" it would not be possible to signal
> > "mass withdrawal" If CE-PE connection would fail That plainly promised for
> > single-homed CEs in section 8.2:
> > " If no other PE had advertised an Ethernet A-D route for the same segment,
> > then the PE that received the withdrawal simply invalidates the MAC entries
> > for that segment."
> > Or implied in section 17.3:
> > "The Ethernet A-D per ES routes should be used by an implementation to
> > optimize the withdrawal of MAC/IP Advertisement routes."
> >
> > Have I missed something?
> >
> > Eduard
> >
> > _______________________________________________
> > BESS mailing list
> > BESS@ietf.org
> > https://www.ietf.org/mailman/listinfo/bess
> >
>
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>
>
>
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