Hi authors,
I read draft-ietf-bess-rfc7432bis-04 and I have the follwing questions and
comments:
1) In section 7.11.1, F bit (flow label capability) of L2 Attr Extended
Community is conveyed in Inclusive Multicast routes only,
and F bit will not be conveyed in Etherne A-D per EVI routes.
It will mean that the Inclusive Multicast route (which is used for BUM packets
only in RFC7432) will be used for known-unicast packets too?
Because that the flow label is not pushed onto BUM packets, it is only pushed
onto known-unicast packets.
Is my understanding correct?
2) If my previous understanding is correct, then I have the following questions
and I can't find explicit describing in rfc7432bis.
When PE1 received an Inclusive Multicast route with (tunnel
type=ingress-replication, Tunnel Identifier of PMSI tunnel attr = IP1, nexthop
= IP2, originator IP address = IP3),
so which one of the following cases should be inserted with a flow label?
2.1) a RT-2 route whose nexthop is IP1 and ESI is 0;
2.2) a RT-2 route whose nexthopp is IP2 and ESI is 0;
2.3) a RT-2 route whose nexthop is IP3 and ESI is 0;
2.4) a RT-2 route whose nexthop is IP1(or IP2) and ESI is an all-active ESI,
but the Ethernet A-D per EVI route's nexthop is IP4
2.5) a RT-2 route whose nexthop is IP4 and ESI is a single-active ESI and MPLS
label is L2, but the Ethernet A-D per EVI route's nexthop is IP1(or IP2) and
MPLS label is L1.
In question 2.5, I also don't find any explicit describing about which MPLS
label should be used in such case.
so which MPLS label should be used L2 or L1 in such case according to
rfc7432bis?
I think it will be more clear than this way if the Flow label capability is
carried by RT-2 routes themselves.
3) How to interpret "a given MAC address is only reachable only via the PE
announcing the associated MAC/IP Advertisement route" ?
I mean that: When PE1 receives a RT-2 route whose nexthop is IP1, and the
corresponding Etherne A-D per EVI route (whose nexthop is also IP1) conveys a
non-zero B bit, but there is another Ethernet A-D per EVI route whose P bit is
not zero, but its nexthop is IP4 (not IP1, who has announced that RT-2 route),
should that RT-2 route be installed into the dataplane and be used to
forwarding traffics?
This case may happens in some temporary conditions.
<rfc7432bis>
This means that for a given [EVI, BD], a given MAC address is only
reachable only via the PE announcing the associated MAC/IP
Advertisement route - this PE will also have advertised an Ethernet
A-D per EVI route for that [EVI, BD] with an L2-Attr extended
community in which the P bit is set. I.e., the Primary DF Elected PE
is also responsible for sending known unicast frames to the CE and
receiving unicast and BUM frames from it. Similarly, the Backup DF
Elected PE will have advertised an Ethernet AD per EVI route for
[EVI, BD] with an L2-Attr extended community in which the B bit is
set.
</rfc7432bis>
4) When flow label is not used (as per RFC7432) in Ingress Replication mode,
I try to find out whether the downstream assinged VPN label for known unicast
must be different than for BUM traffic.
And I don't find any explicit describing for this, and I just noticed that in
EVPN VXLAN they can be the same.
So when flow label is not used in MPLS EVPN,
can the downstream assinged VPN label for known unicast be the same as for BUM
traffic following rfc7432bis?
If this is just for flow-label only, I think it will be better to say "If
flow-label is used, the downstream assigned VPN label for known unicast
can/should be different than for BUM traffic"
<rfc7432bis>
* If a PE receives a unicast packet with two labels, then it can
differentiate between [VPN label + ESI label] and [VPN label +
Flow label] and there should be no ambiguity between ESI and Flow
labels even if they overlap. The reason for this is that the
downstream assigned VPN label for known unicast is different than
for BUM traffic and ESI label (if present) comes after BUM VPN
label. Therefore, from the VPN label, the receiving PE knows
whether the next label is a ESI label or a Flow label - i.e., if
the VPN label is for known unicast, then the next label MUST be a
flow label and if the VPN label is for BUM traffic, then the next
label MUST be an ESI label because BUM packets are not sent with
Flow labels.
</rfc7432bis>
Thanks,
Yubao_______________________________________________
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