Re: [Pce] Follow up about my question on the mic

Aijun Wang <> Tue, 27 July 2021 02:55 UTC

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Date: Tue, 27 Jul 2021 10:54:58 +0800
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Subject: Re: [Pce] Follow up about my question on the mic
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Hi, Mike:


Thanks for your questions. Please see the replies inline.

If you have more questions based on the followings answers, we can discuss
them accordingly.


Best Regards


Aijun Wang

China Telecom


From: <> On Behalf Of Mike
Koldychev (mkoldych)
Sent: Tuesday, July 27, 2021 6:36 AM
Subject: [Pce] Follow up about my question on the mic


Hi Authors,


Just following up about my 2 questions during the PCE WG session about


Question 1: Is every prefix going to be advertised (via the RR) to every
node in the native-ip domain, even if those nodes are never on-path for that

[WAJ] Yes, the behavior of RR is unchanged.

If my understanding is correct, the "BGP peer nodes" (R1 & R7 in Figure 4)
would receive the PPA (Prefixes) and would inject these prefixes into the
RR. The RR would then flood these prefixes (as regular BGP IP routes) to
every single node in the domain (R2, R4, R5, R6) with the next-hop being set
to R1 or R7. Please let me know if my understanding is correct or am I
missing something. So even though R5 and R6 in this example are off-path,
they would receive the prefix route from the RR?

[WAJ] Yes, R5 and R6 will also receive such prefix advertisements via the
normal RR behavior. But on router R5&R6, the route to the BGP nexthop
(R1&R7) is learned from the IGP protocol, not from the EPR(Explicit Peer
Route) Object. Then after the recursive process, the forwarding path on
R5&R6 will be along the normal non-optimal path.


Question 2: Have you thought about ECMP/UCMP (Equal/Unequal Cost Multipath)?
How would you implement it in your protocol?

[WAJ] Currently, we consider only the ECMP application. If PCE wants to
deploy multiple ECMP paths between two adjacent nodes, it can send two EPR
Objects to the corresponding PCC, with the "Route Priority" field be set to
the same value.