Les, Pls see inline..
Juniper Business Use Only -----Original Message----- From: Les Ginsberg (ginsberg) <ginsb...@cisco.com> Sent: Tuesday, March 28, 2023 11:02 AM To: Shraddha Hegde <shrad...@juniper.net>; lsr@ietf.org Subject: RE: UPA and planned/unplanned signalling [External Email. Be cautious of content] Shraddha - Thanx for the response. So the way you are proposing to use UPA on the receiving nodes is: 1)For unplanned loss of reachability trigger BGP-PIC for immediate response 2)For planned loss of reachability, don't trigger BGP-PIC - simply trigger a best path calculation considering the high cost of reaching the node about to go into maintenance. You can "get away with doing this" because you assume that when you receive the UPA indicating planned maintenance that the node is still reachable i.e., maintenance hasn't actually started yet. Do I understand you correctly? <SH> That is correct. This does help me to understand your motivation, but I am not fully appreciating the benefits. Whether you trigger BGP-PIC or not, you will have to do a new best path calculation. I don't see that not triggering BGP-PIC provides a benefit worth pursuing. But maybe we just will have to agree to disagree on that. <SH> ok If there is consensus to keep the two bits, I would suggest that the UP flag be a modifier of the U flag i.e., the U flag is always set (planned or unplanned), the UP flag is set in addition to the U flag when the trigger is planned maintenance. The UP flag would be ignored if sent without U flag set. This would provide a modest simplification for those implementations which don't care about the distinction - just look at the U flag. For those implementations that want to make the distinction you seem to favor, they would inspect both flags. ?? <SH> The flags should be defined to mean one thing or the other which is how it is defined currently. I do not like the proposal of defining the meaning of the flags based on how one implementation wants to interpret them. It is quite surprising to me that looking at two different flags is presumably more complex for some implementations. However, I am not going to argue beyond this on this topic. I am fine with whatever co-authors decide on this. Les > -----Original Message----- > From: Shraddha Hegde <shrad...@juniper.net> > Sent: Monday, March 27, 2023 9:25 PM > To: Les Ginsberg (ginsberg) <ginsb...@cisco.com>; lsr@ietf.org > Subject: RE: UPA and planned/unplanned signalling > > Hi Les, > > Pls see inline for replies. > > > Juniper Business Use Only > > -----Original Message----- > From: Les Ginsberg (ginsberg) <ginsb...@cisco.com> > Sent: Tuesday, March 28, 2023 9:10 AM > To: Shraddha Hegde <shrad...@juniper.net>; lsr@ietf.org > Subject: UPA and planned/unplanned signalling > > [External Email. Be cautious of content] > > > Shraddha - > > To follow up on our discussion over chat at the LSR meeting yesterday... > > At a remote ABR, if BGP had already been told about a planned node > maintenance event (by means that is outside the scope of the UPA > draft), then BGP would have moved traffic away from the node on which > the maintenance event is scheduled in advance of the arrival of the > UPA advertisement. In such a case the arrival of the UPA advertisement > would be of no significance. Since traffic has already moved away it > does not matter whether BGP processes the UPA or does not. > > If, however, BGP had NOT been told about planned maintenance in > advance, the arrival of the UPA should be treated in the same way > regardless of whether the trigger was a planned maintenance event or > not. The node associated with the address advertised in the UPA has > become unreachable and BGP needs to act accordingly. > <SH> This is the case when BGP is not aware of the planned maintenance > and is learning that info from IGP. > You are right that the final outcome of the planned maintenance vs > unreachability is same that the traffic needs to be moved away From > the remote PE. The difference is in how that is achieved. In case of > unreachability, the action need to be immediate and mechanisms such as > BGP-PIC needed. In case of planned maintenance, it would just be > costing out Igp metric for the PE and hence the control plane > convergence. > There may be implementations which just choose to trigger one > mechanisms for both scenarios and draft does not Mandate/suggest any > of this and is left to implementations. > > > > I therefore see no value add in differentiating between > planned/unplanned in the UPA advertisement. > > I hope this is clear. > Please point out what I might have missed. > > Thanx. > > Les _______________________________________________ Lsr mailing list Lsr@ietf.org https://www.ietf.org/mailman/listinfo/lsr
