Hi Peter, Thanks for your reply. Please see inline [Bruno2]
Orange Restricted > -----Original Message----- > From: Peter Psenak <[email protected]> > Sent: Thursday, June 16, 2022 11:22 AM > To: DECRAENE Bruno INNOV/NET <[email protected]>; [email protected] > Subject: Re: [Lsr] draft-ppsenak-lsr-igp-ureach-prefix-announce > > Hi Bruno, > > thanks for your feedback, please see inline (##PP): > > On 15/06/2022 16:09, [email protected] wrote: > > Hi Peter, authors, all > > > > Thanks for the draft. I find it a useful contribution to the problem space. > > > > IMHO the use of MAX_PATH_METRIC is a good idea in particular since it > > can be made backward compatible and provides incremental benefits with > > incremental deployment. > > > > I also have two disagreements on the current draft. Both are minor IMO, > > but authors may have a different opinion. > > > > 1. This draft defines a new signaling from an egress ABR to all ingress > > ABR/PE. As such, this require all these nodes to agree on this > > signaling. So I’d call for a STD track document. > > ##PP > there is no new signalling defined in the draft. We are using what has > been defined in the RFC5305/RFC5308 [Bruno2] By "signaling", I did not meant "protocol extension". I meant "signaling of information". https://dictionary.cambridge.org/fr/dictionnaire/anglais/signal Draft proposes an IGP announcement to signal something, more specifically that the prefix becomes unreachable > > > 2. IMO, the behavior defined in this draft is not backward compatible > > with the specification of MAX_PATH_METRIC in an IP prefix. > > ##PP > I see no backward compatibility issue > > > > RFC5305 says: > > > > If a prefix is advertised with a metric larger then MAX_PATH_METRIC > > > > (0xFE000000, see paragraph 3.0), this prefix MUST NOT be considered > > > > during the normal SPF computation.This allows advertisement of a > > > > prefix for purposes other than building the normal IP routing table. > > > > As per the above, one (ABR) may (is allowed and free to do so) already > > advertise both an aggregate prefix IP1/N with a regular metric and a > > more specific prefix IP2/32 with MAX_PATH_METRIC. > > > > With the above advertisement, all nodes compliant with RFC 5305 will > > install IP1/N in their FIB and not consider IP2/32 during their SPF and > > as a consequence not install it in their FIB. > > > > In term of reachability, all nodes have IP reachability to all IP @ in > > IP1 including IP2. > > > > If one node now implements the draft, it will remove reachability for > > IP2. And hence all my BGP routes using IPv2 for next-hop will be removed. > > ##PP > there is no such thing specified in the draft. What the drafts says is > that if the receiver is configured to do so, it can pass the UPA to the > applications that may be interested in it. How they act on it is outside > of the draft and ISIS as such. [Bruno2] In the draft, I'm not seeing the text "if the receiver is configured to do so". That would be a useful change (even though not enough to me) > I'm not sure where did you get the "remove reachability for IP2". [Bruno2] From the title "Unreachable Prefix Announcement". 1) I think we'll agree that there was reachability before the announcement. 2) the draft is about announcing that the "Prefix" becomes "Unreachable". That seems to be "removing reachability for the prefix". I'm open to using a different terminology such as "Announcing the Prefix to be Unreachable" but I don't think that this would change the conclusion. There is other text in the draft, such as "The functionality being described is called Unreachable Prefix Announcement (UPA)." > > > > > This looks clearly like a change in behavior to me, plus one which > > introduce loss of reachability in an existing network. > > > > 3) The solution that I would suggest is: > > > > - advertise the “unreachable prefix” with metric MAX_PATH_METRIC > > > > - define a new “Extended Reachability Attribute Flags” ([RFC 7794]) > > explicitly signaling that the reachability to this prefix has been lost: > > > > Unreachable Flag (U_flag). Set if this prefix is to be considered > > unreachable. > > ##PP > I see no reason for the new flag. RFC5305/RFC5308 already provide a way > to signal unreachable prefix. That's all we need. [Bruno2] RFC5305/RFC5308 provides a way to advertise a prefix that "MUST NOT be considered during the normal SPF computation". That is different from "a way to signal unreachable prefix" If you believe that all you need is RFC5305/RFC5308 I guess this means that we don't need draft-ppsenak-lsr-igp-ureach-prefix-announce Thanks, --Bruno > thanks, > Peter > > > > This would allow for explicit signaling of the reachability (vs implicit > > currently) and would be backward compatible with existing specification > > and deployments. > > > > Regards, > > > > --Bruno > > > > _________________________________________________________________________________________________________________________ > > > > Ce message et ses pieces jointes peuvent contenir des informations > > confidentielles ou privilegiees et ne doivent donc > > pas etre diffuses, exploites ou copies sans autorisation. Si vous avez recu > > ce message par erreur, veuillez le signaler > > a l'expediteur et le detruire ainsi que les pieces jointes. Les messages > > electroniques etant susceptibles d'alteration, > > Orange decline toute responsabilite si ce message a ete altere, deforme ou > > falsifie. Merci. > > > > This message and its attachments may contain confidential or privileged > > information that may be protected by law; > > they should not be distributed, used or copied without authorisation. > > If you have received this email in error, please notify the sender and > > delete this message and its attachments. > > As emails may be altered, Orange is not liable for messages that have been > > modified, changed or falsified. > > Thank you. > > > _________________________________________________________________________________________________________________________ Ce message et ses pieces jointes peuvent contenir des informations confidentielles ou privilegiees et ne doivent donc pas etre diffuses, exploites ou copies sans autorisation. Si vous avez recu ce message par erreur, veuillez le signaler a l'expediteur et le detruire ainsi que les pieces jointes. Les messages electroniques etant susceptibles d'alteration, Orange decline toute responsabilite si ce message a ete altere, deforme ou falsifie. Merci. This message and its attachments may contain confidential or privileged information that may be protected by law; they should not be distributed, used or copied without authorisation. If you have received this email in error, please notify the sender and delete this message and its attachments. As emails may be altered, Orange is not liable for messages that have been modified, changed or falsified. Thank you. _______________________________________________ Lsr mailing list [email protected] https://www.ietf.org/mailman/listinfo/lsr
