Re: [spring] One question on E-flag of ABR/ASBR in OSPF SR extension
Peter Psenak <ppsenak@cisco.com> Thu, 18 May 2017 08:59 UTC
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Date: Thu, 18 May 2017 10:54:14 +0200
From: Peter Psenak <ppsenak@cisco.com>
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To: Chao Fu <chao.fu@ericsson.com>, "spring@ietf.org" <spring@ietf.org>
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Subject: Re: [spring] One question on E-flag of ABR/ASBR in OSPF SR extension
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Hi Chao, On 18/05/17 09:44 , Chao Fu wrote: > Hi, > > Should we clarify how to set E-flag for ABR/ASBR in OSPF SR extension? > > In > https://www.ietf.org/id/draft-ietf-ospf-segment-routing-extensions-14.txt, > the draft describes how to set NP-flag on ABR and ASBR (Section 5 [Page > 14]): > > The NP-Flag (No-PHP) MUST be set for Prefix-SIDs allocated to inter- > > area prefixes that are originated by the ABR based on intra-area or > > inter-area reachability between areas. When the inter-area prefix is > > generated based on a prefix which is directly attached to the ABR, > > the NP-Flag SHOULD NOT be set. > > The NP-Flag (No-PHP) MUST be be set for Prefix-SIDs allocated to > > redistributed prefixes, unless the redistributed prefix is directly > > attached to the ASBR, in which case the NP-flag SHOULD NOT be set. > > However, the E-flag (Explicit-Null Flag) is not described. Should we > clarify it also? I think E-flag SHOULD NOT be set if the prefix is not > directly attached to the ABR or ASBR, and if necessary, it SHOULD be set > if the prefix is directly attached to the ABR or ASBR. The existing draft says: "If the NP-flag is not set then the received E-flag is ignored." Given that the draft clearly states when the NP-flag is set on ABR/ASBR above statement should be sufficient. thanks, Peter > > Regards, > > Chao Fu > > > > _______________________________________________ > spring mailing list > spring@ietf.org > https://www.ietf.org/mailman/listinfo/spring >