Subject: [OSPF] draft-ietf-ospf-segment-routing-extensions

From: <[email-masked]>
Date: Thu, 18 May 2017 09:02:07 +0000

Hi Chao,

Thanks for the review and comments.
As the comment is related to an OSPF WG document, I'm forwarding your comment on the OSPF WG, where it will be better tracked.

Regards,
Bruno

From: spring [mailto:[email-masked]] On Behalf Of Chao Fu
Sent: Thursday, May 18, 2017 9:45 AM
To: [email-masked]
Subject: [spring] One question on E-flag of ABR/ASBR in OSPF SR extension

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.

Regards,
Chao Fu

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