Hi Saumya, Thank you for sharing your perspective and the alternative design considerations.
While relying on a full session bounce (Peer Down / Peer Up) aligns with traditional BGP operational habits where a down event impacts all address families, doing so in BMP can be quite disruptive in modern, large-scale multi-AF deployments—especially when a filter change only targets a single specific address family (e.g., modifying IPv4 filtering while leaving IPv6 completely untouched). Regarding the three points you raised: 1. Forcing "all or none" publication or relying entirely on the collector to absorb everything can introduce unnecessary bandwidth overhead and heavy processing burdens on the collector side, particularly when dealing with massive routing tables. 2. Using wildcards is an interesting angle, but we still need a clean, non-destructive signaling mechanism to tell the collector when a targeted slice of data is being refreshed or adjusted due to a policy change. Instead of keeping things heavy with full session bounces or shifting all complexities to the collector, we would like to invite you to take a look at draft-geng-grow-bmp-sync-options-and-state (specifically the BMP Route-Refresh message and sync options). This draft provides a lightweight, incremental, and targeted mechanism to synchronize specific RIB views and address families without tearing down the underlying BMP session. It cleanly solves the ambiguity of route withdrawals and filter changes without the heavy overhead of a session bounce. If you find this approach reasonable, we would love to collaborate with you and invite you to join us in driving this forward in the GROW working group! Looking forward to your thoughts. Best regards, Shunwan (on behalf of the co-authors of draft-geng-grow-bmp-sync-options-and-state) From: Dikshit, Saumya <[email protected]> Sent: Friday, July 31, 2026 12:37 PM To: Srivastava, Mukul <[email protected]>; Zhuangshunwan <[email protected]>; Srivastava, Mukul <[email protected]>; gengnan <[email protected]>; Reshad Rahman <[email protected]> Cc: Grow <[email protected]>; [email protected] Subject: Re: [GROW] Re: Question on draft-geng-grow-bmp-rel-enhancement Hi @Srivastava, Mukul<mailto:[email protected]>, @[email protected]<mailto:[email protected]> In a typical deployment, or with BGP operations, a bgp peer down shall impact routes of all AFs published over that peers. So deletion is implicit. Few bullets: -Shall we mandate publishing all or none from the device (per bgp peering) based on filter. - leave to discretion on collector side on what to absorb from all published. - for optimal publishing, can we use wild cards to call out all routes across all AFs. Thanks, Saumya. ________________________________ From: Srivastava, Mukul <[email protected]<mailto:[email protected]>> Sent: Friday, July 31, 2026 1:11:14 am To: Zhuangshunwan <[email protected]<mailto:[email protected]>>; Srivastava, Mukul <[email protected]<mailto:[email protected]>>; Dikshit, Saumya <[email protected]<mailto:[email protected]>>; gengnan <[email protected]<mailto:[email protected]>>; Reshad Rahman <[email protected]<mailto:[email protected]>> Cc: Grow <[email protected]<mailto:[email protected]>>; [email protected]<mailto:[email protected]> <[email protected]<mailto:[email protected]>> Subject: Re: [GROW] Re: Question on draft-geng-grow-bmp-rel-enhancement Hi Shunwan Considering you example - Assuming a BMP session is advertising v4 and v6 AF to a station. Then a local filter policy was changed on the router to send only V4 prefixes to the collector. If we don’t want to bounce the session and stop sending any update on v6 prefixes, then collector has no clue what happened to those v6 prefixes. If you chose to withdraw those v6 prefixes which were previously advertised, then collector has no clue if the routes where really deleted at the router or this withdrawal is because of the local filter policy change. We can invent complex solution like informing collector about the policy change or some other indication, so the collector knows that those v6 prefixed are being withdrawn due to filter policy change. Things are get complex easily. In any production network, I can’t imagine that such filter configuration change will be frequent. So, bouncing session provides clean option. Sure it comes with the overhead that you mentioned. I think there were some draft (might have expired) to refresh specific address from a BMP producer. Thanks Mukul From: Zhuangshunwan <[email protected]<mailto:[email protected]>> Date: Wednesday, July 29, 2026 at 7:14 AM To: Srivastava, Mukul <[email protected]<mailto:[email protected]>>; Dikshit, Saumya <[email protected]<mailto:[email protected]>>; gengnan <[email protected]<mailto:[email protected]>>; Reshad Rahman <[email protected]<mailto:[email protected]>> Cc: Grow <[email protected]<mailto:[email protected]>>; [email protected]<mailto:[email protected]> <[email protected]<mailto:[email protected]>> Subject: RE: [GROW] Re: Question on draft-geng-grow-bmp-rel-enhancement Hi Mukul, Thank you for bringing this statement to my attention. I have a few questions regarding the text in Section 4: "Also should any characteristic of the filtering change, the sender MUST trigger a Peer Down then followed by a new Peer Up." Given that a BGP session is established over a single underlying TCP connection and typically carries multiple address families (AFI/SAFI) simultaneously—such as IPv4 Unicast (afi=1, safi=1) and IPv6 Unicast (afi=2, safi=1)—I have some concerns: If a filtering policy change applies only to a specific address family (e.g., IPv4 Unicast), wouldn't triggering a Peer Down (followed by a Peer Up) unnecessarily disrupt and impact other unaffected address families (e.g., IPv6 Unicast) sharing the same session? Additionally, is there an existing mechanism or proposal where a BMP message can be triggered to notify and refresh only the specific address family affected by the filter change (e.g., afi=1, safi=1), without interfering with other address families? I would love to hear your thoughts on this. Best regards, Shunwan From: Srivastava, Mukul <[email protected]<mailto:[email protected]>> Sent: Tuesday, July 28, 2026 11:26 PM To: Dikshit, Saumya <[email protected]<mailto:[email protected]>>; gengnan <[email protected]<mailto:[email protected]>>; Reshad Rahman <[email protected]<mailto:[email protected]>> Cc: Grow <[email protected]<mailto:[email protected]>>; [email protected]<mailto:[email protected]> Subject: [GROW] Re: Question on draft-geng-grow-bmp-rel-enhancement Hi Saumya >>>>> " but it stops short of stating that the F flag itself be set >>>>> consistently in the Stats message's Peer Header for that same session. [MS] - The draft has below statement in section 4 - " Also should any characteristic of the filtering change, the sender MUST trigger a Peer Down then followed by a new Peer Up. " This intends to say that if filtering changed for any reason, we should start afresh. This indirectly means all session should have uniform “F” flag setting. I am ok to add some explicit statement, as you suggested to clarify this. The current statement matches BMP local-rib RFC 9069 where route filtering flag as first introduced. >>> That said, it doesn't fully close Reshad/Nan's original question: >>> adj-ribs-filtered-00 only talks about Adj-RIB-In/Out and Stats messages and >>> says nothing about routing-event messages >>> (draft-geng-grow-bmp-rel-enhancement's actual subject). [MS] - IMO, the filtering flag is not application for rel/log messages. There is no fixed set of the routing events pre-defined, out of which, a router may intend to filter out some. So, these messages are different from route-motoring or stats messages. The original comment in the email below was to be cautious to select what should be send as logging event to the BMP station. If some events (like next-hop change) are chatty that shouldn’t be logged, meaning we shouldn’t define an logging event type to report next-hop churn. Thanks Mukul From: Dikshit, Saumya <[email protected]<mailto:[email protected]>> Date: Sunday, July 26, 2026 at 6:24 AM To: Srivastava, Mukul <[email protected]<mailto:[email protected]>>; gengnan <[email protected]<mailto:[email protected]>>; Reshad Rahman <[email protected]<mailto:[email protected]>> Cc: Grow <[email protected]<mailto:[email protected]>> Subject: Re: [GROW] Re: Question on draft-geng-grow-bmp-rel-enhancement Hi Mukul, That's a helpful clarification, thank you. It's good to be reminded that F flag lives in the shared Peer Header rather than being RM-specific, so it's structurally available to Stats messages too. Looking at the current adj-ribs-filtered-00 text again with that in mind, I think it actually pins down exactly the gap: • Section 4 says "In Stats messages, counts MUST reflect the filtered RIB numbers and not the original RIB ones," but it stops short of stating that the F flag itself be set consistently in the Stats message's Peer Header for that same session. • So as written, an implementation could arguably satisfy the letter of the text by adjusting the counts while leaving F unset (or inconsistent) on the Stats side o This is exactly the inconsistency you flagged as unhelpful for correlation. Would it make sense to tighten this into an explicit MUST, something like: • "The Peer F Flag MUST be set consistently across all BMP message types that share this Peer Header for the lifetime of the session (Route Monitoring, Stats Report, Route Mirroring). • An implementation MUST NOT report F=1 in one message type while reporting F=0 (or omitting the equivalent filtered-count adjustment) in another, for the same peer." Since you're already a co-author on adj-ribs-filtered, that operational-consideration addition (Section 5, or as a normative bullet in Section 4) seems like the cleanest, lowest-overhead fix and no new TLV needed for the RIB/Stats side at all. That said, it doesn't fully close Reshad/Nan's original question: adj-ribs-filtered-00 only talks about Adj-RIB-In/Out and Stats messages and says nothing about routing-event messages (draft-geng-grow-bmp-rel-enhancement's actual subject). On that note, would it make sense for rel-enhancement to explicitly say event messages reuse this same Peer F Flag bit (with the same cross-message consistency rule above), rather than defining a separate mechanism? • That would give collectors one consistent signal to check across RM, Stats, and event messages, with a single small text addition on each side rather than a new generic flag. Your thoughts Nan, Reshad, Mukul on this ? Happy to help draft the exact text for either document if useful. Thanks, Saumya From: Srivastava, Mukul <[email protected]<mailto:[email protected]>> Date: Saturday, 25 July 2026 at 8:50 PM To: Dikshit, Saumya <[email protected]<mailto:[email protected]>>; gengnan <[email protected]<mailto:[email protected]>>; Reshad Rahman <[email protected]<mailto:[email protected]>> Cc: Grow <[email protected]<mailto:[email protected]>> Subject: Re: [GROW] Re: Question on draft-geng-grow-bmp-rel-enhancement Hello Saumya >>>>>> If a router locally rate-limits or drops events (per the mitigation text >>>>>> in draft-geng-grow-bmp-rel-enhancement) and separately reports gauges >>>>>> such as the ones in * draft-ietf-grow-bmp-bgp-rib-stats (RFC 9972) or * the policy-driven counters in draft-smc-grow-bmp-route-change-stats, a collector has no way to know that an observed gauge delta might not be fully explained by the event stream it received it may look like an unexplained jump. — [MS] - The BMP stats messages have BMP peer header. The filter flag is part of the BMP peer header. If the filter flag is not set in stats message, while the other msg had filter flag set, then the collector should use caution and know that the data it received was filtered while the stats count is not filtered. I would assume for ideal operation, the router should have flag set/unset for all events/data/stats message for a session. Inconsistency in this flag state between different messages, will not help in meaningful correlation at collector. I think we should add this in the operational consideration for filtered drafts, if it isn’t present already. Thanks Mukul From: Dikshit, Saumya <[email protected]<mailto:[email protected]>> Date: Saturday, July 25, 2026 at 2:37 AM To: gengnan <[email protected]<mailto:[email protected]>>; Reshad Rahman <[email protected]<mailto:[email protected]>> Cc: Grow <[email protected]<mailto:[email protected]>> Subject: [GROW] Re: Question on draft-geng-grow-bmp-rel-enhancement Hi Nan, Reshad, I was going through the draft and couldn’t help bringing up another angle, (though not-unrelated) to the email chain discussion : The same blind spot effects statistics consumers, not just event-log consumers. If a router locally rate-limits or drops events (per the mitigation text in draft-geng-grow-bmp-rel-enhancement) and separately reports gauges such as the ones in * draft-ietf-grow-bmp-bgp-rib-stats (RFC 9972) or * the policy-driven counters in draft-smc-grow-bmp-route-change-stats, a collector has no way to know that an observed gauge delta might not be fully explained by the event stream it received it may look like an unexplained jump. Rather than defining filtering-indication independently for events (in this draft) and for RIB streams (bmp-adj-ribs-filtered), would it make sense to define one small, generic TLV/flag, that any BMP consumer event, RM, or SR message can check? This would definitely help in achieving "telemetry completeness" More than happy and willing to sketch this as a short contribution if there's appetite, as we hit a related need while defining the per-peer gauges in draft-smc-grow-bmp-route-change-stats. Thanks, Saumya. From: gengnan <[email protected]<mailto:[email protected]>> Date: Thursday, 23 July 2026 at 3:39 PM To: Reshad Rahman <[email protected]<mailto:[email protected]>> Cc: Grow <[email protected]<mailto:[email protected]>> Subject: [GROW] Re: Question on draft-geng-grow-bmp-rel-enhancement Hi Reshad, As stated in Section 3 of draft-ietf-grow-bmp-adj-ribs-filtered: > ... be informative to the rest of the system that they should not make > decisions assuming that this stream is transmitting all the information about > it. The same logic seems to apply to event reporting. If critical events are filtered locally without any signal to the collector, monitoring systems may draw incorrect conclusions based on incomplete data. It would therefore be valuable to consider a mechanism to convey this filtering state for events. Best, Nan From: Reshad Rahman <[email protected]<mailto:[email protected]>> Sent: Thursday, July 23, 2026 1:43 AM To: Grow <[email protected]<mailto:[email protected]>> Subject: [GROW] Question on draft-geng-grow-bmp-rel-enhancement Hi, Appropriate caution SHOULD be taken when picking routing events to report, as next-hop related updates may produce heavy message loads during network instability. Mitigation measures SHOULD be deployed on both reporting and receiving sides. For example, local endpoints can apply event filtering controls, while receivers maintain corresponding processing mechanisms to handle potential high-volume event bursts gracefully. During the meeting today the text above was highlighted by Nan (based on feedback from Prasad). I have no issue with the feedback and text, but is there any indication of filtering sent to the collector? draft-ietf-grow-bmp-adj-ribs-filtered which was presented earlier adds a Peer F flag for Adj-Rib-In/Out, IIUC that doesn't cover events in draft-geng-grow-bmp-rel-enhancement? IMO we want indication of filtering for "critical" events. Regards, Reshad.
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