Re: [auth48] AUTH48: RFC-to-be 9494 <draft-ietf-idr-long-lived-gr-06> for your review

[[e-mail]]

Hi RFC Editor, _John_

Thanks for the updated draft.

I've read the diff and don't have comments.
I have read the whole document and don't have firm request for change.


I may have some weak suggestions below, so only to be retained if someone else support them.(e.g., John 😉 )

John, I apologize for some late comments.

----
§5.2
Although this document has a single Figure, I generally find useful for Figures to have a reference. So my suggestion would be to add a reference (e.g., Figure 1)

-----
§3.1 says  "This [LLGR] capability MUST be advertised in conjunction with the Graceful Restart capability ;"
§4.1 says "The Graceful Restart capability MUST be advertised in conjunction with the LLGR capability." (i.e., the other way around)

I'm not sure whether "conjunction" is "bijective" or not.
- If not, both sentences would not mean the same thing.
- if yes, I don't think that this is exactly what we mean.

What we mean, in very simple terms, is: If the LLGR capability is sent, then the GR capability MUST be sent.
But we don't want to imply the other way around. (Since this RFC does not update RFC4724, I don't think that someone could understand it wrongly)

I'll leave anyone else to suggest text. (or just drop the comment as being paranoiac)

---
§4.1

OLD: We observe that, if support for conventional Graceful Restart is not
   desired for the session, the conventional GR phase can be skipped by
   omitting all AFIs/SAFIs from the GR capability, advertising a Restart
   Time of zero, or both.

NEW:
We observe that, if support for conventional Graceful Restart is not
   desired for the session, the conventional GR phase can be skipped by
   omitting all AFIs/SAFIs from the GR capability, _or_ advertising a Restart
   Time of zero, or both.

(adding "or" before " advertising a Restart Time of zero")
Totally up to you. An explicit "or" would typically be required in French to distinguish from an implicit "and". May be "or" is implicit in English.

---


§4.2

" Similar to [RFC4724], once the session is re-established, if the F
   bit for a specific address family is not set in the newly received
   LLGR Capability, or if a specific address family is not included in
   the newly received LLGR Capability or if the LLGR and accompanying GR
   Capability are not received in the re-established session at all,
   then the Helper MUST immediately remove all the stale routes from the
   peer that it is retaining for that address family."

My reading is that the above sentence could be read as changing RFC4724 by saying that if a specific address family is not included in the newly received LLGR Capability then the Helper MUST immediately remove all the [GR] stale routes, including during the GR "Restart Time".

I would suggest the minimal change below
OLD: once the session is re-established
NEW: once the session is re-established after the duration of the "Restart Time"

------
§4.2

"  While the session is down, the expiration of a "Long-lived Stale
   Time" timer is treated analogously to the expiration of the "Restart
   Time" timer in Graceful Restart"

I would suggest
OLD: the expiration of the "Restart Time" timer in Graceful Restart
NEW: the expiration of the "Restart Time" timer in [RFC 4724]

Because "the expiration of the "Restart Time" timer in Graceful Restart" could be read as the new behavior defined in this section, with text starting with " Once the "Restart Time" period ends (including the case in which the "Restart Time" is zero), the LLGR period is said to have begun and  the following procedures MUST be performed"

----
§4.3

" A BGP speaker that has advertised the "Long-lived Graceful Restart
   Capability" to a neighbor MUST perform the following upon receiving a
   route from that neighbor with the "LLGR_STALE" community"

Possibly
OLD: advertised the "Long-lived Graceful Restart Capability" to a neighbor
NEW: exchanged the "Long-lived Graceful Restart Capability" with a neighbor

Reason: if the LLGR capability is not received from the neighbor, possibly than neighbor does not support LLGR and hence was not the one setting the "LLGR_STALE" community. This seems to open the possibility of a (possibly distant) attacker to influence routing on the receiver.

---
§4.6

"If this strategy for partial deployment is used, the network operator
   should set the LOCAL_PREF to zero for all long-lived stale routes
   throughout the Autonomous System.  This trades off a small reduction
   in flexibility (ordering may not be preserved between competing long-
   lived stale routes) for consistency between routers that do, and do
   not, support this specification.  Since the consistency of route
   selection can be important for preventing forwarding loops, the
   latter consideration dominates."

John, the above text seems to indicate that the whole AS should use LOCAL_PREF zero rather than honoring "LLGR_STALE" community. This seems to call for §4.6 to also ask to remove the "LLGR_STALE" community. (otherwise a downstream BGP speaker compliant with LLGR would react on this community.

---
§5.2
Minor comment as this is part of an example.
OLD: Routers A and D are AS border routers, each advertising some route, R, into the AS
NEW: Routers A and D are AS border routers, each advertising some route, R, with same preference, into the AS

---
§5.2
" Since different routers within an AS might have different notions as
   to whether their respective sessions with a given peer are up or
   down, they might apply different selection criteria to routes from
   that peer."

Agreed.
Another case if when a BGP receiver change the timers received in the LLGR capability (and we called for them to be modifiable). Do we want to also raise that case? (I'm not asking for. Raising the point just in case )

Thanks,
Regards,
--Bruno


Orange Restricted

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Subject: AUTH48: RFC-to-be 9494 <draft-ietf-idr-long-lived-gr-06> for your review

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--------------------------------------
RFC9494 (draft-ietf-idr-long-lived-gr-06)

Title            : Support for Long-lived BGP Graceful Restart
Author(s)        : J. Uttaro, E. Chen, B. Decraene, J. Scudder
WG Chair(s)      : Susan Hares, Keyur Patel, Jeffrey Haas

Area Director(s) : Alvaro Retana, John Scudder, Andrew Alston

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