On 21/09/2017 12:13, Matt Griswold wrote: > * Brian Carpenter <brian.e.carpen...@gmail.com> [170918 21:44 -0700]: >> Minor Issues: >> ------------- >> >>> 3.1.1. Maintenance Considerations >>> >>> Initiators of the administrative shutdown could consider using >>> Graceful Shutdown [I-D.ietf-grow-bgp-gshut] to facilitate smooth >>> drainage of traffic prior to session tear down, and the Shutdown >>> Communication [I-D.ietf-idr-shutdown]... >> >> This strikes me as vague. "Could consider"? Surely if this is >> a BCP, they MUST use some mechanisms and perhaps SHOULD use these >> particular mechanisms. Otherwise the document doesn't specify >> anything much at all for this case. > > Graceful Shutdown is just one of multiple ways an Operator can > accomplish that.
Understood, so perhaps it's a MAY not a SHOULD, but the text still really only seems to say "do the right thing" without saying what that is. To be honest the whole document is a bit like that - written for members of the club who know how to run BGP, rather than for a newcomer who wants to know how to run BGP. > >>> 3.2. Involuntary BGP Session Teardown Recommendations >> ... >>> In the absence notifications from the lower layer (e.g. ethernet >>> link down) consistent with the planned maintenance activities in a >>> switched layer-2 fabric, the Caretaker of the fabric could choose >>> to cull BGP sessions on behalf of the Operators connected to the >>> fabric. >> >> This seems incomplete. Firstly, I'm assuming that it should start >> "In the absence of notifications...". > > Fixed! > >> Secondly, if there are no fault indications, what causes the >> Caretaker to cull sessions? What's the trigger? Is the Caretaker >> supposed to know by magic that layer 2 maintenance is planned? > > The Caretaker controls the layer 2 network, so yes, would do this as > part of the maintenance process. Again: not clear to a newcomer. >> ... >>> In this scenario, BGP Session Culling is accomplished through the >>> application of a combined layer-3 and layer-4 packet filter >>> deployed in the switched fabric itself. >> >> Please add "as described in the next sub-section" because otherwise >> the reader can easily be confused. > > Added. > >>> 3.2.1. Packet Filter Considerations >>> >>> The following considerations apply to the packet filter design: >>> >>> o The packet filter MUST only affect BGP traffic specific to the >>> layer-2 fabric, i.e. forming part of the control plane of the >>> system described, rather than multihop BGP traffic which merely >>> transits >> >> That's a goal, but it doesn't tell me how to achieve the goal. >> What packet signature tells me which packets are specific to the >> fabric? I suspect this might overlap with the last bullet - if so, >> you might consider re-ordering the bullets. >> ... >>> o The packet filter MUST affect all relevant Address Family >>> Identifiers >> >> Define "relevant". > > Removed "relevant". > >> And in Appendix A, explain precisely how the example prefixes are >> used: what makes them relevant? Are they normally announced by BGP to >> all the IXP's BGP peers? > > They are the IXP LAN addresses, as explained above the examples. Yes, I realise that, but again you're assuming that the reader has a complete picture in her mind. Maybe there's actually a need for a scenario description in the Introduction, or at least a reminder that in normal operation, paths through the fabric in question may be known throughout the BGP realm, and the objective is to delete those paths before starting maintenance. > Thanks for your review! You're welcome, Brian _______________________________________________ GROW mailing list GROW@ietf.org https://www.ietf.org/mailman/listinfo/grow