Re: [Gen-art] Genart last call review of draft-ietf-grow-bgp-session-culling-04

[Brian E Carpenter <[e-mail]>]

Hi Matt,
On 22/09/2017 07:08, Matt Griswold wrote:
> * Brian E Carpenter <[e-mail]> [170921 14:19 +1200]:
>> On 21/09/2017 12:13, Matt Griswold wrote:
>>> * Brian Carpenter <[e-mail]> [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
> 
> You're right, I will update it to MAY.
> 
>> 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.
> 
> That's really by design, the document is for people who know and run
> BGP, I think putting too much basic BGP knowledge would make it
> monotonous. Any ideas on how to meet in the middle?

Your suggestion below "Adding a brief scenario paragraph should work,
I'll write something up." would do it, I think. (I should add that my
perspective is that of someone who understands in theory how BGP is supposed
to work but has never personally practiced it - I'm not suggesting you
need to cover everything, just supply a few clues.)

> 
>>>> 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.
> 
> The updated language is:
> 
>   Throughout this document the "Caretaker" is defined to be in control
>   of the lower layer network, while "Operators" directly administrate
>   the BGP speakers.
> 
> I think that clears it up?

Yes.

> 
>>>> 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.
> 
> Again, that section is for IXP Caretakers so I don't think we need to
> go into IXP operational details too much. Adding a brief scenario
> paragraph should work, I'll write something up.

Great.

    Brian