Re: [Idr] Last Call: <draft-ietf-idr-shutdown-08.txt> (BGP Administrative Shutdown Communication) to Proposed Standard

Jakob,
Hi, Jakob:

I understand this is not a good use of time.  But since it is in the
spec, I would like to understand the reasons.  If there are good reasons
for doing things differently, then they should be documented in the spec
so that people do not question again.

On 5/8/17 12:13 PM, Jakob Heitz (jheitz) wrote:
> It is deliberately kept short to minimize the potential for abuse.

128 is ok, and 129- 255 would be considered abuse?

In protocol design we have had so many mistakes related to small
length fields.  There is rarely an issue because one field has an
extra byte. 

> We could have argued about the length. Should it be 100, 120, 127,
> but it's not an argument worth wasting time on.

Yes, that is precisely the reason that this value "128" should not be
specified.

> Not using the whole range of the length byte opens the door to using
> the rest of the range to indicate a future new information field.

You mean "129-255" are reserved rather than "invalid"?  Then that should
be made clear in the spec.

Thanks.  -- Enke

> 
> Thanks,
> Jakob.
> 
> 
>> -----Original Message-----
>> From: Enke Chen (enkechen)
>> Sent: Sunday, May 07, 2017 8:44 PM
>> To: ietf@ietf.org
>> Cc: draft-ietf-idr-shutdown@ietf.org; idr@ietf.org; idr-chairs@ietf.org; Enke Chen (enkechen) <enkechen@cisco.com>
>> Subject: Re: [Idr] Last Call: <draft-ietf-idr-shutdown-08.txt> (BGP Administrative Shutdown Communication) to
>> Proposed Standard
>>
>> Hi, Folks:
>>
>> Just spotted this (apologies for not catching it earlier):
>>
>> The draft specifies only 0 - 128 as valid in the one-octet length field.
>> Not sure if there is a strong reason for such an apparent over-specification.
>>
>> It seems to me that the spec can and should be simplified by removing the
>> restriction, that is, to allow any value (0 - 255) to be valid.  That would
>> also eliminate one error condition for the implementation.
>>
>> Thanks.  -- Enke
>>
>> ---
>> 2.  Shutdown Communication
>>
>> Length:  this 8-bit field represents the length of the Shutdown
>>       Communication field in octets.  The length value MUST range from 0
>>       to 128 inclusive.
>>
>> 4.  Error Handling
>>
>>    If a Shutdown Communication with an invalid Length value,
>> ----
>>
>> On 5/5/17 10:54 AM, The IESG wrote:
>>>
>>> The IESG has received a request from the Inter-Domain Routing WG (idr) to
>>> consider the following document:
>>> - 'BGP Administrative Shutdown Communication'
>>>   <draft-ietf-idr-shutdown-08.txt> as Proposed Standard
>>>
>>> The IESG plans to make a decision in the next few weeks, and solicits
>>> final comments on this action. Please send substantive comments to the
>>> ietf@ietf.org mailing lists by 2017-05-19. Exceptionally, comments may be
>>> sent to iesg@ietf.org instead. In either case, please retain the
>>> beginning of the Subject line to allow automated sorting.
>>>
>>> Abstract
>>>
>>>
>>>    This document enhances the BGP Cease NOTIFICATION message
>>>    "Administrative Shutdown" and "Administrative Reset" subcodes for
>>>    operators to transmit a short freeform message to describe why a BGP
>>>    session was shutdown or reset.  This document updates RFC 4486.
>>>
>>>
>>>
>>>
>>>
>>> The file can be obtained via
>>> https://datatracker.ietf.org/doc/draft-ietf-idr-shutdown/
>>>
>>> IESG discussion can be tracked via
>>> https://datatracker.ietf.org/doc/draft-ietf-idr-shutdown/ballot/
>>>
>>>
>>> No IPR declarations have been submitted directly on this I-D.
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Idr mailing list
>>> Idr@ietf.org
>>> https://www.ietf.org/mailman/listinfo/idr
>>>