Re: [Int-dir] Intdir early review of draft-ietf-bier-ping-08

[Brian Haberman <[e-mail]>]

Hey Greg,

On 5/11/23 3:06 PM, Greg Mirsky wrote:
> 
>>
>>>> 2. Section 3.1
>>>>
>>>>       * It is unclear if the two header formats described here both
>> occur in
>>>> a
>>>>       transmitted frame or if the second header format is a modified
>> version
>>>> of
>>>>       the first header. If it is the former, it seems odd to have to
>>>> duplicate
>>>>       versions, message type, protocol, and reserved fields.
>>>>
>>> GIM>> Thank you for pointing that out. Indeed, these are the same. I've
>>> updated the figures. Please let me know if it helped to make the text
>>> clearer.
>>>
>>>>
>>>>        * Is there a requirement that the timestamp formats be the same in
>>>> both
>>>>        the Echo Request and the Echo Reply? If not, is there a
>> requirement
>>>> that
>>>>        BFRs MUST support both formats?
>>>>
>>> GIM>> A good question. I believe that there is no requirement for the
>>> Sender and Responder to use the same timestamp format, as the format used
>>> can be explicitly indicated for each actor separately. As a result, a BFR
>>> can support one format or both. The decision of which one to use may be
>>> based on the comparison of the accuracy of the timestamp each method
>>> provides.
>>>
>>
>> Any concerns with routers not supporting/recognizing all specified
>> timestamp formats?
>>
> GIM2>> RFC 8877  <https://datatracker.ietf.org/doc/rfc8877/>provides an
> excellent analysis of timestamp formats being used in known networking
> protocols:
> 
>     - NTPv4 64-Bit Timestamp Format (RFC 5905)
>     - NTPv4  32-Bit Timestamp Format (RFC 5905)
>     - The PTPv2 64-Bit Truncated Timestamp Format
> 
> It seems like the situation where a networking system doesn't support
> either NTPv4 or PTPv2 format is highly unlikely. WDYT?

I am aware of existing systems that support the NTP formats, but not the 
PTP ones (they don't do PTP). However, as this soon-to-be-RFC will 
require updates to systems, I would suggest putting in language 
requiring support for those formats. Given that supporting the PTPv2 
format does not require support for PTP, that seems pretty reasonable.

Brian