Re: [Bier] Comments on draft-ietf-bier-pmmm-oam-04

[Suneesh <[e-mail]>]

Thanks Greg for the update, please find my comments inline below.

Regards,
Suneesh

On Thu, Nov 22, 2018 at 12:09 AM Greg Mirsky <[e-mail]> wrote:

> Now with the updated address to reach Giuseppe.
>
> On Wed, Nov 21, 2018 at 10:37 AM Greg Mirsky <[e-mail]>
> wrote:
>
>> Hi Suneesh,
>> thank you for the feedback and the detailed questions. Please find my
>> responses and notes in-line below tagged GIM>>.
>>
>> Regards,
>> Greg
>>
>> On Mon, Nov 19, 2018 at 9:24 AM Suneesh <[e-mail]> wrote:
>>
>>> Hi Greg,
>>>
>>> I have following comments on PMMM draft, please share your thoughts.
>>>
>>> Q1. Can you please share how the draft is viewed as a hybrid model?
>>>
>> GIM>> RFC 7799 provided the definition of active and passive measurement
>> methods. Hybrid methods are "in between" these two groups. Even though the
>> Alternate marking in BIER domain may use already preallocated field, it
>> does change the content of the header by applying the marking values in the
>> OAM field. Thus it is neither passive, nor active method but "in between",
>> i.e., hybrid. Would you agree?
>>
> Suneesh>>> Agreed

>
>>> Ref: Section-3:
>>>
>>> <snip>
>>>    the marking method in BIER layer can be viewed as the example of the
>>>    hybrid performance measurement method
>>> </snip>
>>>
>>>
>>> Q2. Can you please define what is meant by sub-flows
>>>    a). Is the sub-flow set of flows on which marking method is applied OR
>>>    b). sub-flow-1 with say marking 0 and sub flow-2 with say marking 1 OR
>>>    c). Being a hybrid model, draft proposes to duplicate the multicast
>>> stream which is having marking and treated those as sub-flows?
>>>
>> GIM>> We use the term "sub-flow" as you've described in b).
>>
> Suneesh>>> Would be great if we can capture in the draft for more clarity

> Ref: Section-4: Theory of Operation
>>> <snip>
>>>    Using the marking method a BFR creates distinct sub-flows in the
>>>    particular multicast traffic over BIER layer
>>> </snip>
>>>
>>>
>>> Q3. Is there any recommended values for 'number of packets' or/and 'time
>>> duration' for alternate marking method
>>>     a). Just to know what is recommended to avoid say number of
>>> packets/time duration = 1
>>>
>> GIM>> You're right, 1 or even 2 would not be useful. 3 packets? May be.
>>
>>>
>>> Q4. Lets say that the nodes is like A->B->C->D->F->G->H->I, the segment
>>> of interest is B->C->D for performance measurement
>>>   a). Does the alternate marking values will clear from node D onwards?
>>>   b). If not, what is recommended if we wish to measure between G->H->I
>>>
>> GIM>> Very good question. It is expected that the marking values be
>> cleared at the edge of BIER domain and thus an operator may enable
>> measurements on segment G-H-I at any time.
>>
> Suneesh>> Please consider adding it to the draft

>
>>> Ref: Section-4: Theory of Operation
>>>
>>> <snip>
>>>   Any combination of markings, Loss and/or Delay, can be applied to a
>>> multicast flow by
>>>   any Bit Forwarding Router (BFR) at either ingress or egress point to
>>>    perform node, link, segment or end-to-end measurement to detect
>>>    performance degradation defect and localize it efficiently.
>>> </snip>
>>>
>>> Q5. Can we somewhere capture that 'proto' field of BIER header should
>>> not be "OAM request/reply", though we are using OAM bits in header.
>>>
>>> <snip>
>>>    The OAM field MUST be used only
>>>    for the performance measurement of data traffic in BIER layer.
>>> </snip>
>>>
>>>
>> GIM>> I think it would be too restrictive. One may want to measure
>> performance of BIER OAM.
>>
> Suneesh >>> I understood your point. Thanks.


> Regards,
>>> Suneesh
>>>
>>