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

[Greg Mirsky <[e-mail]>]

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?
>
>>
>> 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).
>
>>
>> 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.
>
>>
>> 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.
>
>>
>> Regards,
>> Suneesh
>>
>