Re: [Ioam] Internal WG Review: In-situ OAM (ioam)

["Carlos Pignataro (cpignata)" <[e-mail]>]

Hi, Stewart,


> On Feb 10, 2017, at 4:32 AM, Stewart Bryant <[e-mail]> wrote:
> 
> 
> 
> On 09/02/2017 19:30, Carlos Pignataro (cpignata) wrote:
>> Hi, Stewart,
>> 
>> Many thanks for the comments, please see inline.
>> 
>>> On Feb 9, 2017, at 1:50 PM, Stewart Bryant <[e-mail]> wrote:
>>> 
>>> 
>>> 
>>> On 09/02/2017 17:18, Carlos Pignataro (cpignata) wrote:
>>>> Passive means ‘solely by observation and without modification to the packet’ (https://tools.ietf.org/html/draft-ietf-ippm-active-passive-06#section-3.6).
>>> Carlos, that is not quit where we are going with passive. We use packet marking to batch the packets for loss measurement, and we are planning to trigger delay/jitter measurement through marking.
>>> 
>> I’ll follow down this tangent for a bit.
>> 
>> I understand and as you know I’m well aware of the (alternate) packet marking techniques and different methods.
>> 
>> However, the *current* definition is quite unambiguous:
>> 
>> https://tools.ietf.org/html/rfc7799#section-3.6
>> “
>> 3.6.  Passive Methods
>> 
>>    Passive Methods of Measurement are:
>> 
>>    o  based solely on observations of an undisturbed and unmodified
>>       packet stream of interest (in other words, the method of
>>       measurement MUST NOT add, change, or remove packets or fields or
>>       change field values anywhere along the path).
>> “
>> 
>> Since both those datapoints are rooted in IPPM, I’d suggest working through the definitions on IPPM and how marking fits (since it is not only on observation points)
>> 
>> Now, bringing this back to the relevance of the In-situ OAM (ioam) charter, my only point is that In-situ OAM is neither passive nor active.
> 
> ... and the point I make is that packet marking (which I think we have established is the only viable way of making accurate loss measurements in connectionless networking) is also neither active of passive according to these definitions.

That is correct, it is Hybrid Type I. Sorry if I misunderstood when you said “ Carlos, that is not quit where we are going with passive. We use packet marking […]”. 

But in any case, I do not believe the draft charter claims to do marking (more on this below though).

I wonder, as an aside, if there’s any take-away for draft-ietf-ippm-alt-mark-03’s title “Alternate Marking method for passive performance monitoring”.

> 
>> 
>>> As you know marking is much easier in MPLS that IP.
>>> 
>>> I think the key distinguisher is really that in-situ is about embedding OAM meta-data in user data traffic.
>> This is a good point.
>> 
>> I agree.
>> 
>> I believe this is already clear in the charter, all the way from the very first sentence:
>> 
>> “ It is based on telemetry information which is embedded within live data packets.”
>> 
>> Do you believe this is not clear in the charter? Do you have specific suggestions or concrete recommendations that can improve the charter text?
> 
> I suppose you could say: It is based on telemetry information which is embedded within live data packets and is distinct from packet parking methods being developed elsewhere in the IETF.
> 

That’s one potential approach. To me, though, “embedded within live data packets” is different from “marking packets”; that said, I do not see how it can hurt.

There is one additional wrinkle though: IOAM is not limited to Performance Management (PM), but more generally includes things like path tracing. So perhaps adding the text above might cause confusions.

> I have not thought it through, but I am wondering what distinguishes the packet types you list (IPv4, IPv6, VXLAN-GPE, LISP, NSH, SRv6, Geneve) from other packet types, the obvious one being MPLS. Not that I am at all keen on trying to get this into the simple fast forwarders we use for MPLS. In other words what is the generic class of packets you are targetting?
> 

Encapsulations?

Thanks!

— Carlos.

> Stewart
> 
>> 
>> Thanks!
>> 
>>> - Stewart
>> 
>> —
>> Carlos Pignataro, [e-mail]
>> 
>> “Sometimes I use big words that I do not fully understand, to make myself sound more photosynthesis."
>> 
>