Re: [Gen-art] Genart telechat review of draft-ietf-lime-yang-connectionless-oam-methods-09

[Brian E Carpenter <[e-mail]>]

On 17/10/2017 14:40, Qin Wu wrote:
...

>> The same is applied to jitter. As clarified in the introduction, the 
>> definition of 'jitter' is used to monitor reachability of destinations, troubleshoot failures, monitor performance.
> 
> Yes, but what *is* jitter physically? There is no scientific definition of 'jitter' in the IETF. Do you mean IPDV as defined in RFC3393 or something else?
> 
> [Qin]:Jitter is packet jitter (https://en.wikipedia.org/wiki/Jitter). You are right, one typical example of packet jitter is IPDV defined in RFC3393, but we don't want to limit it to IPDV, we also allow support other protocol and other measurement methodology,
> e.g., we could also consider to use MAPDV2 defined in [ITU-T G.1020], what protocol is used and what methodology is used can be indicated by the parameter 'protocol-id' parameter and 'protocol-id-meta-data' in this model.

I don't see how this specification can be used for interoperable
implementations unless you define a specific meaning of 'jitter'.
If the network management system assumes RFC3393 but half the
routers in the network implement G.1020, there is no interoperability.

> I assume that by 'delay' you mean RFC7679 rather than RFC2681, but that seems straightforward,  and so do the other metrics used in session-packet-statistics and session-error-statistics.
> 
> [Qin]: Correct, it is one way delay instead of two way delay. 

Again - it is useful to specify one-way delay, for interoperability.
(Whether the routers can measure one-way delay is another question;
they might be forced to measure RTT and assume delay = RTT/2 .)

Regards
    Brian