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
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