From: Christer Holmberg <christer.holmberg@ericsson.com>
To: Emil Ivov <emcho@jitsi.org>
Thread-Topic: UPDATE mechanism for Trickle ICE - Comment on
 draft-ivov-mmusic-trickle-ice-sip-01
Thread-Index: Ac7Oi3Z+e3UP57hvROCS8x6y31/feAAJw8IAACFHcIAAAcFGAAAEeh/hAAAm54r//+FhgIAAIpUB///8bUCAAAAHAP/+8S7AgAIsaoD//9DwgAAJK5MA//6RbBA=
Date: Thu, 24 Oct 2013 13:01:32 +0000
Message-ID: <7594FB04B1934943A5C02806D1A2204B1C4F0FED@ESESSMB209.ericsson.se>
References: <00a401cece8b$7b00f780$7102e680$@co.in>
 <CAPvvaaK3YOOB-Ta8+eoRcfQ8NrNRDdDf5a3VvOaN0vK=0unf7A@mail.gmail.com>
 <00ce01cecf48$6c0b5500$4421ff00$@co.in>,
 <5266BB46.4070305@jitsi.org>
 <7594FB04B1934943A5C02806D1A2204B1C4EBB51@ESESSMB209.ericsson.se>,
 <5266C0A7.5040305@jitsi.org>
 <7594FB04B1934943A5C02806D1A2204B1C4EBBEA@ESESSMB209.ericsson.se>
 <5266DAB0.7020001@jitsi.org>
 <7594FB04B1934943A5C02806D1A2204B1C4EC9F2@ESESSMB209.ericsson.se>
 <5267CA43.8020304@jitsi.org>
 <7594FB04B1934943A5C02806D1A2204B1C4EDE3A@ESESSMB209.ericsson.se>
 <5267E052.6020401@jitsi.org>
In-Reply-To: <5267E052.6020401@jitsi.org>
Accept-Language: en-US
Content-Language: en-US
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
Cc: 'mmusic' <mmusic@ietf.org>
Subject: Re: [MMUSIC] UPDATE mechanism for Trickle ICE - Comment on
 draft-ivov-mmusic-trickle-ice-sip-01
Precedence: list

Hi,

>>>> First, I completely messed up with the candidate types. Sorry for=20
>>>> the confusion :)
>>>>
>>>> Anyway, it doesn't really matter what type of candidates are=20
>>>> trickled
>>>> - it's about whether trickled candidates can be affected by=20
>>>> Offers/Answers.
>>>
>>> And by affected you really mean invalidated. OK, I think I understand n=
ow.
>>>
>>> I don't think there's anything in 5245 that defines semantics which wou=
ld invalidate existing candidates.
>>
>> Generally, in SDP Offer/Answer, when an SDP attribute is not present, it=
 means that it's invalidated, or the default value (if such has been specif=
ied) is assumed.
>
> What I meant was that 5245 explicitly states that all previously signalle=
d candidates MUST be signalled in updated Offers, so candidate removal in t=
he middle of ICE processing is not something that is defined for ICE.
>
> Also, non-signalled candidates, like peer reflexive, are not required to =
be signalled in update Offers, so their absence in an offer cannot in any w=
ay be construed as a request for their removal.

So, IF we can define the same for trickled candidates, then there might not=
 be an issue.

We have to remember, though, that a trickled candidate is not a new candida=
te "type". The candidate types you trickle are the same types you send in O=
ffer/Answer - tickle is simply an alternative candidate transport mechanism=
.

>> But, that really depends on whether the candidates are considered part=20
>> of the SDP state or not. IF so, trickled candidates would update that=20
>> state, in the same way SDP Offers/Answers do.
>
> Right, and I've already mentioned that I don't see any reason to consider=
 them as part of the SDP state, just as you wouldn't consider peer-reflexiv=
e candidates to be part of it.

If a trickled candidate is eventually selected, doesn't a "clean up" SDP Of=
fer have to be sent (as for any other non-default candidate), where the c- =
line is aligned with the candidate? In that case the candidate becomes part=
 of the SDP state :)

Regards,

Christer