Re: [tsvwg] [nwcrg] WGLC on FECFRAME sliding window extensions and RLC FEC
Emmanuel Lochin <emmanuel.lochin@isae-supaero.fr> Wed, 02 May 2018 10:27 UTC
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To: Vincent Roca <vincent.roca@inria.fr>
Cc: "tsvwg@ietf.org" <tsvwg@ietf.org>, nwcrg@irtf.org
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From: Emmanuel Lochin <emmanuel.lochin@isae-supaero.fr>
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Date: Wed, 02 May 2018 12:27:05 +0200
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Subject: Re: [tsvwg] [nwcrg] WGLC on FECFRAME sliding window extensions and RLC FEC
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Hi Vincent, I'm fine with all your answers/corrections. Cheers EL Le 02/05/2018 à 11:24, Vincent Roca a écrit : > Hello Emmanuel, > > Thanks a lot for your review. I’ve just posted version -02 that takes > your suggestions into account. > More precisely: >> >> Having reviewing draft-ietf-tsvwg-fecframe-ext, I found this document >> quite clear, well-written and self-contained. I just have the >> following suggestions: >> >> >> The authors argue that "/FECFRAME provides FEC protection for >> arbitrary packet flows over unreliable transports such as UDP/". >> RFC5348 proposes TFRC, an unreliable rate-based protocol which does >> not send data packets in a continuous manner at the same peak rate >> mimicking TCP average sending rate behavior or RFC4341 proposes DCCP >> CCID#2 congestion control which is an equivalent TCP window-based >> algorithm without retransmission. >> >> I reckon it is a good idea to dissociate transport layers operations >> from sliding encoding operations. But keeping in mind these both >> protocols (TFRC or DCCP/CCID#3 and DCCP/CCID#2) and considering the >> sentence "The data packets of continuous media flow(s) can be sent >> immediately, without delay." : "sent" is understood as "sent over the >> network" while this is not true depending on which unreliable >> transport protocol is used, so it should be "passed to the transport >> layer" as "sent over the network" only apply to UDP which does not >> schedule, pace or stop the sending. Actually some parts of this draft >> seem to consider that when source data or redundancy packets are >> built, they are simply sent over the network without delay. This is >> not always the case, so to be accurate I would suggest to correct by >> "passed to the transport layer" as correctly illustrated Fig. 1. > > VR: You’re right. In addition to congestion control, traffic shaping > may also delay packet transmissions (this is what > we considered in our work where we considered a CBR link, re-using > 3GPP use-cases). > > NEW: > The datapackets of continuous media flow(s) may be passed to the > transport layer immediately, without delay. > > >> Same applies for : "since repair symbols can be generated and sent >> on-the-fly, » > > VR: Fixed. > > NEW: > since repair symbols can be generated and passed to the > transport layer on-the-fly, […] > > >> "In practice FEC Source Packets can be sent as soon as available, >> without having to wait for FEC encoding to take place". This sounds >> like a priority scheduling between source data packets against repair >> packets. May be "Encoding operations should not influence data >> packets processing: FEC Source Packets should never be delayed and >> should always remain available to be passed to the transport layer. » > > VR: In fact there are several design options WRT to the question of > "when to send source and repair packets ». > See: > https://datatracker.ietf.org/meeting/98/materials/slides-98-tsvwg-sessb-63-fecframe-drafts-00 (slide > 17). > I don’t see good reasons to enter that type of detail in this > document, so I’ve opted to a more neutral sentence > (using « may ») than what was there and what you propose (where > « should » is too strong). > > OLD: > In practice FEC Source Packets can be sent as soon as > available, without having to wait for FEC encoding to take place. > > NEW: > In practice FEC Source Packets may be passed to the > transport layer as soon as available, without having to wait for FEC > encoding to take place. > > >> "Protection amount" is defined but not used in this document. The >> definition suggests a kind of cross-layer with the transport protocol >> or a kind of application flow control. Should be either discussed nay >> suppressed. > > VR: Removed. It was inherited from RFC6363 definitions, but there > also, it was not explicitly used in the text. > > >> EL > > Cheers, > > Vincent -- Emmanuel LOCHIN Professeur ISAE ISAE SUPAERO - Institut Supérieur de l'Aéronautique et de l'Espace 10 avenue Edouard Belin - BP 54032 - 31055 TOULOUSE CEDEX 4 FRANCE - http://www.isae-supaero.fr Tel +33 5 61 33 84 85 - Fax (+33) 5 61 33 83 45 Web : http://personnel.isae.fr/emmanuel-lochin/
- [tsvwg] WGLC on FECFRAME sliding window extension… Wesley Eddy
- Re: [tsvwg] [nwcrg] WGLC on FECFRAME sliding wind… Emmanuel Lochin
- Re: [tsvwg] WGLC on FECFRAME sliding window exten… Gorry Fairhurst
- Re: [tsvwg] WGLC on FECFRAME RLC FEC Gorry Fairhurst
- Re: [tsvwg] [nwcrg] WGLC on FECFRAME sliding wind… Vincent Roca
- Re: [tsvwg] [nwcrg] WGLC on FECFRAME sliding wind… Emmanuel Lochin
- Re: [tsvwg] WGLC on FECFRAME RLC FEC Vincent Roca
- Re: [tsvwg] WGLC on FECFRAME RLC FEC Gorry Fairhurst
- Re: [tsvwg] WGLC on FECFRAME sliding window exten… Wesley Eddy
- Re: [tsvwg] [nwcrg] WGLC on FECFRAME sliding wind… Jonathan DETCHART
- Re: [tsvwg] [nwcrg] WGLC on FECFRAME sliding wind… Vincent Roca
- Re: [tsvwg] [nwcrg] WGLC on FECFRAME sliding wind… Ali C. Begen