Re: [AVTCORE] Header Compression and RFC5285bis
"Roni Even" <ron.even.tlv@gmail.com> Wed, 11 May 2016 11:06 UTC
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From: Roni Even <ron.even.tlv@gmail.com>
To: 'Stephen Casner' <casner@acm.org>
References: <56FFE98E.2070406@ericsson.com> <071a01d1aa8e$9e4c1800$dae44800$@gmail.com> <alpine.OSX.2.20.1605110646350.94339@auge.local>
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Date: Wed, 11 May 2016 14:06:14 +0300
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Cc: 'Magnus Westerlund' <magnus.westerlund@ericsson.com>, 'IETF AVTCore WG' <avt@ietf.org>
Subject: Re: [AVTCORE] Header Compression and RFC5285bis
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Steve, Thanks, will add this sentence Roni > -----Original Message----- > From: Stephen Casner [mailto:casner@acm.org] > Sent: Wednesday, May 11, 2016 8:49 AM > To: Roni Even > Cc: 'Magnus Westerlund'; 'IETF AVTCore WG' > Subject: RE: [AVTCORE] Header Compression and RFC5285bis > > Roni, > > I think it would be appropriate to include another sentence before the one > you propose: "The use of RTP header extensions may reduce the > effectiveness of header compression." > > -- Steve > > On Tue, 10 May 2016, Roni Even wrote: > > > Hi Magnus, > > I am updating the document based on other comments from Colin. > > The current text says "The interactions of the RTP header extension and > > header compression is explored further in [RFC2508] and [RFC3095]." > > Do you think we need more text here? Any suggestions Roni > > > > > -----Original Message----- > > > From: avt [mailto:avt-bounces@ietf.org] On Behalf Of Magnus > > > Westerlund > > > Sent: Saturday, April 02, 2016 6:47 PM > > > To: IETF AVTCore WG; Stephen Casner > > > Subject: [AVTCORE] Header Compression and RFC5285bis > > > > > > Hi, > > > > > > Stephen Casner raised a private comment on the > > > draft-ietf-avtext-sdes-hdr-ext-05 when he did the IANA expert review. > > > This was that both > > > draft-ietf-avtext-sdes-hdr-ext-05 and RFC5285bis doesn't discuss > > > impact of header compression due to the presence of RTP header > extensions. > > > > > > I have to agree that this is something that at least RFC5285bis > > > should > > have a > > > discussion on. There are some impact. > > > > > > In the case of Robust Header Compression (ROHC) (RFC 5795 and RFC > > > 5225) the impact to my understanding is the following. RFC5225 and > > > the RTP profile don't compress the actual header extension at all. > > > The X bit in > > the > > > header is compressed and it is classified in Section A.5 as Rarely > > changing. > > > The assumption here is that what value is set on a previous packet > > > will be maintained on the next. > > > > > > Looking at the emerging usages that is mostly right, but there will > > > be > > periods > > > where the x bit may be flipping its value. The usage I am > > > considering is > > these > > > initial inclusion of the MID, CNAME etc. However for example a video > > > stream, it is sufficient to include the header extension in a single > > packet out > > > potentially many for an particular video image/frame. Thus one might > > > have > > a > > > on, off, next TS, on, then off on subsequent packets. > > > > > > The impact of the classification as Rarely changing is that when a > > > change > > is > > > needed a larger header than otherwise needed will be sent. > > > Thus the impact will be that each on and off behaviour will result > > > in one > > and > > > maybe two larger ROHC headers to get the change across compared to > > > if no RTP header extensions would have been present. > > > > > > I haven't looked at CRTP, but I would guess similar impact. > > > > > > Cheers > > > > > > Magnus Westerlund > > > > > > -------------------------------------------------------------------- > > > -- Services, Media and Network features, Ericsson Research EAB/TXM > > > ---------------------------------------------------------------------- > > > Ericsson AB | Phone +46 10 7148287 > > > Färögatan 6 | Mobile +46 73 0949079 > > > SE-164 80 Stockholm, Sweden | mailto: > magnus.westerlund@ericsson.com > > > -------------------------------------------------------------------- > > > -- > > > > > > _______________________________________________ > > > Audio/Video Transport Core Maintenance avt@ietf.org > > > https://www.ietf.org/mailman/listinfo/avt > > > > > >
- [AVTCORE] Header Compression and RFC5285bis Magnus Westerlund
- Re: [AVTCORE] Header Compression and RFC5285bis Roni Even
- Re: [AVTCORE] Header Compression and RFC5285bis Stephen Casner
- Re: [AVTCORE] Header Compression and RFC5285bis Roni Even
- Re: [AVTCORE] Header Compression and RFC5285bis Roni Even
- Re: [AVTCORE] Header Compression and RFC5285bis Stephen Casner