Subject: [rtcweb] SRTP/AVPF/TCP in draft-ietf-rtcweb-transports-01

From: "Parthasarathi R" <[email-masked]>
Date: Wed, 2 Oct 2013 23:10:25 +0530

Hi Harald,

Could you please let me know the specification which indicates SRTP/AVPF/TCP
profile in Sec 2.2 of draft-ietf-rtcweb-transports-01. 

Thanks
Partha

---

From: Harald Alvestrand <[email-masked]>
Date: Wed, 02 Oct 2013 22:19:36 +0200

> profile in Sec 2.2 of draft-ietf-rtcweb-transports-01. 
That's a good question!

http://tools.ietf.org/html/rfc4571 defines TCP/RTP/AVP, but there
doesn't seem to be a corresponding defintion for SRTP/AVPF over TCP.

Neither is the RFC 4571 profile registered at IANA - I think both that
and the DTLS forms should have been at
http://www.iana.org/assignments/rtp-parameters/rtp-parameters.xhtml#rtp-parameters-7
- but this registry seems so short, I wonder if I'm missing something.

-- 
Surveillance is pervasive. Go Dark.

---

From: "Mandyam, Giridhar" <[email-masked]>
Date: Wed, 2 Oct 2013 20:31:57 +0000

Does RFC 6544 work (http://tools.ietf.org/html/rfc6544) for a normative reference on SRTP/AVP over TCP?
-Giri

From: [email-masked] [mailto:[email-masked]] On Behalf Of Harald Alvestrand
Sent: Wednesday, October 02, 2013 1:20 PM
To: Parthasarathi R
Cc: [email-masked]
Subject: Re: [rtcweb] SRTP/AVPF/TCP in draft-ietf-rtcweb-transports-01

Hi Harald,

Thanks

Partha

That's a good question!

http://tools.ietf.org/html/rfc4571 defines TCP/RTP/AVP, but there doesn't seem to be a corresponding defintion for SRTP/AVPF over TCP.

Neither is the RFC 4571 profile registered at IANA - I think both that and the DTLS forms should have been at http://www.iana.org/assignments/rtp-parameters/rtp-parameters.xhtml#rtp-parameters-7 - but this registry seems so short, I wonder if I'm missing something.

--

---

From: Magnus Westerlund <[email-masked]>
Date: Thu, 3 Oct 2013 05:22:32 +0000

Harald,

Yes you are missing something. The registry you pointed at are the one for RTP profiles. The one containing the combinations with transport are SDP specific.

http://www.iana.org/assignments/sdp-parameters/sdp-parameters.xhtml#sdp-parameters-2

Cheers

Magnus

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Från: Harald Alvestrand <[email-masked]>
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Ämne: Re: [rtcweb] SRTP/AVPF/TCP in draft-ietf-rtcweb-transports-01

Hi Harald,

Thanks
Partha

That's a good question!

---

From: Harald Alvestrand <[email-masked]>
Date: Thu, 03 Oct 2013 17:20:12 +0200

> http://www.iana.org/assignments/sdp-parameters/sdp-parameters.xhtml#sdp-parameters-2

Thanks!

For consistency's sake, shouldn't all the SDP parameters that contain
"RTP" also be listed in the RTP registry?

I'm thinking that -transport- may have to grow an IANA section that
registers TCP/RTP/SAVPF, and it needs to decide whether to register it
in one or both.

(Of course, the TCP/ prefix is only used in some of the examples in the
RFC defining RTP over TCP - as a matter of taste, I don't like having
protocol in the profile name, so would be happy not doing so if the SDP
experts say this is OK by the rules, but then I need to adjust the
language to not use the word "profile" in this place.)

---

From: "Parthasarathi R" <[email-masked]>
Date: Thu, 3 Oct 2013 22:39:13 +0530

Hi Harald/Magnus,

Thanks for the clarification.  Please clarify whether TCP/RTP/SAVPF will be
registered in IANA as separate MMUSIC specification or any another simple
mechanism exists to add IANA registry. 

I'm interested in seeing the usage of DTLS key exchange for SRTP within
TCP/RTP/SAVPF profile. Even though DTLS is designed for connectionless
protocol, I assume that it works with TCP (connection oriented) protocol as
well. The optimized version of TCP/RTP/SAVPF shall use TLS as a SRTP key
exchange mechanism. Please correct me in case I'm missing something.

Thanks

Partha

From: Harald Alvestrand [mailto:[email-masked]] 
Sent: Thursday, October 03, 2013 8:50 PM
To: Magnus Westerlund
Cc: Parthasarathi R; [email-masked]
Subject: Re: SV: [rtcweb] SRTP/AVPF/TCP in draft-ietf-rtcweb-transports-01

Harald, 
 
Yes you are missing something. The registry you pointed at are the one for
RTP profiles. The one containing the combinations with transport are SDP
specific. 
 
http://www.iana.org/assignments/sdp-parameters/sdp-parameters.xhtml#sdp-para
meters-2

Thanks!

For consistency's sake, shouldn't all the SDP parameters that contain "RTP"
also be listed in the RTP registry?

I'm thinking that -transport- may have to grow an IANA section that
registers TCP/RTP/SAVPF, and it needs to decide whether to register it in
one or both.

(Of course, the TCP/ prefix is only used in some of the examples in the RFC
defining RTP over TCP - as a matter of taste, I don't like having protocol
in the profile name, so would be happy not doing so if the SDP experts say
this is OK by the rules, but then I need to adjust the language to not use
the word "profile" in this place.)

---

From: Harald Alvestrand <[email-masked]>
Date: Thu, 03 Oct 2013 20:54:54 +0200

I've modified my copy of the transport draft as follows:

   ICE TCP candidates, either using TURN [RFC6062] or not [RFC6544] MAY
   be supported; this may allow applications to achieve peer-to-peer
   communication across UDP-blocking firewalls.

   NOTE IN DRAFT: The profile used is RTP/SAVPF.  RFC 4571 registers the
   profile "TCP/RTP/AVP", but there's no registration for "TCP/RTP/
   SAVPF", which corresponds to the RTP/SAVPF profile recommended
   elsewhere in the RTCWEB specifications.  RFC 6544 shows examples both
   with and without the TCP/ prefix.  Should we suggest that in general,
   the prefix should not be used?  If the prefix should be used, TCP/
   RTP/SAVPF needs to be registered.

I must admit that I don't follow the logic behind RTP profile names in
SDP these days; they seem to vaccilate between transport protocol and no
transport protocol.
I think I prefer "no transport protocol", keeping the profile name
constant across different transports, but this is probably a subject
that either rtp-usage or jsep needs to tackle explicitly.

            Harald

---

From: Justin Uberti <[email-masked]>
Date: Thu, 3 Oct 2013 12:03:01 -0700

On Thu, Oct 3, 2013 at 10:09 AM, Parthasarathi R <[email-masked]
> wrote:

>  Hi Harald/Magnus,****
>
> ** **
>
> Thanks for the clarification.  Please clarify whether TCP/RTP/SAVPF will
> be registered in IANA as separate MMUSIC specification or any another
> simple mechanism exists to add IANA registry. ****
>
> ** **
>
> I’m interested in seeing the usage of DTLS key exchange for SRTP within
> exchange mechanism. Please correct me in case I’m missing something.
>

Yes, this should work. It will use the RTP-over-TCP framing for the DTLS
records (i.e. 16-bit-length prefix). I don't think if it makes sense to
support TLS instead of DTLS in this case since there are no guarantees that
the TCP transport will be lossless (i.e. if the TCP buffers fill, endpoints
may choose to start dropping packets instead of continuing to buffer).

> ****
>
> ** **
>
> Thanks****
>
> Partha****
>
> ** **
>
> *From:* Harald Alvestrand [mailto:[email-masked]]
> *Sent:* Thursday, October 03, 2013 8:50 PM
> *To:* Magnus Westerlund
> *Cc:* Parthasarathi R; [email-masked]
> *Subject:* Re: SV: [rtcweb] SRTP/AVPF/TCP in
> draft-ietf-rtcweb-transports-01****
>
> ** **
>
> On 10/03/2013 07:22 AM, Magnus Westerlund wrote:****
>
> Harald, ****
>
> ** **
>
> Yes you are missing something. The registry you pointed at are the one for RTP profiles. The one containing the combinations with transport are SDP specific. ****
>
> ** **
>
> http://www.iana.org/assignments/sdp-parameters/sdp-parameters.xhtml#sdp-parameters-2****
>
>
> Thanks!
>
> experts say this is OK by the rules, but then I need to adjust the language
> to not use the word "profile" in this place.)
>
>
> ****
>
> _______________________________________________
> rtcweb mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/rtcweb
>
>

---

From: Magnus Westerlund <[email-masked]>
Date: Mon, 7 Oct 2013 10:21:10 +0200

On 2013-10-03 19:09, Parthasarathi R wrote:
> simple mechanism exists to add IANA registry.

I think we might need a MMUSIC or AVTCORE SDP field proto cleanup
document. It is not only TCP/RTP/SAVPF that is missing, also AVPF and
SAVP is missing.

But, before diving into this. Are there really consensus that we will
use IP/TCP/RFC4571 framing/RTP(SAVPF) rather than using TURN over TCP to
get a stack saying IP/TCP/TURN/RTP(SAVPF)?

Their SDP identification are quite different. The later uses m= lines
indicating RTP/SAVPF with the TURN part in the ICE candidates.

> protocol, I assume that it works with TCP (connection oriented) protocol
> as well. The optimized version of TCP/RTP/SAVPF shall use TLS as a SRTP
> key exchange mechanism. Please correct me in case I’m missing something.

In that case you definitely need an MMUSIC document. This as we need to
figure out if using TLS to represent DTLS was a misstake as I think you
need to separate DTLS and TLS when sent over TCP for the different
purposes in that case.

Cheers

Magnus Westerlund

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---

From: Harald Alvestrand <[email-masked]>
Date: Mon, 07 Oct 2013 10:46:04 +0200

> get a stack saying IP/TCP/TURN/RTP(SAVPF)?

I have seen this thread suggesting two stacks:

- TURN over TCP to a TURN server, UDP to final destination
- RFC 4571 framing (I think) over TCP, all the way to the final destination

The latter would be done using ICE TCP candidates according to RFC
63something. I haven't yet seen one suggesting using the TURN framing
all the way to the final destination; I'm not sure I've seen a way of
signalling that either.

I think I've seen rough consensus that we should (SHOULD) support the
former. Ihaven't seen anything stronger than a MAY support the latter,
so for Transport, the only concern is that if we reference it, we
reference it correctly.

---

From: "Parthasarathi R" <[email-masked]>
Date: Mon, 7 Oct 2013 22:35:29 +0530

Hi Harald/Magnus,

I agree with you that we need to reference the correct transport in
draft-ietf-rtcweb-transports. I noticed that RTP over TCP
(http://www.ietf.org/mail-archive/web/pntaw/current/msg00041.html)
discussion is going on in ptnaw mailing alias. As there is a possibility of
two different stack for RTCWeb and it is an open item, let us discuss and
conclude in ptnaw mailing alias before updating in RTCWeb transport.
 
Also I agree with Magnus that it is better to discuss in MMUSIC for SDP
field proto cleanup for TCP/RTP/SAVPF, TCP/RTP/SAVP, TCP/RTP/AVPF. I'll
start the mail thread in Mmusic after seeing the interest in ptnaw mailing
alias.

Thanks
Partha

> -----Original Message-----
> Sent: Monday, October 07, 2013 2:16 PM
> To: Magnus Westerlund; Parthasarathi R
> Cc: [email-masked]