Subject: [MMUSIC] Reviewing draft-ietf-dccp-udpencap

From: Pasi Sarolahti <[email-masked]>
Date: Wed, 15 Jun 2011 10:42:03 +0300

Hi,

In DCCP WG we are soon concluding draft-ietf-dccp-udpencap ("Datagram Congestion Control Protocol (DCCP) Encapsulation for NAT Traversal (DCCP-UDP)"). This draft has parts related to the work done in MMUSIC (especially Section 5), and it was presented in the MMUSIC meeting in last IETF. The authors have modified the text based on the input received, and we are now looking for volunteer(s) from MMUSIC to review whether the new text (mostly in Section 5) looks ok, before moving forward with the draft.

The draft can be found at http://tools.ietf.org/html/draft-ietf-dccp-udpencap-08 

- Pasi

---

From: "Miguel A. Garcia" <[email-masked]>
Date: Wed, 15 Jun 2011 15:32:34 +0200

A quick review of Section 5 of this document:

- I think it is a good idea to clearly indicate which SDP attributes are 
newly created and which ones are reused from other RFCs. I therefore 
recommend to add the following sentences somewhere to the corresponding 
sections:

5.3:
RFC 4145 [RFC4145] defines the "setup" attribute whose purpose is to 
indcate which of the end points should initiate the connection 
establishment. This document reuses the "setup" attribute to similarly 
indicate which end point initiates the DCCP-UDP connection establishment.

5.4:
RFC 5245 [RFC5245] defines the "candidate" attribute whose purpose is to 
provide one of many possible candidate addresses for communication. This 
document reuses the "candidate" attribute to indicate native or 
encapsulated candidate addresses

- In 5.2 last paragraph, I am missing some normative statements, for example:

If RTCP is multiplexed with RTP, endpoints MUST encode the DCCP port used 
for RTCP in the "rtcp" attribute specified in RFC 3605 [RFC3605]. An SDP 
offerer MAY indicate its willingnes to multiplex RTP and RTCP onto a 
single DCCP port by adding an "rtcp-mux" attribute as specified in RFC 
5761 [RFC5761]. If the answer also includes the "rtcp-mux" attribute (as 
per RFC 5761 [RFC5761]), then RTP and RTCP are multiplexed onto a single 
DCCP port, otherwise separate DCCP ports are used for RTP and RTCP.  In 
each case, only a single UDP port is used for the DCCP-UDP encapsulation.

- I didn't find any description of the "dccp-service-code". However, it 
is written in the examples in Section 5.5. Is this a leftover from a 
previous version of the document?

- I agree with your comment at the end of Section 5.5 indicating that an 
example using ICE would be beneficial.

- Section 7.3. There are two references pointing to Section 5.1 in the 
document, but they should actually point to Section 5.2

- I think the following references should be made normative: ICE-TCP, 
RFC3264, RFC 4566, RFC5245, RFC5761

BR,

        Miguel

On 15/06/2011 9:42, Pasi Sarolahti wrote:
> _______________________________________________
> mmusic mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/mmusic
>

-- 
Miguel A. Garcia
+34-91-339-3608
Ericsson Spain

---

From: Gorry Fairhurst <[email-masked]>
Date: Thu, 16 Jun 2011 08:42:12 +0100 (BST)

See in-line on dccp-service-code.

Gorry

On Wed, 15 Jun 2011, Miguel A. Garcia wrote:

> RFC 4145 [RFC4145] defines the "setup" attribute whose purpose is to indcate 
> which of the end points should initiate the connection establishment. This 
> document reuses the "setup" attribute to similarly indicate which end point 
> initiates the DCCP-UDP connection establishment.
>
> 5.4:
> document reuses the "candidate" attribute to indicate native or encapsulated 
> candidate addresses
>
>
[After re-reading this I note that this section speaks of "native" DCCP
whereas there was an earlier suggestion that this should be called 
"DCCP-STD", Colin and I should ensure this is consistent in the next 
revision.]

> If RTCP is multiplexed with RTP, endpoints MUST encode the DCCP port used for 
> RTCP in the "rtcp" attribute specified in RFC 3605 [RFC3605]. An SDP offerer 
> MAY indicate its willingnes to multiplex RTP and RTCP onto a single DCCP port 
> by adding an "rtcp-mux" attribute as specified in RFC 5761 [RFC5761]. If the 
> answer also includes the "rtcp-mux" attribute (as per RFC 5761 [RFC5761]), 
> then RTP and RTCP are multiplexed onto a single DCCP port, otherwise separate 
> DCCP ports are used for RTP and RTCP.  In each case, only a single UDP port 
> is used for the DCCP-UDP encapsulation.
>
> - I didn't find any description of the "dccp-service-code". However, it is 
> written in the examples in Section 5.5. Is this a leftover from a previous 
> version of the document?
>
I suggest a couple of lines to be clear to anyone composing  SDP:

RFC 5762 [RFC5762] defines the "dccp-service-code" attribute whose purpose 
is to identify the intended service/application to process a DCCP 
connection request [RFC5595]. The "dccp-service-code" attribute is the 
same for both DCCP-STD and DCCP-UDP encapsulations.

> example using ICE would be beneficial.

So, as soon as we have this, I think we can then finalise the text!

> document, but they should actually point to Section 5.2
Noted, will fix.

> RFC3264, RFC 4566, RFC5245, RFC5761
Seems OK to me, I'll see if Colin agrees.

>> In DCCP WG we are soon concluding draft-ietf-dccp-udpencap ("Datagram 
>> Congestion Control Protocol (DCCP) Encapsulation for NAT Traversal 
>> (DCCP-UDP)"). This draft has parts related to the work done in MMUSIC 
>> (especially Section 5), and it was presented in the MMUSIC meeting in last 
>> IETF. The authors have modified the text based on the input received, and 
>> we are now looking for volunteer(s) from MMUSIC to review whether the new 
>> text (mostly in Section 5) looks ok, before moving forward with the draft.
>> 
>> The draft can be found at 
>> http://tools.ietf.org/html/draft-ietf-dccp-udpencap-08
>> 
>> - Pasi
>>

---

From: "Miguel A. Garcia" <[email-masked]>
Date: Thu, 16 Jun 2011 10:28:12 +0200

Hi Gorry:

Your suggestions look ok to me.

BR,

        Miguel

-- 
Miguel A. Garcia
+34-91-339-3608
Ericsson Spain