Re: [bfcpbis] Alexey Melnikov's Discuss on draft-ietf-bfcpbis-sdp-ws-uri-08: (with DISCUSS and COMMENT)

"Ram Mohan R (rmohanr)" <rmohanr@cisco.com> Thu, 19 January 2017 04:00 UTC

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From: "Ram Mohan R (rmohanr)" <rmohanr@cisco.com>
To: Alissa Cooper <alissa@cooperw.in>
Thread-Topic: [bfcpbis] Alexey Melnikov's Discuss on draft-ietf-bfcpbis-sdp-ws-uri-08: (with DISCUSS and COMMENT)
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Date: Thu, 19 Jan 2017 04:00:11 +0000
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Cc: "draft-ietf-bfcpbis-sdp-ws-uri@ietf.org" <draft-ietf-bfcpbis-sdp-ws-uri@ietf.org>, "bfcpbis-chairs@ietf.org" <bfcpbis-chairs@ietf.org>, Alexey Melnikov <aamelnikov@fastmail.fm>, "bfcpbis@ietf.org" <bfcpbis@ietf.org>, "Charles Eckel (eckelcu)" <eckelcu@cisco.com>, The IESG <iesg@ietf.org>
Subject: Re: [bfcpbis] Alexey Melnikov's Discuss on draft-ietf-bfcpbis-sdp-ws-uri-08: (with DISCUSS and COMMENT)
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Hi Alissa,

I don’t have a strong opinion on this. Either way (having a single attribute or two different SDP attributes) would work.

Implementations can still retrieve the value (URI) of that attribute and based on the proto line (TCP/WS/BFCP or TCP/WSS/BFCP) match the URI against ws or wss schema defined in RFC6455.  I would expect such a validation to happen across layers.
The SDP stack parser to look at the proto line transport value (TCP/WS/BFCP or TCP/WSS/BFCP) and check for presence of a=websocket-uri attribute. The value of this attribute (ws or wss schema) can be passed *as is* to the application (in this case BFCP client application) which will validate it against the schema in RFC 6455.

I am OK to incorporate this comment to have a single SDP attribute. 

Regards,
Ram

-----Original Message-----
From: Alissa Cooper <alissa@cooperw.in>
Date: Thursday, 19 January 2017 at 1:58 AM
To: "Ram Mohan R (rmohanr)" <rmohanr@cisco.com>
Cc: Alexey Melnikov <aamelnikov@fastmail.fm>, The IESG <iesg@ietf.org>, "draft-ietf-bfcpbis-sdp-ws-uri@ietf.org" <draft-ietf-bfcpbis-sdp-ws-uri@ietf.org>, "bfcpbis@ietf.org" <bfcpbis@ietf.org>, "Charles Eckel (eckelcu)" <eckelcu@cisco.com>, "bfcpbis-chairs@ietf.org" <bfcpbis-chairs@ietf.org>
Subject: Re: [bfcpbis] Alexey Melnikov's Discuss on draft-ietf-bfcpbis-sdp-ws-uri-08: (with DISCUSS and COMMENT)
Resent-From: <alias-bounces@ietf.org>
Resent-To: <rmohanr@cisco.com>, <gsalguei@cisco.com>
Resent-Date: Thursday, 19 January 2017 at 1:58 AM

    Hi Ram,
    
    I had some further conversation with Alexey on the side and wanted to come back to a question he posed: is there a reason why a=ws-uri and a=wss-uri both need to be specified? Why can’t a single label be specified, say a=websocket-uri, and then have normative language requiring the scheme in the URI itself to match what’s in the associated m-line (ws:// for TCP/WS/BFCP and wss:// for TCP/WSS/BFCP)? Won’t it be more efficient for implementations to grab the URI itself anyway and check that the scheme matches the m-line?
    
    Thanks,
    Alissa
    
    > On Jan 17, 2017, at 9:40 AM, Ram Mohan R (rmohanr) <rmohanr@cisco.com> wrote:
    > 
    > Alissa,
    > 
    > I am fine with the proposed text.
    > 
    > Thanks,
    > Ram
    > 
    > -----Original Message-----
    > From: Alissa Cooper <alissa@cooperw.in>
    > Date: Tuesday, 17 January 2017 at 8:07 PM
    > To: Alexey Melnikov <aamelnikov@fastmail.fm>
    > Cc: The IESG <iesg@ietf.org>, "draft-ietf-bfcpbis-sdp-ws-uri@ietf.org" <draft-ietf-bfcpbis-sdp-ws-uri@ietf.org>, "bfcpbis@ietf.org" <bfcpbis@ietf.org>, "Charles Eckel (eckelcu)" <eckelcu@cisco.com>, "bfcpbis-chairs@ietf.org" <bfcpbis-chairs@ietf.org>, "Ram Mohan R (rmohanr)" <rmohanr@cisco.com>
    > Subject: Re: [bfcpbis] Alexey Melnikov's Discuss on draft-ietf-bfcpbis-sdp-ws-uri-08: (with DISCUSS and COMMENT)
    > 
    >    Alexey, would the following changes clarify things?
    > 
    >    Section 4.1
    >    OLD
    >    the server side, which could be either
    >       the offerer or answerer, MUST add an "a=ws-uri" or "a=wss-uri"
    >       attribute in the media section
    >    NEW
    >    the server side, which could be either
    >       the offerer or answerer, MUST add an "a=ws-uri" or "a=wss-uri”
    >       attribute (but not both) in the media section
    > 
    >    Section 4.3
    >    OLD
    >    If the answers assigns SDP "setup" attribute with "passive", then it
    >       MUST have a URI in either "a=ws-uri" or "a=wss-uri" attribute
    >       depending on whether the application uses WebSocket or
    >       secureWebSocket.
    >    NEW
    >    If the answers assigns SDP "setup" attribute with "passive", then it
    >       MUST have a URI in either "a=ws-uri" or "a=wss-uri" attribute
    >       (but not both) in the media section, depending on whether the application uses WebSocket or
    >       secureWebSocket.
    > 
    >    Ram, would you be okay with those clarifications?
    > 
    >    Alissa
    > 
    > 
    >> On Jan 16, 2017, at 10:09 AM, Ram Mohan R (rmohanr) <rmohanr@cisco.com> wrote:
    >> 
    >> Hi Alexey,
    >> 
    >> -----Original Message-----
    >> From: Alexey Melnikov <aamelnikov@fastmail.fm>
    >> Date: Monday, 16 January 2017 at 8:25 PM
    >> To: "Ram Mohan R (rmohanr)" <rmohanr@cisco.com>, The IESG <iesg@ietf.org>
    >> Cc: "draft-ietf-bfcpbis-sdp-ws-uri@ietf.org" <draft-ietf-bfcpbis-sdp-ws-uri@ietf.org>, "bfcpbis@ietf.org" <bfcpbis@ietf.org>, "Charles Eckel (eckelcu)" <eckelcu@cisco.com>, "bfcpbis-chairs@ietf.org" <bfcpbis-chairs@ietf.org>
    >> Subject: Re: [bfcpbis] Alexey Melnikov's Discuss on draft-ietf-bfcpbis-sdp-ws-uri-08: (with DISCUSS and COMMENT)
    >> 
    >>   Hi Ram,
    >> 
    >>   On Mon, Jan 16, 2017, at 02:49 PM, Ram Mohan R (rmohanr) wrote:
    >>> Hi Alexey,
    >>> 
    >>> Please see inline <Ram>
    >>> 
    >>> -----Original Message-----
    >>> From: Alexey Melnikov <aamelnikov@fastmail.fm>
    >>> Date: Monday, 16 January 2017 at 7:57 PM
    >>> To: "Ram Mohan R (rmohanr)" <rmohanr@cisco.com>, The IESG <iesg@ietf.org>
    >>> Cc: "draft-ietf-bfcpbis-sdp-ws-uri@ietf.org"
    >>> <draft-ietf-bfcpbis-sdp-ws-uri@ietf.org>, "bfcpbis@ietf.org"
    >>> <bfcpbis@ietf.org>, "Charles Eckel (eckelcu)" <eckelcu@cisco.com>,
    >>> "bfcpbis-chairs@ietf.org" <bfcpbis-chairs@ietf.org>
    >>> Subject: Re: [bfcpbis] Alexey Melnikov's Discuss on
    >>> draft-ietf-bfcpbis-sdp-ws-uri-08: (with DISCUSS and COMMENT)
    >>> 
    >>>   Hi Ram,
    >>> 
    >>>   On Mon, Jan 16, 2017, at 06:09 AM, Ram Mohan R (rmohanr) wrote:
    >>>> Hi Alexey,
    >>>> 
    >>>> Thanks for your feedback. Please see inline <Ram>
    >>>> 
    >>>> -----Original Message-----
    >>>> From: bfcpbis <bfcpbis-bounces@ietf.org> on behalf of Alexey Melnikov
    >>>> <aamelnikov@fastmail.fm>
    >>>> Date: Saturday, 14 January 2017 at 3:49 AM
    >>>> To: The IESG <iesg@ietf.org>
    >>>> Cc: "draft-ietf-bfcpbis-sdp-ws-uri@ietf.org"
    >>>> <draft-ietf-bfcpbis-sdp-ws-uri@ietf.org>, "bfcpbis@ietf.org"
    >>>> <bfcpbis@ietf.org>, "Charles Eckel (eckelcu)" <eckelcu@cisco.com>,
    >>>> "bfcpbis-chairs@ietf.org" <bfcpbis-chairs@ietf.org>
    >>>> Subject: [bfcpbis] Alexey Melnikov's Discuss on
    >>>> draft-ietf-bfcpbis-sdp-ws-uri-08: (with DISCUSS and COMMENT)
    >>>> 
    >>>>   Alexey Melnikov has entered the following ballot position for
    >>>>   draft-ietf-bfcpbis-sdp-ws-uri-08: Discuss
    >>>> 
    >>> 
    >>>>   ----------------------------------------------------------------------
    >>>>   DISCUSS:
    >>>>   ----------------------------------------------------------------------
    >>>> 
    >>>>   This is generally a well written document, but I have a small list of
    >>>>   issues that I would like to discuss before recommending its approval:
    >>>> 
    >>>>   1) Are a=ws-uri and a=wss-uri mutually exclusive? (Section 4.3 is a
    >>>>   good
    >>>>   place to mention what to do if both are specified).
    >>>> 
    >>>> <Ram> Yes kind of. In a given media line (m= line) we will either have
    >>>> a=ws-uri or a=wss-uri. That said a response from a BFCP server using
    >>>> webSocket as a transport can
    >>>> have two media lines one with ws and other with wss. Something like:
    >>>> 
    >>>> Answer (server):
    >>>>  m=application 50000 TCP/WSS/BFCP *
    >>>>  a=setup:passive
    >>>>  a=connection:new
    >>>>  a=wss-uri:wss://bfcp-ws.example.com?token=3170449312
    >>>>  m=application 50000 TCP/WS/BFCP *
    >>>>  a=setup:passive
    >>>>  a=connection:new
    >>>>  a=ws-uri:ws://bfcp-ws.example.com?token=3170449312
    >>> 
    >>>   [Alexey]: This is exactly my problem, you should specify how a
    >>>   recipient
    >>>   should handle your example above. If you only have 1 attribute, the
    >>>   problem goes away entirely.
    >>> 
    >>> <Ram> in the above case, they are still two different m= lines. The
    >>> receiver (after offer/answer is done) of this SDP connects to the URI
    >>> mentioned in that m= line. 
    >>> Note I just re-used the same URL/port in the example above. If there are
    >>> multiple m=application media lines (they will be for different
    >>> applications) being negotiated in SDP, one application may use secure WS
    >>> and other application may use non-secure WS. The client after it receives
    >>> the answer SDP will just setup the connection to the URI specified in the
    >>> attribute.  
    >> 
    >>   Sorry, I was thinking about different example:
    >> 
    >>   m=application 50000 TCP/WSS/BFCP *
    >>      a=setup:passive
    >>      a=connection:new
    >>      a=wss-uri:wss://bfcp-ws.example.com?token=3170449312
    >>      a=ws-uri:ws://bfcp-ws.example.com?token=3170449312
    >> 
    >>   You have 2 conflicting URIs for the same m= line. Is this possible?
    >> 
    >> <Ram> No this is not possible. If the transport is TCP/WSS/BFCP we should have only a=wss-uri. If transport is TCP/WS/BFCP we should have only a=ws-uri.
    >> 
    >> Regards,
    >> Ram
    >> 
    >>> I don’t see any problem in here.  
    >>> 
    >>> Regards,
    >>> Ram
    >>> 
    >>>>   Why not a single attribute, considering that both ws: and wss: URIs
    >>>>   are
    >>>>   possible?
    >>>> 
    >>>> <Ram> I would still prefer two attributes. We just followed the
    >>>> convention / approach that was used in [RFC6455].  
    >>> 
    >>> 
    >> 
    >> 
    > 
    > 
    >