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Re: [MMUSIC] RTSP transport header, port parameter changes

Can a separate IP address be specified for RTCP, as the port can? draft-ietf-mmusic-sdp4nat has this capability, and its needed for cases where the network is natting into more than one IP address.

-Jonathan R.

Magnus Westerlund wrote:
Hi,

At the wednesdays telecon we discussed on how to update the transport header to support STUN and symmetric RTP
for traversal of NATs. It was decided to allow the ports to be specified explicitly for RTP and RTCP. Therefore I have written up a proposal for new text for the transport header below:

We where discussing making the port attributes totally flexible. However as I started looking at the section I discovered that port, client_port, server_port are RTP-specific. So my proposed changes does therefore only solves what is necessary for RTP. An alternative to this change would be to reclassify the port attributes to be general attributes and then they should have total flexibility. That would also require some text on how to related to the RTP media transport setup.

I also included a client_ssrc parameter. This would be used for symmetric RTP to make the symmetric port opening more robust. I will try to write up a mail regarding using symmetric RTP for RTSP sessions.

Please read and comment

Magnus

--------------------------------------------------------
changed parts of section 12.40 Transport header in relation to draft-ietf-mmusic-rfc2326bis-02.txt.

RTP-specific:

These parameters are only valid if the media transport protocol is
RTP. The parameters containing port numbers are all subject to the
following consideration: All port numbers where prior specified as
a value or range, see "old-port-spec" in ABNF below. To support NAT
traversal RTP has been updated to allow non-continuous port specif-
ication not following the even/odd rule. As long as both the RTP
and RTCP port is specified explicitly they are allow to take any
valid port number. Therefore the RTP specific port parameters has
been updated to support this. The updated format ("new-port-spec")
SHOULD only be used when required to specify non-continuous port
numbers. Before using the "new-port-spec" format the client MUST
determine server support of the "play.basic" option tags.

port: This parameter provides the RTP/RTCP port pair for a multi-
cast session. This parameter SHOULD NOT use the "new-port-
spec" format. It is should be specified as a range, e.g.,
port=3456-3457

client_port: This parameter provides the unicast RTP/RTCP port pair
on the client where media data and control information is to
be sent. It is specified either as a range, e.g., port=3456-
3457 or as two explicit numbers port=3457/4976

server_port: This parameter provides the unicast RTP/RTCP port pair
on the server where media data and control information is to
be sent. It is specified either as a range, e.g., port=3456-
3457 or as two explicit numbers port=3457/4976

ssrc: The ssrc parameter indicates the RTP SSRC [23] value that
should be (request) or will be (response) used by the media
server. This parameter is only valid for unicast transmission.
It identifies the synchronization source to be associated with
the media stream, and is expressed as an eight digit hexide-
cimal value. In cases that a sender will use multiple SSRCs it
SHOULD NOT use this parameter.

client_ssrc: The client_ssrc parameter indicates the RTP SSRC [23]
value that will be used by the client. This parameter is only
valid for unicast transmission. It identifies the synchroniza-
tion source to be associated with the media stream, and is
expressed as an eight digit hexidecimal value. In cases that a
client will use multiple SSRCs it SHOULD NOT use this parame-
ter.


Transport = "Transport" ":" 1#transport-spec
transport-spec = transport-id *parameter
transport-id = transport-protocol "/" profile ["/" lower-transport]
; no LWS is allowed inside transport-id
transport-protocol = "RTP" / token
profile = "AVP" / token
lower-transport = "TCP" / "UDP" / token
parameter = ";" ( "unicast" / "multicast" )
/ ";" "source" "=" address
/ ";" "destination" [ "=" address ]
/ ";" "interleaved" "=" channel [ "-" channel ]
/ ";" "append"
/ ";" "ttl" "=" ttl
/ ";" "layers" "=" 1*DIGIT
/ ";" "port" "=" port-spec
/ ";" "client_port" "=" port-spec
/ ";" "server_port" "=" port-spec
/ ";" "ssrc" "=" ssrc
/ ";" "client_ssrc" "=" ssrc
/ ";" "mode" "=" mode-spec
/ ";" trn-parameter-extension
port-spec = old-port-spec / new-port-spec
old-port-spec = port [ "-" port ]
new-port-spec = port "/" port ; RTP/RTCP port
trn-parameter-extension = par-name "=" trn-par-value
par-name = token
trn-par-value = *unreserved
ttl = 1*3(DIGIT)
port = 1*5(DIGIT)
ssrc = 8*8(HEX)
channel = 1*3(DIGIT)

address = host ;As defined in RFC 2732 [30]
mode-spec = <"> 1#mode <"> / mode


--
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
jdrosen@dynamicsoft.com                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com

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