Media Server
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... expect them to change in the future.
Multifunction media servers provide network media services to clients ...
... MSCML [21]. This document
describes how to identify to a multifunction media server what sort
of session the client ...
... In the context of SIP control of media servers, we take advantage of
the fact that the standard SIP URI ...
... URI has a user part. Multifunction
media servers do not have users. Thus we use the user address, or
the left-hand-side of the URI ...
... o Only devices that choose to conform to this standard have to
implement it.
o This document only applies to multifunction SIP-controlled media
servers.
o This document has no impact on non-multifunction SIP-controlled
media servers.
...
... o This document only applies to multifunction SIP-controlled media
servers.
o This document has no impact on non-multifunction SIP-controlled
media servers.
o The mechanism described in this document has absolutely no impact
on SIP ...
... o The mechanism described in this document has absolutely no impact
on SIP devices other than media servers.
The last bullet point is crucial. In particular, the user part ...
... device. The user parts defined here only apply to multifunction
media servers that chose to implement the convention. With the
exception of a conforming media server, these user names ...
... media servers that chose to implement the convention. With the
exception of a conforming media server, these user names and
conventions have no impact on the user part ...
... restrict the use of these user names at devices other than a
multifunction media server.
Note that the set of services ...
... For per-service security, the media server SHOULD use the security
protocols described in RFC 3261prop [10 ...
... media server MAY issue 401 challenges for authentication. The
media server SHOULD support the sips: scheme for the announcement
service. The media server ...
... media server SHOULD support the sips: scheme for the announcement
service. The media server MUST support the sips: scheme for the
dialog and conference services. The level of authentication ...
... service is a matter of local policy.
The media server, upon receiving an INVITE, notes the service
indicator ...
... INVITE, notes the service
indicator. Depending on the service indicator, the media server will
either honor the request or return a failure response code.
...
... association with a unique service
instance on the media server. For example, a given media server can
host ...
... service
instance on the media server. For example, a given media server can
host multiple, separate conference sessions ...
... client issues a SIP INVITE to the media server,
specifying the requested service and any appropriate parameters.
...
... service and any appropriate parameters.
If the media server can perform the requested service, it does so,
following the processing steps described in the service definition ...
... document.
If the media server cannot perform the requested service or does not
recognize the service indicator ...
... user part of the URI. Moreover, 606 is not
appropriate, as some other media server may be able to satisfy the
request. RFC 3261prop [10 ...
... service instance, and no such service instance exists on the media
server, the media server MUST respond with the response code 404 NOT
...
... service instance, and no such service instance exists on the media
server, the media server MUST respond with the response code 404 NOT
FOUND. This is appropriate as the service ...
... response code 404 NOT
FOUND. This is appropriate as the service itself exists on the media
server, but the particular service instance does not. It is as if
the user was not home.
...
... as a prompt file, to a terminal device. Note the multimedia resource
may be any multimedia object that the media server supports. This
service can play a single object with multiple streams, such as a
...
... Playing an announcement after call setup is straightforward. First,
the requesting device issues an INVITE to the media server requesting
the announcement service. The media server ...
... media server requesting
the announcement service. The media server negotiates the SDP and
responds with a 200 OK. After receiving ...
... receiving the ACK from the requesting
device, the media server plays the requested object and issues a BYE
to the requesting device.
...
... to the requesting device.
If the media server supports announcements, but it cannot find the
referenced URI, it MUST respond with the 404 response code ...
... send the reason phrase "Announcement content not found".
If the media server receives an INVITE for the announcement service
...
... missing".
If there is an error retrieving the announcement, the media server
MUST respond with a 400 response code and SHOULD send the reason
...
... response code and SHOULD send the reason
phrase "Announcement content could not be retrieved". In addition
the media server SHOULD include a Warning header with appropriate
explanatory text explaining what failed.
...
... address, "annc", specifies the announcement
service on the media server. The service has several associated URI
parameters that control the content and delivery ...
...
repeat
Specifies how many times the media server should repeat the
announcement or sequence named by the "play=" parameter. The
value "forever" means the repeat should be effectively unbounded.
...
... announcement or sequence named by the "play=" parameter. The
value "forever" means the repeat should be effectively unbounded.
In this case, it is RECOMMENDED the media server implements some
local policy, such as limiting what "forever" means, to ensure
errant clients ...
...
duration
Specifies the maximum duration of the announcement. The media
server will discontinue the announcement and end the call if the
maximum duration has been reached. The duration is measured in
...
... requested locale and the available languages in the event the
media server cannot honor the locale request precisely. For
example, if the request has locale=ca_FR, but the media server ...
... media server cannot honor the locale request precisely. For
example, if the request has locale=ca_FR, but the media server
only has fr_FR available, the media server ...
... media server
only has fr_FR available, the media server should use the fr_FR
variant. Implementations SHOULD provide a default locale to use
...
... extension
Provides a mechanism for extending the parameter set. If the
media server receives an extension it does not understand, it MUST
silently ignore the extension parameter and value.
...
... proxy inserting the
parameters is the last proxy before the media server. If the service
provider deploys a proxy for load balancing ...
... or media gateway controller between the caller and the media server.
However, the announcement service works as described below even if
...
... The proxy issues an INVITE to the media server, requesting the
appropriate prompt to play coded in the play= parameter. The media
server responds with 200 OK. The proxy ...
... INVITE to the media server, requesting the
appropriate prompt to play coded in the play= parameter. The media
server responds with 200 OK. The proxy relays the 200 OK to the
caller ...
... media server.
With the call established, the media server plays the requested
prompt. When the media server completes the play of the prompt, it
...
... With the call established, the media server plays the requested
prompt. When the media server completes the play of the prompt, it
issues a BYE to the proxy. The proxy ...
... voicexml=http://vxmlserver.example.net/cgi-bin/script.vxml
A Media Server MAY accept additional SIP request URI parameters and
...
...
DTMF grammar. Thus, the media server MUST support the https scheme
for the voicexml parameter for secure fetching of scripts. Likewise,
...
... dynamic grammars often do have user-identifying information. As
such, the VoiceXML browser implementation on the media server MUST
support https fetching of grammars and subsequent documents.
...
... Returned information often is sensitive. For example, the
information could be financial information or instructions. Thus,
the media server MUST support https posting of results.
...
... vxml-keyword without a corresponding vxml-value, the
media server MUST reject the request with a 400 BAD REQUEST response
code. In addition, the media server MUST state ...
... media server MUST reject the request with a 400 BAD REQUEST response
code. In addition, the media server MUST state "Missing VXML Value"
in the reason phrase.
...
... in the reason phrase.
The media server presents the parameters as environment variables in
the connection object. Specifically, the parameter appears in the
...
... connection.sip tree.
If the Media Server does not support the passing of keyword-value
pairs to the VoiceXML interpreter session ...
... session. If the URI does not already exist on the
media server and the requested resources are available, the media
server creates a new mixing session ...
... URI does not already exist on the
media server and the requested resources are available, the media
server creates a new mixing session. If there is an existing URI ...
... URI for
the session, then the media server interprets it as a request for the
new session to join ...
... host portion of
the URI identifies a particular media server. The "conf" user name
conveys to the media server ...
... media server. The "conf" user name
conveys to the media server that this is a request for the mixing
service. The uniqueIdentifier can be any value that is compliant
...
... 22], this URI
convention tells the media server that the application server is
requesting it to act as a Focus. The conf-id value identifies the
...
...
As a focus in the conferencing framework, the media server MUST
support the ";isfocus" parameter in the Request URI ...
... that the presence or absence of the ";isfocus" parameter has no
protocol impact at the media server.
It is worth noting that the conference URI ...
... It is worth noting that the conference URI shared between the
application and media servers provides enhanced security, as the SIP
...
... control interface does not have to be exposed to participants. It
also allows the assignment of a specific media server to be delayed
as long as possible, thereby simplifying resource management.
...
... user part, but does not have a
conf-id parameter, the media server MUST respond with a 404 NOT
FOUND.
...
... FOUND.
NOTE: The media server could create a unique conference instance
and return the conf-id string to the User Agent ...
... application server or proxy is a better place to do such an
operation. Moreover, such action would make the media server into
a Conference Factory in the terminology of conference-framework
...
... conference-framework
[22]. That is not the appropriate behavior for a media server.
Since some conference use cases, such as business conferencing, have
...
...
Since some conference use cases, such as business conferencing, have
billing implications, the media server SHOULD authenticate the
application server ...
... and so on. However, none of that protocol machinery has an impact on
the operation of the Application Server to Media Server interface,
which is the focus of this protocol document ...
... conference-framework [22], the Application
Server is the Conference Factory, and the Media Server is the
Conference Focus.
...
... Application Server or
from the Application Server to the Media Server.
Each leg can drop out either under the supervision of the UAC ...
... Application Server will either issue a BYE on behalf of the UAC or
issue it directly to the Media Server, corresponding to the
respective disconnect case.
...
... wishes for them. What this document does is give special meaning for
these user names at media servers that implement this specification.
If a media server chooses not to implement this specification,
...
... user names at media servers that implement this specification.
If a media server chooses not to implement this specification,
nothing breaks. If a user wishes to use one of the user names
...
...
The key point is, one cannot confuse the namespace at a Media Server
with the namespace for an organization. For example, let us take the
...
... Conversely, one directs requests for the media service annc directly
to the Media Server, e.g., sip:annc@ms21.ap.example.net. Moreover,
by definition, requests for Ann Charles, or anything other than the
announcement service ...
... by definition, requests for Ann Charles, or anything other than the
announcement service, will NEVER be directly sent to the Media
Server. If that were not true, no phone in the world could use the
user part "eburger", as eburger is a reserved user part ...
... domain. Clearly, this is not the case.
If one wishes to make their media server accessible to the global
Internet, but retain one of the Media Server ...
... media server accessible to the global
Internet, but retain one of the Media Server-specific user names in
the domain ...
... Proxy can easily translate whatever opaque name one
chooses to the Media Server-specific user name. For example, if a
domain ...
... address,
sip:annc@example.com, would resolve to the actual device where annc
resides. The latter would resolve to the media server announcement
server address, sip:annc@mediaserver.example.com, as an example.
...
... server address, sip:annc@mediaserver.example.com, as an example.
Note that this convention makes it easier to provision this service.
With a fixed mapping at the multifunction media server, there are
less provisioning data elements to get wrong.
...
...
The "users" proposed by this document, "annc", "conf", and "dialog"
are all users at a Media Server, just as the "root", "bin", and
"nobody" users are "users" at a Unix host ...
... network. The only
network elements that need to know about the convention are the Media
Server and client. Even proxies doing mapping resolution, as in the
...
... closed network, where the Application Servers and Media Servers are
in the same administrative domain, this does not work across domains ...
... descriptor is that we can use all of the standard SIP machinery,
without modification. For example, Media Servers with different
capabilities can SIP Register ...
... VoiceXML-only device will register the "dialog" user,
while a multi-purpose Media Server will register all of the users.
Note that this is why the URI ...
... proxy server to
provide high-available services. For example, two Media Servers can
register with a SIP ...
... SIP redirect server for the annc user. If one of the
Media Servers fails, the registration will expire and all requests
for the announcement service ...
... for the announcement service ("calls to the annc user") will get sent
to the surviving Media Server.
...
... well-known addresses may not be
desirable. The Media Server SHOULD authenticate and authorize
requesting endpoints ...
... confidential information. Moreover, many of the interactions require
integrity protection. Thus, the Media Server MUST implement the
sips: scheme. In addition, application developers are RECOMMENDED to
use the security services ...
... sips: scheme. In addition, application developers are RECOMMENDED to
use the security services offered by the Media Server to ensure the
integrity and confidentiality ...
... create the
possibility for denial of service attacks. The media server SHOULD
have local policies to deal with this, such as time-limiting how long
"forever" is, analyzing where multiple requests come from,
...
... work developing netann, in conjunction with many application
developers, media server manufacturers, and service providers, some
of whom are listed in the Acknowledgements section. All I did was do
...
... Van Dyke, J., Burger, E., Ed., and A. Spitzer, "Media Server Control Markup Language (MSCML) and Protocol", Work in Progress, December 2004. ...