Re: [RFCv2] doc: Proposal for LTE/IMS API

[=?unknown-8bit?q?R=C3=A9mi?= Denis-Courmont <remi.denis-courmont@nokia.com>]

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On Tuesday 08 February 2011 16:29:17 ext Sjur Brændeland, you wrote:
> From: Sjur Brændeland <sjur.brandeland@stericsson.com>
> 
> Thanks for lots of useful feedback from last RFC,
> here is my next revision on the LTE/IMS API.
> Comments are still very much welcome!
> 
> Changes from RFC-V1:
> 	- Renamed IMS to IpMultimediaSubsystem (some places)
> 	- Changed registration of IMS application.
> 	- Moved IMS Identities to a separate interface
> 	- Dropped the entire TFT/QoS info.
> 	  Instead oFono checks the QoS SIP Preconditions.
> 	  IMS application is notified about changes in QoS,
> 	  and asks oFono if the QoS SIP preconditions are
> 	  satisfied.
> ---
>  doc/ims-api.txt |  162
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed,
> 162 insertions(+), 0 deletions(-)
>  create mode 100644 doc/ims-api.txt
> 
> diff --git a/doc/ims-api.txt b/doc/ims-api.txt
> new file mode 100644
> index 0000000..5404e61
> --- /dev/null
> +++ b/doc/ims-api.txt
> @@ -0,0 +1,162 @@
> +Ip Multimedia Subsystem hierarchy [experimental]
> +=================================
> +
> +Service		org.ofono
> +Interface	org.ofono.IpMultimediaSubsystem
> +Object path	[variable prefix]

I guess this is meant to be a modem object path, but it seems the oFono 
documentation is already a bit sloppy on this point.

> +Methods		dict GetProperties()
> +
> +			Returns all IMS properties. See the
> +			properties section for available properties.
> +
> +		void Register(string type)
> +
> +			Register a IMS Application. It must register
> +			with one of the types:
> +			"voice", "messaging", "voice_messaging".

I am not very familiar with the underlying protocol... If it really makes 
sense to register both services simultaneously, then I think we should have an 
array of strings. Or if there are no benefits, then why bother with 
'voice_messaging' anyway.

> +			This registration will inform modem's radio
> +			stack that the IMS application has registered
> +			for Voice and/or Messaging over IMS.
> +			This registration may impact "UE Mode of operation"
> +			and the ISR feature in the radio stack.
> +
> +			The registered application is tracked, if the
> +			application exits the registration will be
> +			automatically released.
> +
> +			Related AT command: AT+EISR.

Is this a standard command? As it is not in the 3GPP namespace (AT+C...), it 
might be nice to provide a reference pointer.

> +			Possible Errors: [service].Error.InvalidArguments
> +
> +		void UnRegister(object path)
> +
> +			Un-register a IpMultimediaSubsystemAgent.
> +
> +			Possible Errors: [service].Error.InvalidArguments
> +
> +		boolean PreConditionCheck(string Type, string PeerAddress,
> +					uint16 PeerPort,  uint16 LocalPort)
> +
> +			This method is used by the IMS application to check
> +			if the QoS SIP precondition is fulfilled.
> +
> +			The IMS application should call this method when
> +			receiving a PreConditionChanged() signal.
> +			The IMS Application is not allowed to start alerting
> +			before it has confirmed that it has a voice-ready
> +			Dedicated Bearer and QoS set up in the network.
> +
> +			The legal parameter for Type currently is currently
> +			"voice" only. In future "video" (Conversational Video,
> +			Live Streaming) will be added.
> +
> +			PeerAddress can be IPv4 or IPv6 address. PeerPort and
> +			LocalPort is the RTP port used for the media stream.
> +
> +			This method returns true if the Traffic Flow Template
> +			read from the modem matches the address information
> +			provided, and the QCI and Bit Rates fulfills the
> +			requirements for the specified type.
> +
> +			Related AT commands: AT+CGEQOSRDP, AT+CGTFTRDP
> +
> +			NOTE:	Should the "Type" parameter be removed?
> +				Maybe IMS-video still is a bit futuristic.

That stuff is per context. Should it not be in the context object rather than 
in the IMS manager?

> +
> +Signals		PropertyChanged(string property, variant value)
> +
> +			This signal indicates a changed value of the given
> +			property.
> +
> +		void PreConditionChanged()
> +
> +			This signal is sent when the network has changed
> +			the QoS or Packet Filters for a Bearer.
> +			The IMS application can then check the QoS SIP
> +			preconditions by calling PreConditionCheck().
> +
> +			Only QoS information relevant for IMS will be
> +			signaled, i.e. QCI=1 for voice and QCI=2 for video.
> +
> +			Related AT commands: AT+CGEREP,
> +			+CGEV: NW ACT, +CGEV: NW MODIFY
> +
> +Properties
> +		array{object} Identities [readonly]
> +
> +			Array of IP Multimedia Identities objects and
> +			properties.
> +			NOTE:	It is assumed that Identities will not change.
> +
> +		boolean VoiceOverPs [readonly]
> +
> +			IMS voice is enabled by network
> +			Related AT command: AT+CIREP.
> +
> +		string CsHandoverProgress [readonly, optional]
> +
> +			Indicates the handover progress status during a CS
> +			fallback procedure. The possible values are:
> +				"started"  - CS Fallback procedure has started
> +				"complete" - CS Fallback procedure has completed
> +				"failure"  - CS Fallback has failed
> +				"idle"     - No CS call or fallback is ongoing
> +
> +			Related AT URC: +CIREP
> +
> +		array{string} PcscfAddresses [readonly]
> +
> +			Domain Name or IP Address of the SIP Proxy.
> +			The P-CSCF address returned in EPS signaling as
> +			as part of the Default Bearer setup will be used.
> +			The addresses may be of type IPv4 and/or IPv6.
> +			If no P-CSCF data is available the information from
> +			EFp-cscf will be used.
> +
> +			Related AT command: AT+CGCONTRDP
> +
> +			NOTE:	If an operator can have more than one
> +				IMS-APN with different set of pcscf servers,
> +				this property must be moved to the
> +				ConnectionContext object.

Should this be in the context object? The AT command is per CID. Would it make 
any sense for a network to have different P-CSCF based on the bearer?

> +IP Multimedia Identities hierarchy [experimental]
> +==================================
> +
> +Service		org.ofono
> +Interface	org.ofono.IpMultimediaIdentities
> +Object path	[variable prefix]
> +
> +
> +Methods		dict GetProperties()
> +
> +			Returns all IMS identitiy properties.
> +
> +			Possible Errors: [service].Error.InvalidArguments
> +
> +			NOTE:	No PropertyChanged signal is supported.
> +				Technically it is possible for provisioning
> +				to update these identities, but 3gpp TS31.103
> +				discourages this.
> +
> +Properties	string PrivateIdentity [readonly]
> +
> +			The Private Identity is used to allow the UE access
> +			to the IMS network (registration, authorization,
> +			administration and billing).
> +
> +		array{string} PublicIdentity [readonly]
> +
> +			The Public Identity is used to identify a specific
> +			IMS user (there may be more than one associated
> +			with one Private Identity). This information is conveyed
> +			to the IMS Network during registration so that the
> +			network can know what IMS users that are registered and
> +			available for service (e.g. a reception of a voice
> +			session).
> +
> +		string HomeDomainName[readonly]
> +
> +			Identity used for IMS registration.


-- 
Rémi Denis-Courmont
Nokia Devices R&D, Maemo Software, Helsinki