First, quoting from a msg from Christian Huitema - Subject:Re: General Media Descriptor - SDP, sent Sept 17/99, 9am: -----------
A reasonable assumption is that [we] the current MGCP parameters will be defined in the combination of at least two packages, one generic (Usage of echo cancellation, Usage of silence suppression or voice activity detection, Usage of signal level adaptation and noise level reduction, or "gain control") and one specific to RTP (Encoding Method, Packetization period, Bandwidth, Type of Service, Usage of reservation service, Usage of RTP security).
There is however one subparameter of MGCP's LocalConnectionOptions that does not fit squarely into the "package" approach. The "Type of network" is used to specify whether the new connection should be built over IP, Frame relay, ATM, etc. This is quite useful in multi-protocol gateways, specially if we decide that termination names have no structure and no implied meaning. If a gateway receives a command such as: Transaction=x{ ctx=$ { add=${...}}}, how can it decide whether to create an RTP connection, rather than using AAL2?
I suggest that a "type of network" attribute be added as a generic subparameter in the LocalControl definition.
-- Christian Huitema
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Here is what I propose go into the generic and rtp packages (i.e. added to draft-ietf-megaco-basicpkg-00.txt, and to APC-1666).
Question: I have put Preferred Encoding and Decoding Methods as part of the rtp package - do they go there, or should they be in the generic package?
3.x Generic Package Package Id: g
3.x.1 Properties
The following properties are to be used in the LocalControlDescriptor of the StreamDescriptor. The LocalControlDescriptor contains parameters used by the MGC to direct the handling of the stream by the MG. The scope of this information is local to the MG-MGC association.
3.x.1.1 Echo Cancellation
PropertyId: ec
Description By default, the telephony gateways always perform echo cancellation. However, it is necessary, for some calls, to turn off these operations.
Values The echo cancellation parameter can have two values: - "on" (when the echo cancellation is requested) and - "off" (when it is turned off.) The default is "on".
3.x.1.2 Silence suppression PropertyId: ss
Description The media gateway may perform silence suppression, or voice activity detection, and avoid sending packets during periods of silence. However, it is necessary, for example for modem calls, to turn off this detection.
Values The silence suppression parameter can have two values, "on" (when the voice activity detection is requested) and "off" (when it is turned off.) The default is "off."
3.x.1.3 Gain Control PropertyId: gain
Description Gain control, or usage of of signal level adaptation and noise level reduction is used to adapt the level of the signal. However, it is necessary, for example for modem calls, to turn off this function.
Values The gain control parameter may either be specified as "automatic", or as an explicit number of decibels of gain. The default is to not perform gain control, which is equivalent to specifying a gain of 0 decibels.
3.x.1.4 Network Type PropertyId:network
Description: The MGC may instruct the MG to prepare the connection on a specified type of network.
Values: The type of network is encoded as in the "connection-field" parameter of the SDP standard. Possible values are IN (Internet), ATM and LOCAL. The parameter is optional; if absent, the network is determined by the MG.
[Tom - you are proposing that this be a list of packages I think. Is that what we want, or do we want strings such as RTP/IP4, or RTP, or AAL2,....]
3.15 RTP Package ID: rtp
This package is used to support packet based multimedia data transfer by means of the Real-time Transport Protocol (RTP).
3.15.1 Properties The following properties are to be used in the LocalControlDescriptor of the StreamDescriptor. The LocalControlDescriptor contains parameters used by the MGC to direct the handling of the stream by the MG. The scope of this information is local to the MG-MGC association.
3.15.1.1 Preferred Encoding Method PropertyId: em
Description Allows the MGC to specify the encoding method to be used by the MG.
Values The encoding will be compatible with the SDP and RTP profiles.
The encoding method shall be specified by using one or several valid encoding names, as defined in the RTP AV Profile or registered with the IANA.
The MGC may state exactly one value, which the MG will then use for the connection.
The MGC may provide a loose specification, such as a list of allowed encoding methods, and if this is the case, they are put in order of preference, most preferred first.
The MGC may simply provide a bandwidth indication, leaving the choice of encoding/decoding method and packetization period to the MG.
3.15.1.2 Preferred Decoding Method PropertyId: dm
Description
Values The decoding will be compatible with the SDP and RTP profiles:
The decoding method shall be specified by using one or several valid decoding/encoding names, as defined in the RTP AV Profile or registered with the IANA.
The MGC may state exactly one value, which the MG will then use for the connection,
The MGC may provide a loose specification, such as a list of allowed decoding methods, and if this is the case, they are put in order of preference, most preferred first.
The MGC may simply provide a bandwidth indication, leaving the choice of encoding/decoding method and packetization period to the MG.
3.15.1.3 Preferred packetization period PropertyId: ptime
Description Allows the MGC to specify the decoding method to be used by the MG.
Values The packetization period is encoded as either the length of time in milliseconds represented by the media in a packet, as specified in the "ptime" parameter of SDP, or as a range value, specifying both the minimum and maximum acceptable packetization periods.
The MGC may state exactly one value, which the MG will then use for the connection.
The MGC may provide a loose specification, such as a range of packetization periods, and if this is the case, they are put in order of preference, most preferred first.
The MGC may simply provide a bandwidth indication, leaving the choice of encoding/decoding method and packetization period to the MG.
3.15.1.4 Bandwidth PropertyId: ba
Description The bandwidth specification shall not contradict the specification of encoding methods and packetization period. If an encoding method is specified, then the gateway is authorized to use it, even if it results in the usage of a larger bandwidth than specified.
Values The bandwidth is encoded as either a single value or a range, expressed as an integer number of kilobit per seconds.
The MGC may state exactly one value, which the MG will then use for the connection.
The MGC may simply provide a bandwidth indication, leaving the choice of encoding/decoding method and packetization period to the MG.
3.15.1.5 Type of service PropertyId: tos
Description The Type of Service specifies the class of service that will be used for the connection.
Values When the connection is transmitted over an IP network, the parameters encodes the 8-bit type of service value parameter of the IP header. When the Type of Service is not specified, the gateway shall use a default or configured value.
3.15.11.6 Reservation Service PropertyId: resv
Description The gateways can be instructed to perform a reservation, for example using RSVP, on a given connection. When reservation has been asked on a connection, the gateway will:
* start emitting RSVP "PATH" messages if the connection is in "send- only", "send-receive", "conference", "network loop back" or "net- work continuity test" mode (if a remote connection descriptor has been received,)
* start emitting RSVP "RESV" messages as soon as it receives "PATH" messages if the connection is in "receive-only", "send-receive", "conference", "network loop back" or "network continuity test" mode.
The RSVP filters will be deduced from the characteristics of the connection. The RSVP resource profiles will be deduced from the connection's bandwidth and packetization period.
Values When a reservation is needed, the MGC will specify the reservation profile that should be used, which is either "controlled load" or "guaranteed service." The absence of reservation can be indicated by asking for the "best effort" service, which is the default value of this parameter.
3.15.1.7 RTP security PropertyId: encr
Description The MGC can request the MG to enable encryption of the audio Packets.
Values It does so by providing a key specification, as specified in RFC 2327. By default, encryption is not used.
3.15.1.8 Maximum Jitter Buffer PropertiyId: jit
Description This property puts a maximum size on the jitter buffer.
Values This property is specified in milliseconds. ---------
Nancy -------------------------------------------------------------------------- Nancy M. Greene Internet & Service Provider Networks, Nortel Networks T:514-271-7221 (internal:ESN853-1077) E:ngreene@nortelnetworks.com
From: Chip Sharp[SMTP:chsharp@CISCO.COM] Sent: Friday, October 15, 1999 8:53 AM To: megaco@standards.nortelnetworks.com Subject: LocalControl Descriptor Parameters
Maybe I'm missing something obvious, but In the ABNF and the spec it says that the parameters for the LocalControlDescriptor are propertyParm = pkgdName propertyValue
This implies that the parameters for the LocalControlDescriptor are defined in packages. However, in the only package I've seen submitted to SG16 and discussed (APC-1666), I don't see any parameters defined for LocalControlDescriptor. For example, where is the package that defines parameters such as Codec=G.711, echocontrol=ON, gain=2dB, etc.?
Thanks, Chip Support NetAid! http://www.netaid.org
Chip Sharp Consulting Engineering Cisco Systems Telco Bio-region Reality - Love it or Leave it.
Nancy M. Greene Internet & Service Provider Networks, Nortel Networks T:514-271-7221 (internal:ESN853-1077) E:ngreene@nortelnetworks.com