LocalControl Descriptor Parameters
Nancy-M Greene
ngreene at NORTELNETWORKS.COM
Fri Oct 15 15:08:04 EDT 1999
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
----------
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 at nortelnetworks.com
> ----------
> From: Chip Sharp[SMTP:chsharp at CISCO.COM]
> Sent: Friday, October 15, 1999 8:53 AM
> To: megaco at 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 at nortelnetworks.com
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