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SG
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... delivery from an ISDN Signaling Gateway (SG) to a Media Gateway
Controller (MGC) as described in the Framework ...
... Q.921/Q.931 boundary primitives
* Support for communication between Layer Management modules on SG
and MGC
* Support for management of SCTP ...
... Gateways. Practically speaking, an AS is modeled at
the SG as an ordered list of one or more related Application Server
Processes (e.g., primary, secondary, tertiary).
...
... adaptation layer peer messages.
Backhaul - A SG terminates the lower layers of an SCN protocol and
backhauls the upper layer ...
... MGC for call processing. For the
purposes of this document, the SG terminates Q.921 and backhauls
Q.931 ...
... Interface Identifier identifies the
physical interface at the SG for which the signaling messages are
sent/received. The format of the Interface Identifier ...
... network operator policy. The values used are of local significance
only, coordinated between the SG and ASP. Significance is not
implied across SGs served by an AS ...
... is received over a standard ISDN network termination. The SG then
provides interworking of transport ...
...
The IUA layer at the SG maintains the availability state of all
dynamically registered remote ASPs ...
... ASPs, in order to manage the SCTP
associations and the traffic between the SG and ASPs. As well, the
active ...
... call processing capability. All Q.921-User
messages incoming to an SG are assigned to a unique Application
Server, based on the Interface Identifier of the message.
...
...
It is recommended that the SG and ASP be able to support both client
and server operation. The peer endpoints ...
... role of server for initiating SCTP associations. The
default orientation would be for the SG to take on the role of server
while the ASP ...
... Support for Communication between Layer Management Modules on SG ...
... that will facilitate communication between Layer Management modules
on the SG and MGC. These primitives are shown below:
M-TEI STATUS ...
... SCTP
association(s) between the SG and MGC. The IUA layer can be
instructed by the Layer Management ...
... The ASP status is stored inside IUA layer on both the SG and MGC
sides. The M-ASP STATUS primitive can be used by Layer Management ...
... TDM) timeslot. In addition, for a given
interface the SG MUST be able to identify the associated signaling
channel ...
... channel. IUA layers on both SG and MGC MAY maintain the status of
ISDN Terminal Endpoint Identifiers ...
... Interface Identifier, AS, and ASP in the SG is shown below:
/---------------------------------------------------+
...
... state transition procedures are described in Section 4.3.1.
At a SG, an Application Server list MAY contain active and inactive
...
... ASPs within a logical Application Server is kept
updated in the SG to reflect the active Application Server
Process(es).
...
... SCTP association fails, the IUA layer on both the SG
and ASP sides MAY generate Release primitives to take the data links ...
... signaling channel
at the SG for which the signaling messages are sent/received. The
format of the Interface Identifier ...
... policy. The integer values used are of local significance only,
coordinated between the SG and ASP.
...
... SG receives an IUA Establish Request from the MGC, the SG
shall send the Q.921 Establish Request primitive to the Q.921 ...
... ASP Up (ASPUP) message is sent by an ASP to indicate to an SG
that it is ready to receive traffic or maintenance messages.
...
... locally significant among the ASPs that support an AS. The SG should
save the ASP Identifier ...
... ASP Down (ASPDN) message is sent by an ASP to indicate to an SG
that it is NOT ready to receive traffic or maintenance messages.
...
... The ASPAC message is sent by an ASP to indicate to an SG that it is
Active and ready to be used.
...
... ASP Up message (see Section 3.3.2.1.).
An SG that receives an ASPAC with an incorrect Traffic Mode Type for
...
... ASP to be used from within a list of ASPs. The
SG will respond with an ASPIA Ack message and either discard incoming
...
...
The "Invalid Interface Identifier" error would be sent by an SG if an
ASP sends a message with an invalid (unconfigured) Interface
Identifier ...
...
The "Unsupported Traffic Handling Mode" error would be sent by an SG
if an ASP sends an ASP Active ...
... ASP Active with an unsupported Traffic Handling
Mode. An example would be a case in which the SG did not support
load-sharing.
...
... also be sent by an ASP if it received a defined and recognized
message that the SG is not expected to send (e.g., if the MGC
receives an IUA ...
... The "Unsupported Interface Identifier Type" error would be sent by an
SG if an ASP sends a text-formatted Interface Identifier and the SG ...
... SG if an ASP sends a text-formatted Interface Identifier and the SG
only supports integer-formatted Interface Identifiers ...
...
The "Unassigned TEI" error may be used when the SG receives an IUA
message that includes a TEI ...
...
The "Unrecognized SAPI" error would handle the case of using an SAPI
that is not recognized by the SG. The "Invalid TEI, SAPI
combination" error identifies errors where the TEI ...
... IUA when Layer Management at the
SG SHOULD be performing this function).
The "Refused - Management ...
... The "ASP Identifier Required" is sent by an SG in response to an ASP
Up message that does not contain an ASP Identifier ...
... ASP Identifier parameter when the
SG requires one. The ASP SHOULD resend the ASP Up message with an
...
... The "Invalid ASP Identifier" is sent by a SG in response to an ASP Up
message with an invalid (i.e., non-unique) ASP ...
...
These notifications are sent from an SG to an ASP upon a change in
status of a particular Application Server ...
... AS. In the Insufficient ASP Resources case, the
SG is indicating to an ASP-INACTIVE ASP(s) in the AS ...
... ASP MUST be placed
in the message. For the ASP Failure case, the SG is indicating to
ASP(s) in the AS ...
... service allows the
ASP to request the SG to establish the datalink to the terminal (via
the IUA ...
... IUA header MUST be ignored by the SG. The SG will respond to
this message with TEI Status Indication(s).
...
... AS that it is configured, is
maintained in the IUA layer on the SG. The state of an ASP changes
...
... the Upper Layer Protocol (IUA) on an SG. The local SCTP will send
this indication when it detects the loss of connectivity to the ASP ...
... Restart indication to the upper layer
protocol (IUA) on an SG. The local SCTP will send this indication
when it detects a restart ...
... timer T(r) will be started and all incoming SCN messages will be
queued by the SG. If an ASP becomes active before T(r) expires, the
...
... If T(r) expires before an ASP becomes active, the SG stops queuing
messages and discards all previously queued messages. The AS will
...
... association with the remote IUA peer at
an SG. Upon reception of an eventual SCTP-Communication Up confirm
primitive from the SCTP ...
... The Layer Management and the IUA layer on SG can communicate the
status of the application server using the M-AS ...
... The Layer Management and the IUA layer on both the SG and ASP can
communicate the status of an SCTP ...
...
When an ASP Up message is received at an SG and internally the remote
ASP is in the ASP-DOWN ...
... state and not considered locked out for local
management reasons, the SG marks the remote ASP in the state
...
... Layer Management with an M-ASP_Up indication
primitive. If the SG is aware, via current configuration data, which
Application Servers ...
... Identifier for that ASP. The SG MUST send an ASP Up Ack message in
response to a received ASP Up ...
...
If for any local reason (e.g., management lockout) the SG cannot
respond with an ASP Up Ack message, the SG ...
... SG cannot
respond with an ASP Up Ack message, the SG responds to an ASP Up
message with an Error message ...
... ASP Up message is received (other than ASP Down;
see Section 4.3.3.2), the SG MAY discard them.
If an ASP Up ...
... ASPs initiate the ASP Up procedure it is assumed that the Error
message would normally come from the SG.
...
...
If the Application Server can be successfully activated, the SG
responds to the ASP with an ASPAC ...
... ASP Active message is received
(i.e., the ASP has not registered with the SG or the SG has no static
configuration data ...
... (i.e., the ASP has not registered with the SG or the SG has no static
configuration data for the ASP ...
... ASP
Active Ack message as the ASP Active Ack and Data messages from an SG
may be sent on different SCTP streams. Message loss is possible as
...
... The ASP MUST wait for the ASP Active Ack message from the SG before
sending any Data messages or it will risk message loss. If the SG ...
... SG before
sending any Data messages or it will risk message loss. If the SG
receives QPTM messages before an ASP Active ...
... receives QPTM messages before an ASP Active is received, the SG
SHOULD discard these messages.
...
... There are two modes of Application Server traffic handling in the SG
IUA: Over-ride and Load-sharing. The Type parameter in the ASPAC ...
... message indicates the mode used in a particular Application Server.
If the SG determines that the mode indicates in an ASPAC is
incompatible with the traffic ...
... traffic handling mode currently used in the AS,
the SG responds with an Error message indicating Unsupported Traffic
...
... AS, reception of an ASPAC message at
an SG causes the redirection of all traffic for the AS to the ASP ...
... ASP
that sent the ASPAC. The SG responds to the ASPAC with an ASP Active
Ack message to the ASP ...
... AS is now
considered Inactive and will no longer receive traffic from the SG
within the AS. The SG ...
... AS, reception of an ASPAC message at
an SG causes the direction of traffic to the ASP sending the ASPAC ...
... assumptions of the collection of ASPs in the AS. The SG responds to
the ASPAC with an ASP Active Ack ...
... the ASP sends an ASP Inactive message to the SG. This action MAY be
initiated at the ASP by an M-ASP_INACTIVE ...
... There are two modes of Application Server traffic handling in the SG
IUA when withdrawing an ASP ...
... ASP that sends the ASPIA message is already considered
by the SG to be ASP-INACTIVE. An ASPIA Ack message ...
... buffering the incoming messages for T(r) seconds, after
which messages MAY be discarded. T(r) is configurable by the network
operator. If the SG receives an ASP Active message from an ASP in
...
...
In the case where a Notify ("AS-Pending") message is sent by an SG
that now has no ASPs active ...
... message flows for the
establishment of traffic between an SG and two ASPs in the same
Application Server ...
... message flows for the
establishment of traffic between an SG and three ASPs in the same
Application Server ...
... message flows for the
establishment of traffic between an SG and an ASP in which some of
the Interface Identifiers ...
... Interface Identifiers have been misconfigured on the ASP side.
The SG in this case has Interface Identifiers 1-5 configured for
ASP1 ...
... AS-ACTIVE)----------------->|
In this case, the SG notifies ASP2 that the AS has moved to the Down
...
... AS has moved to the Down
state. The SG could have also (optionally) sent a Notify message
when the AS moved to the Pending state ...
... heartbeat loss or
detection of SCTP failure), the initial SG-ASP1 ASP Inactive message
exchange ...
... | | | |
In this case, the SG has knowledge of the minimum ASP resources
required (implementation dependent), for example, if the SG ...
... SG has knowledge of the minimum ASP resources
required (implementation dependent), for example, if the SG knows
that n+k = 2+1 for a load-share AS and n currently equals 1.
...
... association between MGC
and SG is established (Section 5.1) prior to the following message
flows.
...
... An example of the message flows for communication between Layer
Management modules between SG and ASP is shown below. An active
...
... association between ASP and SG is established (Section 5.1) prior to
the following message flows.
...