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Network Working Group Brian Bidulock
INTERNET-DRAFT OpenSS7 Corporation
Expires in six months January 2, 2003
Load Grouping Extension
for
Signalling User Adaptation Layers
<draft-bidulock-sigtran-loadgrp-01.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 or RFC 2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
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Abstract
This Internet-Draft describes an extension parameter and procedure
to the Signalling User Adaptation Protocols [IUA...TUA], based on the
Stream Transmission Control Protocol (SCTP) [RFC 2960] which permits
an Application Server Processes (ASP) to indicate its placement within
a Load Group and permits an Signalling Gateway (SG) to distribute
traffic over Load Groups under Application Server Process (ASP)
control.
The described procedure provides for Override, Load-share and
Broadcast traffic mode operation within a Load Group consisting of one
or more Application Server Processes (ASPs) resulting in a mixture of
traffic modes within an Application Server (AS). The parameters and
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procedures described here supplement the UA Load Selection [LOADSEL]
extension parameters and procedures for improved distribution of
traffic over ASPs and Signalling Gateway Processes (SGPs).
1. Introduction
1.1. Scope
This Internet-Draft provides the Load Distribution parameter and
associated procedures in extension to the parameters and procedures of
the Signalling User Adaptation Layers (UAs) [IUA...TUA], and the UA
Load Selection [LOADSEL] extension, for the purpose of permitting
Application Server Process control over grouping of ASPs into
Application Servers as part of the procedures of these UA protocols.
This Load Grouping extension is intended to be compatible with UA
implementations not supporting this extension.
1.2. Change History
Changes from Version 0.0 to Version 0.1:
- added this section,
- updated release version and dates,
- updated references,
- updated postscript diagrams,
- minor formatting changes,
- reworked the procedures section,
- added interworking rules,
- change Load Selection to Load Selector to match LOADSEL
[LOADSEL],
- added examples,
- updated author's address.
1.3. Terminology
LOADGRP supplements the terminology used in the UA documents
[IUA...TUA] and the UA Load Selection [LOADSEL] extension by adding
the following terms:
Load Distribution (LD) - a Traffic Mode Type which is applicable
within a Load Group.
Load Group (LG) - a group of ASPs that share the same traffic
distribution within an Application Server. An ASP is permitted to
belong to more than one Load Group for a given AS.
Load Selector (LS) - an identifier that uniquely identifies a Load
Group within an Application Server. This identifier is only
guaranteed unique within the scope of an Application Server and
must be combined with a Routing Context or (set of) Interface
Identifier(s) to uniquely define a Load Group at a Signalling
Gateway.
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Signalling User Adaptation Layer (UA) - one or more of the Stream
Control Transmission Protocol (SCTP) [RFC 2960] Signalling User
Adaptation Layers [IUA...TUA].
1.4. Overview
Existing UA procedures with regard to traffic distribution and ASP
traffic management provide a mechanism to select the algorithm for
coordinating state and distributing traffic over a number of
Application Server Processes (ASPs) serving an Application Server.
These existing procedures provide only simplified distribution
approaches which are not amenable to large scale systems that need to
adapt to dynamic traffic loading or need live reconfiguration for
maintenance purposes.
LOADGRP extensions to the Signalling User Adaptation Layers
[IUA...TUA] permits close control over the grouping of Application
Server Processes serving an Application Server that provides the
capability to group ASPs into load groups not existing in the current
scheme.
Under the existing approach, each Application Server Process acts
independently with respect to an Application Server. This approach
does not provide for the grouping of ASPs into work groups, not does
it provide coordinated control of the role of groups of ASPs serving
an ASP. As a result, the existing scheme does not scale well in this
regard.
LOADGRP provides for the grouping of ASPs into load groups with a
traffic distribution mode (Load Distribution) within the load group
that is independent of the Application Sever traffic mode.
1.4.1. Existing Traffic Distribution
Figure 1 illustrates the existing traffic distribution algorithm
that is used across the Signalling User Adaptation Layers.
When an SGP distributes a Signalling User Adaptation Layer message
toward the Application Server based on the Routing (Link) Key, it
selects an ASP that is active for the AS according to a Traffic Mode
Type that is associated with the AS. The Traffic Mode Type describes
three general distribution algorithms: Override, Load-share and
Broadcast.
The detailed actions taken for these distribution algorithms are
described in Section 4 of the Signalling User Adaptation Layer
specifications [IUA...TUA]; however, they can be summarized as
follows:
Traffic Mode Type Override:- When distributing messages to an
Override Application Server, the SGP selects the ASP which is
active for the Application Server. In an Override Application
Server, at most one ASP can be active for the AS at any given point
in time. The active ASP for the AS is selected.
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____
Traffic /....\
Mode Type ____|__....|
_______ | |...|
| |------------------->| ASP |...|
| SGP |-----\ |_______|...|
|_______|----\ \ ____|__....|
\--\ \ \ | |...|
\ \ \---------->| ASP |...|
_______ \ \ |_______|...|
| | \ \ |......| Application
| SGP | \ \ |......| Server
|_______| \ \ |......|
\ \ |......|
\ \ ____|__....|
\ \ | |...|
\ \---->| ASP |...|
\ |_______|...|
\ ____|__....|
\ | |...|
\-->| ASP |...|
|_______|...|
|......|
\____/
Figure 1. Existing Traffic Distribution
Traffic Mode Type Load-share:- When distributing messages to a Load-
share Application Server, the SGP selects one of the ASPs that are
active for the Application Server using an implementation dependent
load-sharing algorithm based on some unspecified aspect of the
traffic or static configuration data.
Traffic Mode Type Broadcast:- When distributing messages to a
Broadcast Application Server, the SGP sends a copy of the message
to each of the ASPs that are active for the Application Server.
(The ASPs themselves decide which, if any, of the ASPs will process
the message.)
In general, for the Signalling User Adaptation Layers, the Traffic
Mode Type is a characteristic of the Application Server, and an
Application Server can only have associated with it only one Traffic
Mode Type, and thus, only one traffic distribution algorithm can be
used across the ASPs that are serving a given Application Server.
LOADGRP enhances the traffic distribution algorithms of the
existing Signalling User Adaptation Layers by introducing an
additional level of distribution.
1.4.2. Extended Traffic Distribution
Figure 2 illustrates the extended traffic distribution algorithms
that are used across the Signalling User Adaptation Layers as a result
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____ ____
Traffic Load /....\ /....\
Mode Type Group|...___||__....|
_______ |..| |...|
| |---+---------------->| ASP |...|
| SGP | \ |..|_______|...|
|_______|-\ \ |...___||__....|
\ \ |..| |...|
\ \------------>| ASP |...|
_______ | |..|_______|...|
| | | |......||......| Application
| SGP | | \____/ |......| Server
|_______| | ____ |......|
| Load /....\ |......|
| Group|...___||__....|
| |..| |...|
+---------------->| ASP |...|
\ |..|_______|...|
\ |...___||__....|
\ |..| |...|
\------------>| ASP |...|
|..|_______|...|
|......||......|
\____/ \____/
Figure 2. Load Group Traffic Distribution
of the messages and procedures in LOADGRP.
LOADGRP introduces the concept of a Load Group. A Load Group is a
logical grouping of Application Server Processes (ASPs) into traffic
groups serving an Application Server. Signalling Gateway Processes
(SGPs) distribute traffic first over Load Groups and then distribute
traffic within the Load Group. Each Load Group describes and is
identified by a Load Selector [LOADSEL] within the Application Server.
The Load Selector identifies the traffic flows that will be
distributed to an associated Load Group within an Application Server.
When an SGP distributes a Signalling User Adaptation Layer message
toward an Application Server based on the Routing (Link) Key, it first
selects an Load Group that is active for the Application Server
according a traffic distribution algorithm determined by the Load
Distribution that is associated with the Application Server and the
Load Selector position of the Load Group within the AS.
The Traffic Mode Type continues to describe three general
distribution algorithms: Override, Load-share and Broadcast. The
change in the behavior of the SGP when selecting an ASP for traffic
distribution introduced by LOADGRP is that the SGP also takes into
account the concept of a Load Group as identified within an AS by its
Load Selector.
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The extended procedures can be summarized as follows:
Traffic Mode Type Override:- When distributing messages to an
Override Application Server, the SGP first selects the Load Group
that is active for the Application Server. In an Override
Application Server, at most one Load Group can be active for the AS
at any given point in time. The active Load Group for the AS is
selected.
Traffic Mode Type Load-share:- When distributing messages to a Load-
share Application Server, the SGP selects one of the Load Groups
that are active for the Application Server using an implementation
dependent load-sharing algorithm based on the Load Selector
[LOADSEL] associated with the Load Group.
Traffic Mode Type Broadcast:- When distributing messages to a
Broadcast Application Server, the SGP sends a copy of the message
to each of the Load Groups that are active for the Application
Server. (The Load Groups themselves decide which, if any, of the
Load Groups will process the message.)
After selecting an Load Group according to the Traffic Mode Type
for the Application Server, the SGP then selects an ASP within the
Load Group based on the Load Distribution that is associated with the
Load Group. The Load Distribution describes the same three general
distribution algorithms that are provided in the Traffic Mode Type:
Override, Load-share and Broadcast. When selecting an active ASP
within a Load Group, the procedures that the SGP will follow can be
summarized as follows:
Load Distribution Override:- When distributing messages within an
Override Load Group, the SGP selects the ASP which is active for
the Load Group. In an Override Load Group, at most one ASP can be
active for the Load Group at any given point in time. The active
ASP for the Load Group is selected.
Load Distribution Load-share:- When distributing messages within a
Load-share Load Group, the SGP selects one of the ASPs that are
active for the Load Group using an implementation dependent load-
sharing algorithm based on some unspecified aspect of the traffic
or static configuration data.
Load Distribution Broadcast:- When distributing messages within a
Broadcast Load Group, the SGP sends a copy of the message to each
of the ASPs that are active for the Load Group. (The ASPs
themselves decide which, if any, of the ASPs will process the
message.)
The result of LOADGRP is that two levels of traffic distribution
are provided for, permitting more flexible membership of ASPs serving
Application Servers, and provides the Application Server Process with
more control over the traffic patterns for which it is active.
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1.5. Sample Configurations
Although LOADGRP does not restrict either Traffic Mode Type or Load
Distribution to a static assignment, there are, for example, six (6)
combinations of static Traffic Mode Type and Load Distribution
assignment under this scheme. Not all of these combinations provide
for interesting or useful configurations as follows:
Table 1. Sample Configurations
+----+----------+----------+---------------------------------------+
| | Traffic | Load | |
|Mode| Mode | Distri- |Description |
| | Type | bution | |
+----+----------+----------+---------------------------------------+
| 1 |Override |Load-share|This mode permits a load-share group |
| | | |of ASPs to override another load-share |
| | | |group of ASPs. |
+----+ +----------+---------------------------------------+
| 2 | |Broadcast |This mode allows "mirrored" ASPs to |
| | | |override each other. |
+----+----------+----------+---------------------------------------+
| 3 |Load-share|Override |This mode allows ASPs to override each |
| | | |other within a traffic slot of a load- |
| | | |share group. |
+----+ +----------+---------------------------------------+
| 4 | |Broadcast |This mode permits "striping" and |
| | | |"mirroring" with load-sharing under |
| | | |ASP control. |
+----+----------+----------+---------------------------------------+
| 5 |Broadcast |Override |This mode permits a joining ASP to |
| | | |knock another ASP out of a Broadcast |
| | | |slot for an Application Server. |
+----+ +----------+---------------------------------------+
| 6 | |Load-share|This mode permits "mirroring" and |
| | | |"striping" including automatic load- |
| | | |sharing within a mirror image. |
+----+----------+----------+---------------------------------------+
2. Conventions
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when they
appear in this document, are to be interpreted as described in [RFC
2119].
3. Protocol Elements
The following subsections describe the parameters which are added
by LOADGRP, their format and the message in which they are used.
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3.1. Parameters
LOADGRP adds one new parameter: the Load Distribution parameter.
3.1.1. Load Distribution
The Load Distribution parameter is used in the REQ REQ, REQ RSP,
ASPAC and ASPAC ACK messages. It is used in conjunction with the
Traffic Mode Type parameter [M2UA...TUA] and Load Selector parameter
[LOADSEL] to further refine the traffic distribution algorithm for an
ASP in a Load Group serving an Application Server. The Load Selector
parameter identifies the Load Group for which the ASP is registering,
activating or deactivating and the Load Distribution parameter
identifies the traffic distribution that is to be used within the Load
Group.
The Load Distribution parameter is formatted as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag = 0x001a | Length = 8 |
+ - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - +
| Load Distribution |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
EDITOR'S NOTE:- The parameter tag values shown as 0x001a
above will be assigned by IANA within the common parameter
range of the SIGTRAN UAs and may change its value in further
versions of this document.
The Load Distribution parameter contains the following fields:
Load Distribution field: n x 32-bits (unsigned integer)
The Load Distribution has the same purpose for the Load Group that
the Traffic Mode Type has for the Application Server: it identifies
the traffic distribution algorithm to be used within the Load Group.
Valid values for Load Distribution are as follows:
1 Override
2 Load-share
3 Broadcast
3.2. Messages
LOADGRP adds the Load Distribution parameter as an OPTIONAL
parameter to be used in conjunction with the common Traffic Mode Type
in the following messages: [1]
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REG REQ Registration Request message
ASPAC ASP Active message
ASPAC ACK ASP Active Ack message
3.2.1. Registration Request (REG REQ)
LOADGRP supplements the Registration Request (REG REQ) message by
permitting the following optional parameters to be included in the
Routing (Link) Key [M2UA...TUA] parameter or Link Key [IUA...M2UA]
parameter within the message:
Extension Sub-parameters
-----------------------------------------
Load Distribution Optional
The Load Distribution parameter is used in the Routing (Link) Key
to further refine the traffic distribution to be received by the
registering ASP.
The format of the resulting Routing Key or Link Key parameter is as
follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local-RK(LK)-Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Mode Type (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Load Selection (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Load Distribution (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ \
/ Routing Context /
\ or \
/ Interface Identifier(s) /
\ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
When an ASP wishes to register within a Load Group associated with
an Application Server, it includes the Load Selection parameter and
Load Distribution in the Routing (Link) Key for that Application
Server in the REG REQ message.
The Load Distribution parameter indicates the traffic distribution
method to be used within the Load Group as identified by the Load
Selection.
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No other changes to the REG REQ message, Routing Key or Link Key
parameters format are provided by LOADGRP[1].
3.2.2. Registration Response (REG RSP)
LOADGRP adds the following Registration Status values to the
)Registration Status field in the REG RSP message:
16 Error - Unsupported/Invalid Load Distribution
EDITOR'S NOTE:- The Registration Status value shown as 16
above will be assigned by IANA as a value of the UA-specific
Registration Status parameter for each SIGTRAN UA and may
change its value in further versions of this document.
3.2.3. ASP Active (ASPAC)
LOADGRP supplements the ASPAC message by permitting the following
optional parameters to be included in the message:
Extension Parameters
-----------------------------------------
Load Distribution Optional
The format of the resulting ASPAC message is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag = 0x000b | Length = 8 |
+ - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - +
| Traffic Mode Type |
+---------------------------------------------------------------+
\ \
/ Routing Context /
\ or \
/ Interface Identifier(s) /
\ \
+-------------------------------+-------------------------------+
| Tag = 0x001a | Length = 8 |
+ - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - +
| Load Distribution |
+-------------------------------+-------------------------------+
| Tag = 0x001d | Length = 8 |
+ - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - +
\ \
/ Load Selector(s) /
\ \
+-------------------------------+-------------------------------+
| Tag = 0x0004 | Length |
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+ - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - +
\ \
/ Info String /
\ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
EDITOR'S NOTE:- The parameter tag values shown as 0x001a
above will be assigned by IANA within the common parameter
range of the SIGTRAN UAs and may change its value in further
versions of this document.
When an ASP wishes to activate only within a Load Group associated
with an Application Server, it includes the Load Selector and Load
Distribution parameters in the ASPAC message.
The Load Distribution parameter indicates the traffic distribution
method to be used within the Load Group as identified by the Load
Selector.
No other changes to the ASPAC message format are provided by
LOADGRP[1].
3.2.4. ASP Active Ack (ASPAC ACK)
LOADGRP supplements the ASPAC ACK message by permitting the
following optional parameters to be included in the message:
Extension Parameters
-----------------------------------------
Load Distribution Optional
The format of the resulting ASPAC ACK message is as follows:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag = 0x000b | Length = 8 |
+ - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - +
| Traffic Mode Type |
+---------------------------------------------------------------+
\ \
/ Routing Context /
\ or \
/ Interface Identifier(s) /
\ \
+-------------------------------+-------------------------------+
| Tag = 0x001a | Length = 8 |
+ - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - +
| Load Distribution |
+-------------------------------+-------------------------------+
| Tag = 0x001d | Length = 8 |
+ - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - +
\ \
/ Load Selector(s) /
\ \
+-------------------------------+-------------------------------+
| Tag = 0x0004 | Length |
+ - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - +
\ \
/ Info String /
\ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
EDITOR'S NOTE:- The parameter tag values shown as 0x001a
above will be assigned by IANA within the common parameter
range of the SIGTRAN UAs and may change its value in further
versions of this document.
When an ASP has requested activation within a Load Group or the SG
otherwise activates the ASP within a Load Group the SG responds with
an ASPAC ACK message including the Load Selector that identifies the
Load Group and optionally includes the Load Distribution for the Load
Group in which the ASP has been activated. If the ASP included the
Load Distribution parameter in the ASPAC message, the SG MUST include
the Load Distribution parameter in the response ASPAC ACK message.
The Load Distribution parameter indicates the traffic distribution
method to be used within the Load Group as identified by the Load
Selector.
No other changes to the ASPAC ACK message format are provided by
LOADGRP[1].
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3.2.5. Error (ERR)
LOADGRP supplements the Error (ERR) message by adding the following
values to the common mandatory Error Code parameter in the ERR
message:
28 Unsupported Load Distribution
EDITOR'S NOTE:- The Error Code value shown throughout this
document as 28 will be assigned by IANA as a value of the
common Error Code parameter for SIGTRAN UAs and may change its
value in further versions of this document.
This new error code is interpreted as follows:
The "Invalid/Unsupported Load Distribution" error would be sent by an
SGP if an ASP sends an ASP Active with an invalid or unsupported
Load Distribution. An example would be a case in which the SGP
did not support override within a Load Group.
No other changes to the ERR message or Error Code parameter values
are provided by LOADGRP. See Section 4 for extension procedures
associated with the ERR message.
4. Procedures
LOADGRP provides for an additional level of control over the
traffic distribution patterns within an Application Server. LOADGRP
provides the Load Distribution parameter which may be optionally
included in the REG REQ, ASPAC and ASPAC ACK messages. In addition,
it supplements the ASP State Maintenance and ASP Traffic Maintenance
procedures.
4.1. ASP State Maintenance
In addition to the SGP maintaining the state of each remote ASP in
each Application Server that the ASP is configured to receive traffic,
under LOADGRP, the SGP MAY also maintain the state of each remote ASP
in each Load Group within an Application server that the ASP is
configured to receive traffic. The Load Group state is maintained
separate from the ASP and AS states.
4.1.1. Load Group State
The state of the Load Group is maintained in the Signalling User
Adaptation Layer on the SGPs. The state of the Load Group changes due
ASP state transitions. The possible states of a Load Group are:
LG-DOWN: The Load Group is unavailable. This state implies
that all related ASPs are in the ASP-DOWN state for
this Load Group. Initially, the Load Group will be in
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this state.
LG-INACTIVE: The Load Group is available but no application traffic
is active (i.e, one or more related ASPs are in the
ASP-INACTIVE state, but none are in the ASP-ACTIVE
state within the Load Group).
LG-ACTIVE: The Load Group is available and application traffic is
active. This state implies that at least one ASP is
in the ASP-ACTIVE state within the Load Group.
4.1.2. Application Server State
Where ASPs are configured for operation within Load Groups under
LOADGRP, the Application Server state is interpreted as provided in
the Signalling User Adaptation Layer specifications [M2UA...TUA].
4.2. ASP Traffic Maintenance
4.2.1. ASP Up Procedures
LOADGRP extends the ASP Up procedures to include the concept of the
Load Group.
Whenever an SGP moves an ASP to the ASP-UP state, it also moves the
ASP to the ASP-INACTIVE state in all Load Groups in all Application
Servers for which the ASP is configured. This may have the effect of
changing the Load Group state, requiring the generation of NTFY
messages as described under ""Notify Procedures"" below.
4.2.2. ASP Down Procedures
LOADGRP extends the ASP Down procedures to include the concept of
the Load Group.
Whenever an SGP moves an ASP to the ASP-DOWN state, it also moves
the ASP to the ASP-DOWN state in all Load Groups in all Application
Servers to which the ASP belongs. This may have the effect of
changing the Load Group state, requiring the generation of NTFY
messages as described under ""Notify Procedures"" below.
4.2.3. ASP Active Procedures
When activating, LOADGRP extends the UA activation procedures by
permitting an optional Load Distribution parameter to be included in
the ASP Active (ASPAC) and ASP Active Ack (ASPAC ACK) messages. The
Load Selector parameter is used to indicate for which Load Group the
concerned Application Server is becoming active [LOADSEL] and the Load
Distribution parameter is used to indicate the traffic mode of the
Load Group.
LOADGRP supplements the ASP Active Procedures as follows:
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When an ASP sends an ASPAC message to activate the ASP within an
Application Server, the ASP MAY choose to activate within a Load Group
for the specified AS by including the Load Selector parameter in the
ASPAC message.
When an SGP receives an ASPAC message with a Load Selector
parameter in the message, or where the SGP is otherwise configured to
activate the ASP in a configured Load Group, when the SGP moves the
ASP to the ASP-ACTIVE state for the AS, it also moves the ASP to the
ASP-ACTIVE state for the Load Group identified by the Load Selector
parameter. In either case, if the activation is successful, the SGP
includes the Load Selector parameter in the ASPAC ACK message.
If the Load Selector in the ASPAC message is invalid, the SGP
responds with ERR("Invalid Load Selector"). If the Load Selector
parameter is not present in the ASPAC message and the SGP is
configured to require one, or the Load Selector parameter is not valid
or not configured for the Application Server, the SGP responds with
ERR("Missing Parameter"). If the Load Selector parameter contains an
invalid or unsupported Load Distribution value, or the Load
Distribution parameter is missing but the SGP cannot determine the
distribution applicable to the Load Group without one, the SGP
responds with ERR("Unsupported Load Distribution").
There are three modes of Application Server traffic handling in the
SGP at the Application Server level and three modes of AS traffic
handling at the Load Group level: Override, Load-share and Broadcast.
When included, the Traffic Mode Type parameter in the ASPAC message
indicates the traffic handling mode to be used in a particular
Application Server between Load Groups. When included, the Load
Distribution parameter indicates the traffic handling mode to be used
between ASPs within the Load Group indicated by the Load Selector
parameter.
In the case of an Override mode AS, reception of an ASP Active
message at an SGP may move a Load Group to the LG-ACTIVE state. When
an LG moves to the LG-ACTIVE state in an Override mode AS, this causes
the (re)direction of all traffic for the AS to the active Load Group.
Distribution of traffic within the Load Group is determine on the
basis of the Load Distribution mode of the Load Group. Any previously
active Load Group is now considered to be in state LG-INACTIVE and
SHOULD no longer receive traffic from the SGP within the AS. The SGP
then MUST send a Notify message NTFY("Alternate ASP Active") and
include the Load Selector parameter in the Notify message indicating
the Load Group that has become active.
In the case of a Load-share mode AS, the reception of an ASP Active
message at an SGP that moves a Load Group to the LG-ACTIVE state
causes the direction of specific traffic flows associated with the
Load Selector to the Load Group. The assignment of traffic flows to
Load Selector values is implementation dependent, but could be based
on specific information in the protocol data message.
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In the case of a Broadcast mode AS, reception of an ASP Active
message at an SGP that results in moving a Load Group to the LG-ACTIVE
state within the AS causes the direction of traffic to the newly
active Load Group in addition to all the other LGs that are currently
active for the AS. The algorithm at the SGP for broadcasting traffic
within an AS to all the active ASPs is a simple broadcast algorithm,
where every message is sent to each of the active Load Groups.
4.2.4. ASP Inactive Procedures
When deactivating, LOADGRP extends the UA activation procedures by
permitting an optional Load Selector parameter to be included in the
ASP Inactive (ASPIA) and ASP Inactive Ack (ASPIA ACK) message. The
Load Selector parameter is used to indicate for which Load Group the
concerned Application Server is becoming inactive.
LOADGRP supplements the ASP Active procedures of the UAs as
follows:
When an ASP wishes to withdraw from a specific Load Group within an
Application Server, the ASP sends an ASP Inactive message to the SGP
with a Load Selector parameter included in the message. In the case
where the ASP does not include the Load Selector parameter in the ASP
Inactive message, the SGP must know via configuration data which Load
Groups the ASP is a member. Upon receiving an ASP Inactive message
with included or implied Load Selector, the SGP moves the ASP to the
ASP-INACTIVE state in each of the Load Groups indicated.
4.2.5. Notify Procedures
When the SGP or IPSP notifies its UA peer with a NTFY messages
which concerns an ASP, it MUST include the Load Group (if available)
along with the ASP Identifier in the message. The NTFY messages to
which this applies are:
NTFY("AS-ACTIVE"), NTFY("AS-PENDING"), NTFY("AS-INACTIVE") -
When the SGP or IPSP notifies the active and inactive ASPs in an AS
that it has detected the transition of the Application Server to the
AS-ACTIVE, AS-PENDING or AS-INACTIVE state, or that it has detected
the transition of a Load Group to the LG-ACTIVE state for the AS, it
MUST include the Load Selector, if available, indicating the Load
Group which has changed state along with the ASP Identifier, if any,
in the NTFY message.
When the Routing Context (Interface Identifier) associated with the
Application Server cannot be implied at the ASP from static
configuration data, the Routing Context (Interface Identifier) MUST
also be placed in the NTFY message.
NTFY("ASP Failure") -
When the SGP or IPSP notifies the active and inactive ASPs in an AS
that it has detected the failure of an ASP or the failure of an
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association to an ASP (i.e. SCTP Communication Lost Indication), it
MUST include the Load Selector (if available) with the ASP
Identifier in the message.
When the Routing Context (Interface Identifier) associated with the
Application Servers cannot be implied at the ASP from static
configuration data, the Routing Context (Interface Identifier) MUST
also be placed in the NTFY("ASP Failure") message.
The notifying SGP or IPSP MAY also place the Load Selector parameter
into the NTFY("ASP Failure") message to indicate the traffic which
was applicable to the load selection at the time of the failure.
The purpose of this procedure is to inform the active and inactive
ASPs, not only of the ASP failure, but of the identity of the ASP
and the load selection for which the failed ASP was responsible.
NTFY("Alternate ASP Active in AS") -
When the SGP or IPSP notifies the previously active ASP in a
override AS that an alternate ASP has become active, it MUST include
the Load Selector indicating the Load Group, if any, with the ASP
Identifier, if available, in the NTFY message.
The purpose of this procedure is to inform the previously active
ASP, not only of the that another ASP has taken over the traffic for
which the notified ASP was previously responsible, but to also
indicate the identify of the overriding ASP and the load selection
that was overridden.
When an ASP becomes ASP-INACTIVE for a Load Group or Application
Server for the first time, the SGP MAY send NTFY messages indicating
the state of the Application Server and the Load Groups in the
application server to the newly inactive ASP. Application Server
state is notified by sending the appropriate NTFY message without a
Load Selector parameter present in the message. Load Group state is
notified by sending the appropriate NTFY message with a Load Selector
parameter indicating the Load Group in the message.
4.3. Registration
UAs permit Application Server Processes to register for the Routing
Context (Interface Identifier) associated with a Routing Key (Link
Key). LOADGRP extends the registration procedure to also permit the
Application Server Process to register a )Load Distribution against a
Load Selector identifying a Load Group in addition to the Routing
Context (Interface Id).
This is performed by extending the registration procedure of Load
Selection [LOADSEL] by adding the Load Distribution parameter to the
REG REQ message during regsitration. The Load Distribution parameter
is analogous to the Traffic Mode Type parameter.
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In addition to the normal registration procedures of the UAs, the
following additional error conditions can occur:
"Error - Unsupported/Invalid Load Distribution"
This error MUST be sent in an Registration Response (REG RSP)
message whenever the SG determines that the Load Distribution
associated with a Load Group is invalid, is not supported by the
SG, or is required to determine the Load Distribution algorithm of
the Load Group but is missing from the Load Selection in the REG
REQ message.
4.4. Interworking Procedures
5. Examples
Figure 3 illustrates the example configuration that is used for all
the examples in this section. The example configuration consist of:
- Two SGs (SG1 and SG2) acting as STPs in the SS7 network and
consisting (for example) of a single SGP. Each SG is connected to
each of the ASPs in the example configuration.
- Four ASPs (ASP1, ASP2, ASP3 and ASP4). Each ASP is connected to
both of the SGs in the example configuration.
- Two Load Selectors (LS1 and LS2) are associated with the
Application Server. The traffic that corresponds to each Load
Selectors and the Load Distribution within each Load Selector is
different in each example.
SCTP
Associations ________ _________
_________ ............| | / \
| |..: .......| ASP1 | | AS1 |
| |..... : |________| | |
________| SG1 |....: : | ......... |
/| |...:: : ________ | : : |
\ / |_________| :::..:......| | | : LS1 : |
\ / | :: :......| ASP2 | | :.......: |
\ / | :: :: |________| | |
X | :: :: | |
/ \ | :: :: ________ | |
/ \ ____|____ ::...::.....| | | |
/ \ | |..:....::.....| ASP3 | | ......... |
_______\| |..:.....:: |________| | : : |
| SG2 |..:......: | : LS2 : |
| |..:..... ________ | :.......: |
|_________| :....:......| | | |
:......| ASP4 | | |
|________| \_________/
Figure 3. Example Configuration
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5.1.1. Initialization
Figure 4 illustrates the common initialization procedure use for
all of the examples. Each ASP establishes an SCTP Association with
SG1 and sends and ASP Up message to which it receives and ASP Up
response. The ASPs are not statically configured to serve specific AS
or LS within the AS, so no Notify messages are received. The same
sequence of messages are also exchanged with SG2.
SG1 SG2 ASP1 ASP2 ASP3 ASP4 AS1
: : : : : : :
(1) :<----:-Establish Association------>: : : : :
:<----:-ASPUP-----------------------: : : : :
:-----:-ASPUP ACK------------------>: : : : :
: : : : : : :
(2) :<----:-Establish Association-------:--->: : : :
:<----:-ASPUP-----------------------:----: : : :
:-----:-ASPUP ACK-------------------:--->: : : :
: : : : : : :
(3) :<----:-Establish Association-------:----:--->: : :
:<----:-ASPUP-----------------------:----:----: : :
:-----:-ASPUP ACK-------------------:----:--->: : :
: : : : : : :
(4) :<----:-Establish Association-------:----:----:--->: :
:<----:-ASPUP-----------------------:----:----:----: :
:-----:-ASPUP ACK-------------------:----:----:--->: :
: : : : : : :
(5) : : (Same message exchange for SG2) : : : :
: : : : : : :
Figure 4. Example - Initialization
5.2. M3UA with Override LG, Load-share AS, based on CIC
This example is for an M3UA [M3UA] configuration with the
Application Server (AS1) configured with a Traffic Mode Type of Load-
share. The Application Server (AS1) has associated with it a Routing
Key (RK1) that consists of a Destination Point Code that corresponds
to the AS1 (MGC1) point code (PC1), an Originating Point Code that
corresponds to a remote MGC2 point code (PC2), and the SI value for
ISUP (SI=5). The Load Selectors (LS1 and LS2) correspond to two sets
of CIC values which correspond to two different trunk groups between
MGC1 and MGC2 (TG1 and TG2).
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5.2.1. Activation
SG1 SG2 ASP1 ASP2 ASP3 ASP4 AS1
: : : : : : :
(1) :<----:-ASPAC(LS1/RC1)--------------: : : : :
:-----:-ASPAC ACK(LS1/RC1)--------->: : : : :
:-----:-NTFY(AS_Act)(LS1/RC1)------>: : : : :
: : : : : : :
:<----:-DATA(LS1)------------------>:<---:----:----:------>:
: : : : : : :
(2) :<----:-ASPAC(LS2/RC1)--------------:----: : : :
:-----:-ASPAC ACK(LS2/RC1)----------:--->: : : :
:-----:-NTFY(AS_Act)(LS2/RC1)------>: : : : :
:-----:-NTFY(AS_Act)(LS2/RC1)-------:--->: : : :
: : : : : : :
:<----:-DATA(LS1)------------------>:<---:----:----:------>:
:<----:-DATA(LS2)-------------------:--->:<---:----:------>:
: : : : : : :
(3) :<----:-ASPAC(LS2/RC1)--------------:----:----: : :
:-----:-ASPAC ACK(LS2/RC1)----------:----:--->: : :
:-----:-NTFY(Alt ASP)(LS2/RC1/ASP3)-:--->: : : :
: : : : : : :
:<----:-DATA(LS1)------------------>:<---:----:----:------>:
:<----:-DATA(LS2)-------------------:----:--->:<---:------>:
: : : : : : :
(4) :<----:-ASPIA(LS2/RC1)--------------:----: : : :
:-----:-ASPIA ACK(LS2/RC1)----------:--->: : : :
: : : : : : :
:<----:-DATA(LS1)------------------>:<---:----:----:------>:
:<----:-DATA(LS2)-------------------:----:--->:<---:------>:
: : : : : : :
Figure 5. M3UA Example - Activation
Figure 5 illustrates activation of the ASPs for Load-share Load
Distribution within the Override Application Server. The sequence of
events is as follows:
(1) ASP1 sends an ASP Active message to SG1 identifying Load
Selector LS1 within Application Server AS1/RC1, optionally
including a Load Distribution indicating ""Load-share,"" and
receives an acknowledgment and a notification. Data is
transferred between the SG and ASP1 for Load Group LS1 within
AS1.
(2) ASP2 sends an ASP Active message to SG1 identifying Load
Selector LS2 within Application Server AS1/RC1 and receives an
acknowledgment and notification. ASP1 also receives
notification that LS2 is active for AS1/RC1. Data is
transferred between the SG and ASP2 for AS1/RC1 load-shared on
CIC between LS1/ASP1 and LS2/ASP2.
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(3) ASP3 sends an ASP Active message to SG1 identifying Load
Selector LS2 within Application Server AS1/RC1 and receives an
acknowledgment. Because LS2 is an Override Load Group, ASP2
gets a notification that ASP3 is now the active ASP for
LS2/AS1/RC1. Data is transfer to ASP3 for LS2 and remains
transferred to ASP1 for LS1.
(4) ASP2 sends an ASP Inactive message to SG1 identifying Load
Selector LS1 within Application Server AS1/RC1 and receives an
acknowledgment. Because ASP2 is not active in LS2, and LS2 is
an Override Load Group, SG1 continues to load-share between LS1
to ASP1 and LS2 to ASP3.
5.2.2. Failure of ASP1
SG1 SG2 ASP1 ASP2 ASP3 ASP4 AS1
: : : : : : :
(1) :<----:-DATA(LS1)------------------>:<---:----:----:------>:
:<----:-DATA(LS2)-------------------:--->:<---:----:------>:
: : : : : : :
(2) :<- - :-COMM LOST - - - - -XXXX- - -: : : : :
:-----:-NTFY(ASP Fail)(ASP1)--------:--->: : : :
:-----:-NTFY(ASP Fail)(ASP1)--------:----:--->: : :
:-----:-NTFY(ASP Fail)(ASP1)--------:----:----:--->: :
:-----:-NTFY(AS_Pending)(LS1/RC1)---:--->: : : :
:-----:-NTFY(AS_Pending)(LS1/RC1)---:----:--->: : :
:-----:-NTFY(AS_Pending)(LS1/RC1)---:----:----:--->: :
: : : : : : :
(3) :<----:-ASPAC(LS1/RC1)--------------:----:----:----: :
:-----:-ASPAC ACK(LS1/RC1)----------:----:----:--->: :
:-----:-NTFY(AS_Active)(LS1/RC1)----:--->: : : :
:-----:-NTFY(AS_Active)(LS1/RC1)----:----:--->: : :
:-----:-NTFY(AS_Active)(LS1/RC1)----:----:----:--->: :
: : : : : : :
(4) :<----:-DATA(LS1)-------------------:----:----:--->:<----->:
:<----:-DATA(LS2)-------------------:--->:<---:----:------>:
: : : : : : :
Figure 6. M3UA Example - Failure of ASP1
Figure 6 illustrates the failure of ASP1. The sequence of events
is as follows:
(1) Data for LS1 within AS1 is exchanged between SG1 and ASP1.
Data for LS2 within AS1 is exchanged between SG1 and ASP2.
(2) Communication is lost between SG1 and ASP1. ASP2, ASP3, and
ASP4 are notified of the failure of ASP1 and the change of
state of AS1 to AS-PENDING for LS1. Data for LS2 in AS1 is
unaffected.
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(3) ASP4 (spare) responds to the AS-PENDING notification and
activates for LS1 in AS1/RC1. ASP2, ASP3 and ASP4 receive an
AS-ACTIVE notification. Data for LS1 in AS1 is now exchanged
with ASP4. Data for LS2 in AS1 continues to be exchanged with
ASP2.
5.2.3. Sparing
SG1 SG2 ASP1 ASP2 ASP3 ASP4 AS1
: : : : : : :
(1) :<----:-DATA(LS1)------------------>:<---:----:----:------>:
:<----:-DATA(LS1)------------------>:<---:----:----:------>:
: : : : : : :
(2) :<----:-ASPAC(LS1/RC1)--------------:----:----:----: :
:-----:-ASPAC ACK(LS1/RC1)----------:----:----:--->: :
:-----:-NTFY(Alt ASP)(ASP4)-------->: : : : :
: : : : : : :
(3) :<----:-DATA(LS1)-------------------:----:----:--->:<----->:
:<----:-DATA(LS1)-------------------:----:----:--->:<----->:
: : : : : : :
(4) :<----:-ASPDN-----------------------: : : : :
:-----:-ASPDN ACK------------------>: : : : :
: : : : : : :
Figure 7. M3UA Example - Sparing
Figure 7 illustrates a sparing situation where one ASP takes over
traffic from another so that the original ASP can be taken out of
service. The sequence of events is as follows:
(1) Data for LS1 in AS1 is exchange between SG1 and ASP1.
(2) ASP4 (spare) activates for LS1 in AS1 and receives an
acknowledgment. ASP4 has overridden ASP1 and a notification is
sent to ASP1 that indicates that ASP4 in now the "Alternate ASP
Active for AS".
(3) Data for LS1 in AS1 is now being exchanged between SG1 and
ASP4.
(4) ASP1 can now be taken down and out of service.
5.3. SUA with Load-share LG, Load-share AS based on GT
This example is for an SUA [SUA] configuration with the Application
Server (AS1) configured with a Traffic Mode Type of Load-share. The
Application Server (AS1) has associated with it (RK1) that consists of
Destination Point Code and Subsystem Number that corresponds to the
AS1 (HLR1) point code (PC1). The Load Selectors (LS1 and LS2)
correspond to two sets of Global Titles which correspond to Mobile and
GSTN numbering.
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5.3.1. Activation
SG1 SG2 ASP1 ASP2 ASP3 ASP4 AS1
: : : : : : :
(1) :<----:-ASPAC(LS1/RC1)--------------: : : : :
:-----:-ASPAC ACK(LS1/RC1)--------->: : : : :
:-----:-NTFY(AS_Act)(LS1/RC1)------>: : : : :
: : : : : : :
:<----:-DATA(LS1)------------------>:<---:----:----:------>:
: : : : : : :
(2) :<----:-ASPAC(LS2/RC1)--------------:----: : : :
:-----:-ASPAC ACK(LS2/RC1)----------:--->: : : :
:-----:-NTFY(AS_Act)(LS2/RC1)------>: : : : :
:-----:-NTFY(AS_Act)(LS2/RC1)-------:--->: : : :
: : : : : : :
:<----:-DATA(LS2)-------------------:--->:<---:----:------>:
: : : : : : :
(3) :<----:-ASPAC(LS1/RC1)--------------:----:----: : :
:-----:-ASPAC ACK(LS1/RC1)----------:----:--->: : :
: : : : : : :
:<----:-DATA(LS1)------------------>:<---:----:----:------>:
:<----:-DATA(LS1)-------------------:----:--->:<---:------>:
: : : : : : :
(4) :<----:-ASPIA(LS1,LS2/RC1)----------:----:----:----: :
:-----:-ASPIA ACK(LS1,LS2/RC1)------:----:----:--->: :
: : : : : : :
(5) : : (Same message exchange for SG2) : : : :
: : : : : : :
Figure 8. SUA Example - Activation
Figure 8 illustrates activation of the ASPs for Load Selectors
within the Load-share Application Server. The sequence of events is
as follows:
(1) ASP1 sends an ASP Active message to SG1 identifying Load
Selector LS1 within Application Server AS1/RC1 and receives an
acknowledgment and a notification. Data is transferred between
the SG and ASP1 for Load Selector LS1 within AS1.
(2) ASP2 sends an ASP Active message to SG1 identifying Load
Selector LS2 within Application Server AS1/RC1 and receives an
acknowledgment and a notification. ASP1 also receives
notification that AS1/RC1 is active for LS2. Data is
transferred between the SG and ASP2 for Load Selector LS2
within AS1.
(3) ASP3 sends an ASP Active message to SG1 identifying Load
Selector LS1 within Application Server AS1/RC1 and receives an
acknowledgment. Data is load-shared between the SG and ASP1
and ASP3 for Load Selector LS1 within AS1.
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(4) ASP4 sends an ASP Inactive message to SG1 identifying Load
Selector LS1 and LS2 within Application Server AS1/RC1 and
receives an acknowledgment.
(5) The same exchange is repeated for SG2.
5.3.2. Failure of ASP1 and ASP2
SG1 SG2 ASP1 ASP2 ASP3 ASP4 AS1
: : : : : : :
(1) :<----:-DATA(LS1)------------------>:<---:----:----:------>:
:<----:-DATA(LS1)-------------------:----:--->:<---:------>:
:<----:-DATA(LS2)-------------------:--->:<---:----:------>:
: : : : : : :
(2) :<- - :-COMM LOST - - - - -XXXX- - -: : : : :
:-----:-NTFY(ASP Fail)(ASP1)--------:--->: : : :
:-----:-NTFY(ASP Fail)(ASP1)--------:----:--->: : :
:-----:-NTFY(ASP Fail)(ASP1)--------:----:----:--->: :
: : : : : : :
:<----:-DATA(LS1)-------------------:----:--->:<---:------>:
:<----:-DATA(LS2)-------------------:--->:<---:----:------>:
: : : : : : :
(3) :<- - :-COMM LOST - - - - -XXXX- - -: - -: : : :
:-----:-NTFY(ASP Fail)(ASP2)--------:----:--->: : :
:-----:-NTFY(ASP Fail)(ASP2)--------:----:----:--->: :
:-----:-NTFY(AS_Pending)(LS2/RC1)---:----:--->: : :
:-----:-NTFY(AS_Pending)(LS2/RC1)---:----:----:--->: :
: : : : : : :
:<----:-DATA(LS1)-------------------:----:--->:<---:------>:
: : : : : : :
(4) :<----:-ASPAC(LS2/RC1)--------------:----:----:----: :
:-----:-ASPAC ACK(LS2/RC1)----------:----:----:--->: :
:-----:-NTFY(AS_Active)(LS2/RC1)----:----:--->: : :
:-----:-NTFY(AS_Active)(LS2/RC1)----:----:----:--->: :
: : : : : : :
:<----:-DATA(LS1)-------------------:----:--->:<---:------>:
:<----:-DATA(LS2)-------------------:----:----:--->:<----->:
: : : : : : :
Figure 9. SUA Example - Failure of ASP1 and ASP2
Figure 9 illustrates the failure of ASP1 followed by the failure of
ASP2. The sequence of events is as follows:
(1) Data for LS1 within AS1 is load-shared between ASP1 and ASP3.
Data for LS2 within AS1 is transferred to ASP2.
(2) Communication is lost between SG1 and ASP1. ASP2, ASP3, and
ASP4 are notified of the failure of ASP1. Data for LS1 in AS1
is now transferred to ASP3 only. Data for LS2 in AS1 is
unaffected and is still transferred to ASP2.
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(3) Communication is lost between SG1 and ASP2. ASP3 and ASP4 are
notified of the failure of ASP2 as well of the AS1 state change
to AS-PENDING for LS2. Data for LS2 is queued at the SG.
(4) ASP4 (spare) responds to the AS-PENDING notification and
activates for LS2 in AS1/RC1. ASP3 and ASP4 receive an AS-
ACTIVE notification for LS2. Data for LS2 in AS1 is now
transferred to ASP4.
5.3.3. Sparing
SG1 SG2 ASP1 ASP2 ASP3 ASP4 AS1
: : : : : : :
(1) :<----:-DATA(LS1)------------------>:<---:----:----:------>:
:<----:-DATA(LS1)-------------------:----:--->:<---:------>:
: : : : : : :
(2) :<----:-ASPAC(LS1/RC1)--------------:----:----:----: :
:-----:-ASPAC ACK(LS1/RC1)----------:----:----:--->: :
: : : : : : :
:<----:-DATA(LS1)------------------>:<---:----:----:------>:
:<----:-DATA(LS1)-------------------:----:--->:<---:------>:
:<----:-DATA(LS1)-------------------:----:----:--->:<----->:
: : : : : : :
(3) :<----:-ASPIA(LS1/RC1)--------------: : : : :
:-----:-ASPIA ACK(LS1/RC1)--------->: : : : :
: : : : : : :
:<----:-DATA(LS1)-------------------:----:--->:<---:------>:
:<----:-DATA(LS1)-------------------:----:----:--->:<----->:
: : : : : : :
(5) :<----:-ASPDN-----------------------: : : : :
:-----:-ASPDN ACK------------------>: : : : :
: : : : : : :
Figure 10. SUA Example - Sparing
Figure 10 illustrates a sparing situation where one ASP takes over
traffic from another so that the original ASP can be taken out of
service. The sequence of events is as follows:
(1) Data for LS1 in AS1 is load-shared by SG1 between ASP1 and
ASP3.
(2) ASP4 (spare) activates for LS1 in AS1 and receives and
acknowledgment. Data for LS1 in AS1 is now load-shared by SG1
between ASP1, ASP3 and ASP4.
(3) ASP1 deactivates for LS1 in AS1 and receives and
acknowledgment.
(4) Data for LS1 in AS1 is now load-shared by SG1 between ASP3 and
ASP4.
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(5) ASP1 can now be taken down and out of service.
5.4. TUA with Broadcast LG, Load-share AS based on DID
This example is for an TUA [TUA] configuration with the Application
Server (AS1) configured with a Traffic Mode Type of Broadcast. The
Application Server (AS1) has associated with it (RK1) that consists of
Destination Point Code and Subsystem Number that corresponds to the
AS1 (HLR1) point code (PC1). The Load Selectors (LS1 and LS2)
correspond to two sets of Dialog Ids which correspond to even and odd
Dialog Ids.
5.4.1. Activation
SG1 SG2 ASP1 ASP2 ASP3 ASP4 AS1
: : : : : : :
(1) :<----:-ASPAC(LS1/RC1)--------------: : : : :
:-----:-ASPAC ACK(LS1/RC1)--------->: : : : :
:-----:-NTFY(AS_Act)(LS1/RC1)------>: : : : :
: : : : : : :
:<----:-DATA(LS1)(CorrId)---------->:<---:----:----:------>:
:<----:-DATA(LS1)------------------>:<---:----:----:------>:
: : : : : : :
(2) :<----:-ASPAC(LS2/RC1)--------------:----: : : :
:-----:-ASPAC ACK(LS2/RC1)----------:--->: : : :
:-----:-NTFY(AS_Act)(LS2/RC1)------>: : : : :
:-----:-NTFY(AS_Act)(LS2/RC1)-------:--->: : : :
: : : : : : :
:<----:-DATA(LS2)(CorrId)-----------:--->:<---:----:------>:
:<----:-DATA(LS2)-------------------:--->:<---:----:------>:
: : : : : : :
(3) :<----:-ASPAC(LS1/RC1)--------------:----:----: : :
:-----:-ASPAC ACK(LS1/RC1)----------:----:--->: : :
:-----:-NTFY(AS_Act)(LS1,LS2/RC1)---:----:--->: : :
: : : : : : :
:<----:-DATA(LS1)(CorrId)---------->:<---:--->:<---:------>:
:<----:-DATA(LS1)------------------>:<---:--->:<---:------>:
: : : : : : :
(4) :<----:-ASPIA(LS2/RC1)--------------:----:----:----: :
:-----:-ASPIA ACK(LS2/RC1)----------:----:----:--->: :
: : : : : : :
(5) : : (Same message exchange for SG2) : : : :
: : : : : : :
Figure 11. TUA Example - Activation
Figure 11 illustrates activation of the ASPs for Load Selectors
within the Broadcast Application Server. The sequence of events is as
follows:
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Internet Draft UA LOADGRP January 2, 2003
(1) ASP1 sends an ASP Active message to SG1 identifying Load
Selector LS1 within Application Server AS1/RC1 and receives an
acknowledgment and a notification. Data is transferred between
the SG and ASP1 for Load Selector LS1 within AS1. The initial
Data Messages for LS1 within AS1 are tagged with a Correlation
Id.
(2) ASP2 sends an ASP Active message to SG1 identifying Load
Selector LS2 within Application Server AS1/RC1 and receives an
acknowledgment and a notification. ASP1 also receives
notification that AS1/RC1 is active for LS2. Data is
transferred between the SG and ASP2 for Load Selector LS2
within AS1. The initial Data Messages for LS2 within AS1 are
tagged with a Correlation Id.
(3) ASP3 sends an ASP Active message to SG1 identifying Load
Selector LS1 within Application Server AS1/RC1 and receives an
acknowledgment. Data is broadcast the SG and ASP1 and ASP3 for
Load Selector LS1 within AS1. The initial Data Messages for
LS2 within AS1 are tagged with a Correlation Id.
(4) ASP4 sends an ASP Inactive message to SG1 identifying Load
Selector LS1 and LS2 within Application Server AS1/RC1 and
receives an acknowledgment.
(5) The same exchange is repeated for SG2.
5.4.2. Failure of ASP1 and ASP2
SG1 SG2 ASP1 ASP2 ASP3 ASP4 AS1
: : : : : : :
(1) :<----:-DATA(LS1)------------------>:<---:--->:<---:------>:
:<----:-DATA(LS2)-------------------:--->:<---:----:------>:
: : : : : : :
(2) :<- - :-COMM LOST - - - - -XXXX- - -: : : : :
:-----:-NTFY(ASP Fail)(ASP1)--------:--->: : : :
:-----:-NTFY(ASP Fail)(ASP1)--------:----:--->: : :
:-----:-NTFY(ASP Fail)(ASP1)--------:----:----:--->: :
: : : : : : :
:<----:-DATA(LS1)-------------------:----:--->:<---:------>:
:<----:-DATA(LS2)-------------------:--->:<---:----:------>:
: : : : : : :
(3) :<- - :-COMM LOST - - - - -XXXX- - -: - -: : : :
:-----:-NTFY(ASP Fail)(ASP2)--------:----:--->: : :
:-----:-NTFY(ASP Fail)(ASP2)--------:----:----:--->: :
:-----:-NTFY(AS_Pending)(LS2/RC1)---:----:--->: : :
:-----:-NTFY(AS_Pending)(LS2/RC1)---:----:----:--->: :
: : : : : : :
:<----:-DATA(LS1)-------------------:----:--->:<---:------>:
: : : : : : :
(4) :<----:-ASPAC(LS2/RC1)--------------:----:----:----: :
:-----:-ASPAC ACK(LS2/RC1)----------:----:----:--->: :
:-----:-NTFY(AS_Active)(LS2/RC1)----:----:--->: : :
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Internet Draft UA LOADGRP January 2, 2003
:-----:-NTFY(AS_Active)(LS2/RC1)----:----:----:--->: :
: : : : : : :
:<----:-DATA(LS2)(CorrId)-----------:----:----:--->:<----->:
:<----:-DATA(LS2)-------------------:----:----:--->:<----->:
:<----:-DATA(LS1)-------------------:----:--->:<---:------>:
: : : : : : :
(5) :<----:-ASPDN-----------------------: : : : :
:-----:-ASPDN ACK------------------>: : : : :
: : : : : : :
Figure 12. TUA Example - Failure of ASP1
Figure 12 illustrates the failure of ASP1 followed by the failure
of ASP2. The sequence of events is as follows:
(1) Data for LS1 within AS1 is broadcast to ASP1 and ASP3. Data
for LS2 within AS1 is sent to ASP2.
(2) Communication is lost between SG1 and ASP1. ASP2, ASP3, and
ASP4 are notified of the failure of ASP1. Data for LS1 in AS1
is directed toward ASP3 only. Data for LS2 in AS1 is
unaffected.
(3) Communication is lost between SG1 and ASP2. ASP3 and ASP4 are
notified of the failure of ASP1 as well of the AS1 state change
to AS-PENDING for LS2. Data for LS2 is queued at the SG.
(4) ASP4 (spare) responds to the AS-PENDING notification and
activates for LS2 in AS1/RC1. ASP3 and ASP4 receive an AS-
ACTIVE notification. Data for LS2 in AS1 is now exchanged with
ASP4. Initial DATA messages for LS2 in AS1 are tagged with a
Correlation Id.
5.4.3. Sparing
SG1 SG2 ASP1 ASP2 ASP3 ASP4 AS1
: : : : : : :
(1) :<----:-DATA(LS1)------------------>:<---:--->:<---:------>:
: : : : : : :
(2) :<----:-ASPAC(LS1/RC1)--------------:----:----:----: :
:-----:-ASPAC ACK(LS1/RC1)----------:----:----:--->: :
: : : : : : :
:<----:-DATA(LS1)(CorrId)-----------:----:----:--->:<----->:
:<----:-DATA(LS1)------------------>:<---:--->:<-->:<----->:
: : : : : : :
(3) :<----:-ASPIA(LS1/RC1)--------------: : : : :
:-----:-ASPIA ACK(LS1/RC1)--------->: : : : :
: : : : : : :
(4) :<----:-DATA(LS1)-------------------:----:--->:<-->:<----->:
: : : : : : :
(5) :<----:-ASPDN-----------------------: : : : :
B. Bidulock Version 0.1 Page 28
Internet Draft UA LOADGRP January 2, 2003
:-----:-ASPDN ACK------------------>: : : : :
: : : : : : :
Figure 13. TUA Example - Sparing
Figure 13 illustrates a sparing situation where one ASP takes over
traffic from another so that the original ASP can be taken out of
service. The sequence of events is as follows:
(1) Data for LS1 in AS1 is broadcast from SG1 to ASP1 and ASP3.
(2) ASP4 (spare) activates for LS1 in AS1 and receives and
acknowledgment. Data for LS1 in AS1 is now being broadcast
from SG1 to ASP1, ASP3 and ASP4. Initial data for LS1 in AS1
is tagged with a Correlation Id.
(3) ASP1 deactivates for LS1 in AS1 and receives and
acknowledgment.
(4) Data for LS1 in AS1 is now broadcast from SG1 to ASP3 and ASP4.
(5) ASP1 can now be taken down and out of service.
6. Security
LOADGRP does not introduce any new security risks or considerations
that are not already inherent in the UA [IUA...TUA] Please see the
"Security" sections of the UA [IUA...TUA] for security considerations
and recommendations that are applicable to each UA.
7. IANA Considerations
LOADGRP adds the following parameter tag value (described in
Section 3) to the Common Parameter numbering space for the UAs
[IUA...TUA].
Tag Value Parameter Name
------------------------------
0x001a Load Distribution
EDITOR'S NOTE:- The Load Distribution parameter tag value
shown throughout this document as 0x001a will be assigned by
IANA within the common parameter range of the SIGTRAN UAs and
may change its value in further versions of this document.
LOADGRP adds the following value to the Error Code parameter of the
UAs.
28 Unsupported Load Distribution
EDITOR'S NOTE:- The Error Code value shown as 28 above will
Internet Draft UA LOADGRP January 2, 2003
be assigned by IANA as a value of the common Error Code
parameter for SIGTRAN UAs and may change its value in further
versions of this document.
LOADGRP adds the following value to the Registration Status field
of the Registration Result parameter for the UAs [M2UA...TUA].
16 Error - Invalid/Unsupported Load Distribution
EDITOR'S NOTE:- The Registration Status value shown as 16
above will be assigned by IANA as a value of each UA-specific
Registration Status parameter for each SIGTRAN UA and may
change its value in further versions of this document.
Acknowledgments
The authors would like to thank Tolga Asveren, Ken Morneault, Barry
Nagelberg, Benjamin J. Wilson, Jacques Rajchgod, Greg Sidebottom and
Gery Verwimp for their valuable comments and suggestions.
Notes
[1] For a detailed description of these messages, see Section 3 of
the specific UA document [M2UA...TUA].
References
IUA.
K. Morneault, S. Rengasami, M. Kalla and G. Sidebottom, "ISDN
Q.921-User Adaptation Layer," RFC 3057, The Internet Society
(November, 2000). [Normative]
DUA.
R. Mukundan, N. Mangalpally, K. Morneault and A. Vydyam,
"DPNSS/DASS 2 Extensions to the IUA Protocol," <draft-ietf-
sigtran-dua-04.txt>, Internet Engineering Task Force - Signalling
Transport Working Group (October 2002). Work In Progress.
[Informative]
V5UA.
E. Weilandt, N. Khanchandani and S. Rao, "V5.2-User Adaption
Layer (V5UA)," <draft-ietf-sigtran-v5ua-03.txt>, Internet
Engineering Task Force - Signalling Transport Working Group (June
2002). Work In Progress. [Informative]
GR303UA.
R. Mukundan, K. Morneault, "GR-303 extensions to the IUA
Protocol," <draft-ranjith-sigtran-gr303ua-00.txt>, Internet
Engineering Task Force - Signalling Transport Working Group
B. Bidulock Version 0.1 Page 30
Internet Draft UA LOADGRP January 2, 2003
(October 2002). Work In Progress. [Informative]
M2UA.
K. Morneault, R. Dantu, G. Sidebottom, B. Bidulock and J. Heitz,
"Signaling System 7 (SS7) Message Transfer Part 2 (MTP2) - User
Adaptation Layer," RFC 3331, Internet Engineering Task Force -
Signalling Transport Working Group (September, 2002).
[Normative]
M3UA.
G. Sidebottom, K. Morneault and J. Pastor-Balbas, (eds),
"Signaling System 7 (SS7) Message Transfer Part 3 (MTP3) - User
Adaptation Layer (M3UA)," RFC 3332, Internet Engineering Task
Force - Signalling Transport Working Group (September, 2002).
[Normative]
SUA.
J. Loughney, G. Sidebottom, L. Coene, G. Verwimp, J. Keller and
B. Bidulock, "SS7 SCCP-User Adaptation Layer (SUA)," <draft-ietf-
sigtran-sua-14.txt>, Internet Engineering Task Force - Signalling
Transport Working Group (June 30, 2002). Work In Progress.
[Normative]
ISUA.
B. Bidulock, "SS7 ISUP-User Adaptation Layer (ISUA)," <draft-
bidulock-sigtran-isua-00.txt>, Internet Engineering Task Force -
Signalling Transport Working Group (January 5, 2003). Work In
Progress. [Normative]
TUA.
B. Bidulock, "SS7 TCAP-User Adaptation Layer (TUA)," <draft-
bidulock-sigtran-tua-01.txt>, Internet Engineering Task Force -
Signalling Transport Working Group (January 2, 2003). Work In
Progress. [Normative]
RFC 2960.
R. Stewart, Q. Xie, K. Morneault, C. Sharp, H. J. Schwarzbauer,
T. Taylor, I. Rytina, H. Kalla, L. Zhang and V. Paxson, "Stream
Control Transmission Protocol (SCTP)," RFC 2960, The Internet
Society (February 2000). [Normative]
LOADSEL.
B. Bidulock, "Load Selection Extension for Signalling User
Adaptation Layers (LOADSEL)," <draft-bidulock-sigtran-
loadsel-01.txt>, Internet Engineering Task Force - Signalling
Transport Working Group (January 2, 2003). Work In Progress.
[Informative]
RFC 2119.
S. Bradner, "Key words for use in RFCs to Indicate Requirement
Levels," RFC 2119 - BCP 14, Internet Engineering Task Force
(March 1997). [Normative]
B. Bidulock Version 0.1 Page 31
Internet Draft UA LOADGRP January 2, 2003
Author's Addresses
Brian Bidulock Phone: +1-780-490-1141
OpenSS7 Corporation Email: [email protected]
1469 Jeffreys Crescent URL: http://www.openss7.org/
Edmonton, AB T6L 6T1
Canada
This draft expires July, 2003.
B. Bidulock Version 0.1 Page 32
Internet Draft UA LOADGRP January 2, 2003
List of Tables
Table 1 Sample Configurations ................................. 7
List of Illustrations
Figure 1 Existing Traffic Distribution ........................ 4
Figure 2 Load Group Traffic Distribution ...................... 5
Figure 3 Example Configuration ................................ 18
Figure 4 Example - Initialization ............................. 19
Figure 5 M3UA Example - Activation ............................ 20
Figure 6 M3UA Example - Failure of ASP1 ....................... 21
Figure 7 M3UA Example - Sparing ............................... 22
Figure 8 SUA Example - Activation ............................. 23
Figure 9 SUA Example - Failure of ASP1 and ASP2 ............... 24
Figure 10 SUA Example - Sparing ............................... 25
Figure 11 TUA Example - Activation ............................ 26
Figure 12 TUA Example - Failure of ASP1 ....................... 28
Figure 13 TUA Example - Sparing ............................... 29
Table of Contents
Status of this Memo ........................................... 1
Abstract ...................................................... 1
1 Introduction ................................................ 2
1.1 Scope ..................................................... 2
1.2 Change History ............................................ 2
1.3 Terminology ............................................... 2
1.4 Overview .................................................. 3
1.4.1 Existing Traffic Distribution ........................... 3
1.4.2 Extended Traffic Distribution ........................... 4
1.5 Sample Configurations ..................................... 7
2 Conventions ................................................. 7
3 Protocol Elements ........................................... 7
3.1 Parameters ................................................ 8
3.1.1 Load Distribution ....................................... 8
3.2 Messages .................................................. 8
3.2.1 Registration Request (REG REQ) .......................... 9
3.2.2 Registration Response (REG RSP) ......................... 10
3.2.3 ASP Active (ASPAC) ...................................... 10
3.2.4 ASP Active Ack (ASPAC ACK) .............................. 11
3.2.5 Error (ERR) ............................................. 13
4 Procedures .................................................. 13
4.1 ASP State Maintenance ..................................... 13
4.1.1 Load Group State ........................................ 13
4.1.2 Application Server State ................................ 14
4.2 ASP Traffic Maintenance ................................... 14
4.2.1 ASP Up Procedures ....................................... 14
4.2.2 ASP Down Procedures ..................................... 14
4.2.3 ASP Active Procedures ................................... 14
4.2.4 ASP Inactive Procedures ................................. 16
4.2.5 Notify Procedures ....................................... 16
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4.3 Registration .............................................. 17
4.4 Interworking Procedures ................................... 18
5 Examples .................................................... 18
5.1.1 Initialization .......................................... 19
5.2 M3UA with Override LG, Load-share AS, based on CIC ........ 19
5.2.1 Activation .............................................. 20
5.2.2 Failure of ASP1 ......................................... 21
5.2.3 Sparing ................................................. 22
5.3 SUA with Load-share LG, Load-share AS based on GT ......... 22
5.3.1 Activation .............................................. 23
5.3.2 Failure of ASP1 and ASP2 ................................ 24
5.3.3 Sparing ................................................. 25
5.4 TUA with Broadcast LG, Load-share AS based on DID ......... 26
5.4.1 Activation .............................................. 26
5.4.2 Failure of ASP1 and ASP2 ................................ 27
5.4.3 Sparing ................................................. 28
6 Security .................................................... 29
7 IANA Considerations ......................................... 29
Acknowledgments ............................................... 30
Notes ......................................................... 30
References .................................................... 30
Author's Addresses ............................................ 32
List of Tables ................................................ 33
List of Illustrations ......................................... 33
Table of Contents ............................................. 33
B. Bidulock Version 0.1 Page 34
Internet Draft UA LOADGRP January 2, 2003
Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of developing
Internet standards in which case the procedure for copyrights defined
in the Internet Standards process must be followed, or as required to
translate into languages other than English.
The limited permission granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on
an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT
NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN
WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
B. Bidulock Version 0.1 Page 35
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