home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Internet Standards
/
CD2.mdf
/
ccitt
/
1992
/
q
/
q716.asc
< prev
next >
Wrap
Text File
|
1991-12-31
|
35KB
|
995 lines
All drawings appearing in this Fascicle have been done in Autocad.
Recommendation Q.716
SIGNALLIG CONNECTION CONTROL PART
(SCCP) PERFORMANCES
1 General
1.1 Overview
The Signalling Connection Control Part (SCCP) of Signalling System No. 7
is designed as a general message transport system common to the various
sub-systems which are using its services.
SCCP must satisfy the requirements of these various sub-systems and
therefore the most stringent sub-system requirements are considered when defining
a value for a performance parameter (most stringent at the time of the
specification). To this end, the requirements of ISDN-UP, the OMAP, the dialogue
between an exchange and a Service Control Point (using the Transaction
Capabilities), in particular, were investigated. It is assumed that a SCCP which
satisfies the requirements of these users mentioned above will also meet those of
future users.
SCCP performances are defined by parameters of two kinds:
- quality of service parameters as seen by a user of the SCCP;
- internal parameters which are not seen by the user but which contribute
to a quality of service parameter: for example the transfer delay in a
relay point which contributes to the total transit delay of messages as
seen by the user.
The definitions of all these parameters are presented in Section 2 of this
Recommendation. Then the values allowed for the internal parameters are defined
in Section 3. Values for the quality of service parameters are given in
Recommendation Q.709 which deals with HSRCs.
1.2 Definitions
Two concepts must be defined when dealig with SCCP performances: SCCP
route and SCCP relation. These concepts are similar to the one defined for the
MTP (i.e. signalling route and signalling relation). They are defined as follows:
- SCCP route: A SCCP route is composed of an ordered list of nodes where
the SCCP is used (origin, relay(s), destination) for the transfer of
SCCP messages from an originating SCCP user to the destination SCCP
user.
- SCCP relation: A SCCP relation is a relation between two SCCP users
which allows them to exchange data over it. A SCCP relation can consist
of one or several SCCP routes.
Five types of nodes where SCCP functions are involved are defined as
follows:
- originating node (origin of a UDT message or of a signalling
connection).
- destination node (destination of a UDT message or of a signalling
connection).
- relay point: signalling point where the translation functions of the
SCCP for connectionless classes are implemented.
- relay point without coupling: signalling point where the relay
functions of the SCCP connection oriented classes, but without the
coupling of signalling connection sections function, are implemented.
- relay point with coupling: signalling point where the relay functions
of the SCCP connection oriented classes, including the coupling of
signalling connection sections function, are implemented.
Fascicle VI.7 - Rec. Q.716 PAGE1
2 Definition of performance parameters
Some parameters which are defined in this section cannot be measured from
the outside of a signalling point and therefore no values are attributed to them
in Section 3 where only measurable values are given. This is true for some
internal parameters such as for example the transit time of a CR message for the
relay function at a relay point without coupling: this parameter does not include
in its definition the time due to the MTP and therefore in Section 3 values are
given to the transit time at a relay point which icludes both the time spent in
the SCCP and the MTP.
In networks containing implementations from a number of different vendors,
it may be necessary where a parameter has a send and receive component to specify
that parameter on such a basis. This will then ensure that the overall
requirement is satisfied.
2.1 Performance parameters for the connectionless classes
2.1.1 Quality of service parameters
The following parameters define the quality of service as seen by a user
of the connectionless classes of the SCCP:
- undetected errors
This parameter gives the probability that a UDT message is delivered
with user data which is defective.
- residual error probability
This parameter gives the probability that a UDT message is
lost, duplicated or delivered incorrectly by the set
constituted of SCCP and the MTP (called Network Service
Part or NSP). An incorrectly delivered UDT is one in which
the user data are delivered in a corrupted condition (see
undetected errors above), or the user data are delivered to
an incorrect NSAP.
For class 1 only, a UDT message is considered as
incorrectly delivered if it is delivered out of sequence by
the NSP.
- out of sequence probability
This parameter gives the probability that UDT messages are
delivered out of sequence to the user by the NSP.
Note - This parameter is relevant only for class 1.
- total transit delay of a UDT message
This parameter is the elapsed time between a N-UNITDATA
request issued by a SCCP user at the originating node and
the correponding N-UNIDATA indication issued to the SCCP
user at the destination node.
This parameter is composed of several internal parameters:
- sending time of a UDT message by the SCCP
- MTP overall transfer time
- transit time of a UDT message for the relay function at a relay
point
- receiving time of a UDT message by the SCCP
Depending on the configuration, the second parameter could appear one
or several times and the third parameter could appear zero, one or
several times. This is illustrated in Figure 1/Q.716.
A probabilistic approach has to be taken to give values to this
parameter, considering the various possible SCCP routes and the
existence of queues at several points.
- unavailability of a SCCP relation
This parameter characterizes the inability for two SCCP users to
communicate via the NSP.
This parameter is determined by the unavailability of the individual
components of a SCCP relation: SCCP at the two endpoints, one or
several signalling relations and zero, one or several relay points.
This unavailability can be reduced by the duplication of routes at the
SCCP level.
PAGE10 Fascicle VI.7 - Rec. Q.716
Figure 1/Q.716 - T1109960-88
2.1.2 Internal parameters
The following parameters are internal to the network service but they
contribute to the quality of service as components of a parameter of the previous
section for connectionless classes of the SCCP.
- sending time of a UDT message by the SCCP
This parameter is the elapsed time between a N-UNIDATA
request and the corresponding MTP-TRANSFER request at the
originating node.
Note - The value of this parameter may differ substantially
depending whether or not a translation function is used in
the SCCP.
- MTP overall transfer time
This parameter is already defined in Recommendation Q.706 as parameter
T0 in S 4.3.3.
- transit time of a UDT message for the relay function at a
relay point
This parameter is the elapsed time between a MTP-TRANSFER
indication primitive corresponding to an incoming UDT
message at a relay point (i.e. a signalling point where are
implemented the SCCP translation functions), and the
associated MTP-TRANSFER request primitive corresponding to
the outgoing UDT message (which may differ from the
incoming one by the called party address).
A probabilistic approach has to be taken to give values to
this parameter, considering the existence of queues and
that it is possible for the translation functions to be
congested.
- receiving time of a UDT message by the SCCP
This parameter is the elapsed time between a MTP-TRANSFER
indication and the corresponding N-UNIDATA indication at
the destination node.
- unavailability of a relay point
This parameter characterizes the unavailability of the
translation functions of the SCCP at a relay point.
Fascicle VI.7 - Rec. Q.716 PAGE1
2.2 Performance parameters for the connection oriented classes
2.2.1 Quality of service parameters
The following parameters define the quality of service as seen by a user
of the connection oriented classes of the SCCP.
- signalling connection establishment time
This parameter is the elapsed time between a N-CONNECT
request and the corresponding N-CONNECT confirmation
primitive for a successful signalling connection
establishment.
This delay is composed of two parameters: one which depends
of the user at the destination node and one which depends
of the NSP. The first one which is the elapsed time between
a N-CONNECT indication and response at the destination will
be specified for each user. The second one is an internal
parameter of the SCCP and will be called SCCP component of
the signalling connection establishment time. It will be
specified in this SCCP performances Recommendation.
Moreover it is possible to specify here the maximum
signalling connection establishment time. It is equal to
the connection establishment timer (see Recommendation
Q.714).
- signalling connection establishment failure probability
A signalling connection establishment failure is defined as
a connection refusal or a time-out for the connection
establishment timer coming from the SCCP.
The dimensioning of the SCCP regarding the number of local
reference numbers will impact this signalling connection
establishment failure probability. The unavailability of a
SCCP relation is also an internal parameter impacting this
probability.
The connection refusals coming from the called user must
not be taken into account. This also applies for the
time-out coming from this called user.
Note - It is possible for the connection refusals to
distinguish between the one coming from the user and the
one coming from the SCCP, but that is impossible for the
time-out of the connection establishment timer.
- throughput
This parameter is specified independently for each
direction of transmission and corresponds to a number of
octets of user data (contained in NSDU) transferred per
second on a signalling connection.
Note - Only successfully transferred user data are taken
into account; that means: to the correct destination,
error-free and without missequencing.
- overall transit time of DT messages
This parameter is the elapsed time between a N-DATA request
and the corresponding N-DATA indication.
This parameter is composed of several internal parameters:
- sending time of a DT message by the SCCP,
- MTP overall transfer time,
- transit time of a DT message for the relay function at a relay
point with coupling,
- receiving time of a DT message by the SCCP.
Depending of the configuration of the signalling connection, the second
parameter could appear one or several times and the third parameter
could appear zero, one or several times (see Figure 1/Q.716).
A probabilistic approach has to be taken to give values to this
parameter, considering the various possible SCCP routes and the
existence of queues at several points.
- undetected errors
This parameter gives the probability that a DT message is
delivered with user data which is defective.
- residual error rate for DT messages
This parameter gives the probability that a DT message is
PAGE10 Fascicle VI.7 - Rec. Q.716
lost, duplicated, missequenced or incorrectly delivered by
the NSP.
A DT message is incorrectly delivered if user data is
delivered in a corrupted condition (see undetected errors
above), or the user data are delivered to an incorrect
NSAP.
Fascicle VI.7 - Rec. Q.716 PAGE1
- out of sequence probability for DT messages
This parameter gives the probability that DT messages are
delivered out of sequence to the user by the NSP.
- signalling connection unsolicited reset and premature
release probability
This parameter gives the probability that a connection
release or reinitialization due to the SCCP occurs on a
signalling connection during a given time.
The unavailability of a SCCP relation is an internal
parameter to be considered when calculating the probability
of a connection release occurence due to the SCCP.
- signalling connection reset delay
This parameter is the elapsed time between a N-RESET
request and the corresponding N-RESET confirmation
primitive for a successful signalling connection reset.
2.2.2 Internal parameters
The following parameters are internal to the network service but they
contribute to the quality of service as components of a parameter of the previous
section for connection oriented classes of the SCCP.
- SCCP component of the signalling connection establishment
time
This parameter is composed of two times:
- the elapsed time between a N-CONNECT request primitive at the
origin node and the corresponding N-CONNECT indication primitive at
the destination node.
- the elapsed time between a N-CONNECT response primitive at the
destination node and the corresponding N-CONNECT confirmation
primitive at the origin node.
It is composed of several internal parameters:
- Sending time of a CR message by the SCCP
- MTP overall transfer time
- Transit time of a CR message for the relay function at a relay
point without coupling
- Transit time of a CR message for the relay function at a relay
point with coupling
- Receiving time of a CR message by the SCCP
- Sending time of a CC message by the SCCP
- Transit time of a CC message for the relay function at a relay
point with coupling
- Receiving time of a CC message by the SCCP
Depending on the configuration these parameters can appear zero, one or
several times.
A probabilistic approach has to be taken to give values to this
parameter, considering the various possible configurations and the
existence of queues at several points.
- sending time of a CR message by the SCCP
This parameter is the elapsed time between the N-CONNECT
request primitive and the corresponding MTP-TRANSFER
request primitive (for the transfer of the CR message).
Note - The value of this parameter may differ substantially
depending wether or not a translation function is used in
the SCCP.
- MTP overall transfer time
This parameter is already defined in Recommendation Q.706 as parameter
T0 in S 4.3.3.
- transit time of a CR message for the relay function at a
relay point without coupling
This parameter is the elapsed time between a MTP-TRANSFER
indication primitive corresponding to an incoming CR
message at a relay point without coupling, and the
associated MTP-TRANSFER request primitive corresponding to
the outgoing CR message.
- transit time of a CR message for the relay function at a
relay point with coupling
This parameter is the elapsed time between a MTP-TRANSFER
PAGE10 Fascicle VI.7 - Rec. Q.716
indication primitive corresponding to an incoming CR
message at a relay point with coupling, and the associated
MTP-TRANSFER request primitive corresponding to the
outgoing CR message (which may differ from the incoming one
only by the called party address).
Fascicle VI.7 - Rec. Q.716 PAGE1
- receiving time of a CR message by the SCCP
This parameter is the elapsed time between a MTP-TRANSFER
indication primitive (for an incoming CR message), and the
corresponding N-CONNECT indication primitive.
- sending time of a CC message by the SCCP
This parameter is the elapsed time between a N-CONNECT
respose primitive and the corresponding MTP-TRANSFER
request primitive (for the transfer of the CC message).
- transit time of a CC message for the relay function at a
relay point with coupling
This parameter is the elapsed time between a MTP-TRANSFER
indication primitive corresponding to an incoming CC
message at a relay point with coupling, and the associated
MTP-TRANSFER request primitive corresponding to the
outgoing CR message.
- receiving time of a CC message by the SCCP
This parameter is the elapsed time between a MTP-TRANSFER
indication primitive (for an incoming CC message), and the
corresponding N-CONNECT confirmation primitive.
- unavailability of a SCCP relation
This parameter characterizes the inability for two SCCP users to
communicate via the NSP.
This parameter is determined by the unavailability of the individual
components of a SCCP relation: SCCP at the two endpoints, one or
several signalling relations and zero, one or several relay points with
coupling and without coupling.
The unavailability can be reduced by the duplication of routes at the
SCCP level.
- unavailability of a relay point
This parameter characterizes the unavailability of the SCCP at a relay
point.
- sending time of a DT message by the SCCP
This parameter is the elapsed time between a N-DATA request
primitive and the corresponding MTP-TRANSFER request
primitive (for the transfer of a DT message).
- transit time of a DT message for the relay function at a
relay point with coupling
This parameter is the elapsed time between a MTP-TRANSFER
indication primitive corresponding to an incoming DT
message at a relay point with coupling, and the associated
MTP-TRANSFER request primitive corresponding to the
outgoing DT message.
- receiving time of a DT message by the SCCP
This parameter is the elapsed time between a MTP-TRANSFER
indication primitive (for an incoming DT message), and the
corresponding N-DATA indication primitive.
2.3 Correspondence between the QOS parameters and the class
The correspondence between the quality of service parameters defined in SS
2.1.1 and 2.2.1 above and their applicability to the various classes of the SCCP
are illustrated in Table 1/Q.716 below.
3 Specified values for internal parameters
3.1 Internal parameters for classes 0 and 1
Transit time of a UDT message in a relay point
The transit time of a UDT message in a relay point is composed
of the transit time of a UDT message for the relay function in a
relay point and of the time elapsed in the MTP at this relay point
for the UDT message: it is measurable externally. It is described
in Figure 2/Q.716 and it should not exceed the values given in
Table 2/Q.716.
TABLE 1/Q.716
Protocol class
Parameter 0 1 2 3
Undetected errors Y
PAGE10 Fascicle VI.7 - Rec. Q.716
Y Y Y
Residual error probability Y Y Y Y
Out of sequence probability N Y Y Y
Total transit delay of a message Y Y Y Y
Unavailability of a SCCP relation Y Y Y Y
Signalling connection establishment time N N Y Y
Signalling connection establishment failure probability N N Y Y
Fascicle VI.7 - Rec. Q.716 PAGE1
Throughput N N Y Y
Signalling connection unsolicited reset and premature N N Y Y
release probability
Signalling connection reset delay N N N Y
Figura 2/Q.716 - T1109970-88
TABLE 2/Q.716
Traffic load for Transit time of a UDT message in a relay
the point (in ms)
translation Mean 95%
function
Normal 50 - 155 100 - 310
+15% 100 - 233 200 - 465
+30% 250 - 388 500 - 775
Note - All values are provisional.
The normal traffic load for the translation function is the load for which
the point is dimensioned.
These figures assume a message length distribution as given in Table
2/Q.706 (short messages with a mean message length of 120 bits). For long
messages (272 octets of SIF) it is necessary to add about 30 ms to each figure,
to take into account the emitting time at 64 kbit/s much longer for long messages
than for short messages.
Unavailability of a relay point
The unavailability of a relay point should not exceed 10-4.
3.2 Internal parameters for classes 2 and 3
PAGE10 Fascicle VI.7 - Rec. Q.716
Transit time of a CR message at a relay point without coupling
The transit time of a CR message at a relay point without
coupling is composed of the transit time of a CR message for the
relay function in a relay point without coupling and of the time
elapsed in the MTP at this relay point without coupling for the CR
message: it is measurable externally. It should not exceed the
values given in Table 3/Q.716.
TABLE 3/Q.716
Traffic load for Transit time of a CR message in a relay
the point without coupling (in ms)
relay function Mean 95%
Normal 50 - 155 100 - 310
+15% 100 - 233 200 - 465
+30% 250 - 388 500 - 775
Note - All valus are provisional.
Fascicle VI.7 - Rec. Q.716 PAGE1
The normal traffic load for the relay function is the load for which the
point is dimensioned.
These figures assume a message length distribution as given in Table
2/Q.706 (short messages with a mean message length of 120 bits). For long
messages (128 octets of SCCP user data) it is necessary to add about 15 ms to
each figure, to take into account the emitting time at 64 kbit/s much longer for
long messages than for short messages.
Transit time of a CR message in a relay point with coupling
The transit time of a CR message at a relay point with
coupling is composed of the transit time of a CR message for the
relay function in a relay point with coupling and of the time
elapsed in the MTP at this relay point with coupling for the CR
message: it is measurable externally. It should not exceed the
values given in Table 4/Q.716.
TABLE 4/Q.716
Traffic load for Transit time of a CR message in a relay
the point with coupling (in ms)
relay function Mean 95%
Normal 75 - 180 150 - 360
+15% 150 - 270 300 - 540
+30% 375 - 450 750 - 900
Note - All values are provisional.
The normal traffic load for the relay function is the load for which the
point is dimensioned.
These figures assume a message length distribution as given in Table
2/Q.706 (short messages with a mean message length of 120 bits). For long
messages (128 octets of SCCP user data) it is necessary to add about 15 ms to
each figure, to take into account the emitting time at 64 kbit/s much longer for
long messages than for short messages.
Transit time of a CC message in a relay point with coupling
The transit time of a CC message at a relay point with
coupling is composed of the transit time of a CC message for the
relay function in a relay point with coupling and of the time
elapsed in the MTP at this relay point with coupling for the CC
message: it is measurable externally. It should not exceed the
values given in Table 5/Q.716.
TABLE 5/Q.716
Traffic load for Transit time of a CC message in a relay
the point with coupling (in ms)
relay function Mean 95%
Normal 30 - 110 60 - 220
+15% 60 - 165 120 - 330
+30% 150 - 275 300 - 550
PAGE10 Fascicle VI.7 - Rec. Q.716
Note - All values are provisional.
Fascicle VI.7 - Rec. Q.716 PAGE1
The normal traffic load for the relay function is the load for which the
point is dimensioned.
These figures assume a message length distribution as given in Table
2/Q.706 (short messages with a mean message length of 120 bits). For long
messages (128 octets of SCCP user data) it is necessary to add about 15 ms to
each figure, to take into account the emitting time at 64 kbit/s much longer for
long messages than for short messages.
Transit time of a DT message in a relay point with coupling
The transit time of a DT message (DT1 or DT2) at a relay point
with coupling is composed of the transit time of a DT message for
the relay function in a relay point with coupling and of the time
elapsed in the MTP at this relay point with coupling for the DT
message: it is measurable externally. It should not exceed the
values given in Table 6/Q.716.
TABLE 6/Q.716
Traffic load for Transit time of a DT message in a relay
the point with coupling (in ms)
relay function Mean 95%
Normal 30 - 110 60 - 220
+15% 60 - 165 120 - 330
+30% 150 - 275 300 - 550
Note - All values are provisional.
The normal traffic load for the relay function is the load for which the
point is dimensioned.
These figures assume a message length distribution as given in Table
2/Q.706 (short messages with a mean message length of 120 bits). For long
messages (255 octets of SCCP user data) it is necessary to add about 30 ms to
each figure, to take into account the emitting time at 64 kbit/s much longer for
long messages than for short messages.
Unavailability of a relay point without coupling
The unavailability of a relay point without coupling should
not exceed 10-4.
Unavailability of a relay point with coupling
The unavailability of a relay point with coupling is for
further study.
PAGE10 Fascicle VI.7 - Rec. Q.716