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Subscriber and Trunk Priority/Category Handling in C-DOT
DSS
A. Some Related Parameters
1. SUB-PRI: Subscriber Priority [CRE-SUB / MOD-SUB-CHAR /
MOD-LINCHAR]
This is a class-of-service
parameter and is used for assigning preferences to subscriber "lines". The
preference level is used for allowing/disallowing calls from lines in
times of congestion. Priority 1 to 8 are assigned via MMC commands, while
9 to 14 are automatically assigned by the system as follows:
| Subscriber Priority at local exchange
|
Meaning |
| 1,7,8 |
ORDINARY
Subscriber |
| 2,3,5,4,6 |
Priority
subscriber |
| 9 |
ORD-CCB |
| 10 |
CCB-STD |
| 12 |
PBX |
| 13 |
Operator |
| 11,14 |
Spare |
The priority of the calls originated from a Trunk Offer
operator is assigned as 13 for the purpose of call routing. However, in
MF-R2, the subscriber category is sent as 5.
2. SUB-CTG : Subscriber Category [CRE-SUB / MOD-SUB-CHAR]
This parameter can have
values from 1 to 64 and is used to differentiate charging of calls
originating from different subscriber "lines". All lines in a BM have the
same category.
3. TRK-PRI: Trunk Priority [CRE-TGP / MOD-TGP-CHAR]
All circuits (trunks) in an Incoming Trunk Group (TGP) are
assigned the same priority for the purpose of outgoing trunk assigned on a
route selection. Calls received from TGPs can be restricted to only some
outgoing TGPs based on the trunk priority. The following points may be
noted:
a) In case of decadic trunk signaling. TGP-PRI overrides
the SUB-PRI received from the originating exchanges.
b) Calls with priority 1 are routed on TGP for priority
1. This is generally reserved for originating calls and is not assigned
for Incoming calls for the purpose of differentiating Initial Charge.
c) In case of R2, calls from priority 2,3,4,5 and 6 are
routed on trunk group with priority 2.
d) Incoming calls with category 5, i.e. as a result of
trunk offer, are sent out only on outgoing trunks meant for priority 13
calls.
B. Assignment of Subscriber Priority at Local Exchange and it’s
Treatment at Transit Center
a) In decadic signaling, the local data of the TGP is
relevant. No significance of the sub priority at the LE.
b) In MF-R2,, the subscriber priority at the LE is
mapped as follows:
|
SUB-PRI at Local Exchange |
Sub category in Mod-R2 |
Treatment at transit
Centre |
| 1,7,8 |
1 |
Local Incoming TGP-PRI
data takes precedence at Transit |
| 2,3,4,5,6 |
2 |
Calls will pass
through OG TGP defined for Priority=2 |
| 13 |
5 |
Calls will pass through OG TGP defined for Priority=13 |
| 9,10,12 |
1 |
Local Incoming TGP-PRI data takes precedence at Transit |
| 11,14 |
Spare |
Spare (not
implemented) |
Note:- If SUB-PRI = 11,14 or undefined category will be
passed treating them as an ordinary Subscriber at the transient center.
c) In case of CCS7 signaling, subscriber priority
information is carried in the IAM message as part of the
Calling-Subscriber-Category field.
| Sub-PRI at LE |
Calling sub cat in IAM |
Treatment in transit Centre |
|
1 |
Ordinary Calling
Subscriber(0000 1010) (0A) |
At the originating Exchange treated
as Priority=1 for the purpose of outgoing trunk selection. The
calling sub cat field in IAM is transparently passed ahead. At the
transit point it selects outgoing TGP depending on the Incoming
TGP Priority. |
|
2,3,4,5,6 |
Calling Subscriber with Priority
(0000 1011) (0B) |
At the originating Exchange treated
at Priority=2,3,4,5,6respectively for the purpose of outgoing
trunk selection. The calling-sub-cat field in the IAM is
transparently passed ahead. At the transit point it selects TGP
for TGP-PRI=1 irrespective of Incoming TGP Priority. |
|
9 |
Coin Collection Box
(1110 0001) (E1) |
At the originating Exchange treated
as Priority=9 for the purpose of outgoing trunk selection. The
calling-sub-cat field in IAM is transparently passed ahead. At the
transit point it selects the TGP for TGP-PRI=1 irrespective of
Incoming TGP Priority. |
|
10 |
Pay Phone (STD-PCO)
(1110 0001) (E1) |
At the originating Exchange treated
as Priority=10 for the purpose of outgoing trunk selection. The
calling-sub-cat field in the IAM is transparently passed ahead. At
the transit point it selects TGP for TGP-PRI=1 irrespective of
Incoming TGP Priority. |
|
12 |
PABX (1110 0100) (E4) |
At the
originating Exchange treated as Priority=12 for the purpose of
outgoing trunk selection. The calling-sub-cat field in the IAM is
transparently passed ahead. At the transit point it selects TGP
for TGP-PRI=1 irrespective of Incoming TGP Priority. |
|
13 |
National Operator with TO (0000
1001) (09) |
At the
originating Exchange treated as Priority=13 for the purpose of
outgoing trunk selection. The calling-sub-cat field in the IAM is
transparently passed ahead. At the transit point it selects TGP
for TGP-PRI=13 irrespective of Incoming TGP Priority. |
|
7 |
(0000 1100) (0C) |
It is treated as Priority=7 for the
purpose of outgoing trunk selection at the originating exchange.
At the transit Exchange it selects TGP for TGP-PRI=1 for outgoing
calls. |
|
8 |
(0000 0000) (00) |
It is treated
as Priority=8 for the purpose of outgoing trunk selection at the
originating exchange. At the transit Exchange it selects TGP for
TGP-PRI=1 for outgoing calls. |
Note: The priority of the calls originated from a Trunk
Offer Operator is assigned Calling-Sub-Cat a operator with Trunk Offer
(0000 1001)
C. Problems Encountered due to the Present
Implementation:-
In case of CCS7 following
problems are observed:-
-
originating subscriber with Priority 7 and 8 are
coded as 0C {0000 1100(data call)} and 00 {0000 0000 (unknown national
use)} respectively which is not as per any specification.
-
Except Operator with Trunk Offer and Ordinary calling
subscriber, all other priority subscribers in the transit network
selection are trated as Priority=1 for the purpose of outgoing trunk
selection irrespective of incoming TGP Priority. How ever
calling-sub-cat in IAM is transparently passed. In case of ordinary
subscriber the TGP priority takes precedence for Out going TGP selection
which is correct implementation.
-
Unlike implementation in R2 signaling, Subscriber
with Priority 2,3,4,5 and 6 selects TGP in the originating Exchange
based on respective priority and not on TGP-PRI=2.
D. Solutions for the Problems Encountered:-
-
As in the case of R2 subscriber with priority 7 and 8,
should be trated as Ordinary calling subscriber both at originating and
trasit Exchange and should be coded as 0000 1010 (0A).
-
Subscribers other than priority and operator with TP
should take incoming TGP priority as priority for Outgoing TGP selection
at the transit network, as is the case in R2 signaling.
-
Subscriber with Priority 2,3,4,5 and 6 should select
TGP at the Originating Exchange for TGP-PRI=2 as in the case of R2.
-
Any other undefined category subscriber at the
transit network should be treated, as Ordinary subscriber as in the
case of R2 and the call should be passed through.
Presented on 13-10-2005.
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