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Nortel Release Link Trunk (RLT) Support

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Cisco PGW 2200 Softswitch Nortel Release Link Trunk (RLT) Support Feature Module

Table Of Contents

Cisco PGW 2200 Softswitch Nortel Release Link Trunk (RLT) Support Feature Module

Feature Description

Call Flows

RLT Messages

Facility Request Message

Facility Accept Message

Facility Reject Message

Benefits

Prerequisites

Restrictions or Limitations

Related Documents

Supported Standards, MIBs, and RFCs

Provisioning Tasks

Provisioning Trunk Groups

Provisioning Specific Property to the Trunk Group

Provisioning the FACILITY Result Type

Provisioning Examples

Software Changes for This Feature

Properties

New Properties

Result Type Definitions

Modified Result Type Definitions

Troubleshooting the Feature

Obtaining Documentation and Submitting a Service Request

Glossary


Cisco PGW 2200 Softswitch Nortel Release Link Trunk (RLT) Support Feature Module


Document Release History

Publication Date
Comments

April 30, 2010

Initial release of document.


Feature History

Release
Modification

9.8(1)

The Nortel Release Link Trunk (RLT) Support feature is introduced on the Cisco PGW 2200 Softswitch software.


This document describes the Nortel Release Link Trunk (RLT) Support feature. The feature is described in the following sections:

Feature Description

Supported Standards, MIBs, and RFCs

Provisioning Tasks

Provisioning Examples

Software Changes for This Feature

Troubleshooting the Feature

Obtaining Documentation and Submitting a Service Request

Glossary

Feature Description

The Nortel RLT Support feature extends the existing RLT mechanism on the Cisco PGW 2200 Softswitch. It enables the Cisco PGW 2200 Softswitch to release a call when it receives a SIP REFER message. With this feature, trunk facilities can be optimized because SS7 circuits are released after call bridging or redirection occurs. Cisco PGW 2200 Softswitch can interwork with the switches that are configured to accept RLT message sequences as following:

Cisco PGW 2200 Softswitch can send out Facility Request (FAR) messages to preceding switches.

Cisco PGW 2200 Softswitch can accept Facility Accept (FAA) or Facility Reject (FRJ) responses.

When FAA is received, Cisco PGW 2200 Softswitch waits for the switch to release the call.

When FRJ is received, Cisco PGW 2200 Softswitch releases the call. It allows the preceding switch to bridge the call to the destination.


Note For more information on the FAR, FAA, and FRJ messages, see the "RLT Messages" section.


For SIP interoperability, when a SIP BYE is received (for example, the called party terminates the call), Cisco PGW 2200 Softswitch sends out an ISUP REL message, even if an FAR message has been sent and no response (FAA or FRJ) has been received. Cisco PGW 2200 Softswitch releases the call if no response is received within 5 seconds.

The RLT behavior selection is based on the dial plan (A/B number analysis). It is not based on the trunk group. Calls from the same incoming SS7 trunk group might have different transfer behaviors.


Note This feature has only been tested on the Cisco PGW 2200 Softswitch for its interworking with Nortel switches. RLT functionality changes on Nortel switches have potential impact on RLT interworking between Cisco PGW 2200 Softswitch and Nortel switches. If message interfaces and RLT call flows have changed, the modification on RLT functionality is required.


Figure 1 shows a typical deployment for this feature. In this deployment, the Cisco PGW 2200 Softswitch receives the SIP REFER message from the SIP server. It can interwork with the SS7 switch that is configured to handle RLT messages. The Cisco PGW 2200 Softswitch can send FAR to the switch and receive FAA or FRJ from the switch.

Figure 1 Typical Deployment for This Feature

Call Flows

This section provides call flows of basic RLT functionality scenarios.

Figure 2 provides the call flow of the FAA received scenario.

Figure 2 Call Flow of FAA Received

Figure 3 provides the call flow of the FRJ received scenario. If the FAR message is rejected by the switch, Cisco PGW 2200 Softswitch clears the call by sending a REL message to the switch (cause code: Normal Call Clearing).

Figure 3 Call Flow of FRJ Received

Figure 4 provides the call flow of the no response received scenario. If the Cisco PGW 2200 Softswitch has not received any response when the timer expires, it sends a REL message (to the SS7 side) or a BYE message (to the SIP side) and releases the line.

Figure 4 Call Flow of No Response Received

RLT Messages

This section describes the messages that Cisco PGW 2200 Softswitch handles with the RLT functionality.

Facility Request Message

The Cisco PGW 2200 Softswitch sends an FAR message to the switch to request the activation of a facility. All parameters and fields of FAR message are hard-coded, except Calling and Called Party Number Length, Odd/Even indicator, and Address signals. After sending an FAR message, the Cisco PGW 2200 Softswitch waits for an FAA or FRJ response.

If both Calling Party Number and Charge Number are present in an IAM message, the Charge Number is used. Cisco PGW 2200 Softswitch sends it back in the Calling Party Number parameter of the FAR. If either number is present, that number is used as the Calling Party Number parameter in the FAR. If neither number is present, no Calling Party Number parameter is sent in the FAR.

The values of following Calling Party Number parameters of FAR are copied from either Charge Number or Calling Party Number:

Nature of Address (NOA)

Numbering Plan Indicator (NPI)

Presentation/Screening Indicators

Table 1 provides the definition of the FAR message.

Table 1 FAR Message Definition 

Parameter Name
Type
Length
Description

Message Type

F1

1 byte

Identifies the type of ISUP message.

Facility Indicator

F

1 byte

Contains information that defines and controls RLT billing.

Called Party Number

O2

3-14 bytes

Contains the Called Party Number that arrives in the Refer-To header of SIP REFER message.

Calling Party Number

O

4-14 bytes

Contains the Calling Party Number that arrives in the initial IAM.

Operator Information

O

14 bytes

Contains information about the answering agent.

1 F = Fixed-length parameters (mandatory).

2 O = Fixed or variable length parameters (optional).


Table 2 provides an example of the FAR message that the Cisco PGW 2200 Softswitch sends out.

Table 2 FAR Message Example 

Type
Hex
Binary
Message Information

F

1F

00011111

Message Type

Facility Request Message (FAR)

F

11

00010001

Facility Indicator Parameter Field

Release link for operator redirect

V

01

00000001

Pointer to start of optional part

1 octet

O

70

01110000

Operator Information Parameter

O

04

00000100

LI of Operator Information Parameter

4 octets

O

0F

00001111

Operator Number

O

27

00

100111

Reorigination Type
Operator Number

The originator receives a dial tone

9999

O

14

0

0010100

OPR
Entry code

None

Station paid, operator-assisted

O

00

0

0000000

TAC
Trouble indicator

No request

None

O

0A

00001010

Calling Party Number Parameter

O

07

00000111

LI of Calling Party Number Parameter

7 octets

O

03

0

0000011

Odd/Even indicator
Nature of Address indicator

Even

National (significant) number

O

14

0001

0100

Numbering Plan
Presentation/Screen indicators

ISDN (Telephony) numbering plan

Presentation restricted/user provided, not screened

O

75

0111

0101

Address signal
Address signal

7

5

O

24

0010

0100

Address signal
Address signal

2

4

O

47

0100

0111

Address signal
Address signal

4

7

O

63

0110

0011

Address signal
Address signal

6

3

O

76

0111

0110

Address signal
Address signal

7

6

O

04

00000100

Called Party Number Parameter

O

07

00000111

LI of Called Party Number Parameter

7 octets

O

03

0

0000011

Odd/Even indicator
Nature of Address indicator

Even

National (significant) number

O

10

0001

0000

Numbering Plan

Reserved

ISDN (Telephony) numbering plan

O

75

0111

0101

Address signal
Address signal

7

5

O

43

0100

0011

Address signal
Address signal

4

3

O

58

0101

1000

Address signal
Address signal

5

8

O

63

0110

0011

Address signal
Address signal

6

3

O

49

0100

1001

Address signal
Address signal

4

9

O

00

00000000

End Of Optional Parameters Fields Indicator Parameter

Facility Accept Message

The switch sends an FAA message to the Cisco PGW 2200 Softswitch in response to an FAR message. This message indicates that the switch has invoked the requested facility.

Table 3 provides the definition of the FAA message.

Table 3 FAA Message Definition 

Parameter Name
Type
Length
Description

Message Type

F1

1 byte

Identifies the type of ISUP message.

Facility Indicator

F

1 byte

Contains information that defines and controls RLT billing.

Call Reference

O2

8 bytes

Contains circuit-independent information that identifies a particular call. Includes the call identity and the point code of the switch for the call.

Generic Digits

O

4-136 bytes

Contains information about a supplementary service in the form of digits. Defines the type of digits it contains and includes encoding method indicators.

1 F = Fixed-length parameters (mandatory).

2 O = Fixed or variable length parameters (optional).


Facility Reject Message

The switch sends an FRJ message forward to the Cisco PGW 2200 Softswitch in response to an FAR message. This message indicates that the switch could not perform the facility request.

Table 4 provides the definition of the FRJ message.

Table 4 FRJ Message Definition 

Parameter Name
Type
Length
Description

Message Type

F1

1 byte

Identifies the type of ISUP message.

Facility Indicator

F

1 byte

Contains information that defines and controls RLT billing.

Cause Indicator

V2

3 bytes

Provides the coding standard, location, and cause value for the call. Indicates why a switch could not perform the action that an FAR message requested. Identifies the network that originated the message.

1 F = Fixed-length parameters (mandatory).

2 V = Variable-length parameters (mandatory).


Benefits

This feature provides the following benefits:

When it is determined that the preceding switch can be used to bridge the call to the destination,

Frees ISUP trunks and increases traffic handling capacity.

Saves resources on the Cisco PGW 2200 Softswitch and media gateway.

Prerequisites

The Cisco PGW 2200 Softswitch must be running software Release 9.8(1). Prerequisites for this release can be found in Release Notes for the Cisco PGW 2200 Softswitch Release 9.8(1) at:

http://www.cisco.com/en/US/docs/voice_ip_comm/pgw/9/release/note/rn981.html

Restrictions or Limitations

The Nortel RLT Support feature has the following limitations:

Nortel RLT functionality only supports SS7 to SIP call scenario and ANSISS7_STANDARD variant. For non Ansi-SS7 to SIP call scenarios, Cisco PGW 2200 Softswitch releases the call for error handling.

Cisco PGW 2200 Softswitch does not support receiving FAR on both originating and terminating Ansi-SS7 side. It does not support receiving FAA and FRJ on terminating Ansi-SS7 side. When the unexpected messages are received, Cisco PGW 2200 Softswitch ignores them without any response.

Cisco PGW 2200 Softswitch can only interwork with the switches that support the RLT functionality.

Related Documents

This document contains information that is strictly related to this feature. The documents that contain additional information related to the Cisco PGW 2200 Softswitch can be found at:

http://www.cisco.com/en/US/products/hw/vcallcon/ps2027/tsd_products_support_series_home.html

Supported Standards, MIBs, and RFCs

This section identifies the new or modified standards, MIBs, and RFCs that are supported by this feature.

Standards

This feature uses the following standards as references:

Digital Switching Systems UCS DMS-250 SS7 RLT Feature Application Guide, 297-2621-345

MIBs

No new or modified MIBs are supported by this feature.

For more information on the MIBs used in the Cisco PGW 2200 Softswitch, see Cisco PGW 2200 Softswitch MIBs at:

http://www.cisco.com/iam/PGW_MIBS/index.html

RFCs

This feature is in compliance with the following RFC:

RFC 3261 (SIP: Session Initiation Protocol)

Provisioning Tasks

This section describes provisioning tasks for this feature.

To use this feature, you need to perform the following main tasks:

Provisioning Trunk Groups

Provisioning Specific Property to the Trunk Group

Provisioning the FACILITY Result Type

For the complete provisioning examples, see the "Provisioning Examples" section.

Provisioning Trunk Groups

Use the following Man-Machine Language (MML) commands to provision trunk groups of different types:

SIP

prov-add:trnkgrp:name="1000",clli="sip-path",svc="sip-path",type="IP_SIP", 
selseq="LIDL",qable="N"

SS7

prov-add:trnkgrp:name="3000",type="TDM_ISUP",svc="ss7svc1",selseq="CASC",qable="N"

Provisioning Specific Property to the Trunk Group

The RltPrefixLength property is specific to the Nortel RLT functionality. It specifies the number of prefix digits to be removed from the RLT redirection number. The redirection number is got from Refer-To header of the SIP REFER message. After prefix removal, the new redirection number is sent in called party number parameter of FAR message to ISUP side.

Use the following command to configure the trunk group property RltPrefixLength:

prov-ed:trnkgrpprop:name="3000",rltprefixlength="5"

Provisioning the FACILITY Result Type

To enable RLT functionality, use the following MML command to provision the FACILITY result type:

numan-add:resulttable:custgrpid="T002",name="fac-1",resulttype="FACILITY",dw1="3",dw2="7",
setname="rs-CSPS-1"

Provisioning Examples

This section provides a provisioning example for this feature. Additional provisioning examples for the Cisco PGW 2200 Softswitch can be found in Cisco PGW 2200 Softswitch Release 9.8 Provisioning Guide. Additional dial plan examples for the Cisco PGW 2200 Softswitch can be found in Cisco PGW 2200 Softswitch Release 9.8 Dial Plan Guide.

________________________________________
; Start a New Provisioning Session
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
prov-sta::srcver="new",dstver="rlt-prov"

________________________________________
; Add a new dialplan named "T002"
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
numan-add:dialplan:custgrpid="T002",overdec="YES"

________________________________________
; Add OPC, DPC, and External Nodes (ITP)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
prov-add:opc:name="opc1",desc="Own Point code",netaddr="1.1.1",netind=2,type="trueopc"
prov-add:dpc:name="dpc1",desc="M3UA",netaddr="1.4.4",netind=2
prov-add:extnode:name="sh-2651-322",desc="sh-2651-322",type="ITP",isdnsigtype="N/A", 
group=1
prov-add:sgp:name="m3ua-sgp1",extnode="sh-2651-322"

________________________________________
;Add an SS7 Signaling Path
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
prov-add:m3uaroute:name="m3uarte1",desc="m3uarte1",opc="opc1",dpc="dpc1", 
extnode="sh-2651-322",PRI=1
prov-add:m3uakey:name="m3uakey1",desc="m3uakey1",opc="opc1",dpc="dpc1",routingcontext=12, 
si="ISUP",networkappearance=1
prov-add:ss7path:name="ss7svc1",desc="To Other Side PGW SS7", 
mdo="ANSISS7_STANDARD",custgrpid="T002",side="network",dpc="dpc1",m3uakey="m3uakey1"
prov-add:association:name="m3ua-assoc1",sgp="m3ua-sgp1",type="M3UA",ipaddr1="IP_Addr1", 
port=2905,peeraddr1="10.0.90.23",peerport=2905,rcvwin=18000,maxinitretrans=10, 
maxinitrto=2000,maxretrans=5,cumsackto=300,bundleto=100,minrto=300,maxrto=3000,hbto=2000, 
ipprecedence="ROUTINE",dscp="AF31",maxretransdest=3

________________________________________
; Add an External Node (AS5400)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
prov-add:extnode:name="sh-5400-308",desc="sh-5400-308",type="AS5400",isdnsigtype="N/A", 
group=0
prov-add:mgcppath:name="mgcp5400-308",desc="Service to sh-5400-308",extnode="sh-5400-308"
prov-add:iplnk:name="iplink5400-308-1",desc="MGCP link-1 to AS-5400-308", 
svc="mgcp5400-308",ipaddr="IP_Addr1",port=2427,peeraddr="10.0.94.9",peerport=2427,pri=1

________________________________________
; Add an SS7 Trunk Group
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
prov-add:trnkgrp:name="3000",type="TDM_ISUP",svc="ss7svc1",selseq="CASC",qable="N"

________________________________________
; Provision the Trunk Group Property rltprefixlength
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
prov-ed:trnkgrpprop:name="3000",rltprefixlength="5" 

________________________________________
; Add Trunks and Route List
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
prov-add:switchtrnk:name="1",trnkgrpnum="3000",span="ffff",cic=1,cu="sh-5400-308", 
endpoint="s7/ds1-6/1@sh-5400-308.cisco.com",spansize=31
prov-add:rttrnkgrp:name="3000",type=1
prov-add:rttrnk:weightedTG="OFF",name="RT-OTHER-PGW-SS7",trnkgrpnum=3000
prov-add:rtlist:name="RTLIST-OTHER-PGW-SS7",rtname="RT-OTHER-PGW-SS7",distrib="OFF"

________________________________________
; Add a SIP Signaling Path
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
prov-add:sippath:name="sip-path",desc="SIP path",mdo="IETF_SIP"
prov-add:siplnk:name="sip-link",desc="SIP link",svc="sip-path",ipaddr="Virtual_IP_Addr1", 
port=5060,pri=1
prov-add:trnkgrp:name="0001",clli="sipin-path",svc="sip-path",type="SIP_IN",selseq="LIDL",
qable="N",default=1
prov-add:profile:name="pf-1",type="SIPPROFILE",custgrpid="T002",mgcdomain="10.0.242.133"
prov-add:trnkgrpprof:name="1",profile="pf-1"

________________________________________
; Add SIP Trunk Groups
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
prov-add:trnkgrp:name="1000",clli="sip-path",svc="sip-path",type="IP_SIP",selseq="LIDL", 
qable="N"
prov-ed:trnkgrpprop:name="1000",custgrpid="T002",MGCdomain="10.0.242.133"
prov-add:siprttrnkgrp:name="1000",url="10.0.1.233",srvrr=0,sipproxyport=5060, 
version="2.0",cutthrough=1,extsupport=1
prov-add:rttrnk:weightedTG="OFF",name="rt1000",trnkgrpnum=1000
prov-add:rtlist:name="rtlist1000",rtname="rt1000",distrib="OFF"

________________________________________
; Dial plan routing to SS7 side
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
numan-add:resultset:custgrpid="T002",name="rs-ss7-pgw"
numan-add:resulttable:custgrpid="T002",setname="rs-ss7-pgw",name="cut30", 
resulttype="BMODDIG",dw1="1",dw2="2"
numan-add:resulttable:custgrpid="T002",name="route-ss7-pgw",resulttype="ROUTE", 
dw1="RTLIST-OTHER-PGW-SS7",setname="rs-ss7-pgw"
numan-add:bdigtree:custgrpid="T002",callside="originating",digitstring="30", 
setname="rs-ss7-pgw"

________________________________________
; Dial plan routing to SIP side
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
numan-add:resultset:custgrpid="T002",name="rs-CSPS-1"
numan-add:resulttable:custgrpid="T002",name="fac-1",resulttype="FACILITY",dw1="3",dw2="7",
setname="rs-CSPS-1"
numan-add:resulttable:custgrpid="T002",setname="rs-CSPS-1",name="cut10", 
resulttype="BMODDIG",dw1="1",dw2="2"
numan-add:resulttable:custgrpid="T002",name="route",resulttype="ROUTE",dw1="rtlist1000", 
setname="rs-CSPS-1"
numan-add:bdigtree:custgrpid="T002",callside="originating",digitstring="10", 
setname="rs-CSPS-1"

________________________________________
; Save the Provisioning Session
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
prov-dply

Software Changes for This Feature

The following sections contain software changes related to this feature:

Properties

Result Type Definitions

Properties

This section describes new and modified properties for this feature. For more information on the other properties, see Cisco PGW 2200 Softswitch Release 9 MML Command Reference.

New Properties

Table 5 describes the new properties for this feature.

Table 5 New Properties for the Nortel RLT Support Feature 

Property
Description

*.RltPrefixLength

Length of the prefix to be removed from the RLT redirection number before the number is sent to ISUP side. Valid value must be larger than 0. Value of 0 means no redirection number manipulation is enabled. If the value is larger than or equal to the total length of the redirection number, Cisco PGW 2200 Softswitch automatically ignores this configuration.

Value Range: 0-255.

Default value: 0.


Result Type Definitions

This section describes the new and modified result types for this feature. For information on other result types, see Cisco PGW 2200 Softswitch Release 9.8 Dial Plan Guide.

Modified Result Type Definitions

Table 6 describes the modified result types for this feature.

Table 6 Modified Result Type Definitions 

Result Number
Result Type
Dataword1
Dataword2
Dataword3
Dataword4
Analysis Points
Result Type Valid For
Intermediate
End Point
A-digit analysis
B-digit analysis
Cause
Pre-analysis

7

FACILITY

Type

Treatment

0 (not used)

0 (not used)

 X

 X

 X


The following paragraphs contain definitions of the result type listed in Table 6.

FACILITY

The FACILITY result type is modified for this feature. A new value 7 for Dataword2 is introduced. You must use the dw1=3 and dw2=7 combinations to enable RLT function on the Cisco PGW 2200 Softswitch. For other data words combinations and their usages, see Cisco PGW 2200 Softswitch Release 9.8 Dial Plan Guide.

The Nortel RLT Support feature introduces the following new data word value:

Treatment (dw2)—This dataword provides the actions required based on the Type dataword value (dw1). Valid values are 1-7. The Nortel RLT Support feature introduces the new value 7 for dw2 (Treatment) in software Release 9.8(1) S9P9.


Note For more information on the FACILITY result type, see Cisco PGW 2200 Softswitch Release 9.8 Dial Plan Guide.


Troubleshooting the Feature

This section provides the troubleshooting solutions for this feature.

The RLT functionality does not work as expected.

 
Action
Description

Step 1 

Check the FACILITY result type.

Ensure that you have provisioned the result type FACILITY for the dial plan. The dw1=3 and dw2=7 combination of FACILITY result type enables RLT function on the Cisco PGW 2200 Softswitch.

For result type details, see the "Result Type Definitions" section.

Step 2 

Check the ANSISS7_STANDARD variant.

Ensure that you have provisioned the ANSISS7_STANDARD variant for SS7 signaling path. For MML command details, see the "Provisioning Examples" section.

Obtaining Documentation and Submitting a Service Request

For information on obtaining documentation, submitting a service request, and gathering additional information, see the monthly What's New in Cisco Product Documentation, which also lists all new and revised Cisco technical documentation, at:

http://www.cisco.com/en/US/docs/general/whatsnew/whatsnew.html

Subscribe to the What's New in Cisco Product Documentation as a Really Simple Syndication (RSS) feed and set content to be delivered directly to your desktop using a reader application. The RSS feeds are a free service and Cisco currently supports RSS Version 2.0.

Glossary

Table 7 Acronym Expansions 

Acronym
Expansion

FAA

Facility Accept

FAR

Facility Request

FRJ

Facility Reject

ISUP

ISDN User Part

MML

Man-Machine Language

NOA

Nature of Address

NPI

Numbering Plan Indicator

PGW

PSTN Gateway

RLT

Release Link Trunk

SIP

Session Initiation Protocol

SS7

Signaling System 7