NSG-Transparent E1 Feature (E1 Over IP)

Introduction

NSG Transparent E1 feature is a mechanism by which raw data present on E1 time slot can be passed transparently from one NSG to another.
It basically transparently relay the data from E1 to IP and vice versa without altering the data i.e. raw data present on any single timeslot from one NSG should be transparently transmitted over UDP in raw mode to another NSG server.

Transparent E1 is usually used  to bridge a channel that is carrying non voice signaling like sms or tcap signaling etc.
Transparent channel cannot be a part of the ISUP (SS7) cic group. But it can be part of the E1 that is carrying ss7 signaling and media.

Scenarios

Network Diagram

------> Telco-1 <----- E1 -----> NSG-1<----- ip ------> NSG-2 <----- E1 ------> Telco-2 <-----

Scenario 1

When NSG is configured as pure Transparent
NOTE: For NSG-1 and NSG-2 span X is configured pure transparent span with channel Y as trasnparent channel

Scenario 2

When NSG is configured as SS7 + Transparent
NOTE: For NSG-1 and NSG-2 span X is configured as SS7 + transparent span with channel Z as signalling channel and channel Y as trasnparent channel

In both cases what ever data is passed to NSG-1 from Telco-1 over E1 on span X channel Y is blindly passed to NSG-2 over IP and then to Teclo-2 on span X channel Y over E1.

Configuration

There are several parameters that needs to be configured for Tranparent E1 Feature.

Parameters Description

Given below the parameters with their description:
 

Based on the two different scenarios as explained earlier their respective sample configuration is given below:

Configuration for Scenario 1

In order to configure channel Y of span X as transparent the below parameter needs to be set in freetdm.conf:
b-channel => X:Y

Below is sample configuration in freetdm.conf.xml illustrating how tranparent parameters can be configured in this scenario:

<transparent_spans>
<span name="wp2">
     <channel id="1">
          <param name="remote-ip" value="192.168.3.118"/>
          <param name="remote-port" value="7002"/>
          <param name="local-ip" value="192.168.3.118"/>
          <param name="local-port" value="7001"/>
     </channel>
</span>
</transparent_spans>

For reference please find the attached sample scenario1.tgz file.

Configuration for Scenario 2

In order to configure channel Y of span X as transparent the below parameter needs to be set in freetdm.conf:
b-channel => X:Y-Z

In this scenario there are two different ways in which transparent channel can be configured.

1. When Transparent channel is not configured as a part of CIC distribution logic:    

<cc_span name="CC1">
     <param name="id" value="1"/>
     <param name="procId" value="1"/>
     <param name="isup_interface" value="1"/>
     <param name="cicbase" value="1"/>
     <param name="ch_map" value="tY,2-15,sX,17-31"/>
     <param name="typeCntrl" value="controlled"/>
     <param name="lpa_on_cot" value="0"/>
     <param name="isup.t10" value="50"/>
     <param name="isup.t35" value="170"/>
     <param name="transparent_iam" value="no"/>
     <param name="itx_auto_reply" value="no"/>
     <param name="cpg_on_progress" value="no"/>
     <param name="cpg_on_progress_media" value="yes"/>
</cc_span>

1. When Transparent channel is not configured as a part of CIC distribution logic:    

<cc_span name="CC1">
     <param name="id" value="1"/>
     <param name="procId" value="1"/>
     <param name="isup_interface" value="1"/>
     <param name="cicbase" value="1"/>
     <param name="ch_map" value="gY,2-15,sX,17-31"/>
     <param name="typeCntrl" value="controlled"/>
     <param name="lpa_on_cot" value="0"/>
     <param name="isup.t10" value="50"/>
     <param name="isup.t35" value="170"/>
     <param name="transparent_iam" value="no"/>
     <param name="itx_auto_reply" value="no"/>
     <param name="cpg_on_progress" value="no"/>
     <param name="cpg_on_progress_media" value="yes"/>
</cc_span>

This part of the configuration is common for both the cases in this scenario

<transparent_spans>
     <span name="wp2">
          <channel id="1">
               <param name="remote-ip" value="192.168.3.118"/>
               <param name="remote-port" value="7002"/>
               <param name="local-ip" value="192.168.3.118"/>
               <param name="local-port" value="7001"/>
          </channel>
     </span>
</transparent_spans>

 For reference please find the attached sample scenario2-case1.tgz & scenario2-case1.tgz file.