TTMER2: Call Paths Testing - "In-circuit" measurements on ISDN and VOIP network elements

Measuring tasks:

Content:

1. Measuring arrangement:

1.1. Details:

Measuring arrangements for the testing of call pathes:

The following table summarizes ports and their identifiers which take part in the interconnection:

RoomB.211B.211B.211B.212B.212B.212B.213
NodeD1 D1 MSS-2MSS-2MSS-1MSS-1 D2D2H3
Port type2wire VFE1GBE/IPGBE/IPE12wire VFE1
G.712 Port id.AD------DA
Definity Port id.1a02031a10 1a11------1a11 1a101a0203
AXD Port id.--- 1/3/11/5/21/4/21/6/1 1/6/2---1/6/1
Cross connectXC212/1a XC211/1--- --- XC212/1e,2e
XC212/1d,2d
XC212/1b

The tested call path (switched voice frequency channel, B channel) terminates in the voice frequency ports (A ports) of the D1 and D2 exchanges. These ports will used alternately by analogue telephones and PCM channel analyzer for setting up connection between ports (call control and connection control) and doing tests (transmission performance analysis), respectively.
The receiver of the PCM channel analyzer can be connected to the D port of the call path, too. This feature allows the separate examination of the individual segments of the call path.

The signal converters of the tested call pathes have been summarized in the following table:

RoomCall PathB.211B.211B.211 B.212B.212B.212B.213
NodeD1D1 MSS-2 MSS-1D2D2H3
conversions (D1->D2 direction)Main2/4 wireA/DTDM/IP/RTP---IP/RTP/TDMD/A4/2 wire
--- Hybrid Media Gatewayoptical line (GBE)Media GatewayHybrid
conversions (D2->D1 direction)Main4/2 wireD/AIP/RTP/TDM---TDM/RTP/IPA/D2/4 wire
conversions (D2->H3 direction)Auxiliary-- -- -- ------ A/D2/4 wireTDM/RTP/IP
conversions (H3->D1 direction)Auxiliary4/2 wireD/A-------- ---IP/RTP/TDM

This call will be an interurban one, because both Definity exchanges (D1, D2) and the VoIP trunk interconnecting the exchanges (MSS-1, GBE, MSS-2) take part in it.

1.2. Parameters of the call path under test (A port):

1.3. Parameters of the call path under test (D port): (Source: the configuration database of the Definity exchanges.)

1.4. Parameters of the routing:

ExchangeDial planFirst digitE1 portTimeslot selectionAvailable timeslots
D1 coordinated4xxx 1a10ascend2,3,4 or 5
D2 coordinated3xxx 1a11ascend2,3,4 or 5
H3 coordinated2xxx Cisco 2600gw1ascend1 to 24

1.5. Parameters of the call path under test (GBE/IP port):

Actually, to find these parameters is a part of Task 2.4.

1.6. Call control:

Basically there is no connection between the A ports of the D1-D2 exchanges. Before starting the measuring - because it is a switched network - we have to set up the call path (the voice frequency channel) under test. While EP2 cannot dial, we will set up connection with telephones binded to the terminal of the channel. The dialing number of the A ports are: 3007 (D1), 4007 (D2).

Sending one of the two dialing numbers (towards of which we want to set up the call) to the caller exchange it will carry on the call setup with the sending of a DSS1 SETUP message in the 16th time slot of its E1 port. This message will be transparently forwarded through MSSs to the called exchange. After alerting and callee's hang up the call path will be established in a time slot according to the above routing table. The signal transmission on these call pathes (B channels) is not necessary transparent in MSSs, it is quasi transparent in good case depending on the configuration.

In the actual measuring arrangement the call control messages of the D1-D2 exchanges do not influence the operation of switches, signal converters (Media Gateways) of MSSs. In this case MSSs will be configured (regarding connection control) through the control interface of MSSN (MGC).

1.7. Connecting the EP2 after the setup of the call path:

After setting up the connection we should detach the telephones from the line and attach EP2 to line so that the DC loop may not be cut off. In this will help us current loops which are two-poles with low impedance on DC, but high impedance in sound frequencies. Connecting a current loop to the line in parallel it closes the line at DC, but not in sound frequencies, so the signals of the EP2 connected to the line will get into the channel. On receiver side current loop can be substituted with a 600 ohm resistor, however, in this case the receiver of the measuring equipment should be set to "high impedance input" mode.

2. Mandatory measuring tasks: