3Com Nbx 100 And Ss3 Nbx Administration Guide

							Call Rerouting for Virtual Tie Lines101
Call Rerouting for 
Virtual Tie LinesTo enable the NBX system to better deal with network problems, you can 
configure the system dial plan so that some virtual tie line (VTL) calls can 
be rerouted if a VTL connection cannot be made.
VTL calls can be rerouted if:
■The dial plan contains an invalid IP address
■The remote NBX system is not responding
■All VTL channels on the remote NBX system are currently busy
■All IP addresses in the IP On-the-Fly address pool are in use
Some VTL calls are not rerouted. Example situations in which a call is not 
rerouted include:
■Placing a VTL call to another system with the intention of hopping off 
(dialing a telephone number local to the other system) when all trunks 
are busy on the other system
■Dialing an invalid telephone number
If you normally connect calls from site A to site B using VTL connections, 
you can define an alternate route to site B using Analog Line Card ports, 
Digital Line Card channels, etc. If a network problem such as a router 
failure occurs, or if all VTL ports on the site A NBX system are busy, VTL 
calls that fail to reach site B are then dialed using the alternate route.
If your VTL call is rerouted, you see additional routing information in the 
display panel on your NBX telephone.
The NBX system log file contains records of failed VTL calls that were 
rerouted.
Example Dial Plan
EntriesIf you normally dial a site code such as 72 to reach site B, and if the 
telephones at the other site use four-digit extensions, the dial plan entries 
to handle the initial call and the rerouting of the call might look like the 
example shown in Figure 35
. 
						

							102CHAPTER 2: DIAL PLAN
Figure 35   Sample Dial Plan Entries for Rerouting VTL Calls
Explanation:
The TableEntry Create command specifies that when a user on the local 
NBX system dials a six-digit number beginning with the digits 72, the call 
is routed via route 6, which is the route that normally contains only the 
VTL extension list (*0006).
To allow VTL calls to be rerouted, route 6 is configured to use both the 
VTL extension list and the Line Cards extension list (*0001). Calls that use 
route 6 can be completed using devices in either of these extension lists.
There are four DestinationRouteOperation lines. The first two lines specify 
the primary way to handle the call, using VTL methods. The last two lines 
specify the backup way to handle the call if the first method fails.
Table Create 1 Internal 4 Digit Extensions
/                  Id Entry  Digits       Min Max Class           Prio Route
/                  -- ------ ------------ --- --- -------------   ---- -----
TableEntry Create   1      8 72             6   6 WAN                0     6
/        Routes
/                       Route Description
/                       ----- -----------
DestinationRoute Create     6 Site B
/                            Route Entry DestinationExtension
/                            ----- ----- --------------------
DestinationRouteEntry Create     6     1 *0006
DestinationRouteEntry Create     6     2 *0001
/                                Route Entry OperId  Operation  Value
/                                ----- ----- ------- ---------  -----
DestinationRouteOperation Create     6     1       1 stripLead  2
DestinationRouteOperation Create     6     1       2 prepend    192*168*155*100*
DestinationRouteOperation Create     6     2       1 stripLead  2
DestinationRouteOperation Create     6     2       2 prepend    1978247 
						

							Managing Existing Virtual Tie Lines103
Successful VTL Call
If there are no network problems:
1The first line (Entry 1, OperId 1) removes the digits 72.
2The second line (Entry 1, OperId 2) prepends the IP address of the NBX 
system at site B in front of the dialed extension number. 
Unsuccessful VTL Call
If a network problem or a lack of VTL ports prevents the VTL call from 
reaching its destination:
1The third line (Entry 2, OperId 1) removes the digits 72.
2The fourth line (Entry 2, OperId 2) prepends an appropriate dial string and 
dials out over an analog telephone line.
Managing Existing 
Virtual Tie LinesAfter VTLs are installed and you have verified that they are working 
properly, you can manage them using the NBX NetSet utility. There are 
NBX NetSet utility functions for:
■Modifying a Virtual Tie Line Name
■Viewing and Resetting Virtual Tie Line Statistics
■Enabling Audio Compression
■Enabling System-wide Silence Suppression
Modifying a Virtual
Tie Line NameYou can change the name of a VTL. The name appears in NBX NetSet 
utility lists, and helps you identify each VTL.
To modify the name of a VTL:
1In the NBX NetSet - Main Menu window, click Device Configuration.
2Click the Virtual Tie Lines tab. The window that appears (Figure 36
) 
contains the list of existing VTLs, and the status of each one. 
						

							104CHAPTER 2: DIAL PLAN
Figure 36   Virtual Tie LInes Tab
3Select a VTL from the list.
4Click Modify. The Modify dialog box appears (Figure 37
).
Figure 37   Modify Virtual Tie Line Dialog Box
5In the New VTL name text box, type the name you want to assign to this 
VTL. Click OK. Verify that the name change is on the Virtual Tie Lines tab. 
						

							Managing Existing Virtual Tie Lines105
Viewing and
Resetting Virtual Tie
Line StatisticsYou can view the statistics for a VTL at any time.
To view statistics for a VTL:
1In the NBX NetSet - Main Menu window, click Device Configuration.
2Click the Virtual Tie Lines tab. 
3From the list, select the VTL.
4Click the Statistics button. The Statistics dialog box (Figure 38
) appears. 
The fields are described in Table 20
.
Figure 38   Virtual Tie Lines Statistics Dialog Box
5To reset all VTL statistics, click Reset.
Another way to reset all VTL statistics is to restart the NBX system.
6When you are finished, click Close. 
						

							106CHAPTER 2: DIAL PLAN
Table 20   Virtual Tie Line Statistics Fields
FieldDescription
NOTE: All statistics apply to the time period since the most recent Reset command 
or since the most recent system reboot, whichever was more recent. To determine 
the starting time for the displayed statistics, compare the Last reset command with 
the time of the Last system reboot. Both are displayed at the bottom of the VTL 
Statistics window.
Number of outgoing 
VTL calls madeThe number of outgoing calls made over all virtual tie lines 
(VTLs) since the most recent reset command or since the time 
the NBX system was last restarted. Each time you restart the 
NBX system, you reset the statistics for all VTLs.
Number of incoming 
VTL calls receivedThe number of incoming calls received over all VTLs since the 
most recent reset command or since the time the NBX 
system was last restarted.
Number of active VTL 
callsThe number of calls currently active on all VTLs.
Maximum number of 
concurrently active 
VTL callsThe maximum number of VTL calls that have been active at 
the same time on this NBX system since the most recent 
reset command or since the time the NBX system was last 
restarted.
Incoming VTL calls 
rejected due to all 
VTLs busyThe number of telephone calls that would have arrived from 
other NBX systems over VTL channels, but could not be 
accepted because all local VTL ports were busy when the 
calls arrived.
Outgoing VTL calls 
rejected due to all 
VTLs busyThe number of telephone calls that would have been sent 
from the local NBX system over VTL channels, but could not 
be sent because all local VTL ports were busy when the calls 
were made.
Rerouted VTL callsThe number of calls that did not reach their destination 
when attempted over VTL channels, and were rerouted using 
another device.
Last reset commandThe date and time of the most recent Reset for this VTL.
Last system rebootThe date and time of the most recent reboot of the NBX 
system. 
						

							Managing Existing Virtual Tie Lines107
Enabling Audio
CompressionYou can enable or disable ADPCM (Adaptive Differential Pulse Code 
Modulation) audio compression on a system-wide basis for VTLs. The 
default condition disables audio compression.
When you enable VTL audio compression on an NBX system the VTL 
software attempts to use audio compression on all VTL calls. If the NBX 
system on the other end of the VTL call is not configured to support 
audio compression, the local VTL software attempts to find a compatible 
communications mode.
To enable VTL audio compression:
1In the NBX NetSet - Main Menu window, click System Configuration.
2Click the System Settings tab.
3Click the System-wide button. The System Configuration - System 
Settings dialog box (Figure 39
) appears.
Figure 39   System-wide Setting Dialog Box 
						

							108CHAPTER 2: DIAL PLAN
4To enable audio compression on VTL calls, click the Audio Compression 
on VTL Calls check box and then click OK.
Enabling
System-wide Silence
SuppressionYou can enable or disable silence suppression on a system-wide basis for 
VTLs. The default condition disables silence suppression. When you 
enable VTL silence suppression on an NBX system, the VTL software 
attempts to use silence suppression on all VTL calls. If the other NBX 
system is not configured to support silence suppression, the local VTL 
software attempts to find a compatible communications mode.
To enable silence suppression on VTLs:
1In the NBX NetSet - Main Menu window, click System Configuration.
2Click the System Settings tab and then click the System-wide button. The 
System Configuration - System Settings dialog box (Figure 40
) appears.
3To enable silence suppression on VTL calls, click the System-wide Silence 
Suppression on VTL Calls check box, and then click OK.
Figure 40   System-wide Setting Dialog Box 
						

							Using a VTL Password109
Using a VTL 
PasswordIf you want to allow users on one NBX system to place VTL calls to 
another NBX system and then place long-distance (toll) calls from that 
location (this is known as hop off), you can configure a VTL password.
When an NBX system receives a VTL call from a user on another NBX 
system, it can allow that user to make long-distance calls if the incoming 
VTL call contains the password. Otherwise, such calls are not allowed. If 
you set up two classes of VTL calls (with and without passwords), you can 
permit or disallow hop off.
To enable an NBX system to handle incoming hop off calls , use the NBX 
NetSet utility to create or modify a VTL password. See How to Configure 
a VTL Password. To enable an NBX system to send hop off VTL calls, 
configure the dial plan to include the VTL password. See Configuring VTL 
Passwords in the Dial Plan.
How to Configure a
VTL PasswordFor each NBX system that can receive VTL calls, you use the NBX NetSet 
utility to configure a local system VTL password.
To configure the password:
1In the NBX NetSet - Main Menu window, click System Configuration.
2Click the Security tab. See Figure 41
.
Figure 41   Security Tab 
						

							110CHAPTER 2: DIAL PLAN
3Click the Virtual Tie Lines Password button. The Change Virtual Tie Lines 
Password dialog box (Figure 42
) appears.
Figure 42   Change Virtual Tie Lines Password Dialog Box
4Type the current administrator password in the Current Admin Password 
text box.
5Type the new VTL password in the New Virtual Tie Line Password text 
box.
Passwords are from 8 to 15 characters in length and must contain only 
letters and numbers. Upper and lower case letters are permitted.
6Retype the new VTL password in the Re-enter New Password text box.
7Click OK.
Configuring VTL
Passwords in the
Dial PlanFor each remote NBX system that controls hop-off by means of a VTL 
password, you must configure that password into the VTL commands in 
the local dial plan.
If you use site codes to access other NBX systems through VTL 
connections, you can configure one set of VTL connections that permit 
hop-off and are accessed one set of site codes. You can configure 
another set of VTL connections that do not permit hop-off and are 
accessed using a different set of site codes.