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VoIP technology has improved greatly in the last year, but many
organizations are still concerned with echo, latency, quality of service (QoS)
issues, and other deterrents to voice calls. In an effort to put those
issues to rest, Quintum Technologies has introduced the Tenor Gateway, which
is a VoIP gateway that intelligently switches calls over both IP networks
and the PSTN. If IP network congestion or a device failure impacts voice
quality, the Tenor Gateway can switch calls over to the PSTN. Other
conventional VoIP gateways only route calls over IP networks. All of this is
possible on the Tenor Gateway because its architecture sits right on the
T1/E1/PRI interface.
Quintum guarantees a high QoS level with their Transparent Auto-Switch
Quality (TASQ) technology, which is present in their Tenor Gateway. TASQ
monitors packet delay for a VoIP call. According to the administrator's
specifications, the call is switched to a PSTN call (unbeknownst to the
caller) if the quality of the VoIP call becomes unacceptable. While this may
not often be needed, it is reassuring to be provided with guaranteed QoS.
INSTALLATION
In a lab environment, the setup for testing equipment such as the Tenor
Gateway is slightly different than in a real setting. In the real world, two
gateways would be in completely different locations and possibly on
different networks altogether. For our purposes, TMC Labs placed two Tenor
Gateways next to each other, connected a crossover cable from one PSTN link
to the other one, and placed an Ethernet cable from each gateway to a hub,
thereby creating a small, internal network. To assign an IP address to each
gateway, we connected a serial cable to a PC and reached the Command Line
Interface (CLI) via HyperTerminal. From the CLI, we set the IP addresses for
the gateways by simply typing config#, unit 1 (or 2 depending on the
gateway), and then the IP address. In real-time environments, setting the IP
address of the gateway should be all that is required, but we had to make a
few other minor configuration changes for the Tenor Gateways so that they
would work in our lab environment.
End users would most likely prefer to use the Web-based manager, called the
Tenor CAM (Configuration/Alarms/Maintenance), because it is much simpler to
use and does exactly what the name implies. However, some users might still
want to use the command line interface because it allows for more
functionality. Also, as compared to other CLIs, this one is straightforward
and relatively painless to figure out.
Once the IP address was set, we entered the address on our Web browser to
access the Tenor CAM of one of the gateways. A screen came up that allowed
us to set a password. It was necessary to synchronize the date and time,
enter the local phone information that the gateway required, and set the
trunk group information. We had to choose between either ISDN PRI or T1
connections. We choose ISDN PRI using the DMS protocol type. We finished the
initial configuration by setting the local directory numbers and the border
element information (which will be discussed more in the Operational Testing
section). With the help of the product manual the process is not
complicated. Additional configuration, alarm, and maintenance features can
also be set or changed from the main Web homepage.
DOCUMENTATION
The documentation consists of a product manual and a Quintum CLI list
booklet. The product manual details the features, hardware components,
installation, Tenor CAM, system alarms, and troubleshooting techniques. It
is generally well laid out, includes a table of contents and index, and
explains its material in an understandable fashion. However, most of the
screenshots are very indistinct, making them look unprofessional and less
helpful when an end user is attempting to configure the gateway. Also, the
index is not informative enough, sometimes leading a user astray. For
example, someone might look up "Border Element" in the index and
be directed to a screenshot located around page 4-11. While that is an image
of a border element screen, the real information that the user is probably
looking for starts on page 5-38. As for the Web GUI itself, it currently
does not include help files that should be associated with it.
The booklet and the PDF do possess accurate information, if a bit confusing
as far as style. The CLI booklet that we received was unprofessional
looking. It seemed to be laid-out literally days before we received it, and
that may very well have been the case, but the biggest problem with the
booklet was that it was difficult to read because of the very small font.
Luckily, there was also a PDF file for it. Even though it was easier to
read, the PDF still had its difficulties. To read the information clearly,
the command list on the right side needed to take up most of the screen,
rendering the bookmark section on the left side unreadable. If a user needs
both sections on the screen, this could become bothersome. The help command
(on the CLI), however, is useful for better understanding the interface.
FEATURES
The following is a list of the major features of the Tenor Gateway:
- Automatically switches from VoIP to PSTN while still on the call if a
specified amount of IP packets are lost; uses Quintum's quality of service
guarantee, TASQ, for monitoring packet delay;
- Can create/change configuration, alarm, and maintenance settings using the
Web-based GUI, Tenor CAM;
- If power is lost to a unit, all call routing operations will bypass it and
route successfully to the PSTN or PBX;
- Supports up to 960 simultaneous calls;
- Besides regular T1/E1/PRI support, the gateway also supports fractional
T1/E1/PRI in increments of 64 Kbps;
- Can call long distance via VoIP to another Tenor Gateway and then hop-off
to a public PSTN line for a local call;
- Has H.323 gatekeeper functionality so that gateways can be pooled within
the same company to create a VoIP network and can connect to a PBX anywhere
in the world; and
- Provides Fax over IP (FoIP) capabilities.
OPERATIONAL TESTING
For our testing, we connected a crossover cable from each PBX port on the
Tenor Gateways to a Gordon Kapes
T1/PRI simulator.
Setting the Gordon Kapes simulator to "user side" mode, and
setting it to the DMS protocol type for each interface, and were able to
synchronize the connections. By hooking up a couple of regular phones to
analog ports on the simulator, we could perform VoIP calls to each phone
through the Tenor Gateways. We were able to make the VoIP calls based on the
configurations we set. While examining the sound quality of the call, no
echo was evident, and there were only slight latency during our interactions
on the phone.
In the scenario we set up for the lab, it is unlikely that the sound quality
would break up too badly because of the limited amount of traffic on the
network. In a real-time setting, traffic over the Internet could increase
dramatically at certain times of the day, and therefore, provide a chance
for packet loss. The Tenor Gateway includes a bandwidth management feature
that allows administrators to allocate how much bandwidth should be allowed
for VoIP calls at different times in the day. For instance, an administrator
might want to lower VoIP use during heavy times of traffic and increase the
use at other times. This feature limits the chance of having a bad
connection.
However, the most important feature that the Tenor Gateway offers is the
ability to automatically switch from a VoIP to a PSTN call without hanging
up the phone. We tested this functionality by turning on a built-in demo
activated from the CLI. This demo switched the VoIP call to a PSTN call
after around twenty seconds. This was enough time to hear the delay of the
VoIP, and then suddenly not hear that delay anymore. The Tenor Gateway
switched over without much notice. In real-time, it might be more
noticeable, depending on the settings of when to switch the call. If it's
set for a high level of packet loss, then the change would be more
noticeable. In any case, the Tenor Gateway did exactly what it was intended
to do.
Our lab setup worked well for our environment, but in a real setting, the
network is much more complex. That's why Quintum incorporated gatekeeper
functionality into the Tenor Gateway for enterprise networks. This master
gatekeeper is called a Border Element, which controls the other
Tenor Gateways in the network. There is also a secondary gateway that acts
as a Border Element to provide fault tolerance and redundancy. For
configuration purposes, there is also a "discovery" functionality
in which a Tenor Gateway sends out a signal to look for the gatekeeper. If
there is none available for that specific network, that particular gateway
automatically becomes the primary Border Element. We found this
functionality to be an extremely useful and inventive method of monitoring
and managing a network.
ROOM FOR IMPROVEMENT
When we first examined the Tenor Gateway, we noticed that there was no
analog port integrated into it. This is an issue that would improve the
product greatly. As it stands now, a channel bank is required in order to
change the connection from digital to analog, which might be needed to make
a VoIP call over a disparate, smaller network within an enterprise, such as
we set up in the labs. However, we did find out that an analog Tenor Gateway
should be available by the time this review is in print, which will be
useful for these types of networks even though it still will not be
incorporated with the larger Tenor Gateways.
We were also a little worried about interoperability issues. Right now, the
Tenor Gateway is only proven to work with other Tenor Gateways. Quintum is
currently working on proving interoperability with other companies'
equipment. While we wouldn't mind seeing an auto detection feature to detect
the switches and protocol types being used on the network, poor
documentation was our key issue with the product. It is a serious problem
that needs to be addressed to make the package more user friendly.
CONCLUSION
Overall, we were very impressed with all that the Tenor Gateway had to
offer. The VoIP calls are of good quality, the switching from VoIP to PSTN
is nearly flawless, the configuration through either the Web interface or
the CLI is not difficult, and the rest of the functionality is commendable.
We definitely recommend the Tenor Gateway.
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To The October 2000 Table Of Contents ]
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