Voice/data switches are the latest craze in the convergence of the network with CTI.
With some voice/data switches, the voice network is completely converged with the data
network, necessitating just a single CAT-5 network wire drawn to the desktop, instead of
two. Besides the "single" wire to the desktop advantage, other advantages
include having IP-based phones, the ability to inexpensively expand the phone system to
branch offices, and advanced CTI features such as desktop call control. Since the
voice/data switch is part of the network, integrating the hardware with operating systems
such as Windows is a much easier task, thus negating the need for proprietary CTI links
and instead using open CTI APIs and Internet telephony APIs such as H.323, TAPI, JTAPI,
and more.
Cisco Systems' Selsius IP-PBX (voice/data switch) is one of the leading products in the
convergence of voice and data networks into a single network. Cisco Systems' Selsius
IP-PBX consists of several modules including their Ethernet IP-based phones, H.323
gateways with analog, T1 and PRI interfaces, and their software program called
CallManager. CallManager runs on a Windows NT server machine, providing complete
administration of the system, as well as managed call setup and call routing. The
CallManager Administration GUI is browser-based and hence - can be administered from
anywhere on the LAN.
INSTALLATION
Cisco's Selsius division sent us three of their Ethernet IP-based phones, including two
12SP+ phones, a larger 30SP+ phone, a single Analog Access Gateway, and a single CD-ROM
containing the software needed. TMC Labs had seen Selsius' product several times in the
past, at trade shows or on office visits, so we're very familiar with the product.
Nevertheless, some of our engineers were a bit shocked when we opened the box and only saw
Ethernet phones, the analog gateway, and a single CD-ROM. One of our newest engineers
remarked, "So where's the box to perform switching/PBX functionality?" We
explained that the Selsius software runs on the Windows NT platform, which is where all
the call switching/routing is handled. Essentially, the core of the Selsius IP-PBX resides
in the CallManager software running on an NT Server, which we will explain in more detail
in the Operational Testing section.
We connected "pre-fab" Cat-5 network cables from the three Ethernet IP-phones
to a 10-BaseT hub (the Selsius phones currently do not support 100-BaseT), as well as the
Analog Access Gateway, which has four analog ports for accessing the PSTN. Each of the
phones also required an AC adapter to power the LCD display and lights that illuminate the
function keys. After connecting the AC adapters to each of the phones and connecting the
network cables, we proceeded to install the Selsius software onto a Windows NT Server 4.0,
300 MHz Pentium with Service Pack 3 running. The installation was very basic, and we went
with all the default settings, which required minimal user intervention.
Next, we ran the Selsius CallManager Administration program (HTML-based) and added our
four devices (3 IP-phones and 1 analog gateway). Adding each device required that we look
for a sticker with a special serial number on the device, which was essentially the MAC
(Media Access Control) address for the particular device. Since MAC addresses are
"unique" across all network devices (NIC cards, printers, voice/data switches,
etc), no conflict on the network should occur. When adding each of the devices from our
browser, each device name was prefaced with three characters to denote the type of device
being added. For example, phone device names were prefaced with SEP (Selsius Extension
Phone) and analog gateway names were prefaced with SAA (Selsius Analog Access).
Next, we needed to modify our DHCP server by adding another option called
"150," since the Selsius phones and gateway devices query the DHCP server on
this number. The value we put into option "150" on the DHCP server was the IP
address of the CallManager server, which is also where the trivial file transfer protocol
(TFTP) service runs a simplified version of FTP that transfers files. Selsius Windows
Trivial File Transfer Protocol (SWTFTP) is an application that transfers device
configuration files (CNF) to Selsius devices from a TFTP server. We were able to start
SWTFTP from the Selsius program group on the Start menu, or in the CallManager
Configuration program's Control Center (browser-based). Essentially, each phone or Access
Gateway requests a configuration file from the TFTP server. The configuration file
contains the CallManager's name or IP address.
When we first turned on the phone or access device it queried DHCP (option
"150"). DHCP responded by assigning an IP address to the phone. The name of the
TFTP server was also sent to the phone, and that information was stored on the DHCP
server, via the option 150 we previously set up. The phone or analog gateway contacted the
TFTP server (running on Windows NT Server) and requested a CNF file, which contains the
CallManager's name or IP address. Once the CNF file was received, a connection between the
phone or analog gateway was established.
DOCUMENTATION
The documentation for this product is online and Web-based (HTML), with no printed
instructions. In fact, to guide us during the installation and configuration phase,
including the addition of devices, we simply used Selsius' HTML-based documentation. This
HTML-based documentation included a step-by-step guide, which was very useful in getting
the system up and running quickly.
We had a couple of difficulties having no "printed manuals," and having to
strictly use HTML-based documentation. For one, if we wanted to print the documentation,
we would have to click on each and every URL link on every page, and print each page
individually. Although the latest version of Internet Explorer does have a feature to
print all "linked documents," this feature is buggy at best and will print pages
we may not necessarily want printed or print in an order, which we did not expect. We did
print all the URL links, but it resulted in a very bulky printout, which was very
difficult to reference, since there were no page numbers or an index on the printed copy.
We found it easier to just use the online documentation, which was searchable.
However, our other problem with using strictly "browser-based" documentation
was that we needed to have two browsers open. One browser to follow the step-by-step
instructions in the HTML guide, and another browser to change the configuration within the
HTML-based CallManager Administration. We should note that CallManager runs on Microsoft's
IIS and utilizes Active Server Pages (ASP). Although the online manual was very well done,
having to switch back and forth between two browsers for each step was a bit tedious and
time consuming. A printed guide with page numbers and an index to refer to during
installation would have assisted in eliminating this problem. Hence, although the online
HTML-based documentation was excellent, it is not a replacement for a manual in printed
form, which brought the documentation down to a 3.9 rating.
FEATURES
- IP phones feature 12 or 30 function keys depending on the model.
- Two-way speakerphone.
- 40-character LCD display.
- Speaker volume and handset volume are adjustable.
- All IP phones are manageable via the CallManager.
- Program information and configuration retained in flash memory.
- Hold, transfer, conference, call parking, speed dial.
- Caller-ID.
- H.323-compliant.
- Active Server pages using IIS to manage the system.
OPERATIONAL TESTING
We did have some difficulty getting the Selsius IP phones to download the configuration
files from the TFTP server. What was strange about this was that the phones were acquiring
the proper IP address and we were able to ping each phone. They also acquired the proper
gateway address, which we checked via the 40-character LCD display on the phones. We
called technical support, and at first, they thought it might be a "network port
conflict" on our network. For example, most FTP servers use port 21, and in the case
of the TFTP server, it's default port numbers include: port 2000 for the Ethernet phones,
port 2001 for Digital Access (such as T1) gateways, and port 2002 for Analog Access
Gateways. Once Selsius told us that the phones utilize certain "network ports"
to communicate with the phones, then we realized that "pinging" the phones did
not necessarily mean everything was "kosher" - a port conflict could have been
our culprit.
Selsius informed us that they have had some instances when other software packages on
the LAN use one or more of these port numbers. Thus, we went into a configuration file and
changed the port numbers, and tried again, but still the phones wouldn't work. After
trying various port settings, we were fairly certain it was not a network port conflict.
We even segmented the Selsius voice/data switch off our regular LAN and put it on its own
10-BaseT hub, but the phones still would not work. We again called technical support and
they suggested reinstalling the software. Such a simple concept (reinstalling), but we
were hesitant to reinstall, since we felt that would require us re-entering the MAC
addresses for all the devices and changing all of our custom configurations. Also, since
we went with the "default settings" during the initial installation, we didn't
think reinstalling would help. Plus TMC Labs engineers like to get the bottom of these
things, rather than brush them off. You might say we're pretty stubborn when it comes to
fixing complex Internet telephony hardware and software problems.
Eventually though, after trying every trick in the book, we gave up at trying to
discover the problem and decided to bite the bullet and reinstall the software. Sure
enough, we reinstalled, again choosing all the "default settings" during the
installation, and of course the IP phones worked on the first try! Essentially, we noticed
that the Ethernet IP-based phones changed from displaying Selsius copyright information to
displaying the time, which means that the phones are ready to go (you get dial tone).
Sure enough, when we picked up the receiver on one of the three test phones, we
received dial tone. We placed an extension-to-extension call from 1000 to 1001, which rang
our only executive SP 30+ phone. One of our testing engineers picked up the line, which
was connected two feet away from the other phone. We talked into the phones and tried to
subjectively discern the amount of latency.
By watching each others' lips move and then hearing the person on the phone receiver,
we found that the latency was almost imperceptible. Cisco's Selsius Systems informed us
that their phones have a latency of roughly 30ms, and their gateways have a latency of
90ms, both of which we found very impressive. The sound quality from our first test call
was equally good. We were able to talk over each other, and test the full-duplex
capabilities, which the product passed with flying colors. The Selsius phones use the ToS
(Type of Service) field to set the precedence of the voice packets across the LAN/WAN. The
default ToS setting is "3" which did not appear to be user configurable.
For a more advanced and "real world" test, we decided to plug one of the
Selsius phones into a network port within TMC Labs and another phone into a network port
about a mile away at our corporate headquarters. A leased line (T1 speed) exists between
the two offices, which is where we would attempt to route the voice IP packets from the
Selsius phones. Since the Selsius phones support gateways for segmented LANs/WANs, we were
pretty certain this test would work without a hitch. Sure enough, we were able to dial
from one of our corporate offices to the other office, simply by dialing "1001."
The voice quality was excellent, and the latency was only slightly slower than when we
were on the same LAN segment.
We should note that the IP phones themselves have two RJ-45 Ethernet connectors, which
allows you to connect both your LAN to the phone, and your PC to the other port. This
negates the need for dual-port Ethernet network cards or a mini-hub at each station.
Unfortunately, the ports on the IP phones are only 10-BaseT, so if you connect a cable
from your PC's network card to the 2nd Ethernet port, your PC will be downgraded to
10-BaseT, even if you have a 10/100-BaseT network card. Thus, for bandwidth-hungry users,
such as desktop publishing users, this may require that a separate network wire be drawn
to their desktop PCs.
Cisco's Selsius IP-PBX (voice/data switch) does a good job of providing silence
suppression to minimize bandwidth utilization during periods when a person is not
speaking. We did notice on a couple of occasions that the silence suppression kicked in
when one of us spoke softly, cutting off some syllables, but it only happened a couple of
times.
For our final test we installed the Conference Bridge module on the same Windows NT
server running CallManager, since a phone system is not complete unless it can perform
call conferencing features. We added a conference bridge device to the list of available
devices in the "Add/Delete Devices" screen within CallManager, and chose the
appropriate information for each field or drop-down box. After setting various parameters,
we were able to pick up one of the IP phones, dial another phone, and then conference a
third phone into the conversation.
ROOM FOR IMPROVEMENT
As stated earlier, a printed documentation would be beneficial, especially for any
interconnects, resellers, or VARs selling or installing these systems.
One item we noticed was lacking in the CallManager Web-based configuration screen was
hyperlinks next to each field to explain each one in detail. We would have liked to click
on a hyperlink next to each field and have another small browser window spawned to explain
what values should be used in any particular situation. Although the online help does a
good job of explaining each field, when trying to quickly set up the system, it's much
easier if the fields and values within the drop-down boxes are explained via a hyperlink
contained within the same Web page. Finally, we would like to see support for G.729, which
we are told will be in the next revision of the phones.
CONCLUSION
Cisco's Selsius IP-PBX is one of the leading products within the voice/data switch arena
and is certainly the best known. The convergence of voice and data onto a single network
promises to deliver a much more manageable telecom and data network. VARs and
interconnects will have to brush up on their networking and Windows NT experience to learn
how to install this product. But the learning curve is much smaller and quicker than that
of traditional PBXs, and seasoned IS administrators should be able to purchase and install
this system on their own. TMC Labs was very impressed with the functionality and overall
architecture of Cisco's Selsius IP-PBX platform, including the IP phones, which are as
close to plug-and-play as you can possibly get! |
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