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July 1997
By Kathleen Cholewka
IP Videoconferencing
IP Videoconferencing: Beat the Clock?
The new ITU-T spec delivers video over IP, but network delays could cause sessions to crawl or stall
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On paper, the H.323 standard looks picture-perfect: The new ITU-T spec delivers videoconferencing over IP--across the Internet, corporate intranet, or company
LAN. There's no need to shell out for pricey ISDN circuits, leased lines, or standalone videoconferencing gear. Just install a low-cost digital camera and H.323 video codec at the desktop and it's time for talking heads. Better yet, some vendors are giving their software codecs away. Out on the network, though, IP videoconferencing could be a real drag--in more ways than one. Internet delays could slow transmission rates to 1 to 2 frames per second, bringing conferences to a standstill. And things may not be much better on corporate intranets: IP videoconferencing shares bandwidth with other apps, so sessions could crawl or stall depending on network load. What's more, videoconferencing could be the ultimate bandwidth hog: Let it loose on the LAN and it could force other applications to move in slo-mo.
"Videoconferencing is one of the most strenuous things you can put
on a network," says Adam Rauch, member of the board of directors of
the International Multimedia Teleconferencing Consortium Inc. (IMT
C,
San Ramon, Calif.). The IMTC sponsors interoperability tests for
videoconferencing gear.
TOOLS OR TOYS?
So is IP videoconferencing a tool or a toy? The answer depends, in
part, on who's talking.
"You can say H.323 is ready today," says Brad Levy, vice president
of sales and marketing for Link-VTC (Boulder, Colo.), a provider of
multipoint videoconferencing services. "But is it reliable? One to
three frames per second is unacceptable for business."
"H.323 products are not as sophisticated as leased-line systems,"
admits Brett Spell, systems engineer at Electronic Data Systems Corp.
(EDS, Falls Church, Va.), "but they're vastly less expensive." EDS is
under government contract to build a collaborative videoconferencing
network for medical imaging. "We're looking to provide a low-cost
solution for the desktop."
Spell's cash considerations could prove very compelling for many
net managers. Up-front costs for IP videoconferencing can dip as low
as $200 per desktop, if
a free software codec is deployed with a
digital camera. Buy a codec and the average per-seat price climbs to
$600. ISDN videoconferencing, in contrast, starts at $1,000 per
seat--and that doesn't include monthly line charges, which can range
from $40 to $150 per connection.
CODEC CONSIDERATIONS
Corporate networkers who want to add IP videoconferencing to their
corporate intranets need to take a close look at the products. Right
now, there are 10 vendors to consider: Five offer software codecs;
five sell hardware codecs (one vendor also sells a card and code
version of its hardware codec).
The place to start is by deciding between software and hardware.
Installation issues are important here, as well as the processing
burden on the host PC. Another issue: Can the codec work with the PC's
operating system and its internal bus? Also, does the product offer
the necessary LAN and WAN connections?
So much for the small stuff: The big issues are frame rate,
transmission capabiliti
es (point to point, multipoint, or multicast?),
and management. As always, price is worth pondering: IP
videoconferencing may be cheap, but products range in price from $50
to $4,000. And net managers who want to integrate IP videoconferencing
with older ISDN systems need to check out the H.323 gateways now
coming to market (see "Gateways to Yesterday").
INSPECTING THE SPEC
Proprietary schemes for videoconferencing have been around for
several years. But H.323 is the first standard that addresses this
technology. Actually, it's not a standard, it's an "umbrella
recommendation," to borrow the language of the ITU's Telecommunication
Standardization Sector (ITU-T). H.323 covers packetization, call
control and signaling, and audio and video compression. The so-called
gatekeeper provision defines how to manage IP addresses and allocate
bandwidth for point-to-point or multipoint IP videoconferencing
sessions.
Even though H.323 won't come up for ratification until next month,
a number of ve
ndors have already released products that comply with
it. The majority of these are codecs, devices that digitize analog
video traffic for transport over a network. These products are
deployed in pairs: The transmitting codec converts the video stream
into IP packets. The receiving codec restores the signal to its
original form.
SOFT OR HARD?
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BUILD YOUR OWN CUSTOM TABLE
IP Videoconferencing Codes
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As indicated, IP videoconferencing vendors are selling software and
hardware codecs (see
Table 1
). On the software side are Internet
Videophone from Intel Corp. (Santa Clara, Calif.), Netmeeting 2.0 from
Microsoft Corp. (Redmond, Wash.), VDOphone from VDOnet Corp. (Palo
Alto, Calif
.), Internet Phone with Video from Vocaltec Inc.
(Northvale, N.J.), and Cu-Seeme from White Pine Software Inc. (Nashua,
N.H.).
On the hardware side are Diva from Eicon Technology Corp.
(Montreal), Osprey 1000 from Multimedia Access Corp. (Dallas), LiveLAN
Version 3 from Picturetel Corp. (Danvers, Mass.), Armada Escort 25
from VCON Inc. (Dallas), and Z350 from Zydacron Inc. (Manchester,
N.H.). Eicon also sells a card-and-software version of Diva.
Software codecs are easier to install--although vendors warn
against distributing the programs from a central server. Hardware
codecs mean cracking open the PC and slotting in a new adapter. That
might not seem like a big deal, but doing it on a dozen desktops is a
great way to spend even more time at work.
But there's a penalty for taking the easy way out. According to
Jeanine Linehan, an analyst at Sage Research (Natick, Mass.), software
codecs put more of a burden on the host's CPU. In fact, vendors of
hardware codecs claim that soft codec
s can use up to 90 percent of a
PC's processing power, making it impossible to run other apps like
e-mail while a videoconference is in session.
Hardware codecs, in contrast, have their own processors. This
enables them to offload functions like call setup, compression and
decompression, and echo-cancellation from the PC, so there's no
performance hit.
But not everyone agrees with this assessment. The IMTC's Rauch
argues that performance is not a simple hardware vs. software issue.
"There are a bunch of factors that add into the equation: network
speed, RAM, the quality of the video capture card, and the power of
the PC. Over a dial-up connection, like 28.8 kbit/s, we don't see any
improvement in performance with hardware codecs."
CASH AND CARRY
When it comes to cash considerations, software codecs are a much
better deal than their hardware counterparts. Microsoft and Intel both
boast an unbeatable price: Netmeeting and Videophone can be downloaded
free over the Internet.
No, Mr. Gates isn't on a charity kick. Over 100 hardware and
software vendors have already announced that they'll develop products
that play with Netmeeting, which is quickly becoming the de facto IP
videoconferencing app. And Microsoft's decision to saturate the market
by giving away its codec could be a very smart way to entice net
managers to get involved with this technology.
But net managers who opt for free codecs are going to get what they
pay for: These are bare-bones implementations of the H.323 spec. In
fact, Microsoft says that it considers Netmeeting to be a base
platform that other developers can fill out.
Codec vendors say spending some cash will pay off. For example,
some codecs feature more advanced compression algorithms, which can
boost video and audio quality. Vocaltec's Internet Phone costs $50 a
pop. White Pine's Cu-Seeme goes for $70 and supports IP multicast.
Expect to pay more for hardware codecs--significantly more. Eicon's
card-and-code combo comes in
at $500; the hardware version of Diva
lists for $1,000. Picturetel's LiveLAN retails for $1,495. And VCON's
Armada Escort 25 ranges from $1,900 to $4,000. At the high end, the
money buys an Ethernet, token ring, or ATM (asynchronous transfer
mode) port on the adapter.
As indicated, EDS's Brett Spell thinks IP videoconferencing is a
real moneysaver. He's using White Pine's Cu-Seeme software codec to
link more than 100 military doctors to a collaborative virtual medical
center. According to his estimates, IP videoconferencing is saving him
$400 per desktop, which works out to $40,000--not counting ISDN line
costs. Some of the doctors dial in to the group's intranet; others
videoconference via the Internet.
Right now, Spell is running the IP videoconferences over the
medical group's Ethernet. He plans on upgrading the network, although
he hasn't decided whether to go with gigabit Ethernet or ATM. "We'll
have a large amount of bandwidth available for good-quality
videoconferencing," he says.
WILL IT PLAY ON THE PC?
Corporate networkers trying to come up with the best codec also
need to consider a few other factors. First, does the product play
with the host operating system? All the codecs work with Windows 95.
Microsoft, VCON, and Volcaltec also run under Windows NT. White Pine
is the only vendor to work with the Macintosh operating system;
Multimedia alone supports Unix.
Second, make sure the codec works with the PC's bus structure. This
isn't an issue with software codecs. Multimedia, Picturetel, VCON, and
Zydacron sell PCI cards. Multimedia's Osprey 1000 also comes with an
MVIP (multivendor integration protocol) connector that can be used to
link to other cards without tying up the PC's backplane. Eicon's Diva
is an ISA (Industry Standard Architecture) card.
Third, make sure the codec delivers the requisite LAN and WAN
connectivity. Again, this isn't an issue with software codecs, since
they simply employ the PC's LAN port, modem, or ISDN terminal adapter.
All o
f the hardware codecs except Multimedia's Osprey 1000 come with
an ISDN BRI (basic-rate interface). That's where the Osprey's MVIP
connector comes in handy: It makes it simple to tie the codec to an
ISDN card equipped with a PRI (primary-rate interface).
GOING FOR A GATEWAY
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Online Extra
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Net managers who've already deployed older, standards-based
videoconferencing systems should make sure that new codecs can play
with these systems. Not everybody can: VDOnet supports H.324 (the
ITU-T standard for videoconferencing over phone lines). Eicon ships
its Diva card with drivers for H.324 and H.320 (the ITU standard for
videoconferencing via ISDN).
Both these products need an H.323 gateway to communicate with other
videoconferencing systems, and these boxes won't ship until the end
of
the year. But Multimedia goes this scheme one better. Its Osprey 1000
can videoconference with H.320 and H.324 systems--without a gateway.
In essence, it acts as three different codecs. The card accepts H.323
video over its host's PCI bus; it ties into an H.320 system by using
its MVIP connector to link to an ISDN card. Alternatively, it can use
MVIP to reach a LAN adapter linked to a modem, and thus participate in
an H.324 conference.
It's important to understand that Osprey does not translate between
videoconferencing protocols. Thus, an end-user participates in one
videoconference at a time--H.323, H.320, or H.324.
H.323 gateways, in contrast, do translate between protocols. But
end-users still can't participate in multiprotocol videoconferences
since the sessions are point-to-point. The advantage to a gateway is
that it enables desktops without ISDN or dial-up connections to reach
other "legacy" videoconferencing systems. In this case, the end-user
reaches the gateway over the LAN.
THE NEED FOR SPEED
So much for the small stuff. The key consideration for any
videoconferencing setup is how many frames per second (fps) it can
crank out. Net managers looking for a baseline need to know that
TV-quality transmissions go off at approximately 33 fps. The best
ISDN-based systems can hit 30 fps--for point-to-point sessions.
That sounds very impressive, but corporate networkers need to
factor something else into the equation. As a rule of thumb, a 30-fps
video stream needs roughly 384 kbit/s in each direction. That means an
ISDN setup that delivers 30 fps has to be tied into a primary-rate
circuit. Think of it another way: Every frame per second transmitted
needs about 12.8 kbit/s, according to George Khater, senior product
manager at Picturetel.
That helps put product claims in a very clear perspective. For
example, Eicon says it can hit 30 fps with both versions of its Diva
codecs--on a point-to-point connection over a corporate LAN. That's no
problem, as long a
s both participants are on the LAN. But if one of
those end-users is dialing in, it could be a very different story. If
the connection is over a T1 (1.544-Mbit/s) line (no trouble at many
remote offices) then 30 fps is still theoretically achievable. But if
a conference participant dials in over a 28.8-kbit/s line, there
simply isn't enough bandwidth to sustain a 30-fps connection. The top
speed on the link would be roughly 2 fps--not exactly business
class.
PROMISES, PROMISES?
Eicon isn't alone in making ambitious or ambiguous performance
claims. VCON and Zydacron also say they can hit 30 fps on
point-to-point connections over a corporate intranet. Multimedia
indicates that its Osprey 1000 can reach 27 fps.
This isn't to say that these speeds are impossible to achieve. It's
just that net managers need to consider the networking angles very
carefully if they expect to see IP videoconferencing deliver on
performance promises. And bear in mind that there's no substitute for
actually ev
aluating products on a production net.
Intel, Picturetel, VDOnet, and Vocaltec all say they can reach 15
fps on a corporate LAN. White Pine says Cu-Seeme can churn through 11
fps; Microsoft indicates that Netmeeting can deliver 10 fps. Corporate
networkers can expect to see faster frame rates when RSVP (resource
reservation protocol) is ratified and widely implemented. The IETF
(Internet Engineering Task Force) signaling scheme gives applications
a way to ask routers to reserve bandwidth on IP nets (see "RSVP: A
Priority Problem?" May 21, 1997,
http://www.data.com/
roundups/rsvp.html
). The ITU-T has indicated that it will incorporate
RSVP into H.323 when the latter is wrapped up.
Trying to use IP videoconferencing over the Internet is even more
of a crapshoot. For instance, Eicon says that its Diva codecs can hit
15 fps on the 'Net. Again, that's theoretically possible--with a big
enough pipe.
But there's another issue. Multiple router hops can add f
our or
five seconds of delay to an IP videoconferencing session, far too much
of a slowdown for anything approaching real time. In contrast, the
latency of a phone call is less than 80 milliseconds.
Despite the caveats, some net managers have already deployed IP
videoconferencing--and are very happy with the results. Randy Lawson,
research engineer at OSF Healthcare System Corp. (Peoria, Ill.), uses
Osprey 1000s on the hospital's intranet to link cardiologists in
different parts of the state. In the past, when a patient needed a
diagnosis, Lawson says the hospital would send videotapes to
specialists via taxi or Federal Express. IP videoconferencing lets
doctors confer in real time. "For users outside the private network,
we still need ISDN, but IP takes care of internal connectivity."
SQUEEZE PLAY
Corporate networkers who want to keep IP videoconferencing sessions
clipping along can boost effective throughput with compression. H.323
includes two compression algorithms: H.261, which
also is used with
ISDN systems, and H.263, which is used with leased-line
videoconferencing. H.323 also specifies three audio-compression
algorithms: G.711, G.729A, and G.723.
Since the compression algorithms are part of the spec, net managers
may believe that there's no difference among products. That's
theoretically true, but here again it comes down to hardware vs.
software. Compression is fairly processor-intensive, as discussed.
Software codecs are going to steal cycles from their host's CPU to put
the squeeze on video. Hardware codecs come with their own on-board
CPUs.
Net managers also should consider the resolution of the images
during the videoconference. Most codecs support one of two sizes: full
CIF (common intermediate format), at 352 by 288 pixels, or QCIF
(quarter CIF), at 176 by 144. QCIF requires one-fourth the bandwidth
of a full-screen transmission. For the most part, the smaller the
image, the better the resolution.
Corporate networkers also should check to see if c
odecs feature
echo cancellation. This helps eliminate the feedback and noise created
by the microphones and headsets used with videoconferencing equipment.
All the vendors except Microsoft offer echo cancellation. Here again,
it's a hardware vs. software issue.
WHAT'S THE POINT?
One of the most important issues to consider when shopping for
H.323 codecs is whether they support multipoint and multicast
sessions. Multipoint videoconferencing allows more than two sites to
participate in one session--a feature commonly found on ISDN systems.
VCON and Multimedia are the only vendors that offer multipoint
capabilities.
But don't expect to set up multipoint sessions anytime soon. The
feature can only be activated in conjunction with an H.323 MCU
(multipoint control unit)--and these products won't ship until year's
end from Videoserver Inc. (Lexington, Mass.) and Accord Video
Telecommunications Inc. (Plainview, N.Y.). MCUs are necessary for
multipoint conferences because they distribute in
dividual video
streams to each end-user.
IP multicast, in contrast, allows a group of end-users to share a
single video stream. This gives net managers a way to restrict
broadcasts so that they're only sent to specific IP addresses--rather
than to every end-station on the network (see "IP Multicast: Making It
Happen," May 21, 1997,
http://www. data.com/tutorials/ip_
multicast.html
). Currently, White Pine's Cu-Seeme is the only codec
that supports IP multicast. But net managers also must buy the
vendor's Meetingpoint, a bridge-like device that assigns end-users to
the video stream. Meetingpoint lists for $995 for 10 users.
A BIG BYTE OUT OF BANDWIDTH?
Net managers will want to keep a close watch on videoconferencing
traffic to make sure that it doesn't gobble up all their
bandwidth--which makes management a key concern. All of the codecs
except Multimedia and Vocaltec offer some form of proprietary
management. VDOnet's VDOphone features a gr
aphical interface that
allows net managers to view videoconferences on the network and
monitor bandwidth, frame rate, and latency. Microsoft's Netmeeting
utilizes the system policies inherent in Windows 95 for
management.
Corporate networkers who want to price out IP videoconferencing
need to get the big picture. In addition to the digital camera and
codec, they may have to buy modems, video capture cards (if they're
using analog cameras), and dial-up Internet accounts. V.34 modems
retail for roughly $200 apiece, although discounts are readily
available. Factor in another $300 for a video capture card, like the
Videostar from Diamond Multimedia Systems Inc. (Vancouver, B.C.).
Internet access is typically available for a flat fee of $20 a month.
These prices don't include labor costs, which will generally run
higher for remote sites.
Net managers also should take a close look at their PCs before they
load on IP videoconferencing codecs. For example, the minimum hardware
and software requiremen
ts for Picturetel's LiveLAN include Windows NT
4.0 or later, 486 or faster CPU, 16 Mbytes RAM, 19 Mbytes of available
hard disk space, and one ISA slot. The Z350 from Zydacron needs
Windows 95, a Pentium 90, 16 Mbytes of RAM, and a PCI bus.
There's another reason to carefully check out those PCs--to see if
they come with a USB (universal serial bus). This bus allows allows
net managers to connect PCs to peripherals like cameras, modems,
microphones, and scanners without configuring switches, jumper wires,
or other physical connectors, like serial or parallel ports. The USB
detects when devices are added or removed and automatically determines
what host resources, including driver software and bus bandwidth, each
peripheral needs.
THE SERVICES SIDE
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CONTACT AUTHOR
kcholewka@data.com
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IP videoconferencing also is starting to catch the eye of ISPs
(Internet service providers). For instance, the Bailey Group Inc.
(Gambier, Ohio) charges $450 a month for Visualcare, a service that
uses White Pine's Cu-Seeme to link patients in retirement homes to
their families. "Customers use 28.8-kbit/s modems and they get 11 to
12 frames per second," says Jim Bailey, president.
Bailey says he can't guarantee with any certainty the best time to
use the Internet for videoconferencing, but notes, "The Internet is
not as clogged as it's rumored to be."
Kathleen Cholewka is WAN equipment editor for Data Communications. She is based in New York and can be reached at
kcholewka@data.com
.
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