IPv6 Networks Advanced Developments
Carlos Friaças, José Baptista, Mónica Domingues, Paulo Ferreira
Fundação para a Computação Científica Nacional (FCCN), Avenida do Brasil n.º 101, Lisbon, Portugal
Keywords: ConferenceXP, GnomeMeeting, H.323, IPv6, OpenH323, OpenMCU, Videoconference.
Abstract: This document focuses IPv6 support on H.323 videoconference protocol and on ConferenceXP architecture.
The last one was designed by Microsoft to develop collaborative tasks and videoconference applications. In
this document videoconference solutions like GnomeMeeting and ConferenceXP Client (and adjacent
services) that implement the analyzed protocols are also presented. This way, guidelines for the deployment
of a videoconference service with IPv6 support are provided.
Videoconference has been allowing people to
overcome physical and political barriers,
contributing for the technological, social and
personal development of companies and private
individuals all over the world.
The new technologies and mainly the data
network concept have opened the horizon to one
technology that aims to become dominant on the
telecommunications world.
With videoconference’s growth importance and
the evolutionary usage of the IPv6 protocol, it is
important to investigate and to analyze solutions
with capacity to operate and to provide
videoconference services in IPv6 environments.
IPv6 videoconference doesn’t bring any crucial
advantage to IPv4’s. It only guarantees that could be
possible to provide a stable and reliable video
conference service such as the one currently
available in IPv4.
In this document, we tried to study the H.323
videoconference protocol in order to analyze its IPv6
capability. The applications directly associated with
H.323, like GnomeMeeting and OpenMCU are also
Without any association to H.323, but directly
connected to the videoconference world, IPv6
support on Microsoft’s project, named
ConferenceXP, is also a target of tests and analysis.
This document is aimed to guide the creation of
videoconference services in IPv6 networks, by
network managers and administrators.
2 H.323
Defined and standardized by ITU-T, H.323 is a
standard that specifies a multimedia content transfer
protocol over network data without guaranteed QoS.
H.323 is totally independent from the network
technologies it operates, allowing it to work on
several protocols like IPv4, IPv6, IPX, among
others, without the need to change its protocol
structure. This protocol also indicates multimedia
contents coding and de-coding patterns,
guaranteeing interoperability between several
manufacturers’ applications that implement H.323.
Currently, H.323 is mostly used on
videoconference and VoIP applications that allow
video and audio transfers. Besides this, H.323 is also
used to transfer data, such as files, written messages,
among others, simultaneously, during a conference
In the multimedia application market, one can
find different packages that implement the H.323
protocol. Just to name some: Microsoft Netmeeting,
Intel VideoPhone, Netscape Conference,
GnomeMeeting (freeware and open source).
Friaças C., Baptista J., Domingues M. and Ferreira P. (2006).
VIDEOCONFERENCE OVER IPV6 - IPv6 Networks Advanced Developments.
In Proceedings of the International Conference on Signal Processing and Multimedia Applications, pages 73-80
DOI: 10.5220/0001568500730080
2.1 Communication Elements
H.323 specifies the existence of four elements on a
communication that can perform simultaneous roles,
or not, depending on the utilization type and/or the
network structure used. The four elements are:
Terminals – Entities that allow users an
interaction with other terminals and/or with other
entities specified by H.323 to enable a
communication. The terminals need to support audio
communication (voice), being video and data
Gatekeepers – When available, they allow the
management and control of network access, and
perform addresses translation (through H.255.0
protocol). They execute the “role” of central point of
communications on their operation zone. This is
defined by the set of terminals, Gateways and MCUs
(Multipoint Control Units), over the Gatekeepers’
Gateways – They allow the interconnection
between resident terminals in different kinds of
networks (eg: PSTN) or between terminals of
different patterns (H.310, H.321, H.323, among
others), doing the translation of the used types, in
order to allow the communication.
MCUs – To allow sessions between three or
more terminals, they are needed. Each MCU is
composed by a MC (Multipoint Controller) and by
one or more MPs (Multipoint Processors). It is MC’s
responsibility to manipulate negotiations between all
terminals, in order to determine common capacities
on audio and video processing. The MP element is
responsible for the treatment of contents.
The usage of all these elements allow the
complete use of all the advantages and benefits
regarding point-to-point and multipoint
communications, on different environments, for
which H.323 was projected.
2.2 H.323 and IPv6
A crucial point to implement videoconference over
IPv4 is the Network Address Translation (NAT)
mechanism. Sometimes its use can originate
connections problems and compromise
videoconference sessions. Efforts were made to
solve this issue, but it is proved that a
videoconference usage without NAT is better.
IPv6 solves this problem by eliminating NAT
usage and providing global IP addresses to everyone
and every device.
According to H.323 specifications, this protocol
could be used on IPv6 networks without any
problem, using TCP and UDP.
With RTP and RTCP protocols, problems
shouldn’t also arise, because they are implemented
over UDP. This way, it is clear that the specification
was conceived in an intelligent way, to avoid future
protocol changes on H.323, so that it can work with
different kinds of networks.
3 OPENH323
The OpenH323 project aims to implement without
any costs and in a public approach, all the
characteristics and functionalities specified by the
ITU-T’s H.323 videoconference protocol. This
implementation aims to be used both by commercial
entities and private individuals, without any
Built over the MPL (Mozilla Public License),
OpenH323 project provides backup and orientation
to build simplified private and commercial projects
that are directly and indirectly related with
videoconference data services.
To use this platform, one needs to install the
pwlib and openh323 packages.
In the scope of OpenH323 project, some open
source applications (terminals and specified services
on H.323) had been created having as development
basis the OpenH323 framework. This demonstrates
the versatility/complementarily of the H.323
protocol through the OpenH323 platform.
3.1 OpenMCU
OpenMCU is an Open Source implementation of a
MCU (specified by H.323 protocol), created on the
scope of the OpenH323 project. It has the standard
basic functionalities, allowing the establishment of
videoconferences between two or more terminals in
a H.323 communication.
In a practical perspective, OpenMCU establishes
unicast connections with each communication
intervenient (H.323 terminals). Through these
connections, it receives data individually and later it
replies the data to the existing terminals in the same
“conference room”.
3.2 GnomeMeeting
GnomeMeeting is an application built over the
GNU/GPL license to perform videoconference or
VoIP calls through H.323. This application allows a
remote interaction with other applications or
hardware devices that support the same protocol.
Built and implemented over OpenH323, it integrates
the characteristics specified by the H.323 protocol,
and also supports a Gatekeeper service, to calls
using externals MCUs, PC-to-Phones calls using
Gateways, among others.
3.2.1 GnomeMeeting and IPv6
The OpenH323 framework is the responsible for the
H.323 protocol implementation on GnomeMeeting.
This is also responsible for the network protocol
management on H.323 communications, which
presents support for the last two standardized
versions of IP protocol (IPv4 and IPv6).
However, it’s important to point out that the
communication performed between the
GnomeMeeting and the Gatekeeper is not yet
implemented for IPv6, which prevents the full
utilization of this service, on IPv6, to
GnomeMeeting users.
3.3 H.323 Tests
On the first GnomeMeeting usage (versions 1.0.2,
1.1.0, 1.2.1 and 1.2.2), a wizard is presented,
allowing for parameters’ configuration (for example,
audio and/or video capture devices, identification
data, among others). Later, accessing Preferences in
the Edit menu, it is possible to change the previous
configurations and/or others (audio and video
devices, Gatekeeper, Gateway, etc.).Notice that it
could be necessary to activate video reception (and
sending), when it exists, on the codec’s section.
3.3.1 Point-to-Point Unicast Connection
In one unicast connection between GnomeMeeting
terminals (or others H.323 implementations) with
IPv6 support, it is necessary to insert the other end’s
IPv6 address (Figure 1). Notice that it’s absolutely
necessary to use brackets to limit an IPv6 address
(for example: [2001:690:900::1]).
Figure 1 represents a simultaneous
videoconference and data exchange.
Besides using the IPv6 address, it is possible to
use the fully-qualified domain name, or the
addresses defined in one Gatekeeper (example: On the GnomeMeeting
current version (1.2.2) this functionality isn’t
available for IPv6 yet.
Figure 1: GnomeMeeting Point-to-Point Connection.
3.3.2 Multipoint Unicast Connection
The realization of this test is only possible with a
MCU in the network. This must be accessible by all
H.323 terminals participants on the IPv6
“multipoint” videoconference.
On a Linux system, after a
pwlib, openh323
openmcu (versions 1.9.1, 1.17.2 and 1.1.9)
source code installation and compilation, the MCU
is started by the following command:
./openmcu –n –v –i 2001:690:900::1
The flag –n guarantees that the MCU won’t look
for a nearby Gatekeeper (this search is done in
IPv4). The flag
–v allows the use of video on
conferences, and the
–i flag specifies the interface
that will receive the connection requests from H.323
Beyond the used parameters, it is also possible to
change the connections’ listening port (
listenport) and change the default “conference
room” name (
--defaultroom), among others.
When the --save flag is used, at the end of
OpenMCU’s execution, a configuration file is
created on the
.pwlib_config directory (inside the
home directory, with the name
openmcu.ini). This
file avoids using flags again on the next OpenMCU
To establish a connection between a terminal and
a MCU, it’s enough to place the MCU’s address on
the terminal and make a call to that address, as if it
was one point-to-point call (unicast).
Figure 2 illustrates the establishment of one
connection to an MCU, where already exist other
VIDEOCONFERENCE OVER IPV6 - IPv6 Networks Advanced Developments
connected terminals. In this case, a connection to the
MCU through port 9999 was established.
Other MCU feature is the possibility to create
“conference rooms”. For one room creation, it’s
necessary to define it on the terminals that will use
it. When this procedure is executed, the room is
automatically created on the MCU on the moment
that the first terminal connects. The “conference
rooms” definition on a terminal has the following
In this case, when the terminal connects to the
MCU (using 2001:690:900::1), it enters one room
FCCN_ROOM. It is important to keep in mind
that dialogues are only possible between terminals
on the same room.
Figure 2: GnomeMeeting and OpenMCU Multipoint
OpenMCU contains a default room
room101) for terminals that don’t specify any
Figure 2). It is possible to remove the default room
in order to stop any connection attempt by the
terminals that don’t specify any room (
defaultroom flag). It is also possible the change
of the default room name (
OpenMCU’s newest versions (newer than
version 1.1.9) have flags completely different from
the presented version, for example the
–i flag has
been removed. This way, on OpenMCU’s recent
versions, it’s impossible to define the interface we
wish to use for communications. This makes
impossible the usage of IPv6, because the interface
automatically selected will only work by default in
ConferenceXP is a Microsoft’s investigation group
initiative. This project aims the implementation of a
technologic platform that allows the development of
new applications that helps enable distance learning
and distributed collaboration tools, among others.
Through ConferenceXP, Microsoft wants, to
promote the research and development of a new
framework to enable distributed applications that
can benefit of its advantages, as well as some other
new technologies (Tablet PCs, wireless networks).
With the contribution of research organizations
and universities, the ConferenceXP project
combines the academic community’s knowledge,
with Microsoft’s technologic experience. The
project focuses on the collaborative implementation
of applications that don’t confine the information
and knowledge shared to the each place’s physical
limits. This is materialized through the high quality
and low latency audio and video contents on real
4.1 ConferenceXP Client
The ConferenceXP Client is an application of
interaction and cooperation with other applications
in virtual collaborative spaces called Venues. These
Venues are terminal points defined by an IP address
(IPv4 or IPv6) and a port.
When one connection is made with
ConferenceXP Client to one Venue, this starts
automatically the ability of video and audio
multipoint send and receive, also allowing the audio
and video parameters definition that will be used.
This application was projected to work over high
capacity networks (at least at 2 Mbps), allowing the
transfer of full-screen videos at 30 frames per
second rate and supporting five different transfer
High – 640 x 480 pixel resolution at 1.5Mbps
Medium High – 320 x 240 pixel resolution at
1Mbps compression;
Medium – 320 x 240 pixel resolution at 512Kbps
Low – 320 x 240 pixel resolution at 256Kbps
Very Low – 160 x 120 pixel resolution at
50Kbps compression.
Beyond the video and audio transfer ability,
ConferenceXP allows its users to transmit
presentations (MS Powerpoint and/or Whiteboard)
concurrently with real time written conversation
The content transaction is made simultaneous
between the different ConferenceXP Clients
involved without any need of a server. This way, the
transfers occur between the several clients on the
network with a possible lower volume of traffic (to
take advantage of the maximum available
resources). For that, ConferenceXP Client appeals to
multicast usage allowing the sending of streams to
all involved clients.
It is also possible to use one unicast connection
between two ConferenceXP Clients, making a
classic point-to-point connection.
4.2 ConferenceXP Services
The ConferenceXP architecture allows the creation
of several services to the Network Transport layer
with the goal of adding and improving Microsoft’s
investigation set of services.
4.2.1 Venue Service
A Venue Service allows users to create and manage
virtual and collaborative spaces, where they can
participate. These spaces (Venues), indicate to the
ConferenceXP Clients info about applications that
try to connect to it (what ports and IP addresses they
should use).
After clients learned the parameters to the
connection from Venue Service, they can start
multicast connections between them.
4.2.2 Archive Service
The Archive Service allows users to save a specific
session on a server using SQL Server, so that it’s
possible to reproduce it later.
This service doesn’t have any kind of IPv6
support yet. Its use (save conferences) is only
possible over IPv4.
4.2.3 Reflector Service
The Reflector Service allows the operation of the
ConferenceXP Clients over unicast only networks
(without multicast support). This server guarantees
functionality, making in a transparent way a virtual
tunnel between the multicast network and the clients
in the unicast network (Figure 3).
Unicast Network
Non-Multicast Router
G1 Multicast Group
Unicast Connection 1
Figure 3: Reflector Service Functioning.
4.3 ConferenceXP Services
In this section, it is our aim to demonstrate the
functioning of videoconference sessions using the
ConferenceXP Client and some of the available
4.3.1 Unicast Point-to-Point Connection
In one unicast point-to-point connection with
ConferenceXP Client (version 3.2), two computers
with .NET 1.1 framework (with its service pack 1)
installed are necessary. These computers need to
have IPv6 connectivity between them.
Satisfied the previous criteria, it is necessary to
proceed to the clients’ configuration. It’s possible in
this configuration to specify the sending audio and
video capture devices, the window layout to present,
on the
Settings -> Audio/Video menu.
Through the
Actions menu, on Start a Two-
Way Unicast Conference, the addresses needed
to directly connect to another client can be
configured (Figure 4).
Figure 4: Point-to-Point Unicast Connection
VIDEOCONFERENCE OVER IPV6 - IPv6 Networks Advanced Developments
The source and destination addresses
configuration procedure (Figure 4) is needed on both
Figure 5: ConferenceXP Client Videoconference.
4.3.2 Multicast Multipoint Connections
using Vennues
The use of Venues implies the acquisition and
installation of a Venue Service (version 2.1) on MS
Windows XP or MS Windows 2003 Server with IIS
available. IIS server plays an important role on the
Venues publicity; therefore, it is through this web
server that the clients will request/receive the
information about the existing Venues (IP addresses
and ports) through SOAP (Simple Object Access
During the Venue Service installation process,
the necessary steps to a correct installation are
presented. One of the steps is the definition of a
virtual directory to IIS, and the respective access
port (Figure 6).
Figure 6: Venue Service Parameters Installation.
On the creation of a new Venue, it is necessary
to define its naming, creator identification, multicast
address and multicast port, used by the clients on the
communications (Figure 7).
Figure 7: A Venue Creation.
On each Venue Advanced Properties, it is
possible to define expressions to avoid its
visualization by users that don’t have the same
expression in their identifications.
Figure 8: Venues Management and their Clients.
With the Venues creation, they start to be
available to the clients connected to the Venue
Service. It is also possible to watch and manage the
connected clients (for example, cancel a client
connection) to the Venue Service (Figure 8).
For clients connected to the Venue Service, it is
necessary to configure them by adding and choosing
the computer address where the service and the
virtual directory are installed (
Settings menu in
Services - Figure 9).
Figure 9: Venue Service Definition on the Client Side.
Once configured the new Venue Service on the
clients’ side, the venues are presented (Figure 10).
Figure 10: Available Venues on the Venue Service.
In this case, after finishing all the configurations,
when one client enters the Venue called
IPV6@FCCN, it starts a communication with all the
clients who chose the same Venue, through
ff08::96 multicast address on port 5004. All
clients in this Venue receive and send contents in
multicast, making use of multipoint connectivity.
Besides the IPv6 Venues support by the Venue
Service, the connectivity between the clients and the
Venue Services is made through IPv4, because this
IPv6 feature is still to be implemented by Microsoft.
4.3.3 Connections to Multicast Conferences
through Unicast
In this section we hope to demonstrate the solution
for a common problem: The lack of multicast
support on commercial networks.
A client in a network without multicast support,
could participate on a conference made on a network
with multicast support, by establishing an unicast
connection to a Reflector Service (Figure 3).
It is a smart option to install Microsoft’s
Reflector Service (version 1.2), on the same system
than the Venue Service, to simplify management. It
is necessary to proceed with the configuration of this
service, so that it can accept IPv6 requests (disabled
by default). On the service installation directory, it is
necessary to edit the
ReflectorService.exe.config file and change
the following instruction:
After changing the configuration file, and
rebooting the service, it is ready to receive IPv4 and
IPv6 requests.
Figure 11: Reflector Service Definition on the Client Side.
VIDEOCONFERENCE OVER IPV6 - IPv6 Networks Advanced Developments
For networks without multicast support,
ConferenceXP clients can participate on multicast
conferences, only by configuring connections to a
Reflector Service (Figure 3).
This configuration is possible by adding the
Reflector Service address through the
menu on the
Services option (Figure 11).
When the client does a Venue selection, a unicast
connection to the Reflector Service is established.
Meanwhile, the Reflector Service will make a
multicast connection to the specified conference
according to the Venue chosen (
Figure 12).
Figure 12: Reflector Service Connections Management.
It is possible for the Reflector Service
administrator to remove a client from a conference
through the Reflector.
The analysis made to the OpenH323 project
demonstrates some poor focus on IPv6 support
implementation. As an example, OpenMCU’s
newest versions reveal flaws on IPv6 support. This
fact, forced us to use an older version to perform the
presented tests.
Directly connected to OpenH323 project’s IPv6
support stagnation, functioning problems on the
GnomeMeeting software were verified. The main
problem was the impossibility of establishing a
connection to Gatekeepers through IPv6.
In summary, despite the identified problems on
the OpenH323 project (applications and services)
and on GnomeMeeting, these tools are able to the
build up of a basic IPv6 videoconference
The ConferenceXP project, due to its embryonic
state, still presents some instability. On the other
hand, there is a concern about perfection, by
considering itself like a project with “legs to walk”
on the IPv6 world.
The ConferenceXP Reflector Service shows the
adaptation capability of this project, allowing
videoconferences between clients, independently of
multicast availability. This way, this project can be
seen as a serious competitor to the existing
videoconference software tools.
With IPv6 transition, we are certain that new
projects, applications and frameworks with abilities
to satisfy the videoconferences service needs in IPv6
environments will rise.
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