NCast N-Way Server User Manual
NCast N-Way Reference Manual
NCast Product Specification
N-Way Reference Manual
Revision 1.3
June 2nd, 2008
Software Release 1.0
Copyright © NCast Corporation, 2008
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Table of Contents
1. Introduction ................................................................................................................................... 4
1.1. Purpose .................................................................................................................................. 4
1.2. Document Overview ............................................................................................................... 4
1.3. Terms and Definitions ............................................................................................................ 4
1.4. Telepresenter Units ................................................................................................................ 5
1.5. N-Way Server Functionality and Modes of Operation ........................................................... 5
2. Server Administration .................................................................................................................. 11
2.1. Configuring N-Way Network Interfaces ................................................................................ 11
2.2. Hostname Setting ................................................................................................................. 12
2.3. Remote Desktop Administration Using VNC ........................................................................ 12
2.4. FTP Upload Accounts .......................................................................................................... 13
2.5. Archive Playback .................................................................................................................. 13
2.6. Defining an N-Way Account ................................................................................................ 13
2.7. Account Creation .................................................................................................................. 14
2.8. Account Modification ............................................................................................................ 15
2.9. Account Channels ................................................................................................................ 16
2.10. Account Viewers ................................................................................................................. 17
2.11. Web Server Configuration .................................................................................................. 18
3. Telepresenter N-Way Access ..................................................................................................... 19
3.1. N-Way Settings ..................................................................................................................... 19
3.2. Channel MTU Settings ......................................................................................................... 20
3.3. Multicast Settings ................................................................................................................. 20
3.4. Operating Restrictions .......................................................................................................... 20
4. Information Pages Reference ..................................................................................................... 22
4.1. Session Page ....................................................................................................................... 22
4.2. Viewers Page ....................................................................................................................... 22
4.3. Statistics Page ...................................................................................................................... 23
4.4. Logs Page ............................................................................................................................ 24
4.5. Configuration Page ............................................................................................................... 24
5. Server Access ............................................................................................................................. 26
5.1. Web Interface ....................................................................................................................... 26
5.2. Streaming Server Interface .................................................................................................. 26
5.3. Secure Shell ......................................................................................................................... 27
5.4. Port Usage ............................................................................................................................ 27
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6. N-Way System Operation – Detailed Examples ......................................................................... 28
6.1. The N-Way Client ................................................................................................................. 28
6.2. N-Way Connectivity - Sending ............................................................................................. 29
6.3. N-Way Connectivity - Receiving ........................................................................................... 29
6.4. N-Way Restriction – Server and Client on the Same LAN ................................................... 30
6.5. N-Way Restriction – Two Tunnels on the Same LAN .......................................................... 30
6.6. N-Way Restriction – Multiple Hops from the LAN ................................................................ 31
7. Client Web Page Linkage ........................................................................................................... 32
7.1. Media Player Links ............................................................................................................... 32
7.2. RTSP Links .......................................................................................................................... 32
7.3. Multicast Links ...................................................................................................................... 32
7.4. RTSP Movies ........................................................................................................................ 33
7.5. Launching Quicktime Player – QTL Files ............................................................................. 33
7.6. Launching Windows Media Player – ASX Files ................................................................... 33
7.7. Embedding Quicktime Player in a Web Page ...................................................................... 33
8. Archive Management, Access and Playback ............................................................................. 35
8.1. The Content Directory .......................................................................................................... 35
8.2. Managing Content ................................................................................................................ 35
8.3. Content Metadata ................................................................................................................. 36
8.4. Content Playback ................................................................................................................. 36
8.5. Podcasting and RSS ............................................................................................................ 38
9. References .................................................................................................................................. 39
9.1. MPEG Compression ............................................................................................................. 39
9.2. Packet Transmission ............................................................................................................ 39
9.3. Multicast ............................................................................................................................... 39
10. Revision History ........................................................................................................................ 40
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1.Introduction
1.1.PURPOSE
The NCast N-Way Reference Manual is intended for the Network engineer who will be tasked with the job of
installing and setting up an N-Way Server. This guide is designed to cover topics in depth and assumes the
reader is familiar with network protocols such as multicast, topics such as webcasting and running of a Linuxbased web server.
1.2.DOCUMENT OVERVIEW
This document is divided into three major sections: introduction to the operation and functionality of an N-Way
Server, instructions on how to configure the server for customer accounts, and configuration of a Telepresenter
for use with N-Way service.
1.3.TERMS AND DEFINITIONS
A complete discussion of network protocols, Internet streaming, webcasting and related topics is beyond the
scope of this document. Other sources cover this material in great detail. The following are brief definitions of
some of the terms used throughout this manual.
AAC – Advanced Audio Coding, a wideband audio encoding and compression algorithm.
IETF – Internet Engineering Task Force, the standards body for Internet protocols.
ISO – International Standards Organization
Latency – The end-to-end time delay between a change in the source image and the
corresponding change in the remotely displayed image.
Lip-sync – The synchronization of independent audio and video streams at a receiving decoder so
that the presentation is in the same time relationship as the source.
MPEG Compression – MPEG is an acronym for Motion Picture Experts Group, an industry-wide
committee that has defined a series of standards for the compression of audio and video source
material.
MTU – The maximum transmission unit is the maximum number of bytes permitted in a
transmitted packet.
Multicast – A family of computer transmission protocols where multiple receivers access a single
transmitted packet stream.
NCCP – NCast Conference Control Protocol provides coordination, control and identification of
participants in a multi-way collaborative conference session.
N-Way – An NCast proprietary service for multicast bridging and webcasting.
RFC – Request for Comments, an Internet protocol standard.
RTSP – Real-Time Streaming Protocol is an IETF approved protocol for control of real-time
streaming on the Internet.
Telnet – An IP network based protocol, which was originally used to connect remote consoles and
terminals to mainframes, but is now used as a general, bi-directional, byte oriented
communications facility. See RFC’s 854 and 855.
Unicast – Refers to a point-to-point connection between two Internet host machines.
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1.4.TELEPRESENTER UNITS
The Telepresenter is a stand-alone network communications appliance which captures RGB (VGA) signals from
a desktop or laptop, compresses the image with an industry standard compression algorithm, packetizes and
transmits the imagery as an internet media stream, receives a media stream from the internet, decompresses the
imagery, and presents the received information to a viewing audience through use of a large-screen computer
(VGA) monitor or via a room projector. Some Telepresenter models also archive the media stream in real-time,
allowing for playback by the recipient at a later date.
The following Telepresenter models are capable of using N-Way services:
Telepresenter S – A small stand-alone unit used primarily for webcasting.
Telepresenter G2 – A rack mounted unit with streaming and archiving capabilities.
Telepresenter M2 – A desktop unit with MPEG-2 video, PCM audio and JPEG graphics.
Telepresenter M2P – A rack mounted unit with streaming, archiving, collaboration and PIP capabilities.
Telepresenter M3 – A rack-mounted unit with streaming, archiving, collaboration, UXGA and PIP
capabilities.
Telepresenter M3 Series 2 – A rack-mounted unit with streaming, archiving, collaboration, WUXGA, HD
and PIP capabilities.
All Telepresenter models share a core operating system and base set of features.
1.5.N-WAY SERVER FUNCTIONALITY AND MODES OF OPERATION
The N-Way Server supports the following major services:
1.5.1.One-to-Many Streaming using RTSP and the Auto Unicast (Announce) Feature
In this configuration a Telepresenter is given the IP address of the server and utilizes a unicast RTP stream to
broadcast directly to the server. The server then “reflects” the streams to clients logged in via RTSP protocol.
The “Auto Unicast (Announce)” facility is a mechanism within the RTSP protocol to automatically provide the
server with the correct SDP media-file information. The server automatically installs an .SDP file for the Session
and client players simply reference that .SDP to begin the connection and begin playing. The .SDP file is also
automatically removed when the Session stops, thus disconnecting any connected clients. The Announce feature
eliminates the need to manually configure and install .SDP files at the server.
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1.5.2.Archive Playback using RTSP
Several models of the Telepresenter allow recording of webcasts or conferences. These files are created as
MPEG media files and stored locally until the file is downloaded and removed from the unit.
A Telepresenter is not designed to be a Video-on-Demand playback server. Continuous playback of captured
files would interfere with the real-time capture and encoding activities of the unit. Nor is there any provision for
backed-up storage of the files. These functions are best done elsewhere in the network.
An N-Way Server is capable of storing archived files and playing them back on demand from its hard-drive. Files
may be uploaded to the server using the automatic FTP upload facilities within the Telepresenter.
There is a configuration page within the Telepresenter to define the FTP server, account and password. The
archived .mp4 file, along with its associated .xml file, can be uploaded immediately after a Session stops, or the
upload can be programmed for later in the day or after business hours when the network will be less busy.
Once the file is residing in the content directory on the server, a simple RTSP link is all that’s needed to play back
the file on demand.
1.5.3.Multicast Bridging
Through the use of N-Way bridging and tunneling protocols, multiple Telepresenters, which are not situated on a
native multicast network, can participate in a conference through the use of the server as a bridge. All the
standard Telepresenter modes of operation (one-way streaming, full-duplex streaming and collaboration mode)
are supported through use of the bridge. The N-Way Server must be located at a network point where multiple
streams (one for each participating unit) can exist and flow without impacting or overloading the network.
Multicast traffic at each end point is forwarded through the tunnel and emerges at the bridge where it is routed to
all participating parties. The simplest conceptual model for this usage is a hub-and-spoke arrangement, where
each remote Telepresenter is at the end of a spoke, and the N-Way Server is the hub located in a high-bandwidth
network operations center.
More complex architectures are possible for special applications (See Chapter 6). If the N-Way Server itself is
located on a multicast network, traffic can flow from the multicast network through the bridge and its tunnels to the
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remote units (but the reverse of that flow is not supported). Also, multicast traffic from the local LAN of each
remote unit maybe forwarded to the bridge. Contact NCast for details on the uses and potential limitations of
network architectures beyond a simple hub-and-spoke arrangement.
In each case, multicast traffic (the media streams) generated by the remote Telepresenter is encapsulated into a
packet which is sent via unicast to the N-Way bridge, where it is unpacked and mixed with all other multicast
streams present at the bridge. The server looks at all the multicast traffic in the mix, and forwards, via the reverse
unicast connection, the media streams desired by a remote unit. Multicast group traffic not requested by a remote
unit is discarded and not forwarded to any remote site.
1.5.4.One-to-Many Streaming using Multicast Bridging and RTSP
In this mode of operation one of the Telepresenters designated as the “Sender” is generating a media stream and
forwarding this stream via a multicast tunnel to the N-Way Server. At the server the media stream packets are deencapsulated and placed onto the local network as a multicast source. A streaming server process running in the
N-Way Server can then accept RTSP protocol requests from remote desktops and forward media streams in the
local multicast mix to the remote clients.
This mode of operation allows many hundreds of viewers (who have only unicast connections) to watch the
encoded output of a single Telepresenter. The N-Way Server must be at a network point where the aggregation
of many unicast streams will not impact functioning of the network.
There is, within each Telepresenter, a similar one-to-many RTSP connection function, and for small groups and
low bandwidth connections the use of an N-Way Server is not required. However, the number of viewers is limited
and it is possible that the sending (encoding) Telepresenter is at a network location where the aggregation of
multiple unicast streams will choke the network connection. In this case, the encoded stream should be tunneled
to a central network point where mass distribution to a large number of clients is workable.
1.5.5.Collaboration Mode Streaming to the Desktop using RTSP
Telepresenters can be used in a special mode called “Collaboration Mode” where each Telepresenter in the
conference can be given floor control in turn, and the other participating units will be viewing the graphics or video
output of the unit, which currently “has the floor”. Thus, the conference coordinator can switch presentations from
a central site to some remote site to allow a remote presenter (a student presenting a report, a foreign workgroup,
a remote knowledge expert, etc.) to speak and be seen by all the participants in the conference. When the remote
presenter is finished, the coordinator continues with his/her presentation from the central site and all the units are
redirected to view the proceedings emanating from the central location.
If this collaborative event is to be viewed by remote desktops, two important technical issues must be resolved.
First, as the source of the graphical or video presentation switches from Telepresenter to Telepresenter, the RTP
stream-id changes with each switch, and most desktop client players are unable to re-sync onto a media stream
with a new and different stream-id. They typically “lock-on” to the first stream-id they find, and ignore media with
all other stream-id’s. The net result is that the viewer sees only media from one presenter, and the picture is
frozen while other presenters have the floor.
Also, in a collaborative conference, each Telepresenter is continuously generating an audio stream, and these
multiple audio streams must be mixed into one sound source somewhere for playback. This function is normally
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handled by each Telepresenter’s audio subsystem, but in the case of a desktop player there is no capability to do
this. So, the server must decompress each incoming audio stream, mix all the streams together, and create a
single outgoing audio stream for the desktops.
Collaboration mode to desktops is fully functional for the M2 series of Telepresenters, but the graphics and audio
components are not currently available for the G2 and M3 units.
1.5.6.One-to-Many Streaming using RTSP and the Auto Unicast (Announce) Feature
In this configuration a Telepresenter is given the IP address of the server and utilizes a unicast RTP stream to
broadcast directly to the server. The server then “reflects” the streams to clients logged in via RTSP protocol.
The “Auto Unicast (Announce)” facility is a mechanism within the RTSP protocol to automatically provide the
server with the correct SDP media-file information. The server automatically installs an .SDP file for the Session
and client players simply reference that .SDP to begin the connection and begin playing. The .SDP file is also
automatically removed when the Session stops, thus disconnecting any connected clients. The Announce feature
eliminates the need to manually configure and install .SDP files at the server.
1.5.7.Archive Playback using RTSP
Several models of the Telepresenter allow recording of webcasts or conferences. These files are created as
MPEG media files and stored locally until the file is downloaded and removed from the unit.
A Telepresenter is not designed to be a Video-on-Demand playback server. Continuous playback of captured
files would interfere with the real-time capture and encoding activities of the unit. Nor is there any provision for
backed-up storage of the files. These functions are best done elsewhere in the network.
An N-Way Server is capable of storing archived files and playing them back on demand from its hard-drive. Files
may be uploaded to the server using the automatic FTP upload facilities within the Telepresenter.
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There is a configuration page within the Telepresenter to define the FTP server, account and password. The
archived .mp4 file, along with its associated .xml file, can be uploaded immediately after a Session stops, or the
upload can be programmed for later in the day or after business hours when the network will be less busy.
Once the file is residing in the content directory on the server, a simple RTSP link is all that’s needed to play back
the file on demand.
1.5.8.Web Server
Finally, an N-Way Server may be used as a web server. An industry-standard Apache web server is provided with
the standard software installation, and this may be configured to run on any interface that is not used for
streaming server access (no port-80 conflicts). The server operator must be familiar with the standard
configuration files utilized by the Apache software.
1.5.9.Administrative Features
Access to N-Way services is organized by accounts, which are defined by the server administrator.
• Each account may be restricted by password and Telepresenter serial number.
• Each account defines a range of multicast addresses permitted for use.
• Each account defines a maximum number of concurrent sessions.
• An account may declare a variable number of access channels for desktop viewing.
• An account creates a list of viewers, each with a separate access password.
• For each account session time and traffic are recorded and may be used for customer billing.
• Real-time web access provides views of current sessions, viewers and traffic.
• System logs are stored in an SQL database for processing on a daily, weekly or monthly basis.
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• Daily, weekly and monthly reports may be generated and emailed to clients.
• Directory based authentication for video-on-demand playback.
NCast welcomes customer feedback and input on these facilities, and will work with clients to add needed
enhancements.
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2.Server Administration
2.1.CONFIGURING N-WAY NETWORK INTERFACES
The first task required for installation of the server is to properly configure the IP interfaces and to supply other
necessary networking information. There are two network interfaces on the server (known as “eth0” and “eth1”)
and these provide the ability to configure the server for two different networks (an inside network and an outside
network, perhaps) or to double the output capacity on a single network through use of parallel interfaces. In any
case, for initial configuration, only the “eth0” interface needs to be set up. This is easily accomplished through
menus on the graphical interface. Log in as “root” (account information for the server is separately supplied) and
bring up the network configuration menu:
Select the interface to be configured “eth0” and supply the usual IP information (DHCP or static IP settings,
netmask and gateway). Also check that the required DNS and Hostname settings are correct. In general, the
server must be on a static IP address as clients will be unable to find the server if a dynamic DHCP address is
used. DHCP service is possible if the DHCP server knows the MAC interface address and assigns a static IP
based on the MAC numbers.
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2.2.HOSTNAME SETTING
The server requires a valid hostname. If not already configured through the above menus, start a terminal session
and enter the hostname command followed by a valid hostname for your network:
hostname nway.server.com
2.3.REMOTE DESKTOP ADMINISTRATION USING VNC
Often the server is located in a centralized Network Operations Center or equipment room and local console
access is either impossible or at a minimum, very inconvenient. A remote desktop facility is available through use
of the VNC protocol (many clients are available for different operating systems). The VNC server is not enabled
by default and must be started through use of the vncserver command. Log in as “root” and from a terminal
session enter:
vncserver
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