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Introduction
IP telephony allows organizations and individuals to lower the costs of existing services
such as data and broadcast video, while broadening their means of communication to
include modern video conferencing, application sharing, and whiteboarding tools.
In the past, organizations have deployed separate networks to handle traditional voice,
data and video traffic. IP telephony blends voice, video and data by specifying a
common IP-protocol transport.
Traditional Telephony
Fax
IP Telephony
Voice, Data, Video Integration
PBX or PSTN
PBX
Public
switch
Fax
Fax
Data Communication
Corporate LAN, WAN,
or Internet
Corporate LAN, WAN,
or Internet
IP Router
Media
Convergence
Server
IP Router
Video Distribution
Fax
UHF/VHF
Broadcast
Server
Cable
Microwave
Figure 1 Voice over IP (VOIP)
IP telephony uses open IETF and ITU standards like, the IP protocol and the H.323
standard. The latter standard is a comprehensive International Union (ITU) standard for
multimedia communications (voice, data and data) over connectionless networks that do
not provide a guaranteed quality of service.
H.323 allows multimedia streaming over current packet switched networks. To counter
the effects of LAN latency, H323 uses as a transport the Real time Transport Protocol.
Quality of Service protocols (QoS) is improving the service of the computernetwork.
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H.323
Audio
Codec
G.711
G.723
G.729
Video
Codec
H.261
H.263
Data
Interface
T.120
Call Setup
Q.931
RAS
Gatekeeper
Interface
Control
H.245
System Control
Transport
RTP
Control
RTCP
TCP/IP
Network
Figure 2
H.323 architecture
H.323 telephony is complicated by the fact that a user’s IP address is highly volatile and
cannot be counted on to remain unchanged between H.323 sessions. The following user
scenario illustrates IP address resolution in accordance with the H.323 standard:
1. John wishes to initiate an H.323 conference with Alice, another user on the LAN.
Once Alice’s video conferencing application creates an Address object and puts
it in listen mode. Alice’s IP address is added to the Internet Locator Service (ILS)
Dynamic Directory.
John
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Alice
Alice registers and
refreshes her IP address
via LDAP
ILS
Dynamic Directory
Server
Figure 4
Alice registers her IP address automatically
2. John’s communication software which is based on the H.323 standard queries
the ILS Dynamic Directory server for Alice’s IP address.
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John
Alice
2
John performs a
resource query for
Alice's IP address via
LDAP
ILS
Dynamic Directory
Server
Figure 5 John queries for Alice’s IP address
3. With Alice’s up-to-date IP address, John initiates an H.323 call to Alice’s
computer. H.323-standard negotiations and media selection occur between the
peer entities on both computers.
1. Objectives
1. Student can build up a LAN which consists of at least two Windows workstations
and a Windows NT server.
Windows NT server, functioning as:
•DHCP server
HOST A
(Windows 95 or higher)
HOST B
(Windows 95 or higher)
•DNS server
•ILS D Dynamic Directory Server
IP-address: 10.0.0.3
FQDN: www.roos.test
IP network address: 10.0.0.0
netmasker: 255.255.255.0
Figure 6 LAN
2. Student can install and configure DHCP server.
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3. Student can install and configure DNS server.
4. Student can install ILS Dynamic Directory Server.
5. Student can install and configure Netmeeting so that the ILS server is used.
6. Student can analyze the data traffic between Netmeeting users with a LAN
monitor.
2. Requirements
hardware
number
description
Operating system
2
host
* minimal Pentium 90-processor
* minimal 16MB internal RAM memory
* network interface card
* sound card, speakers, microphone and
webcam
* VGA- or SVGA-monitor
Windows95 or higher
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Windows NT server
* Pentium 100 MHz or higher
* minimal 64 MB internal RAM memory
* 1 GB free hard disk space
* CD ROM-drive
* Network interface card
* VGA- or SVGA-monitor
* IE 4.01 or higher
Windows NT 4.0
and Service Pack 3 or
higher
1
hub
---
Software
description
URL-number
Netmeeting 3.01 http://www.microsoft.com/windows/netmeeting/download/default.asp
Internet Locator http://www.microsoft.com/windows/NetMeeting/download/ils20x86.asp
Server 2.0
Manuals
description
URL-number
Netmeeting
Resource Kit 3.0
http://www.microsoft.com/windows/netmeeting/download/default.asp
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3. Start situation
The following preps have already been made, before you start:
a) Windows NT server plus the network interface card and driver have been installed.
b) The two Windows workstations plus the following devices and drivers have been
installed:
* network interface plus drivers
* webcams plus drivers
* microphone plus drivers
c) Windows NT server and Windows workstations have been connected to a hub.
4. Exercise
1) Assign an IP address and netmasker to the NIC in the Windows NT 4.0 server,
see figure 6.
2) You have to install the Microsoft DHCP Server, Microsoft DNS Server and the
Networkmonitor Tools and agent on the Windows NT 4.0 server.
Procedure
a) Click on: Start ? Settings ? Control Panel.
b) Click on the Network icon in the Control Panel.
c) Click on the Services tab.
d) Click on the Add tab,
e) Select DHCP Server.
f) Click on the Add tab.
g) Select de DNS server.
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Figure 7 Select DNS server
h) Select Monitor Tools and Agent.
i) Click on Close in the Network menu.
j) Restart the computer.
3) Configure the DNS server.
Procedure
a) Click on: Start ? Programs ? Administrative Tools (Common) ? DNS Manager.
b) Create New Server. IP address DNS server, see figure 6.
c) Create New Primary Zone. Zone name is: test (see figure 6).
d) Create New Domain. Domain name is: roos (see figure 6).
e) Add a A Record to the New Domain. Host Name is www and Host IP address is
10.0.0.3 (see figure 6).
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Figure 8 DNS manager
4) Configure the DHCP server. You have to:
a) Click on: Start ? Programs ? Administrative Tools (Common) ? DHCP
Manager.
b) Create a Scope IP addresses.
Figure 9 DHCP manager
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c) In the Global Scope of the DHCP manager you have to register the IP address of
the DNS server.
Figure 9 Global Scope
5) Configure the TCP/IP stack of the Windows workstations in such a way, that these
workstations are leasing TCP/IP-parameters from the DHCP server.
6) Show the teacher that the DHCP server has send TCP/IP-parameters to the
Windows Workstations. For this purpose tools like ipconfig an winipconfig can be
used.
7) Show the teacher in which way you can check the TCP/IP connection between a
Windows workstation and the Windows NT server, if you use the ping command.
8) Install the Internet Locator Server 2.0 on the Windows NT 4.0 server.
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9) Install Netmeeting 3.01 on the Windows workstations and the Windows NT server.
10) Netmeeting 3.01 has to make a connection with the Internet Locator Server
automatically, when a user starts this program in a Windows workstation. You can
find background information in Microsoft Windows Netmeeting 3 Resource Kit.
Figure 10 Netmeeting configurations
11) Check in the Find Someone menu, if the information about the Netmeeting users has
been registered in the Inter Locator Server.
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Figure 11 Personal information
12) Analyze the data traffic between a Windows workstation and the Windows NT server.
You have to use the Network Monitor on the Windows NT server.
Procedure
a) Make a Netmeeting-connection between a Windows workstation and the
Windows NT server.
b) Start the Capture mode of the Network Monitor.
c) Send a chat message from a Windows workstation to the Windows NT server.
Figure 12 Chat message
d) Stop the Capture mode of the Network monitor and display the captured data.
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e) Look in the trace and find the IP-frame in which the chat message is placed.
Figure 13
Trace
13) The following questions are based on the trace.
a) What is the MAC address of the Windows NT server?
b) How many routers can an IP-frame pass which have been sent by the Windows
workstation?
c) Netmeeting is connected to a TCP port. Determine the number of this TCP-port
in the Windows NT server.
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