3Com Nbx 100 And Ss3 Nbx Administration Guide

							Installing ConneXtions421
Installing 
ConneXtionsTo install the NBX ConneXtions H.323 Gateway:
1Insert the Resource Pack CD into the PC. Click NBX Applications, and 
then click NBX ConneXtions, and then
 click OK.
If the program does not start automatically, click the Windows Start 
menu, and then Run. Type D:autorun, substituting the letter of your 
CD-ROM drive for D, and click OK. 
2Respond to these initial InstallShield dialog boxes:
aIn the Welcome dialog, click Next.
bIn the License Agreement dialog, click Ye s .
cIn the Default Destination Location dialog, click Next or browse for an 
alternative destination location.
dIn the NBX license request dialog, click Ye s .  This confirms that the NBX 
system is legal.
3Specify the Audio Channel Format:
aSelect first option (G.711 only) for uncompressed connections
bSelect one of the other two options to configure G.723.1 connections.
These options require the file 
msg723.acm. See “Verifying the 
G.723 Converter” earlier in this appendix. 
4Information Block - click OK.
5Specify the number of configured H.323 ports for this ConneXtions 
gateway. 3Com recommends that licenses are allocated equally when 
using multiple gateways.
6Optionally, specify a Caller ID Label by entering an outgoing caller 
ID notification label of up to 33 digits. Enter numbers only, no other 
characters or spaces.
Example: 
9787490000
(The Caller ID shows the caller’s extension number followed by the 
[User Name] if the entry is left blank.)
7Specify the Call Processor name. Enter the name H.323 callers see when 
they reach the Auto Attendant. 
						

							422APPENDIX A: CONNEXTIONS H.323 GATEWAY
8Only one Gateway? - Click Ye s if the NBX system has only one H.323 
gateway system.
CAUTION: Multiple gateways must have unique configurations. Multiple 
gateways need a distinguishing “Gateway Number”. Assign the first 
installed gateway to number 0; the second to number 1; and so on. 
3Com recommends that licenses be allocated equally when using 
multiple gateways.
9Enter the Call Processor MAC Address. To find it, log on as an 
administrator in the NBX NetSet utility, and click Reports, followed by the 
System Data tab.
Be sure to record the Call Processor (NCP) MAC Address, not the 
Music-On-Hold MAC address, which also appears in the System Data tab.
10Select the country in which you are using ConneXtions. This defines the 
tones and cadences that ConneXtions uses.
11Specify the UDP and TCP port ranges for use with a firewall. If these 
ranges are not important in your system, use the default settings. You can 
coordinate these settings with the firewall administrator.
12Do you want to interface with a Gatekeeper? Click Ye s if you want to use 
a gatekeeper. Gatekeepers act as the central point for all calls within their 
zones and provide call control services to registered endpoints.
13If you have chosen to use a gatekeeper, enter the IP address of the 
preferred gatekeeper. This forces ConneXtions to try to use this 
gatekeeper first and provides a more secure option. If you want 
ConneXtions to autodiscover a gatekeeper, leave the field empty. You 
might chose to do this if you only have one gatekeeper on your network.
14Choose what you want ConneXtions to do if it cannot register with the 
preferred gatekeeper:
Autodiscover a new Gatekeeper — ConneXtions allows you to make 
direct H.323 (unregistered calls) while attempting to contact an 
alternative gatekeeper on the network. 
Continue unregistered — ConneXtions continues to function without 
using a gatekeeper.
Block Calls — ConneXtions blocks calls if it cannot register with a 
gatekeeper. (You must either have a gatekeeper on the network, or select 
one of the other options which enables ConneXtions to work without a 
gatekeeper present.) If a gatekeeper becomes available, you must stop 
the ConneXtions service and then restart it. 
						

							Installing ConneXtions423
15Do you want to use alternate Gatekeepers? If you select Ye s, the chosen 
gatekeeper maintains a list of alternate gatekeepers to be used if the 
preferred gatekeeper does not respond.
If you choose to use alternate gatekeepers and have also selected to 
autodiscover new gatekeepers if ConneXtions cannot contact the 
preferred gatekeeper, ConneXtions first tries to use alternate gatekeepers 
from the list (in priority order); if this fails, it then tries to autodiscover a 
new gatekeeper.
16Do you want to route calls through the Gatekeeper? You can route H.323 
calls through the gatekeeper for these reasons:
■To control calls more effectively. For example, service providers need to 
be able to control call flow to allow them to bill for calls placed 
through the network.
■To reroute a call to another endpoint if a called endpoint is 
unavailable.
■To maintain interoperability with multi-vendor equipment which 
routes all calls directly using the gatekeeper. 
■To use address resolution in large multi-zone configurations which 
have one or more gatekeepers in each zone.
17You are prompted to set the size of the log files. The default value is 1 
Mb. ConneXtions maintains two log files, named 
ConneXtions01.log 
and 
ConneXtions02.log. Data is logged to only one of these at a time. 
Once the active log file reaches a specified size, data logging switches to 
the second log file. Any data previously stored in that log file is 
overwritten.
18Setup Complete: Click Finish.
Finishing the
InstallationVerify the installation:
1Select the Line Card Ports tab under the Device Configuration heading in 
the NBX NetSet utility.
2Note the MAC Address, extension, status, and group for each port.
3Record the extension numbers for each H.323 port.
4Enter user-friendly port names that appear when a user dials an H.323 
port.
5Close the browser to exit the NBX NetSet utility and end the installation. 
						

							424APPENDIX A: CONNEXTIONS H.323 GATEWAY
Overview of H.323The H.323 standard provides a foundation for audio, video, and data 
communications across IP-based networks, including the Internet. By 
complying with H.323, multimedia products and applications from 
different vendors can interoperate, allowing users to communicate 
without concern for compatibility.
An NBX ConneXtions H.323 Gateway provides connections similar to 
tie lines between existing NBX systems across an IP network. However, it 
can also support voice connections between a 3Com NBX Telephone and 
other H.323-compliant devices.
ConneXtions H.323 Gateways support communication with:
■Extensions on other NBX systems that have a ConneXtions gateway.
■Extensions on PBX systems that have an attached H.323 gateway.
■H.323 gatekeepers.
■Miscellaneous H.323-compliant end-point devices such as:
■H.323 telephones.
■Suitably equipped personal computers.
■An emerging class of wireless handsets.
The quality of H.323 calls over the Internet is determined by the quality of 
the connection provided by your ISP.
The H.323 protocol addresses these main areas:
■Negotiated Connections
■Negotiated Voice Compression
■Standard Extensions
■Remote Internet Device Connections
Negotiated
ConnectionsThe H.323 protocol adds negotiated call setup and tear-down capabilities 
to Internet Protocol (IP) connections. It exists because Internet protocols 
were designed to deliver text messages and computer files in data 
packets. IP networks were not originally concerned about involving a 
person in a real-time conversation as a telephone does.
H.323 provides call setup capability to negotiate the readiness of two 
parties to exchange information and how they do it. It then keeps the  
						

							Overview of H.323425
connection alive until one of the parties ends the connection. A call 
tear-down signal indicates to the network, and to the other party, when a 
call ends. On standard telephone networks, the telephone company uses 
this signal to determine when to start and stop charging for long distance 
calls, but long distance charges do not normally apply to H.323 calls. 
Other reasons for call setup and tear-down signals are to indicate when 
an IP network can release bandwidth to support other calls, and to 
inform other devices, such as voice mail systems, when to stop their 
conversation-related activities.
Negotiated Voice
CompressionIP networks can carry a lot of traffic, creating competition for the 
available bandwidth. Devices have the best access, and the least delay, 
when they communicate messages by using fewer and smaller packets. 
This also means lower cost.
Voice compression offers a way to reduce the number and size of the 
data packets needed to carry each second of a voice conversation. 
However, voice compression needs high-speed processors to remove the 
redundancies that are inherent in the way standard voice is represented.
The international standard for representing voice (G.711) requires 64 Kb 
for each second of conversation. NBX Business and Basic Telephones 
contain a digital signal processor (DSP) that transforms spoken voice into 
this form. An Ethernet interface, also within each telephone, breaks up 
the 64 Kbps stream into frames, adds addressing and error checking, and 
dumps the voice-data frames (now 83 Kbps) onto a 10 Mbps LAN. 
Elsewhere on the LAN (local or remote), the destination telephone detects 
its address, recovers the frames, extracts the bit stream, and reproduces 
the voice.
While LANs have enough bandwidth to support uncompressed digitized 
voice transfers, WAN bandwidth is less generous. For this reason, 
compression is often used to squeeze the digitized voice into a smaller 
bandwidth that can be carried across an Internet in smaller packets.
When an NBX call passes through an H.323 gateway, the ConneXtions 
software performs an intermediate step that extracts the essential voice 
information, encapsulates it in packets, and sends it across an IP network.
G.723 is a compression standard that represents each second of voice 
conversation with 6.3 Kbps. ConneXtions software supports the use of 
this compression standard. With more than one way to represent voice  
						

							426APPENDIX A: CONNEXTIONS H.323 GATEWAY
(G.711 and G.723), H.323 gateways negotiate the type of compression 
they use during each call setup. Negotiation ensures that the compression 
on the transmit side matches the decompression processing on the 
receiving side. With the frame and packet overhead, each G.723 channel 
needs about 19.2 Kbps of the available bandwidth.
Standard ExtensionsConneXtions routes incoming H.323 calls to one designated extension, 
usually the Auto Attendant. Callers can dial additional digits to redirect 
calls to internal extensions, but cannot access outside lines by dialing 9.
Remote Internet
Device ConnectionsA NBX system with a ConneXtions gateway can communicate with 
remote H.323 devices other than NBX Business and Basic Telephones, 
such as:
■Wireless handsets
■Personal computers
■Ordinary telephones (POTS) with adapters
■H.323 gatekeepers
Wireless Handsets
An emerging class of H.323 wireless handsets is being used by some 
large outlet stores as portable PBX telephones. A ConneXtions H.323 
server is well suited for use with these H.323 handsets.
Personal Computers
Microsoft NetMeeting software supports H.323 voice connections over 
the Internet. The personal computer must be equipped with Internet 
access, a sound system, and a microphone.
The current version of Microsoft NetMeeting (3.01) cannot conveniently 
place calls through the Auto Attendant because it has no way of entering 
extension digits after it reaches an IP address (the Auto Attendant). This is 
a temporary limitation that usually disappears when those programs 
upgrade to H.323 version 2. Version 2 requires that compliant devices 
support out-of-band DTMF (touch-tone) signaling.
If you choose ConneXtions as the gateway under the Advanced Calling 
options, and if you configure NetMeeting to “speed-dial” the IP address 
and extension, Microsoft NetMeeting can place calls to an extension. 
						

							The H.323 Connection427
POTS Adapters
You can purchase circuit boards that plug into a personal computer and 
adapt an analog telephone (POTS) for use with an H.323 connection.
H.323 Gatekeepers
The gatekeeper is an H.323 entity on the network that provides address 
translation and controls access to the network for H.323 terminals, 
Gateways, and MCUs. The gatekeeper also provides services to the 
terminals, Gateways, and MCUs, such as managing bandwidth and 
locating Gateways.
The H.323 
ConnectionH.323 calls between local and remote NBX Business and Basic Telephones 
are transparent to users, except for the IP dial plan. The Call Processor 
sets up the local end of the H.323 call as though it were setting up a call 
through a line card. However, this connection actually goes to a network 
interface card (NIC) in a dedicated Windows 2000 or Windows NT system 
that is running the ConneXtions software.
The Call Processor requests an H.323 port in the ConneXtions software 
by sending a frame, with a simulated Ethernet address, that contains a 
requested IP address. The ConneXtions gateway uses this address to 
request a level three connection between the local router and the remote 
router associated with another PBX or NBX system. 
After an IP connection has been established, the ConneXtions software 
begins a series of H.323 exchanges by using TCP packets on the IP 
connection.
These H.323 exchanges set up the call and negotiate the type of voice 
compression that is used. They also cause the remote NBX (or PBX) 
system to begin setting up the remote end of the connection. 
						

							428APPENDIX A: CONNEXTIONS H.323 GATEWAY
Connection 
ConsiderationsAs soon as an end-to-end connection has been set up, all three networks 
(local LAN, WAN, and remote LAN) are ready to pass voice packets. The 
NBX Business and Basic Telephones use their DSP to convert spoken 
words into digital voice packets. The voice packets are transferred across 
the Ethernet to the local H.323 gateway. The gateway strips off the 
Ethernet frames, compresses the voice, and encapsulates it within UDP 
packets which are delivered to the router, again via the Ethernet. The UDP 
packets are placed on the WAN for IP delivery to a remote H.323 
gateway. The remote gateway undoes the process and sends the 
decompressed voice to an extension.
Connection considerations apply to two areas:
■Overall Connectivity
■Quality of Service
Overall ConnectivityAn end-to-end NBX H.323 connection consists of a succession of Physical 
Connections and Logical Connections, both local and external.
Physical Connections
An NBX H.323 gateway has few physical connections. An installer can 
add an H.323 gateway to an existing NBX system by creating one physical 
connection on the LAN that links a network interface card in an operating 
system to a hub or to a switch. The same connection also gives the H.323 
gateway a direct connection to every other device on the near-end LAN. 
Those devices include any NBX Business or Basic Telephone, the Call 
Processor, and the firewall or router.
Alternatively, you can use a second NIC in the gateway system to provide 
a separate connection between the H.323 gateway and the IP router.
Logical Connections
Locally, every device on an NBX LAN has the same physical access to the 
local network traffic as any other device. Consequently, addresses control 
connections because devices can only read information that is addressed 
to them. This makes addressing, and managing addresses, a key concern 
for logical continuity.
Logical continuity concerns extend throughout a network connection 
because the identity of a frame (or packet) and its destination determine 
where it goes, how it is handled, and what happens to it. 
						

							Connection Considerations429
Because so many devices share the same physical media on the Internet 
and on the local network, there is always the possibility of incomplete or 
degraded connections that arise from network congestion, device 
configuration, or addressing problems.
Bridges, switches, routers, and firewalls can help to manage network 
congestion, conversions, and security. Configuration problems with of 
any of these devices can cause connection difficulties.
Bridges and switches are used to segregate areas of congestion within a 
local network (switches are multiport bridges). Routers perform a similar 
function but at the Layer-3 level where they perform conversions 
between LAN and WAN protocols. Firewalls, which are often built into 
routers, protect intranets from unauthorized internet users.
All of these devices can filter packets based on source address, 
destination address or packet type. Depending on how the devices are 
configured, they can let packets pass or they can block them.
Quality of ServiceUnlike switched network connections, Internet voice connections consist 
of a sequence of numbered data packets. Packet transfers across the 
Internet are subject to delays or loss or both. If these delays are great 
(larger than 200 ms), or if the packet loss is excessive, voice quality 
deteriorates noticeably. The round-trip delay is typically no greater than 
400 ms. You can test this by using several “ping” commands. 
Voice conversations occur in “real-time,” so these packets need to be 
delivered in a consistent manner and with the shortest delay. The goal is 
to deliver 32 regularly spaced packets to the recipient every second.
The frequency response, dynamic range, and noise of a voice 
conversation depend on the voice representation. If all data packets reach 
their destination, the system provides voice of a specified quality.
The H.323 standard accommodates alternative voice compression 
standards that allow users to trade some voice quality for bandwidth by 
selecting a different compression standard (G.711 or G.723). 
Consequently, packet loss and delay are crucial to the Quality of Service.
Packet Loss
Packet loss can occur for reasons discussed in Bandwidth
, Congestion, 
and Connections
, next. 
						

							430APPENDIX A: CONNEXTIONS H.323 GATEWAY
Bandwidth 
Bandwidth is the capacity to carry information. By using H.323, the same 
bandwidth that supports one uncompressed G.711 voice connection can, 
instead, support several compressed G.723 conversations with little 
noticeable difference in quality.
Networks differ in the age of their equipment and in the quality of their 
service. Traffic can form a bottleneck if network loads force a wide area 
service provider to route traffic through old equipment.
Congestion
Users notice congestion when voice “breaks up” during a call. 
Congestion can occur anywhere on the network, for example, at an 
overloaded LAN (local or remote), at an overloaded router or firewall, or 
within an overloaded internet. Because voice packets are only significant 
during a conversation, IP networks respond to congestion by discarding 
the data packets they can’t accommodate. Resending or delaying packets 
is not an effective solution.
At the local level, congestion symptoms can be subtle. For example, 
routers from different vendors can respond differently to congestion 
because of the way they prioritize their response to packet congestion.
When considering communications problems, it is important to maintain 
reserve capacity and to use a systematic approach that considers the 
entire, end-to-end, connection.
Connections
Sometimes packet loss is caused by a poor physical connection. This type 
of packet loss is more likely to occur in a LAN than in a WAN. Typical 
causes are faulty wiring, connectors, and termination. High-bandwidth 
LANs (100BASE-T) are more likely to have termination problems than 
low-bandwidth (10BASE-T) LANs.
Packet Delay
Latency and jitter delays affect the Quality of Service.
Latency
Latency is the sum of all the fixed delays in an end-to-end connection. 
Latency prevents a caller from responding immediately to another caller’s 
remarks.