3Com PathBuilder S200 Series User manual

3Com®Corporation
PathBuilder™S200 Series Switch
Voice Over IP

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©1998 3Com Corporation
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Notice (continued)
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without the express prior permission of an officer of 3Com, may not be copied, reproduced,
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This document is for information purposes only and is subject to change without notice.
Part No. T0008-48, Rev. B
First Printing October 1998
Manual is current for Release 5.2M.

Voice Over IP 1
Voice Over IP
Overview
Introduction This document describes the Voice Over IP (VoIP) feature for 3Com’s PathBuilder
S200 series switch Products.
Note
Parameters and applications for voice traffic are discussed in the manual. For
information on SoTCP and serial data applications, refer to the IP and LAN
Feature Protocol documentation.
In This Manual Topic See Page
About Voice over IP (VoIP) .......................................................................... 2
Network Topology ................................................................................... 3
SoTCP Operation ..................................................................................... 4
Establishing a Call ................................................................................... 5
VoIP Applications ......................................................................................... 8
Example VoIP Configuration ................................................................... 9
Configuring VoIP .......................................................................................... 11
SoTCP Parameters ................................................................................... 12
Route Selection Table Parameters ............................................................ 15
SoTCP Map Table Parameters ................................................................. 16
Statistics ........................................................................................................ 18
SoTCP Statistics ....................................................................................... 19
SoTCP Detailed Statistics ........................................................................ 20
Glossary of Terms These terms appear throughout this document:
• ACP - Adjacent Channel Protocol
• VoIP - Voice over IP
• SVC - Switched Virtual Circuit
• UDP - User Datagram Protocol
• SoTCP - Serial Protocol Over TCP

2 Voice Over IP
About Voice over IP (VoIP)
About Voice over IP (VoIP)
What is VoIP? PathBuilder S200 series switch products support Voice over IP (VoIP) to provide
termination and encapsulation of voice and fax traffic for transport over an IP
network (see to Figure 1). 3Com’s proprietary protocol, Serial Protocol over TCP
(SoTCP), provides the encapsulation mechanism for carrying voice traffic over an IP
network.
Figure 1. Voice over IP Network
VoIP Applications VoIP provides new and cost effective solutions for a company’s telephony
communication including:
• Long distance calling over an Intranet or the Internet
• Remote location dial-in and telecommuting
Features Key features include:
• real-time voice and fax over IP networks
• multiple SVCs over a single UDP session
• call management and signalling using TCP
Product Support These PathBuilder S200 series switches support VoIP:
• PathBuilder S21x switch
• PathBuilder S24x, 26x, and 27x switch
PBX
IP Network
Fax
modem
Fax
Fax

Voice Over IP 3
T0008-48/B Revision 5.2
About Voice over IP (VoIP)
Network Topology
Introduction This section describes a typical network topology for the application of VoIP.
Network Topology Figure 2 illustrates a typical network topology for voice traffic.
Figure 2. Example Network Topology
Node Conventions The node conventions described below refer to Figure 2 and are used throughout this
document.
IP Network
PB S200
Source IP Node PB S200 Destination
IP Node
PBX
Voice Device
Voice
Network
Voice Device
Voice
Network
Convention Description
Voice Device or Network The voice device or network sends voice to
the voice port on the source IP node.
Source IP Node The source IP node is a PathBuilder S200
series switch that
• connects directly to the voice device.
• connects directly to the IP network.
• connect directly to a frame relay network
supporting voice.
• encapsulates voice received from the
voice device or network using 3Com’s
SoTCP protocol.
• initiates calls to the peer, the destination
IP node.
Destination IP Node The destination IP node is a PathBuilder
S200 series switch that receives SoTCP
packets sent from the source IP node over the
IP network. The destination IP node
un-encapsulates SoTCP packets and sends
voice traffic to the PBX.The PBX may also
connect to a frame relay network supporting
voice.
PBX The PBX connects to the destination IP node
and receives voice traffic from it.

4 Voice Over IP
About Voice over IP (VoIP)
SoTCP Operation
Introduction This section describes the operation of SoTCP protocol. SoTCP provides the
encapsulation method for carrying voice traffic over an IP network.
SoTCP Packet
Format The SoTCP protocol terminates voice traffic received from a voice device and prefixes the traffic with a 3-byte SoTCP header or 4-byte SoTCP header, depending
on the version of SoTCP protocol. Figure 3 illustrates the SoTCP packet.
Figure 3. SoTCP Packet Format
The SoTCP header contains information that will allow a destination IP node to
reconstruct the voice packet at the remote end.
Transport
Mechanism To carry voice traffic over IP, SoTCP uses two Transport layer protocols, the Transport Control Protocol (TCP) and User Datagram Protocol (UDP).
Each TCP or UDP session may carry multiple switched virtual circuits (SVCs).
SoTCP uses SVC call setup and routing procedures to establish voice SVCs.
3 or 4 Byte SoTCP Header Data
Transport
Layer
Protocol
Traffic Carried Description
TCP Voice Signalling Traffic SoTCP uses TCP to carry voice signalling
traffic because TCP provides reliable,
sequenced packet delivery. Voice
signalling traffic encapsulated by SoTCP
must arrive at the destination node without
error or delay. TCP implements error
recovery for duplicate or lost packets.
UDP Audio and Fax SoTCP transports audio and fax traffic
over UDP session. Unlike TCP, UDP
provides fast and simple transaction
services with minimal protocol overhead.
UDP provides a best-effort, transport
mechanism only and does not ensure
reliable delivery.

Voice Over IP 5
T0008-48/B Revision 5.2
About Voice over IP (VoIP)
Establishing a Call
Introduction This section describes call establishments. Figure 4 shows the packets exchanged for
session and connection establishment and finally, voice transfer.
Figure 4. Session and Connection Establishment
Voice Port Voice Port
ACP call request
TCP call request
TCP Call accept
SoTCP internal call request
ACP call request
ACP call accept
SoTCP internal call accept
ACP call accept
Source IP Node Destination IP Node
Session Setup
Connection Setup
Voice
Voice
Voice
Data Transfer
Open UDP channel

6 Voice Over IP
About Voice over IP (VoIP)
Establishing a
Session Before voice traffic can pass between the voice ports over the network, the source IP must establish a TCP and UDP session with the destination IP node. Each session is
uniquely identified by a source IP address, destination IP address, source port
number, and destination port number. The source and destination node exchange the
following call packets to establish a session:
Establishing a
Connection After opening a TCP and UDP session, the source node must establish an SoTCP connection with the destination IP node. Each TCP session support multiple
connections or SVCs. A unique connection identifier identifies each connection
multiplexed on a TCP session. The source and destination IP nodes exchange the
following call packets to establish a connection:
Stage Packet Transferred Description
1ACP Call Request The voice port sends an ACP (Adjacent
Channel Protocol) Call Request to inform
the source IP node that it wishes to send
voice over the network to the destination
voice port.
Open UDP When a voice port attempts to make a call,
the Source IP node opens a UDP channel.
2TCP Call Request To open a session, the source IP node sends a
TCP call request to the destination IP node.
TCP Call Accept The destination IP node responds to the Call
Request by sending a Call Accept, and
establishes a TCP session.
Stage Packet Transferred Description
1SoTCP Internal Call
Request The source IP node sends an internal SoTCP call request packet with the UDP
port number included, to the destination IP
node. The destination IP node examines the
facilities field in the header to determine
the presence of voice traffic. If voice traffic
is present, the destination IP node opens a
UDP channel.
The destination IP node uses the UDP port
number in the internal SoTCP call request
packet to identify the destination port for
UDP packets.
2ACP Call Request The destination IP node sends an ACP call
request to the remote voice port.
ACP Call Accept To accept the call, the voice port responds
with an ACP Call accept packet.

Voice Over IP 7
T0008-48/B Revision 5.2
About Voice over IP (VoIP)
Data Transfer The SoTCP protocol attaches the 3 or 4-byte header to the packet. The SoTCP
protocol then sends voice packets over the UDP channel.
3SoTCP Internal Call
Accept Once the destination IP node receives the ACP call accept from the remote voice
port, it sends a SoTCP Internal Call Accept
to the source IP node. The remote port’s
UDP port number is included in this packet
to inform the other end of its UDP port
number. The connection between the nodes
is now established.
4ACP Call Accept The source IP node sends an ACP Call
Accept to the voice port and the port may
begin to send voice packets to the
destination.
Stage Packet Transferred Description (continued)

8 Voice Over IP
VoIP Applications
VoIP Applications
Introduction This section describes typical applications of VoIP and the benefits of implementing
voice over an IP network.
Applications VoIP can be used to provide cost effective, long distance phone services over the IP
network. Figure 5 illustrates a network using VoIP to support fax and voice calls
between two branch offices in different locations.
Figure 5. VoIP Applications for Small Branch Offices
In Figure 6, the PathBuilder S24x, 26x, and 27x switches act as gateways to route
calls over the IP network. With this implementation, the caller only needs to call a
local number to start a long distance conversation.
Figure 6. VoIP Applications for Long Distance Telephone Service
Figure 7 illustrates a network supporting voice within an Intranet and voice over a
public or private frame relay network using 3Com’s Voice Relay.
Figure 7. VoIP Applications and Voice Relay Support
PBX
Intranet
Fax
PB S200 PB S200
Intranet
PSTN PSTN
PB S200 PB S200
Intranet Frame
Relay
PB S200 PB S200PB S200

Voice Over IP 9
T0008-48/B Revision 5.2
VoIP Applications
Example VoIP Configuration
Introduction This section shows an example of how to configure VoIP. Figure 8 illustrates how
two PathBuilder S24x, 26x, and 27x switches can support long distance telephone
service between a small branch office and a head office, over the company’s Intranet.
Figure 8. VoIP Configuration Example
Node 100 and Node 200 are configured with FXS Voice ports. The branch office
phone can be configured as an extension phone number off the head office’s PBX.
The nodes connect to the Ethernet LAN and therefore an Ethernet port must be
configured for each node. The associated IP interface parameters must also be
configured. To carry voice traffic over the IP network, the SoTCP parameters must
be configured.
Recommended
Sequence for
Configuration
The following table describes the recommended sequence to configure a PathBuilder
S200 series switch for VoIP. Refer to Figure 9 for the list of configurable parameters.
Note
This example assumes default settings for parameters not otherwise specified in
the tables. For more information on configuring the voice port refer to the Voice
Relay Option Guide.
IP Network
Node 100 PBX
Node 200
Branch Office Head Office
Step Description
1Configure the Node Record.
2Configure the Voice Port and Voice Switching Table.
3LAN and IP Parameters:
• Configure the LAN Port
• Enable the PathBuilder S200 series switch Interface State
• Configure IP Parameters
• Configure IP Interfaces
• Configure the Route Selection Table
4VoIP Parameters:
• Configure the SOTCP Record
• Configure the SOTCP Map Table

10 Voice Over IP
VoIP Applications
Configuration Figure 9 shows the parameters configured for each PathBuilder S200 series switch.
Figure 9. Configurable Parameters to support VoIP
Voice Port Configuration
Port Number: 31
Port Type: Voice
Interface Type:FXS
Signalling Type: 1
E Lead Filter: Disable
Signalling Mode: Normal
Signalling Control: Immediate
PCM Mode: µlaw
Compression Rate: 8K
DSI Control: Enable
Smoothing Delay: 80 msec
Input Signal Level: 0dBm
Output Signal Level: 0dBm
Fax Support: Enable
Call Control: Switched
Ethernet Port Configuration
(Configure for both nodes)
Port Number: 4
Port Type: ETH
LAN Cable Type: AUI
Port MAC Address: 00-00-00-00-00-00
Transmit Queue Limit: 50
Carrier Sense Filter:0
Collision Detect Filter: 0
PB S200 Interface Number: 1
IP Network
Node 100 Node 200 PBX
Voice
Port LAN Port LAN Port Voice Port
Node Record
Nodename: Node100
Node Address: 100
Maximum Routing Hops:15
Maximum Routing Hops for Voice:2
Voice Switching Table Size: 16
Node Record
Nodename: Node200
Node Address: 200
Maximum Routing Hops:15
Maximum Routing Hops for Voice:2
Voice Switching Table Size: 16
Voice Port Configuration
Port Number: 31
Port Type: Voice
Interface Type: FXS
Signalling Type: 1
E Lead Filter: Disable
Signalling Mode: Normal
Signalling Control: Immediate
PCM Mode: µlaw
Compression Rate: 8K
DSI Control: Enable
Smoothing Delay: 80 msec
Input Signal Level: 0dBm
Output Signal Level: 0dBm
Fax Support: Enable
Call Control: Switched
Configure PB S200
Interface State
(Configure for both nodes)
Interface #1 State: Enabled
IP Interface Configuration Table
Entry #: 1
Interface Number: 1
IP Address: 150.20.35.1
IP Address Mask: 255.255.255.0
Accept RIP: Enabled
IP Interface Configuration Table
Entry #: 1
Interface Number: 1
IP Address: 150.20.35.2
IP Address Mask: 255.255.255.0
Accept RIP: Enabled
Node 200
Route Selection Table
Entry # 1
Address: 100
#1 Destination: SOTCP
#1 Priority: 1
Node 100
Route Selection Table
Entry # 1
Address: 200
#1 Destination: SOTCP
#1 Priority: 1
Node 200
SoTCP Map Table
Entry # 1
Destination X.25 Address: 100
Next hop IP Address: 150.20.35.1
Node 100
SoTCP Map Table
Entry # 1
Destination X.25 Address: 200
Next hop IP Address: 150.20.35.2
SoTCP Parameters (Configure for both nodes)
TCP Port Number: 1099
Max. No. TCP Sessions: 10
Max. SVCs per session:1
Max. Total SVCs:10
Serial Connection establishment timeout: 100
TCP Connection establishment/clearing timeout: 200
TCP Keep alive timer: Disabled
Node 100
Voice Switching Table
RX DTMF Digits: 3W
No. of RX Digits: 3
Call Parameter 20031
Node200
Voice Switching Table
RX DTMF Digits: 3W
No. of RX Digits: 3
Call Parameter 10031

Voice Over IP 11
T0008-48/B Revision 5.2
Configuring VoIP
Configuring VoIP
Introduction These sections describe how to configure the VoIP option. The parameters for the
VoIP option are specified in three records:
• “SoTCP Parameters” on page 12.
• “Route Selection Table Parameters” on page 15.
• “SoTCP Map Table Parameters” on page 16.

12 Voice Over IP
Configuring VoIP
SoTCP Parameters
Navigating the CTP Figure 10 shows the CTP path to the SoTCP specific parameters.
Figure 10. SoTCP Parameters
SoTCP Parameter
Descriptions The SoTCP parameter record contain these parameters:
Node: Address: Date: Time:
Menu: Main
Logout
Examine
:
:
Configure
Node: Address: Date: Time:
Menu: Main
Node
Port
:
:
SoTCP
TCP Port Number
Maximum Number TCP sessions
Maximum Number of SVCs per session
Maximum Total Voice SVCs
Maximum Total Data SVC
Serial Connection establishment timeout
TCP Connection establishment/clearing timeout
TCP Keep alive timer
TCP Port Number
Range 256 to 65535
Default 1099
Description Specifies the TCP port number at which SoTCP listens for new
connections. The remote-end musthave the same value configured
for this feature to function.
Boot Type SoTCP Boot

Voice Over IP 13
T0008-48/B Revision 5.2
Configuring VoIP
Maximum Number of TCP Sessions
Range 1 to 40
Default 1
Description Specifies the maximum number of TCP sessions allowed through
SoTCP. Once the maximum number is reached, no more sessions
will be established and the “SoTCP-No more TCP sessions” alarm
will be generated.
Boot Type SoTCP Boot
Maximum Number SVCs per Session
Range 1 to 50
Default 10
Description Specifies the maximum number of switched virtual circuits
(SVCs) that may be multiplexed on a TCP session through SoTCP.
Once the maximum number is reached, no more connections will
be established and the “SoTCP-n-No more connections to SoTCP”
alarm will be generated.
Boot Type Node Boot
Maximum Total Voice SVCs
Range 0 to 30
Default 0
Description Specifies the maximum total number of voice SVCs allowed.
Boot Type Node Boot
Maximum Data SVCs
Range 1 to 1024
Default 10
Description Specifies the maximum number of data SVCs that may be
multiplexed on all TCP connections.
Boot Type Node

14 Voice Over IP
Configuring VoIP
Serial Connection Establishment Timeout
Range 1 to 200. Specified in 50 ms increments.
Default 100
Description Specifies the time SoTCP waits for connection establishment with
the serial device.
When a node receives a call request from a source node, the
SoTCP will send a Call Request packet to the serial protocol and
waits for a Call Accept packet. If the SoTCP protocol does not
receive a Call Accept packet within the timeout, it sends a Call
Clear packet to the source node.
Boot Type SoTCP Boot
TCP Connection Establishment or Clearing Timeout
Range 1 to 200. Specified in 50 ms increments.
Default 100
Description Specifies the time SoTCP waits for the connection establishment
or connection clearing with the peer SoTCP protocol.
Boot Type SoTCP Boot
TCP Keep Alive Timer
Range Enabled, Disabled
Default Enabled
Description Used to enable or disable the TCP Keep Alive Timer.
• Enabled: TCP protocol sends keep alive packets over the
network at a one minute interval. If the destination node does
not respond to the keep alive packets, source node clears TCP
sessions.
• Disabled: TCP protocol does not send keep alive packets over
the network.
Boot Type SoTCP Boot

Voice Over IP 15
T0008-48/B Revision 5.2
Configuring VoIP
Route Selection Table Parameters
Parameters These Route Selection Table parameters should be configured:
Note
A table boot is required for changes to these parameters to take affect.
Entry Number
Range 1 to 16
Default 1
Description Specifies the number used to reference this table record.
Address
Range 0 to 15 digits
Default blank
Description Specifies the network address for calls routed beyond this node.
Destination #1
Range 0 to 32 alphanumeric characters. Use space to blank the field.
Default blank
Description Specifies the destination to which calls are routed. Enter SoTCP.

16 Voice Over IP
Configuring VoIP
SoTCP Map Table Parameters
Navigating the CTP Figure 11 shows the CTP path to the SoTCP map parameters.
Figure 11. SoTCP Map Table Parameters
Node: Address: Date: Time:
Menu: Main
Logout
Examine
:
:
Configure
Node: Address: Date:1 Time:
Menu: Configure
Node
Port
Configure Network Services
Node: Address: Date: Time:
Menu: Configure Network Services
Route Selection Table
:
:
SoTCP Map Table
Entry Number
Destination X.25 Address
Destination IP Address #1
Destination IP Address #2
Destination IP Address #3
Destination IP Address #4