Linksys ATA

Administrator Guide

Document Version 3.1

Chapter 1

Introducing Linksys Analog Telephone Adapters

Technology Background

With symmetric NAT all requests from the same internal IP address and port to a specific destination IP

address and port are mapped to a unique external source IP address and port. If the same internal host

sends a packet with the same source address and port to a different destination, a different mapping is

used. Only an external host that receives a packet can send a UDP packet back to the internal host.

Simple Traversal of UDP Through NAT

Simple Traversal of UDP through NATs (STUN) is a protocol defined by RFC 3489, that allows a client

behind a NAT device to find out its public address, the type of NAT it is behind, and the port associated

on the Internet connection with a particular local port. This information is used to set up UDP

communication between two hosts that are both behind NAT routers. Open source STUN software can

be obtained at the following website:

STUN does not work with a symmetric NAT router. To determine the type of NAT your router uses,

complete the following steps:

Step 1

Enable debugging on the

Linksys ATA

:

1.

Make sure you do not have firewall running on your PC that could block the syslog port (by default

this is 514).

2.

On the administration web server, System tab, set <Debug Server> to the IP address and port number

of your syslog server.

Note that this address and port number has to be reachable from the

Linksys ATA

.

3.

Set <Debug level> to

3

but you do not need to change the value of the <syslog server> parameter.

4.

To capture SIP signaling messages, under the Line tab, set <SIP Debug Option> to

Full

. The output

is named syslog.514.log.

Step 2

To determine the type of NAT your router is using set <STUN Test Enable> to

yes

.

Step 3

View the syslog messages to determine if your network uses symmetric NAT or not.

SIP-NAT Interoperation

In the case of SIP, the addresses where messages/data should be sent to a Linksys ATA system are

embedded in the SIP messages sent by the device. If the Linksys ATA system is sitting behind a NAT

device, the private IP address assigned to it is not usable for communications with the SIP entities

outside the private network.

Note

If the ITSP offers an outbound NAT-Aware proxy, this discovers the public IP address from the remote

endpoint and eliminates the need to modify the SIP message from the UAC.

The Linksys ATA system must substitute the private IP address information with the proper external IP

address/port in the mapping chosen by the underlying NAT to communicate with a particular public peer

address/port. For this, the Linksys ATA system needs to perform the following tasks:

•

Discover the NAT mappings used to communicate with the peer.

±

±

This can be done with the help of an external device, such as a STUN server. A STUN server

Linksys ATA

Administrator Guide

Document Version 3.1

Chapter 1

Introducing Linksys Analog Telephone Adapters

Where to Go From Here

responds to a special NAT-Mapping-Discovery request by sending back a message to the source IP

address/port of the request, where the message contains the source IP address/port of the original

request. The

Linksys ATA

system can send this request when it first attempts to communicate with

a SIP entity over the Internet. It then stores the mapping discovery results returned by the server.

•

Communicate the NAT mapping information to the external SIP entities.

±

±

If the entity is a SIP Registrar, the information should be carried in the Contact header that

overwrites the private address/port information. If the entity is another SIP UA when establishing a

call, the information should be carried in the Contact header as well as in the SDP embedded in SIP

message bodies.

The VIA header in outbound SIP requests might also need to be substituted with

the public address if the UAS relies on it to route back responses.

•

Extend the discovered NAT mappings by sending keep-alive packets.

±

±

Because the mapping is alive only for a short period, the

Linksys ATA

system continues to send

periodic keep-alive packets through the mapping to extend its validity as necessary.

Where to Go From Here

The following documentation provides additional information about features and functionality of

Linksys ATAs:

•

AA Quick Guide

•

IVR Quick Guide

•

SPA Provisioning Guide

The following documentation describes how to use and configure other Linksys VoIP products:

•

SPA9000 Administrator Guide

•

LVS CTI Integration Guide

•

LVS Integration with ITSP Hosted Voicemail Guide

To

Refer to

Use the different administration and

configuration tools provided for managing

Linksys ATAs.

Chapter 2, “Getting Started”

Complete the basic configuration of a Linksys

ATA.

Chapter 3, “Configuring Linksys ATAs”

Configure the Linksys SPA3102 or AG310 for

providing PSTN connectivity.

Chapter 4, “Configuring the PSTN Gateway

(FXO)”

Look up the function and usage for each field or

parameter on the ATA administration web server

pages.

Chapter 5, “Linksys ATA Field Reference”

Look up the expansion of acronyms used in this

document.

Appendix A, “Acronyms”

Define the terms used in this document.

Appendix B, “Glossary”

Understand the operations of ATA user features.

Appendix C, “User Guidelines”

Linksys ATA

Administrator Guide

Document Version 3.1

Chapter 1

Introducing Linksys Analog Telephone Adapters

Where to Go From Here

•

SPA900 Series IP Phones Administrator Guide

•

Linksys Voice over IP Product Guide: SIP CPE for Massive Scale Deployment

Linksys ATA

Administrator Guide

Document Version 3.1

2

Getting Started

This chapter provides a brief description of each Linksys ATA and describes the tools and utilities

available for administration. It includes the following sections:

•

Linksys Analog Telephone Adapters (ATAs), page 2-1

•

Establishing Connectivity, page 2-14

•

Connecting the SPA8000, page 2-16

•

Using the Interactive Voice Response Interface, page 2-18

•

Using the Administration Web Server, page 2-22

The following ATAs provide Layer 2 (data link) and Layer 3 (IP) configuration options:

•

AG310

•

WRP400

•

WRTP54/54G

•

RTP300

For information about configuring these options, including private virtual circuits (PVCs), PPPoE, and

IP routing, refer to the user guide for the specific device.

For information about configuring the Public Switch Telephone Network (PSTN) connectivity options

for the SPA3102 and AG310 refer to

Chapter 3, “Configuring Linksys ATAs.”

Linksys Analog Telephone Adapters (ATAs)

Linksys ATAs convert voice traffic into data packets for transmission over an IP network. This section

illustrates and summarizes the ports and LEDs provided by each model. It includes the following topics:

•

Caring for Your Hardware, page 2-2

•

PAP2T, page 2-3

•

SPA2102, page 2-6

•

SPA3102, page 2-7

•

SPA8000, page 2-9

•

AG310, page 2-2

•

WRP400, page 2-10

Linksys ATA

Administrator Guide

Document Version 3.1

Chapter 2

Getting Started

Linksys Analog Telephone Adapters (ATAs)

•

WRTP54G, page 2-11

•

WRT54GP2, page 2-13

•

RTP300, page 2-4

Caring for Your Hardware

The Linksys ATA is an electronic device that should not be exposed to excessive heat, sun, cold or water.

To clean the equipment, use a slightly moistened paper or cloth towel. Do not spray or pour cleaning

solution directly onto the hardware unit.

AG310

The AG310 provides a high-speed ADSL2/+ modem along with a four-port Ethernet switch and a PSTN

gateway (see

Figure 1-4

).

Note

Througout this document, when references are made to the software configuration of the SPA3102, the

information also applies to the AG310, which provides the same functionality as the SPA3102, as well

as an ADSL modem and a four-port Ethernet switch.

Figure 1-4

AG310

The following tables describe the LEDS on the front panel and the ports on the back panel of the device.