Connecting via SIP and using a SoftPhone

Connecting via SIP

Business Issue/Requirement

Increasingly, telephone connections are made over the Internet using Voice over Internet Protocol (VoIP), rather than via the traditional public phone line service – Public Switched Telephone Network (PSTN). VoIP provides access to new features and functions, and offers cost and operational efficiencies by combining many applications onto a single network.

A conferencing service should support connections via both VoIP and PSTN; and both should be usable in the same conference, allowing participants to call on the network that best meets their needs.

VoIP connections should be simple, reliable and comply with industry standards. The service should support both dial-in and dial-out capability. Clients should be able to connect from behind a firewall.

Increasingly, conference participants are working from home or another remote location, and are equipped with a PC and a broadband connection. A conferencing service should support access via a SoftPhone – a software program that can be installed on a PC, used in conjunction with a headset, and connect via VoIP. This arrangement should also support wideband audio (see below).

ZipDX Feature

In addition to a breadth of PSTN connection options, ZipDX fully supports VoIP using the IETF Session Initiation Protocol (SIP) standard, including these capabilities:

  • ZipDX can be dialed directly from any SIP telephone connected to the public Internet. Different SIP identifiers, called URIs, support a variety of connection scenarios.
  • ZipDX participants can enable the call-me feature and can be reached at their SIP device when it is configured to perform SIP registration with the ZipDX system.
  • For participants connecting from behind a firewall (such as in an office), ZipDX automatically performs “symmetric NAT. ” Some VoIP services cannot operate through firewalls, but this technique allows connection to ZipDX in most circumstances.
  • ZipDX provides a downloadable SoftPhone application (called a client) for Windows PCs. When used in conjunction with a high-quality headset and a broadband connection, the application allows connection to ZipDX conferences in wideband audio. The client can be configured so that the user is automatically recognized when calling ZipDX; no codes required.

Use this Feature

It may be useful to involve your IT contact when setting up to use these features, especially if you are not technically inclined.

  • Callers can dial this SIP URI directly from their device to reach ZipDX: Alternatively (and in fact preferably), {PIN} will allow the caller to be automatically recognized when {PIN} is replaced with that caller’s unique ZipDX PIN selected at registration. ZipDX also supports connections from multiple clients behind an IP-PBX (see Section 14). For individual clients, it is usually best to configure a “speed dial button” with the desired SIP URI. Press the pre-set speed-dial button; ZipDX will greet you and announce any pending conferences.
  • ZipDX supports SIP registration; this must be configured on the telephone as well in your profile at and varies from device to device. For Polycom endpoints, ZipDX offers an automatic registration configuration based on the device serial number (see Section 15).
  • If your client is behind a firewall, insure the firewall does not explicitly block the required ports. Port 5060 is used by all SIP devices. The ports used for RTP are device specific; Polycom typically uses 2222 through 2268. Also insure that 80 (HTTP), 53 (DNS) and 123 (NNTP) are unblocked. If your device shows that you “connect” when you dial the ZipDX SIP URI, but you do not hear any audio, it is likely that the firewall is blocking RTP traffic. If the phone will not “connect” it is likely that port 5060 is blocked.
  • To download the ZipDX SoftPhone client, log in at, select the Profile tab, and look for the SoftPhone link in the upper right. You must be an authorized ZipDX user or account administrator to access the SoftPhone client. Follow the instructions provided to download the software, install the license key provided, and configure the client with your PIN for one-touch access to ZipDX. When you connect, you will hear the ZipDX greeting through your headset (preferred) or speakers.