Nortel Networks claims that it is the only telecom equipment supplier to "remain in both camps," believing that it is absolutely necessary to give the customer the choice between a TDM-based PBX, for the lowest single site costs, and an IP-PBX, where that may make sense.
Nortel is certainly the leader in providing IP-enabled telephony, through an Internet Telephony Gateway (ITG) Trunk card, which plugs into a Meridian 1 PBX and may be programmed to support trunks with an IP-network. Another version of this ITG can have up to 96 users connected to one card on the line side, so that the capacity of Nortel's Meridian Option 81C can go up to 16,000 IP phones. Nortel's ITG Line Card actually has 24 DSP ports.
Most of Nortel's large PBX customers have implemented these ITG cards to carry voice traffic over IP long-haul networks, and this was an excellent way for these organizations to gain VoIP expertise. Microsoft Corporation, for example, connected 87 Meridian 1 PBXs over its IP-VPN and recovered the cost of these ITG installations, with long-distance savings, in less than 6 months.
Nortel offers two remote office units, the models 9110 and 9150, which support IP phones, but overcome the problems of local calling and emergency 911 requirements by using BRI/ISDN trunks. These units have a key capability of dynamic fallback, even during a conversation, between an IP network and the PSTN. If the trunk channel over the customer's IP-VPN fails or degrades badly, the call is switched to the PSTN, but it can return automatically to the IP network upon restoration of service, saving the customer money.
A variety of client endpoints is available for VoIP use. Nortel has two IP phones (the i2004 and i2002), the i2050 softphone, software to make the Palm Pilot SIP-enabled, wireless phones made by Symbol, and an IP-adapter base for the 39xx series of digital sets. If a Nortel IP phone and a PC are to share one LAN outlet, then a three-port switch adapter base for the i series phones must be purchased. The use of these peripherals in a CSE 1000 configuration is shown in Figure 1. Nortel reports that some early IP telephony installations used a dedicated LAN, with no data traffic on the same wiring.
Previously existing subsystems for unified messaging (Call Pilot), contact centers (Symposium), and system management (Optivity) have been adapted to interface with the CSE 1000, which is Nortel's enterprise-level, IP-oriented call server, using the brand name Succession. One CSE 1000 can handle up to 1,000 users and at least 10 servers may be in one network. This server uses the same UNIX-like operating system as Nortel's smaller TDM PBX, the option 11C system, so that it was fairly easy to transfer all 450 telephony features to a pure IP architecture.
The Succession Media Gateway, the unit that provides links to WANs, uses TDM trunk cards that are the same as those purchased for legacy Meridian PBXs, delivering a major cost saving to customers. This media gateway has some local call processing capability and is, therefore, useful for remote locations to provide service survivability.
Nortel's multimedia exchange system, the CSE-MX, is a good example of the benefits that come with IP telephony and new protocols, such as SIP. The CSE-MX is a multimedia application server, which facilitates video conferencing and instant messaging within an enterprise network. With multimedia services the setup of a multiparty video conference, between preregistered participants, should be feasible with a few mouse clicks, and collaborative working between remote offices is greatly improved by the sharing of Web sites, files, visuals, and electronic whiteboard.
The CSE-MX also supports dynamic registration (i.e., "find-me and follow-me" service) for mobile and telecommuting users, and provides a personal call agent. This function can be used for call screening and call routing to user-defined locations, which should result in the need to process fewer voice and electronic mail messages.
