Monday, January 29, 2007

Nortel CS1000E Reliability Executive Overview


IP Telephony has become an attractive offering available from various telecommunication manufacturers. As a modern technology that utilizes the inexpensive transport mechanism existent today called Voice running Over an IP infrastructure (VoIP), IP Telephony can now be a viable solution and cost savings mechanism in the Enterprise arena.

Nortel Networks Communication Server 1000E

The CS 1000E system is a modular solution manufactured by Nortel Networks. One of the significant features of this platform is VxWorks as the native operating system that runs on the hardware. From a system security vulnerability stand point, the CS 1000E is safer and less prone to external attacks inherent to other IP Telephony systems running a Windows based operating system. Numerous operating system exploits and open ports have been found on these Windows based systems.

Call Server

There are two Call Servers in a CS1000E system. One operates in active mode and the second in standby mode. The active Call Server is the heart of the call processing function that controls all IP Phone features and trunk interfaces operating in normal mode. It also performs the function of database server for synchronization of configuration information with the standby Call Server and with all Media Gateways.

The active Call Server performs call control, signaling and routing for all TDM and IP calls placed across the network. The Call Server is a rack mountable unit with a small footprint housing a hot swappable fan unit, and field replaceable power supply.

Signaling Server

The Signaling Server is an off-the-shelf Intel based single board computer that provides call control services such as registration of IP Phones and gateways, translation of call initiation and tear down sequences from IP to Call Server language, IP address translation services, and bandwidth control. The Signaling Server also runs VxWorks real-time operating system.

Software modules reside on this device: a Line Terminal Proxy Server (LTPS), a Signaling Gateway, and an H.323 Gatekeeper. The TPS module essentially is the IP Phone interface, providing registration, TFTP service, and bandwidth control and feature delivery to the IP Phones.

Nortel Signaling Servers can be deployed in a redundant, load-sharing configuration for increased scalability and reliability of the LTPS. Moreover, should both Signaling Servers become unavailable, phones will register with Succession Media Cards located in Succession Media Gateways. This provides tertiary redundancy for the Line Terminal Proxy Server.

Both signaling servers also include the Signaling Gateway software module which translates Nortel Networks IP Telephony protocols into H.323 to communicate with local H.323-compliant devices.

The H.323 Gatekeeper software module resolves addresses unknown to the local CS1000E Call Server. Typically, a primary gatekeeper is deployed on one Signaling Server while another is deployed in "hot standby" mode anywhere in the network. Additionally, other H.323 Gatekeepers are deployed in "failsafe" mode in the event a primary and secondary gatekeeper become unavailable, this provides three levels of redundancy for gatekeepers.

Nortel Media Gateways

Media gateways are the primary means to interface with all TDM lines and trunks. All Media Gateways contain an embedded form of the Call Server software and can be configured to be a Survivable Media Gateway.

Nortel Internet Phones

All Nortel Networks Internet Phones use by default the standard G.711 audio codec algorithm to convert analog voice signals into digital packets, though they could be configured to use any of a list of three other Codec types as well: G729a, G.729ab and G.723.1.

Configuration and Management

Nortel Networks CS 1000E system is delivered on individual units that are each rack mountable and configurable via direct connection into their console ports or via an IP-based terminal server expressly deployed for that purpose. Nortel Networks CS 1000E systems support a very effective and granular CLI on all of its system components. With CLI commands a systems administrator can entirely configure, deploy, modify, monitor and manage the system either directly connected into the system console port or via Telnet from a remote location.

For in depth system configuration and management including trunks, features, routes and gateways, Nortel CS1000E comes with a Management platform called Element Manager. Element Manager is a WEB based application that runs on any browser. Element Manager 4.0 is an integrated systems management platform to control all CS 1000E system components. It allows the system administrator to perform all the necessary system feature implementations, IP Phone settings, line and trunk configuration parameters, dial plan implementation and system monitoring and verification.

Nortel Networks CS1000E enterprise solution also includes various trunk configuration, alerting and monitoring control functions that enhance the overall system functionality. Features such as trunk barring, trunk traffic reporting, trunk failure monitor, trunk verification, and others allow the implementation of a robust, resilient and proactively monitored system.


In conclusion, The CS 1000E system is a secure, robust, extremely redundant and scalable IP-based platform when compared to Windows server based platforms from other manufacturers.

Enterprise organization in search of a reliable, resilient and scalable IP Telephony system to accommodate their needs, and make optimal use of their existent IP network and wiring infrastructure, should not wait any longer. Both of the systems analyzed in this paper offer much more than the bare standard features existent in PSTN environments, although Nortel Networks CS 1000E offers a collection of additional features that give it an overall edge.

The CS 1000E system offered by Nortel Networks is by far the most redundant, resilient and scalable with its component based architecture and its native operating systems that are much less vulnerable than other manufacturer solutions built on top of the Microsoft Windows software architecture. Windows based platforms have the largest list of vulnerability exploits and open services that are prone to external attacks. Numerous software patches and external means of network protection are needed to mitigate such systems vulnerability.

In terms of call volume that each of these systems can handle, Nortel Networks CS 1000E supports a greater load than other manufacturer platforms. The CS 1000E supports 300,000 Busy Hour Call Completions (BHCC) for digital TDM calls and 240,000 BHCC for IP Telephony calls.

CS 1000E operates reliably and call server switchover is seamless.

The CS 1000E use of the VxWorks operating system provides less vulnerable operation in terms of IP functionality and external source's attacks than other manufacturers application based on the Windows operating systems.

The Nortel CS 1000E multi unit solution allows system resilience and minimizes downtime due to built-in components redundancy.

CS 1000E and Internet Phone Functionality:

* Better IP Server security and less OS vulnerability
* More features overall, allowing greater customization by the end user
* More robust Call Server can handle more calls per hour (300K/240K)
* System ready to interface with external PBX or other IP systems
* Fully standards based system and components
* Up to third level of signaling server redundancy
* One built in auto-sensing 10/100baseT Ethernet switched port IEEE 802.3af compliant
* Second auto-sensing 10/100baseT Ethernet switched port for a workstation connection
* IEEE 802.3Q VLAN tagging and IEEE 802.3p priority settings standards compliant
* Multi language support with built-in user selectable options
* Keep alive signaling control with Call Server to facilitate accounting and billing functions
* Dial tone and signaling controlled at the Call Server and Signaling server
* Fast registration and recovery after power up or disconnect (The IP Terminal times taken to regain dial tone varied as follows: i2001, 23 seconds; i2002, 23 seconds and the i2204, 25 seconds on average)

About The Author

John Leonardelli, President, Gale Force Communications. John brings 20 years of voice, data and wireless telecommunications experience in various sales, management and operational roles. John is a Certified IP Telephony Expert where his expertise has been focused on IP Telephony, Contact Centre and complex technical solutions. John has a degree in Electronics Engineering, Telecommunications and Sales Management.