Power protection for Voice over IP

Transcription

1 Power protection for Voice over IP Information from MGE UPS New, mission critical applications are being deployed at a fast rate on enterprise networks. Voice over IP (VoIP) is one of the most important ones, both in terms of deployment numbers and specificities (convergence technology, high requirements for quality of service and availability). Moving to IP telephony is a key decision point in the evolution of an enterprise network. Independent of either the evolutionary or revolutionary approach to migration, in the end, the enterprise will have converted its entire voice network to be VolP-based, while demanding equal characteristics of the traditional telephony, such as availability and voice quality. A new technology, Power over Ethernet, greatly contributes to make these deployments both simple and highly available. This technology, now an IEEE standard (802.3af) endorsed by all network actors under the name Power over Ethernet (PoE), allows to power IP-connected devices such as IP phones and Wireless LAN access points, over the existing LAN cabling infrastructure. This allows not only a very convenient and cost-effective powering of the phones (no local desk DC power needed), but also a simple, centralised power protection of the whole installation directly from the switch/ wiring closet. PowerDsine, said to be the leader in Power over Ethernet technology, and one of the major contributors in the development of the IEEE 802.3af standard, and MGE UPS Systems have joined their efforts to outline in this document, some of the key power-related aspects to consider when deploying VoIP solutions. Using Power over Ethernet products and power protection devices, IT managers and facility managers and users will get the same level of availability from their VoIP architecture as they experience with the traditional circuit switched telephony systems. VoIP market opportunity Enterprise voice over IP, also known as IP telephony, refers to the solution (hardware, software, services) that is used to transmit voice over the above-described enterprise data network, using the internet protocol (IP). Many closely linked applications (such as videoconference over IP, etc.) also exist, which also leads to the more generic acronym XoIP to which most of this paper also applies. Voice over IP brings significant advantages over traditional (circuit-switched) enterprise telephony networks : Reduction in carrier circuit charges (true when voice over IP is carried over the internet) Enhanced applications: integrated messaging, voice-enabled web sites, desktop video conferencing, etc. Integrated management systems and strategies Increased flexibility, reduction in overall complexity, elimination of circuit redundancy. For these reasons, voice over IP is currently experiencing a very fast growth, with analysts estimating compounded annual growth rates of 40% to 70%. The overall PBX market experienced a down year in 2001 but still represented sales just shy of $7-billion in the United States alone. This relatively large market is expected to grow Fig. 1: IP PBX market forecasts (line shipments). over the next few years and could easily reach $8-billion by Total line shipments of 9,9-million in 2001 are predicted to grow to 13 million by As displayed in Fig. 2, the new Iine shipments for IP-enabled and IP-PBX systems are predicted to grow at a faster pace than circuit-switched line shipments and could completely displace circuit-switched new line deployments by 2005, according to Gartner Dataquest. Other researches confirm that in 2003 the value of shipments of IP PBX equipment will, for the first time, surpass revenues generated by legacy PBXs. IP PBX seats are projected to grow from 1,9-million in 2001 to 42-million in The IP Phone handset shipments in 2002 has reached well over 1-million units with 30% growth compared to ln 2003, an additional 50% growth was reached, with vendors like Cisco, 3Com, Nortel, Mitel, Avaya, Alcatel and Siemens, which are the market leaders. All vendors understand the importance and need for Power over Ethernet in VolP installations and are thus designing their next generation IP Phones to be compatible with the Power over Ethernet standard, the IEEE802.3af (see below). 50 Elektron June 2005

2 As a long-term supplier for high availability telephony installations, MGE understands that high availability and reliability are absolute requirements also for IP telephony solutions. By connecting a UPS to a Power over Ethernet Midspan in the communication room, the entire IP telephony network is becoming more reliable and ensures continuous operation during a power outage. Fig. 2: Power over Ethernet architecture in the enterprise. To understand the theoretical availability for power (North America), the following characteristics are presented. The following data varies from site to site and some areas like Florida are expected to experience an order of magnitude higher of non-availability. The data is also representative of Japan and Western Europe: Power over Ethernet and IP telephony What is power over Ethernet? Power over Ethernet is a revolutionary technology that integrates data, voice and power over standard LAN infrastructure. It is the means to supply reliable, uninterrupted power to internet protocol (IP) telephones, wireless LAN access points, network cameras and other Ethernet devices, using existing, commonly used Category 5 cable infrastructure. Power over Ethernet technology saves time and cost of installing separate power cabling, AC outlets and wall warts (AC adapters), as well as eliminates the need for a dedicated uninterrupted power source (UPS) for individual devices. A single UPS placed centrally close to the switches and the Power over Ethernet source will indeed protect both the switches and all the connected devices. The power delivered over the LAN infrastructure is automatically activated when a compatible terminal is identified, and blocked to legacy devices that are not compatible, thus protecting them and the infrastructure. This feature allows users to freely and safely mix legacy and Power over Ethernet-compatible devices, on their network. There are two main implementations of power over ethernet power source equipment (PSE): The mid-span - A patch-panel-like device, residing between an ordinary Ethernet switch or shared media device and the terminais. Midspans are also referred to as Power Hubs or Power Injectors. Power is added to the spare wires on a category 5 cable while the data is passed without interruption. The end-span - Power over Ethernet enabled Ethernet switch. Power over Ethernet is integrated into the switch, and supplied directly from the data ports. Key drivers for power over Ethernet in IP telephony application The main key drivers for Power over Ethernet in the IP telephony market are availability and simplicity of installation: Availability of IP telephony Consider the promise of running telephony over data networks, where you can greatly benefit from new applications, such as unified messaging together with significant costsavings in personnel and equipment using a single voice-data network, Before Power over Ethernet, corporations could not commit their mission-critical voice systems to run on the data networks. Losing data during a power outage is one thing, but losing data and voice during an outage is something else entirely. By supplying power over the same cable as the data network, these systems can now deliver the kind of reliability expected from a business class phone system. Everyone has high expectations for voice service availability. A common goal is to consistently achieve 99,999% availability with 5,3 minutes of downtime per year or less. The average number of outages sufficient to cause IT system malfunction per year at a typical site is approximately 15 90% of the outages are less than five minutes in duration 99% of the outages are less than one hour in duration Total cumulative outage duration is approximately 100 minutes per year. Based on the theoretical availability and the power protection strategy, the availability levels of five nines or higher requires the installation of Power over Ethernet mid-spans backed up by a UPS system with a minimum of one hour battery life. Power over Ethernet technology, when implemented in a VolP installation, ensures full reliability and availability of the telephony network by eliminating power outages effects. Ease of installation Power over Ethernet offers a simple means for IP phone handsets installation, eliminating the need for a separate Ethernet link and dedicated AC power outlet. A single cable is used to transport voice, data and power to desktops. The IP phone is connected to the Ethernet switch and the mid-span, from which it gets data and power, and the PC is connected to an Ethernet port on the phone. Powering IP phones An IP telephone can be powered via one of three options: Power over Ethernet mid-span - power supplied over the Ethernet cable via an external Power over Ethernet mid-span. Power over Ethernet end-span - Power over Ethernet integrated into an Ethernet Switch, which offers standard IEEE 802.3af Power over Ethernet. Power supplied via an AC adapter. ln the market, different power over Ethernet products exists, however, not all are compatible with the power over Ethernet standard 52 Elektron June 2005

3 IEEE 802.3af. Like all global standards, it is very important to maintain an open environment to enable interoperability between different terminal vendors. ln environments where an existing Ethernet switch has been previously installed and is providing VolP QoS capabilities, there is no need to purchase and install a new Ethernet switch to provide Power over Ethernet functionality. ln this case, the simplest means to power the IP phones over the LAN infrastructure is to add an external Power over Ethernet mid-span (see Fig. 4). The advantages include savings in installation costs, preservation of existing infrastructure while supporting pre-standard as well as IEEE 802.3af standard terminals. Power over Ethernet end-span products are currently beginning to be available in the market, however some are not IEEE 802.3af compliant. It is recommended that enterprises will not purchase proprietary solutions (i.e. not 802.3af). Enterprises will be best served by an infrastructure that continues to support an open, multiservice environment. The third way to power IP phones, i.e. through an AC adapter, has significant drawbacks : not only is this more cumbersome as two cables (data and power) have to exist on each user s desk, but also (unless each user is equipped with a local UPS), any utility outage will result in the IP phone not being available. It is much more convenient to plan a centralised UPS at the Ethernet switch and the PoE midspan level that will protect all the IP phones. This is of course also valid if the Ethernet switch/midspan are powered through an outlet that is permanently power protected by a large centralised UPS at the enterprise site level. How to select the appropriate Power over Ethernet mid-span MGE midspans utilised for IP telephony applications, are 24 port units. These units fit low to high port densities of IP phones. As usually done in Ethernet switches installations, 25-30% of the mid-span ports should be left unused for future growth, in case the IP telephony network is expanded, or the number of users is increased. For example, 6 spare ports in the 24-port mid-span should be left unused. How to size and select the appropriate UPS Right-size the UPS The level of power typically consumed in a communication room with Power over Ethernet capabilities is approximately 400% of that consumed by networks without Power over Ethernet. For example, a typical 24-port Ethernet switch consumes an average of 100 W, whereas a simple installation of an Ethernet switch providing a power solution to 24 IP phones requires powering backup in the range of 400 W. Fig. 4: Integration of Ethernet switches, power over Ethernet mid-span, UPS in the network rack. More specifically, with the PoE standard specifying up to 15 W per attached device, the typical Power over Ethernet-compatible terminals consume in the range of : 3-5 W for IP phones, 6-10 W for wireless access points, and 9-12 W for IP cameras. ln a typical communication room, eight stackable Ethernet switches are installed, providing service to 192 users, the power backup requirements can be fulfilled with a UPS of 1,5 kw. However, to achieve the same level of reliability in a converged voice environment with Power over Ethernet, the UPS backup solutions should be in the range of 6 kw. In order to size the UPS requirement, one can use this attached worksheet that gives a quick first estimate. It is advised to plan for future growth and thus include a safety margin in the UPS VA sizing. For this environment, a UPS such as MGE s Pulsar Extreme would be ideal. Backup time considerations are very important and can point towards a larger UPS, that will be able to sustain longer outages for a given load. In the above case, a Pulsar Extreme 3 kva with two XLA battery extensions would provide two hours of backup time to the rack. Note: the example above assumes that the switches and phones are power-protected at the switch closets level. In some companies, the whole building is equipped with outlets that are centrally protected at the site level, through a large centralised UPS. Of course, this represents an equally good solution. To calculate the exact amount of power being used in a Power over Ethernet environment, with a view to saving costs by right-sizing the appropriate UPS, it is important to calculate Elektron June

4 Associates Unicenter. In all cases, look for seamless integration of a network interface in the UPS and availability of the adequate interface software components. Remote management the exact amount of power consumed by the IP phones. This can be done using the SNMP mid-span product, which provides telemetry of power consumption of the device. With this information, one can calculate the exact amount of power consumed by the network in case of power failure, and adapt the size of the UPS accordingly. This tool enables an exact measurement of power consumption and allows the installer to purchase the appropriate UPS. The managed version of the mid-span enables the user to define a power threshold. This capability offers a tool which can be used to locate any deviation from the predefined level of power consumption by presenting a trap. Select a high-availability UPS technology Fig. 5: MGE Midspan 24. There are two major technologies for UPS systems. While line interactive UPSs protect your equipment and sensitive applications against the most common power quality problems at an attractive cost, only on line double conversion UPSs ensure highest quality output against all power issues.with on line double conversion UPSs, input AC is permanently regenerated without draining the batteries for high isolation from AC utility noise. All transfers to or from battery back up mode are completely undetectable and uninterrupted. An automatic failsafe and overload bypass is provided during extreme conditions if the UPS is no longer able to perform its task to ensure fault tolerance operation. This type of availability is often a requirement in voice over IP installation, to reach the same type of availability as exists in traditional circuitswitched telephone systems. Some of the benefits of on line double conversion UPSs are : Ultimate voltage regulation - Constant voltage regulation ensures a steady and precise voltage flow. This is the main difference with line interactive UPS designs, where output voltage will actually fluctuate within a much larger window. Another benefit of double conversion on lline UPSs is their ability to operate in extremely low line conditions (down to 150 Vs input while still delivering 230 V in output to protected equipment) without draining their batteries. Genset compatibility - More and more customers combine the power quality provided by a UPS with the unlimited backup time of a generator. On startup, these devices may generate frequency fluctuations that some UPSs will not tolerate. Assess backup time needed - for selecting a UPS system, it is also important to consider for how long the installation should be able to sustain a power outage. For voice over IP applications typical customers need range between ½ hour to four hours of backup time, and sometimes more. This leads to UPS configurations with long autonomies. Ensure graceful wiring/edge closet integration Often the wiring /edge closets have not been designed to accomodate much equipment. It is important to consider easy integration of the UPSs in the 19 inch racks present in the wiring closet. As many UPSs are optimised for deep servers racks and not for shorter internetworking equipment, they may not fit in wiring closets racks. Also, for maximum uptime, it is important to consider serviceability questions such as : can I easily perform the maintenance of my UPS s (battery replacements, etc.) without disconnecting the loads? Look for remote management capabilities As UPS equipments will be hidden most of the time and far away from the administrator in the switch closets, it is important to look for UPS solutions that are remotely manageable. Depending on the size of the company and its network management policies, different options are available : remote management of the UPS through SNMP or XML via a web browser, integration of the UPS installed base within the company s network management system, such as HP Openview, IBM Tivoli or Computer Fig. 6: MGE s pulsar extreme UPS with battery extension for long backup time. As distribution and edge network equipment are scattered around the buildings or the floors within the enterprise, it is very important that they are remotely manageable using industrystandard tools. On the PoE mid-span side : An option of Power over Ethernet mid-spans is web-based SNMP remote management. This feature allows for remote control of the midspan technology and the gathering of essential telemetry, collected by the units. Remote management provides an immediate alert and response to changes in the IP phones in the field, and enables the remote resetting of devices. Main features of remote management: Integration in MGE s power systems supervision software Enterprise Power Manager auto discovery of midspans (like UPS s), reporting of alerts, etc. Telemetry of IP phones status and presencethe remote management feature will alert to a change in the status of the IP Phone such as fall in power consumption, disappearance and malfunction. Telemetry of power consumption - collects power consumption information, to measure appropriate size of UPS for your network, saving the cost of needless UPS capacity. Power-off IP phones to save costs - at times it may be desirable to power off selected IP phones when not in use, such as over the weekend and holidays. This helps cost conscious enterprises and ensures the ultimate amount of security when the phone is not to be used. On the UPS side : MGE UPSs are all remotely manageable either through SNMP, which allows seamless integration of the UPSs within standard NMS platforms, or through XML technology that allows to securely, remotely access the UPSs embedded web server via any web browser on the network. In a voice over IP environment, the following features are desirable : Interface with the enterprise standards MGE UPSs can be fitted with an internal network interface card that both supports the SNMP protocol, and includes an embedded web server for web-based management Remote administration from a remote computer anywhere on the network, you can through an intuitive graphical interface, monitor UPS parameters such as battery levels, power quality, state of the UPS, receive alerts, etc. 54 Elektron June 2005

5 Automatic actions upon specific events you can program event notifications via , SMS/pager, program actions when battery levels are low such as system shutdowns etc. Easy integration in your company NMS platform UPS can be discovered, mapped and managed via standard platforms such as HP Openview, IBM Tivoli or Computer Associates Unicenter. Fit to other Edge network applications Although this paper focuses on the voice over IP application in particular, much of what it describes, also applies to a host of new applications that can greatly benefit from the power over Ethernet technology and the centralised UPS protection that this allows. Among these, one can cite Wireless LANs Together with voice over IP, wireless LANs are one of the fastest growing segments in the networks market. Wireless LAN access points are low-power devices that are also connected to the edge closet switches and require low DC power. For such application, Power over Ethernet technology is of great benefit, because it dramatically simplifies the cabling problem (get rid of the low power DC power cable to each access point). This is why Power over Ethernet is one of the most demanded features for access points products and most suppliers already support this standard. In many cases, wireless LANs are also mission critical and can benefit from the centralised protection against power losses, provided by a UPS located at the switch closet level. Consider, for instance, the deployment of a hot spot in a public place e.g. an airport or hotel. Customers will expect a high quality service from this infrastructure and will require uptime for this service, in the range of what they are used for with telecommunications services, especially if they have paid a fee for it. Security devices more and more security devices (network cameras, access control devices, etc.) are also designed to the IP standard to easily connect and be monitored through the enterprise IP network. Such low power devices also tend to be more and more powered through the Power over Ethernet technology through the Ethernet cable. Needless to say, availability of such devices in case of a power failure is in most cases an absolute requirement. Summary and conclusions The emergence of a new standard, IEEE 802.3af or power over Ethernet, is changing the way we think about powering network components. It is now possible to power, from a central point located at the distribution/edge switch, a number of network devices through the same standard cable that is used for data communication, and that is already installed in most enterprises. This comes at the time when a series of new network applications and devices can greatly benefit from such technology. It is extremely convenient, cost-effective, easy to manage and reliable to power network devices such as IP phones (but also, wireless access points, and IP-based security devices such as IP cameras), through such an architecture. This is why all network vendors targetting these new, fast growing applications have endorsed the 802.3af standard. Most of them are now shipping networking equipment supporting Power over Ethernet, mostly, through using PowerDsine components. Using MGE power over Ethernet products for IP telephony, and power protection devices, IT and facility managers and users will get the same level of availability from their VoIP architecture as they experience with the traditional circuit switched telephony systems. Contact Christelle Larkins, MGE UPS, Tel (011) , christelle.larkins@mgeups.co.za 56 Elektron June 2005