Poe

Transcript

Product Brief Using Power over Ethernet (PoE) with Colubris Networks Access Points April 2004 Introduction Power of Ethernet (PoE) using IEEE standard 802.3af is fast becoming the prevalent way to effectively and efficiently provide power to networking equipment where standard AC receptacles are not available. Colubris Networks’ 2nd generation of Access Point platforms comes standard with integrated 802.3af-compliant PoE. Colubris Networks’ legacy Access Point platforms, however, did not have integrated PoE. This paper seeks to clarify how to integrate PoE with both first and second generation Colubris products. Also included are some more specific technical descriptions and illustrations that relate to the Colubris 802.3af implementation. Power-over-Ethernet Overview Power-over-Ethernet (PoE) eliminates the need to run 110/220 VAC power to wireless access points (APs) and other devices on a wired LAN. Using PoE, system installers need only to run a single CAT5 Ethernet cable that carries both power and data to each device. This allows greater flexibility in the locating of APs and network equipment while significantly decreasing installation costs in many cases. PoE begins with a CAT5 “injector" that inserts DC Voltage onto the CAT5 cable. The injector is typically installed in the wiring closet near the Ethernet switch or hub. In some cases, the Ethernet switching equipment itself is capable of playing the role of power injector on some or all of its ports. Some wireless APs accept the injected DC power directly from the CAT5 cable through the RJ45 jack. These devices are considered to be "PoE-compatible" or "Active Ethernet Compatible." Devices that are not PoE-compatible can be converted to PoE by way of a DC “picker” or “tap” that is sometimes called an Ethernet “splitter”. This device picks-off the DC voltage that has been injected into the CAT5 cable by the injector and makes it available to the equipment through the regular DC power jack. It is important to note here that Cisco Systems until recently did not support 802.3af standard PoE in its product line. Because of this, products that were 802.3af compliant could not be powered by Cisco equipment, such as Catalyst switches, that had PoE Colubris Networks Confidential Page 1 of 6 10/23/2006 capabilities. Cisco has recently announced, however, that they will support the IEEE standard in calendar year 2004. Colubris PoE Accessory Product Line Table 1 below shows the PoE accessories offered by Colubris for use with its Access Point products. Note that the Colubris PoE accessories are currently manufactured for Colubris by a 3rd party, PowerDsine Systems, Inc. Colubris is a PowerDsine OEM partner. In particular, the PoE splitter is manufactured specifically for use with Colubris platforms. The equivalent off-the-shelf PowerDsine splitter, the model 401-5, is not plug-compatible with the Colubris hardware and enclosure. PowerDsine manufacturers a special “head” for Colubris so that the 401-5 can be used with Colubris models. The power injector is, however, simply a re-packaging of the PowerDsine 6000 Series injectors and is available from Colubris in one, six, and twelve port models. Colubris APs can be powered using either the Colubris branded injectors or off-the-shelf injectors from PowerDsine. Note also that Colubris only sells a North American version of the Power Injector. Injectors for use outside of North America are available directly from PowerDsine or other manufacturers. Description Region Colubris Product Code US/CA US/CA US/CA 71-01-0300 71-01-0200 71-01-0400 Global 71-01-0100 Power over Ethernet Injectors Single-Port Power Injector Six-Port Power Injector Twelve-Port Power Injector Power over Ethernet Splitters Power over Ethernet Splitter Table 1 - Colubris Access Point PoE Accessory List Use of PoE with Colubris Legacy Platforms Colubris platforms that did not include integrated PoE, including the CN100, CN1000, CN1050, CN1054, CN300, and CN3000 require the use of the active splitter offered by Colubris. When used in conjunction with either the Colubris injector or the off-the-shelf PowerDsine unit, legacy Colubris APs can derive their power over the CAT5 cable. Use of PoE with Colubris 2nd Generation Platforms Colubris platforms that feature integrated PoE, including the CN1250, CN1220, CN3200, and CN320, do not require the use of an active splitter. The LAN Port of these devices (10/100BaseTx) can draw power from an 802.3af compliant Power Injector according to Mode B (with no constraint related to the polarity of the signal on pin 4, 5, 7, and 8), a Colubris Networks Confidential Page 2 of 6 10/23/2006 subset of the IEEE 802.3af standard. The following section contains further technical information related to 802.3af modes. When these platforms are used in conjunction with either the Colubris injector or the offthe-shelf PowerDsine unit, these APs can derive their power over the CAT5 cable. Further Technical Detail on IEEE 802.3af PoE Extract from IEEE 802.3af standard describing Modes A and B The text below is extracted from the IEEE 802.3af standard, sections 33.2 and 33.3.1 and is only inserted here for convenience1. The figures and tables have been renumbered for purposes of use within this document, but are otherwise unmodified. The Powered Device (PD) shall be capable of accepting power on either of two sets of Power Interface (PI) conductors. The two conductor sets are named Mode A and Mode B. In each four-wire connection, the two wires associated with a pair are at the same nominal average voltage. Figure 1 in conjunction with Table 2 illustrates the two power modes. Figure 1 - PD and PSE eight-pin modular jack Conductor (Pin #) Mode A Mode B 1 Positive VPort , Negative VPort 2 Positive VPort , Negative VPort 3 Negative VPort , Positive VPort 4 Positive VPort , Negative VPort 5 Positive VPort , Negative VPort 6 Negative VPort , Positive VPort 7 Negative VPort 8 Negative VPort Table 2 – PD pinout 1 Copyright © 2003 IEEE. All rights reserved Colubris Networks Confidential Page 3 of 6 10/23/2006 The PD shall be implemented to be insensitive to the polarity of the power supply and shall be able to operate per the PD Mode-A column and the Mode-B column in Table 2. NOTE—PDs that implement only Mode A or Mode B are specifically not allowed by this standard. PDs that simultaneously require power from both Mode A and Mode B are specifically not allowed by this standard. The PD shall not source power on its PI. The PD shall withstand any voltage from 0V to 57V at the PI indefinitely without permanent damage. Power Sourcing Equipment PSE, as the name implies, is the equipment that provides the power to a single link section. The PSE’s main functions are to search the link section for a PD, optionally classify the PD, supply power to the link section (only if a PD is detected), monitor the power on the link section, and scale power back to the detect level when power is no longer requested or required. An unplugged link section is one instance when power is no longer required. A PSE is electrically specified at the point of the physical connection to the cabling. Characteristics, such as the losses due to over-voltage protection circuits, or power supply inefficiencies, after the PI connector are not accounted for in this specification. PSE Location PSEs may be placed in two locations with respect to the link segment, either coincident with the DTE/Repeater or mid-span. A PSE that is coincident with the DTE/Repeater is an “Endpoint PSE.” A PSE that is located within a link segment that is distinctly separate from and between the MDIs is a “Mid-span PSE.” The requirements of this document shall apply equally to Endpoint and Mid-span PSEs unless the requirement contains an explicit statement that it applies to only one implementation. See Figure 2. Endpoint PSEs may support either Alternative A or B, or both. Endpoint PSEs can be compatible with 10BASE-T, 100BASE-TX and/or 1000BASE-T. Mid-span PSEs shall use Alternative B. Mid-span PSEs are limited to operation with 10BASE-T and 100BASE-TX systems. Operation of Mid-span PSEs on 1000BASE-T systems is beyond the scope of this standard. Colubris Networks Confidential Page 4 of 6 10/23/2006 Figure 2 - PSE location overview Requirement on Mid-Span Power Injector Selection Per the 802.3af standard, it is required that Mode B be used whenever mid-span Power Sourcing Equipment (PSE) is used. The reason for this recommendation is that the MidSpan PSE shall not compromise the signal on the data pairs (pin 1, 2, 3 and 6). Please refer to Figure 2 (in the next section) extracted from the IEEE 802.3af specification for more details. Colubris Networks Confidential Page 5 of 6 10/23/2006 Colubris Implementation of PoE Figure 3 below illustrates how a Colubris AP is powered via 802.3af using Mode B. Figure 3 shows two scenarios: 1) operation with PSE implemented as part of a Switch/Hub device; and 2) operation using a mid span injector. Please note that these diagrams are slightly different from the diagrams extracted from the 802.3af and shown in Figure 2. Figure 3 - Colubris PoE implementation (Mode B) Colubris Networks Confidential Page 6 of 6 10/23/2006