> Voice over Wireless LAN Technical Solution Guide Enterprise Solutions Engineering Document Date: December 15, 2005 Document Version: 1.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Copyright © 2005 Nortel Networks All rights reserved. December 2005. The information in this document is subject to change without notice. The statements, configurations, technical data, and recommendations in this document are believed to be accurate and reliable, but are presented without express or implied warranty. Users must take full responsibility for their applications of any products specified in this document.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Abstract This document is intended to define the Voice over Wireless LAN (VoWLAN) solution to assist sales engineers in creating the best design to fit the customer’s environment while at the same time eliminating common design errors.
Voice over Wireless LAN Solution Guide v1.0 December 2005 TABLE OF CONTENTS 1. EXECUTIVE SUMMARY ................................................................................................................. 6 1.1 CHALLENGES ................................................................................................................................. 6 1.1.1 High overhead of 802.11 .......................................................................................................... 6 1.1.
Voice over Wireless LAN Solution Guide v1.0 December 2005 3.2.2 WLAN Handset 2210/11/12 .................................................................................................... 58 3.3 DNS SERVER ............................................................................................................................... 59 3.4 TFTP SERVER .............................................................................................................................. 59 4.
Voice over Wireless LAN Solution Guide v1.0 December 2005 1. Executive summary Voice over Wireless LAN (VoWLAN) represents the coming together of two important and rapidly growing technologies — WLAN and Internet Protocol (IP) Telephony. By seamlessly integrating the IP Telephony system with WLAN infrastructure, VoWLAN provides users with high-quality mobile voice and data communications throughout the workplace. This document has two main purposes in defining the aspects of a VoWLAN product solution.
Voice over Wireless LAN Solution Guide v1.0 December 2005 1.1.3 Power adjustments and variable capacity The WLAN market has matured to the point that most vendor product solutions have dynamic mechanisms in place for adjusting channels, adjusting power, and filling coverage holes, all in response to changes in the Radio Frequency (RF) environment. Although the robustness of the mechanisms and features varies, all pose the same basic challenge to engineering voice networks.
Voice over Wireless LAN Solution Guide v1.0 December 2005 QoS over the air techniques generally require complementary feature support by client and AP alike, which means that some legacy devices or products that are slower to implement certain features ultimately can impact the overall solution for voice with respect to QoS. The Hybrid Coordination Function (HCF) is designed to smooth this transition by supporting a combination of channel access methods, both new and legacy.
Voice over Wireless LAN Solution Guide v1.0 December 2005 2.1 Applications Following is a brief description of the various voice applications. 2.1.1 WLAN Handset 2210/11/12 voice The WLAN Handsets 2210, 2211, and 2212 work only in a Nortel Succession 3.0 (and later) environment coordinated with a Communication Server (CS) 1000 or Meridian 1. These handsets communicate with the Nortel call server through the Unified Network IP Stimulus (UNIStim) protocol.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Dell Axim X5 (CPU >= 400 MHz) Dell Axim X3/C3i iPAQ h5550/h5555 Toshiba e750/e755 Toshiba e800/e805 2.1.4 MCS Client Multimedia Communication Server (MCS) 5100 is an application services delivery solution that provides productivity, personalization, and collaborative applications that transform the way users communicate.
Voice over Wireless LAN Solution Guide v1.0 December 2005 location. The three architectures can be combined as desired, so they are not mutually exclusive choices. The basic architectures are: Distributed Campus Centralized Campus Branch Office The two AP connection types are: Direct connection Distributed AP (DAP) A direct connection is defined as an AP with a physical connection to a WLAN Security Switch 2300 and which is configured as an extension to the physical port.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Figure 1: Distributed Campus architecture 2.2.1.2 Centralized Campus A second architectural option is to centralize the security switches within a data center environment. The model most suited for this role is the WSS 2380, which has four gigabit interfaces, no PoE ports, and supports up to 120 active APs. Each AP is powered at the edge by a PoE switch or a PoE injector, and has a DAP connection back to the central WSS 2300s.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Figure 2: Centralized Campus architecture 2.2.1.3 Branch Office The WLAN 2300 can also be deployed in a small branch office environment. Usually this type of environment requires only a handful of APs, probably anywhere from one to six. The WSS 2350 is the model best suited for this environment, supporting up to three AP 2330s per WSS 2350, including one PoE port for direct connection.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Figure 3: Branch Office architecture 2.2.1.4 Combining architectures Up to now, architecture has been discussed in binary terms—this topology or that topology. However, the WLAN 2300 solution is not restrictive in this way. The three architectures can be combined in many different ways within the same network, and as will be shown later, VoWLAN is generally not restricted by these architectural choices.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Figure 4: Combined architecture 2.2.1.5 Third-party AP support In some cases, integrating the WLAN 2300 series into an existing fat-AP deployment may be required or desired. For instance, fat APs may have been deployed in a limited fashion and the WLAN 2300 is a new network expansion.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Figure 5: Network with third-party APs The WSS 2300 supports many models of third-party APs with a few restrictions—see WSS 2300 Release Notes. All models of WSS 2300 have support for third-party APs, although implementation specifics may vary. In many cases, Nortel also supports VoWLAN over third-party APs. The APs must be L2 or directly attached to the WSS 2300.
Voice over Wireless LAN Solution Guide v1.0 December 2005 the ES PSU 10 can provide up to 75 W of power to PoE devices through the ES 460-24T-POE. This means that when running on battery or redundant DC power, only about 10 or 11 APs can be powered. If the deployment of the network calls for more than 10 APs on any ES 460-24TPOE switch, Nortel highly recommends the NES as the external power supply option instead of the ES PSU 10.
Voice over Wireless LAN Solution Guide v1.0 December 2005 MLT to the L2 switch. In this configuration, all APs in the branch must be DAPs powered by the L2 switch or a separate PoE injector. In most cases, you should disable spanning tree on the switch port to which a DAP is connected. If spanning tree is not disabled, there is a possibility that the AP will never connect to a WSS 2300 because of timing differences between spanning tree and the AP switch detection timers.
Voice over Wireless LAN Solution Guide v1.0 December 2005 beneficial to overall voice quality and media scalability. These are some of the dynamics to consider when making this choice. Ultimately you want to carefully control the number of data devices sharing radio resources with voice devices, and you should gear your choices towards this end. For example, suppose that you have a large amount of Centrino laptops in the campus. If you enable 802.
Voice over Wireless LAN Solution Guide v1.0 December 2005 maximum call capacity is not that much higher than the 802.11b channel reuse case (only up to four times as much). By contrast, 802.11a offers a much greater channel space. Channel reuse factors can be as high as 12 or more, depending on regulatory region. Borrowing the assumptions from the previous example (50 mW transmit power and channel reuse of 12), the same scenario has none of the same caps on call capacity.
Voice over Wireless LAN Solution Guide v1.0 December 2005 As a new client on the network associates to an AP for the first time, it goes through the same steps a wired client does, such as being put into a logical VLAN, issuing a DHCP broadcast, receiving an offer, and then communicating on the network. In previous WLAN 2200 products, the first parts were determined by local options on the WSS 2270 and SSID, meaning the WSS 2270 could only assign the user to a VLAN that was local to the WSS.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Figure 7: Single telephony VLAN implementation Consolidating VoWLAN handsets into one VLAN/subnet has a few advantages. First, it allows the WTM 2245 design to be greatly simplified. Instead of purchasing and deploying at least one WTM 2245 per voice subnet, you can now install one WTM 2245 for the single voice subnet.
Voice over Wireless LAN Solution Guide v1.0 December 2005 downstream and upstream traffic is tunneled to and from the WSS 2300 that serves the assigned remote subnet. 2.2.2.7 WLAN Handset 2212 VPN design The WLAN Handset 2212 has a VPN feature that enables an IPsec tunnel to a Nortel VPN Router, which is the only IPsec platform supported today. This alters some of the usual design recommendations for the telephony components, such as the WTM 2245.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Figure 9: VPN design over L3 networks In general, make the VPN Router public interface the default gateway for the handsets, and if not the direct gateway for clients, at least ensure that traffic comes from the WLAN into the public interface, not the private interface. Connect the private interface of the VPN Router to the trusted side of the network. Ensure that client DHCP traffic flows through the VPN Router.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Figure 10: Not recommended VoWLAN design The VPN feature is not designed for remote connectivity over a WAN back to the corporate network. This may in some cases work, but it is not supported. The latency, jitter, and packet loss requirements are sure to be violated when crossing WAN connections.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Figure 11: Unsupported branch VoWLAN design 2.2.3 High availability designs You can configure many of the components described in this document to provide high availability. 2.2.3.1 Network access availability The WSS 2300 in coordination with the WLAN Management System 2300 can provide high availability from an RF coverage perspective, known as Auto-RF.
Voice over Wireless LAN Solution Guide v1.0 December 2005 radio power setting. Another option is to set the minimum data rate before client-driven power changes occur to be 2 Mbps or less. This ensures that the handsets will roam (if possible) before power increases occur. In some cases it is better to turn off the auto-tune power feature altogether for the 802.11b radios. 2.2.3.
Voice over Wireless LAN Solution Guide v1.0 December 2005 other words, the user device will not be aware of any problem with the WLAN (other than that traffic flow has stopped) until the AP 2330 detects the WSS 2300 failure. After the detection, the AP resets and associates to a surviving WSS 2300 according to bias settings. The entire time for the AP to become operational again from the point of WSS 2300 failure can be anywhere from 45 seconds to a minute.
Voice over Wireless LAN Solution Guide v1.0 December 2005 because three is the minimum number that can be tiled such that no two neighboring APs are controlled by the same WSS 2300. In this scenario, if any one WSS 2300 fails, the impact to RF coverage will be reduced. The affected cells will still have the main outage during the interval between failure and detection. However, during the reset after the failure is detected, the resiliency will be much improved.
Voice over Wireless LAN Solution Guide v1.0 December 2005 2.3.1 WLAN Handset 2210/11/12 security features For authentication, the WLAN Handsets 2210/11/12 support either open, WEP shared key, or WPA/WPA2 pre-shared key (PSK) mechanisms, while the 2212 model also supports IPsec VPN. Note that the WLAN 2300 series can additionally use MAC authentication to increase the level of confidence in authentication.
Voice over Wireless LAN Solution Guide v1.0 December 2005 WPA-PSK plus MAC authentication is suitable. For WLAN Handsets 2212, Nortel also recommends use of IPsec from a security perspective. In most cases, avoid WEP. Note that Nortel does not recommend mixing VPN handsets and WPA/WPA2 due to the complexities involved. Separate SSIDs are required and MAC authentication rules can potentially become complex.
Voice over Wireless LAN Solution Guide v1.0 December 2005 subtract from medium capacity by virtue of the resulting transmission errors and the retransmission of corrupted frames. The impact of retransmission is far more significant on WLANs than on 802.3 networks because collisions are not detected and remedied within the first 64 bytes of a frame. On 802.11 WLANs, collisions are detected by the failure to receive an ACK within a predetermined window after the transmission is completed.
Voice over Wireless LAN Solution Guide v1.0 December 2005 particular handset that uses G.711 and 20 ms packetization, you can get a maximum of eight calls on an AP. By just switching to 30 ms packetization on the same exact devices, you can now get 10 calls on the same AP. Given all the dependencies, it can be challenging to find the exact number of calls per AP. The sections that follow provide device-specific information and scaling numbers. 2.4.1.
Voice over Wireless LAN Solution Guide 2.4.1.2 v1.0 December 2005 IP Softphone 2050 and MCS Client Providing scalability rules for the IP Softphone 2050 or MCS Client may appear meaningless in this context because the phone runs on the same PC with other data applications. A pure voice capacity number is not going to provide much engineering guidance because that same PC can also send large amounts of data on the medium.
Voice over Wireless LAN Solution Guide v1.0 December 2005 up the other half and were known to scale up to 10, then likely the resulting mix may scale to about nine calls per AP. There is another important difference between the PDA and WLAN Handset 2210/11/12. Because the WLAN Handset 2210/11/12 has a companion device, namely the WTM 2245, perAP call capacity can be tracked and ultimately enforced. The MVC 2050 does not use the WTM 2245 and number of calls per AP cannot be enforced.
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Voice over Wireless LAN Solution Guide v1.0 December 2005 and SVP in combination on the WLAN 2300 series. The WLAN Handsets 2210/11/12 also support WMM, but note that as of today, the officially supported VoWLAN solution between handset and WLAN 2300 series requires that you not enable the WMM features. That is, you must turn off WMM on the WLAN 2300 series when using WLAN 2210/11/12 handsets on the network.
Voice over Wireless LAN Solution Guide 2.5.1.2 v1.0 December 2005 WMM description To accelerate adoption of 802.11e (even before finalization of the standard) the Wi-Fi Alliance defined two tiers of QoS capabilities, each being a subset of 802.11e: WMM and Wi-Fi Multimedia Scheduled Access (WMM-SA). The Wi-Fi Alliance has also started certifying WMM compatibility. The primary difference between the two WMM and WMM-SA is that WMM is based on 802.
Voice over Wireless LAN Solution Guide v1.0 December 2005 WSS 2380 regardless of mode of operation on the AP 2330. When WMM is disabled, the AP 2330 has a binary manner of applying user packets to queues. CoS 6 or 7 marked packets go into the SVP hardware queue on the AP and get SVP treatment, such as zero backoff and other SVP performance enhancements. Other packets go into the data or best-effort queue.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Auto-RF is another set of features that can have a negative impact on the overall quality of calls. As a general rule, dynamic adjustments can create many transient problems with voice calls. If the channel changes, the handset is forced to roam to another AP that may not be close enough to maintain quality. Or the other APs in the neighborhood may already be at full call capacity.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Figure 14: ES family switches performing packet classification 2.5.2.1 Prioritizing/marking CAPP There are a number of ways to prioritize Control and Provisioning Protocol (CAPP), one of which is to key on the system IP address of the WSS 2300. CAPP uses IP protocol 0x04 for transport, but because the ES family cannot filter on user-defined IP protocol values, this is not a viable filter criterion.
Voice over Wireless LAN Solution Guide v1.0 December 2005 The basic concept is to have the WSS 2300 classify and mark all data, voice, and video traffic, with the assumption that the remaining unmarked traffic consists of control traffic. For example, assume you are using a port-based ACL on the WSS 2300 to examine all ingress traffic on the network port.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Figure 16: Nesting of VoIP within SVP and CAPP The ES at Interface B must implement IP filters in order to classify SVP traffic, albeit indirectly. There is no way to define a filter to match a user defined IP protocol number (SVP uses IP protocol 119 or 0x77). This means that you must use an alternative classifying criterion. The easiest thing to do is to define an IP filter based on source/destination addresses.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Figure 17: ERS 5510/5520 performing packet classification These deployment options are presented strictly for the sake of discussion concerning the capabilities of the ERS 5510/5520 given possible locations within various networks. Because the ERS 5520 has PoE ports, and the ERS 5510 does not, only an ERS 5520 can provide Interface A to AP 2330s.
Voice over Wireless LAN Solution Guide v1.0 December 2005 An ERS 5510/5520 connected to the WTM 2245 at Interface C can be configured to simply trust the markings set by the WTM 2245. Also, you would set WTM 2245 to mark traffic with a DSCP value of 0x2e. 2.5.3.4 Prioritizing/marking native VoIP traffic As noted previously, it is assumed that remote VoIP telephones, call servers, and LAN switching equipment are properly marking and classifying traffic.
Voice over Wireless LAN Solution Guide v1.0 December 2005 0x00 to 0x30 (110000) corresponding to the CS6 class. All other DSCP/ToS values are left untouched. Note that this assumes that the WSS 2300 is not connected to the ERS through a one-arm connection such that CAPP and regular (unencapsulated) user traffic are on the same port. An ERS 8300 port connected to an AP2330 at Interface A would be configured to mark all traffic with DSCP value of 0x2e (101110) corresponding to the EF class.
Voice over Wireless LAN Solution Guide v1.0 December 2005 types of devices side by side. The other major source of problems relates to security capabilities among clients. 2.6.1.1 Separating data and voice applications In addition to having different QoS features, PDAs and PCs present another unique challenge that handsets do not have to deal with, namely supporting data and voice on the same device.
Voice over Wireless LAN Solution Guide v1.0 December 2005 the WLAN Handset 2210/11/12 can implement it as well. However, the authentication mechanism may still be a problem if you desire 802.1x. The WLAN 2300 series can support mixed authentication types on the same SSID for such single SSID scenarios, but the truth is that authentication security is only as strong as the least of the authentication types. For example, if MAC authentication is mixed with 802.
Voice over Wireless LAN Solution Guide v1.0 December 2005 1. Assessment – Network Health Checks and WLAN Site Surveys (post-deployment) are critical assessment items. The main goal is to verify the network’s ability to provide voice at the required QoE (Quality of Experience). 2. Predeployment – Prior to deploying VoIP handsets, the network is made ready through the rollout of QoS across the network. Note that this phase assumes the WLAN itself is already deployed. 3.
Voice over Wireless LAN Solution Guide v1.0 December 2005 WLAN Site Survey Technical support for VoWLAN is contingent on customers performing a prior site survey of the WLAN. Currently Nortel recommends the use of the Ekahau Site Survey tool to verify the network deployment, though other site survey tools are acceptable as well. The Ekahau product runs on a PC and uses your WLAN NIC to collect data for analysis. The output of the tool is a number of robust visualizations of the network.
Voice over Wireless LAN Solution Guide v1.0 December 2005 NetIQ Vivinet Assessor Performing a Network Health Check is probably the most critical step to ensuring a smooth rollout for any VoIP deployment. This applies even more so to VoWLAN, because a WLAN is a more challenging QoS environment than modern wired networks. The NetIQ Vivinet Assessor 3.0 or later is the tool of choice for Network Health Checking. (Previously NetIQ Chariot, now an Ixia product, was recommended for Network Health Checking.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Meridian 1 products (as well as virtually all other Nortel products). It can discover the call server equipment that it supports, it can display the information for the slot or port that the call server components are attached to, and it can discover the TLAN and ELAN on a CS 1000 Signaling server.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Figure 20: ENMS 10.4 IPSM convergence view ENMS can provide down to physical slot port connectivity for the wired network. This topology data is extremely useful when shown in the Converged View of a Path Trace. You can set the display to refresh periodically to display the latest information about where an IP Softphone 2050 user is roaming and their IP address changes.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Communication Server 1000 Telephony Manager Communication Server 1000 Telephony Manager is an element manager for the CS 1000 and Meridian 1 call server/PBX products, as well as a platform for receiving traps and collecting call statistics and other performance-related data.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Figure 22: NetIQ Vivinet AppManager – SLA reporting For the CS 1000, Vivnet AppManager provides information about the percentage of devices available versus unavailable, health of interfaces, Voice Call Quality and QoS for Signaling Server, and Voice Gateway Media Cards (VGMC). AppManager also provides summary analysis for data loss, jitter, latency, and R-Value.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Vivinet Diagnostics is a product that can be purchased separately and used in conjunction with Vivinet AppManager. When Vivinet AppManager receives a call quality alert from a Nortel voice system such as a CS 1000 or BCM for a call in progress, AppManager generates an alert.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Enterprise Switch Manager (ESM) Just like Communication Server 1000 Telephony Manager is the main element manager for voice products, Enterprise Switch Manager (ESM) is the main element manager for Nortel wired EDN switching products. Products such as ES and ERS switches are managed, monitored, and configured through ESM. ESM makes simultaneous VLAN configuration across multiple devices quick and easy.
Voice over Wireless LAN Solution Guide v1.0 December 2005 3.2.2 WLAN Handset 2210/11/12 The WLAN Handset 2210/11/12 also supports numerous DHCP extensions for assigning various configuration options. Like the AP 2330, the WLAN Handset 2210/11/12 supplies a vendor class string, which in this case is Nortel-221x-A. Unlike the AP 2330, the WLAN Handset 2210/11/12 does not accept these options from the DHCP server encapsulated in a 43 Vendor Type option (which is the normal way vendor classes work).
Voice over Wireless LAN Solution Guide v1.0 December 2005 the proper signaling server. This can of course get cumbersome if there are a large number of users who travel. 3.3 DNS server Another way that a DAP that is separated from a WSS 2300 by a router can find a WSS 2300 is DNS. If the DAP does not receive a DHCP option 43 containing the IP address of a WSS 2300, then the AP will attempt to resolve through DNS the hostname wlan-switch.domain.com, where domain.
Voice over Wireless LAN Solution Guide v1.0 December 2005 ; WLAN access points must be SVP or View compatible as tested by SpectraLink Corp. Nortel requires all WLAN networks that carry voice be SVP enabled to receive NETS/GNTS support. For SVP compatible APs, see http://www.spectralink.com/service/manuals_config.html. ; Enable SVP in the APs. SVP must be enabled in all APs that carry voice traffic. Not all AP vendors use SVP terminology.
Voice over Wireless LAN Solution Guide v1.0 December 2005 determine holes in coverage that may create dropped calls or poor voice QoS. ; 70 percent of the time, poor voice QoS received in handsets is due to problems in the infrastructure such as no enabling SVP, poor RSSI coverage, cochannel interference, Ethernet duplex mismatch, excessive retransmission of packets or other RF interference.
Voice over Wireless LAN Solution Guide v1.0 December 2005 Contact us For product support and sales information, visit the Nortel web site at: www.nortel.com In North America, dial toll-free 1-800-4Nortel; outside North America dial 987-288-3700.
