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Aruba 802.11ac networks: Validated Reference Designs

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The purpose of this guide is to explain the enhancements in 802.11ac standard and provide guidance towards
migrating to 802.11ac with respect to network design, deployment, and configuration best practices for campus environments like offices, university campus, and dorm environments.
This guide covers the following topics in detail:
- Summary of Recommendations
- 802.11ac Features and Benefits
- 802.11ac Planning and Deployment Guidelines
- Best Practice Recommendations for Deploying 802.11ac WLANs

This guide is intended for those who are willing to learn about the 802.11ac standards and understand the best practices in deploying a high-performing 802.11ac

Published in: Technology
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Aruba 802.11ac networks: Validated Reference Designs

  1. 1. Aruba 802.11ac Networks Validated Reference Design
  2. 2. 2 | Aruba 802.11ac Networks Copyright Information © 2015 Aruba Networks, Inc. Aruba Networks trademarks include , Aruba Networks®, Aruba Wireless Networks®, the registered Aruba the Mobile Edge Company logo, Aruba Mobility Management System®, Mobile Edge Architecture®, People Move. Networks Must Follow®, RFProtect®, Green Island®, ClientMatch®, Aruba Central®, ETips™, Virtual Intranet Access™, Aruba Instant™, ArubaOS™, xSec™, ServiceEdge™, Aruba ClearPass Access Management System™, AirMesh™, AirWave™, Aruba@Work™, Cloud WiFi™, Aruba Cloud™, Adaptive Radio Management™, Secure Air™, Stable Air™, Simple Air™, Mobility-Defined Networks™, Aruba Mobility-Defined Networks™, Meridian™ and ArubaCare™. All rights reserved. All other trademarks are the property of their respective owners. Open Source Code Certain Aruba products include Open Source software code developed by third parties, including software code subject to the GNU General Public License (GPL), GNU Lesser General Public License (LGPL), or other Open Source Licenses. Includes software for Litech Systems Design. The IF-MAP client library copyright 2011 Infoblox, Inc. All rights reserved. This product includes software developed by Lars Fenneberg et al. The Open Source code used can be found at this site: http://www.arubanetworks.com/open_source Legal Notice The use of Aruba Networks, Inc. switching platforms and software, by all individuals or corporations, to terminate other vendor’s VPN client devices constitutes complete acceptance of liability by that individual or corporation for this action and indemnifies, in full, Aruba Networks, Inc. from any and all legal actions that might be taken against it with respect to infringement of copyright on behalf of those vendors. Warranty This hardware product is protected by an Aruba warranty. For details, see the Aruba Networks standard warranty terms and conditions.
  3. 3. Aruba 802.11ac Networks Contents | 3 Contents Contents 3 Introduction 5 Summary of Recommendations 7 Wired Network Considerations 7 RF Planning 7 WLAN Optimizations 8 802.11ac Features and Benefits 11 Wide RF Channel Bandwidths 11 OFDM Subcarriers 12 More Spatial Streams 13 Spatial Streams 13 Understanding MIMO and MU-MIMO 13 Space Time Block Coding, Maximum Ratio Combining, and Short Guard Interval 15 Space Time Block Coding 15 Maximal Ratio Combining 15 Short Guard Interval 15 Transmit Beamforming 15 Modulation and Rates 16 Error Correction Methods 18 Frame Aggregation, A-MPDU, and A-MSDU 18 Power-Save Enhancements 19 Backward Compatibility 20 Protection, Dynamic Bandwidth, and Channelization 20 802.11ac Planning and Deployment Guidelines 23 Wired Network Considerations 24 AP Power Requirements 24 AP Uplink Considerations 25 Access Network Uplink Consideration 25 Jumbo Frames 26
  4. 4. 4 | Contents Aruba 802.11ac Networks VLAN Design 26 Wireless VLAN Design 26 RF Planning 27 AP Mounting Recommendations 27 Ceiling Mount Deployment 27 Wall Deployment 27 Site Survey 28 Factors Attenuating Wireless Signals 30 Wi-Fi and Non-Wi-Fi Interference Sources 30 Forwarding Mode Recommendations 31 Tunnel Mode 31 Decrypt-Tunnel Mode 32 Channel Width Selection 32 Capacity planning 33 WLAN Optimizations 35 Adaptive Radio Management (ARM) 35 Channel and Power Settings 35 ClientMatch 37 ClientMatch Capabilities 37 Band Steering 37 Sticky Client Steering 37 Dynamic Load Balancing 38 Broadcast/Multicast (BC/MC) Optimization 38 AirGroup 39 Dynamic Multicast Optimization (DMO) 39 Dynamic Multicast Optimization 39 Multicast Rate Optimization 40 Traffic Shaping 41 Wi-Fi Multimedia and Quality of Service (QoS) 41 End-to-End QoS 42
  5. 5. Aruba 802.11ac Networks Introduction | 5 Chapter 1 Introduction Wi-Fi has evolved from being a nice-to-have service to a mission-critical solution in enterprise communications. With the introduction of 802.11ac technology, which provides gigabit speed, many companies are moving towards all-wireless offices. Gone are the days where employees used desktops with wired connections and desk phones. The advancements in Wi-Fi technology has made the workplace mobile. Because of mobility, employees can have quick and easy access to data irrespective of their physical location, which improves user productivity and reduces IT cost. It is common for an employee to carry two or more devices – for example, smartphone, tablet, and laptop. Most of these newer devices do not come with Ethernet ports and hence Wi-Fi is their primary mode of network access. Mobile technology has reached the next frontier – video. Whether it is delivering buffered video like YouTube to smartphones or streaming HDTV video around the office or home, video has become a significant driver of network traffic. This is mainly because video requires twice more bandwidth than other IP services and is a continuous traffic stream as compared to transactional and bursty traffic like email or Web browsing. Support for voice and video traffic becomes important for an all-wireless workplace that uses Unified Communications and Collaborations (UCC) applications like Microsoft Lync for webinars and video conferencing. The recent move to cloud-based services by companies also adds stress to today's network bandwidth due to the shift to having documents downloaded on demand to mobile devices rather than being stored locally. Ratified as a standard by IEEE in December 2013, 802.11ac is the latest enhancement in the 802.11 standards family for improving the network performance. The purpose of this guide is to explain the enhancements in 802.11ac standard and provide guidance towards migrating to 802.11ac with respect to network design, deployment, and configuration best practices for campus environments like offices, university campus, and dorm environments. This guide covers the following topics in detail: l Summary of Recommendations l 802.11ac Features and Benefits l 802.11ac Planning and Deployment Guidelines l Best Practice Recommendations for Deploying 802.11ac WLANs This guide is intended for those who are willing to learn about the 802.11ac standards and understand the best practices in deploying a high-performing 802.11ac WLAN network by using wireless LAN controllers and Access Points (APs) from Aruba Networks, Inc.
  6. 6. Aruba 802.11ac Networks Summary of Recommendations | 7 Chapter 2 Summary of Recommendations All the recommendations in this chapter are general guidelines for 802.11ac deployments. Based on your network; radio frequency (RF) guidelines might change and hence it is strongly recommended to appropriately tweak some RF parameters. Network admins should carefully adjust one parameter at a time and test it out before using it in production environments. Wired Network Considerations The following table summarizes Aruba’s recommendation for wired networks to support 802.11ac WLAN deployments. For detailed description, see Chapter 4: 802.11ac Planning and Deployment Guidelines. Feature Recommendation PoE Requirements l It is preferred to use 802.3at (PoE+) switches to power the APs. AP Uplink Consideration l If this is a Greenfield deployment, it is recommended to plan two Ethernet cables per AP- 220 Series for providing PoE fallback and future-proofing your network. Ethernet Cable l Cat 5e Ethernet cables. l Cat 6a Ethernet Cables preferable. Access Network Uplink Consideration l Access switch terminating APs should have a 10 Gbps uplinks. Controller Uplink l It is recommended to at least have a 10 Gbps redundant uplink from the controller. Jumbo Frame l It is recommended to have end-to-end Jumbo Frame support on your network to get maximum benefits of frame aggregation and improve 802.11ac performance. VLAN Design l Design your network to have separate wired and wireless VLANs to avoid unnecessary broadcast and multicast traffic. l Configure a single flat VLAN for all the wireless clients. l Configure Broadcast Multicast Optimization knobs. Table 1: Recommendations for Wired Network RF Planning The following table summarizes Aruba’s recommendations for AP placement, AP mounting and channel width selection when planning for deploying 802.11ac WLAN. For detailed description, see chapter 4: 802.11ac Planning and Deployment Guidelines.
  7. 7. 8 | Summary of Recommendations Aruba 802.11ac Networks Feature Recommendation AP Mounting Recommendation Ceiling Mount AP Placement l Place AP’s approximately 40 to 60 feet apart. l Minimum Received Signal Strength Indicator (RSSI) should be -65 dB throughout your coverage area. l SNR should always be greater than 25 dB. l APs should be deployed in honeycomb pattern. l Plan your network for 5 GHz performance. AP Forwarding Mode l Tunnel Mode is preferred. l Decrypt-Tunnel mode. Channel Width Selection l In Greenfield deployments, deploy 80 Mhz channels including the use of DFS channels if no radar signal interference is detected near your facility, else deploy 40 MHz channels. Consider 40 MHz or 20 MHz channel width for better channel separation. l In Brownfield deployments, 80 MHz channel is recommended with DFS channels only if no radar signal interference detected near your facility. Also make sure that your legacy clients are not having wireless issues with 80 MHz channels in which case deploy 40 MHz channels. Client Density per AP l Plan to have around 40 to 60 active clients per radio per AP. Table 2: Recommendations for RF Planning WLAN Optimizations The following table summarizes the recommendations for WLAN optimization. For detailed description, see Chapter 5: WLAN Optimizations. Feature Default Value Recommended Value Description Scanning Enable Enable l Enables AP to scan other channels Transmit Power 802.11a and 802.11g radio: Min 9/Max 127 Open Office: 5 GHz: Min 12/Max 15 2.4 GHz: Min 6/Max 9 Walled Office or Classroom: 5 GHz: Min 15/Max 18 2.4 GHz: Min 6/Max 9 l Sets the transmit power value NOTE: l The difference between minimum and maximum Tx power on the same radio should not be more than 6 dBm. l Tx power of 5 GHz radio should be 6 dBm higher than that of 2.4 GHz radio. Client Match Enable Enable l Optimizes user experience by steering clients to the best AP Table 3: WLAN Optimization Recommendations
  8. 8. Feature Default Value Recommended Value Description Convert Broadcast ARP Requests to Unicast Enable Enable l Helps to convert broadcast ARP and DHCP packets to unicast Drop Broadcast and Multicast Disable Enable l Restricts all the broadcast and multicast traffic flooding into AP tunnels (“Convert Broadcast ARP Requests to Unicast” feature must be enabled) AirGroup Disable Enable it if MDNS, DLNA or other zero-configuration services are needed. l Allows Airplay and ChromeCast type of applications even if “Drop Broadcast and Multicast” feature is enabled Dynamic Multicast Optimization (DMO) Disable l Enable it if multicast streaming is needed. l Set DMO client threshold to 80. l Prioritize multicast stream using controller uplink ACL. l Converts multicast frames to unicast frames to deliver them at higher rates NOTE: l IGMP Snooping or Proxy feature needs to be enabled for DMO to work. Multicast Rate Optimization Disable Enable l Sends multicast frames at the highest possible common rate l Enable it even if DMO is enabled Airtime Fairness Default Access Fair Access l Provides equal air time to all the clients WMM Disable Enable it if you want to prioritize voice/video traffic on your network. l Enables WMM capabilities to prioritize voice/video traffic Table 3: WLAN Optimization Recommendations Aruba 802.11ac Networks Summary of Recommendations | 9
  9. 9. Aruba 802.11ac Networks 802.11ac Features and Benefits | 11 Chapter 3 802.11ac Features and Benefits The following section outlines the enhancements that were introduced in 802.11ac standard. 802.11ac is the latest amendment to the 802.11 standard and it increases speed close to threefold compared to 802.11n standard to provide an Ethernet-like user experience. Some of the key enhancements included in 802.11ac standard are: l Wide RF Channels l More Spatial Streams l MU-MIMO l Transmit Beamforming l 256 QAM Modulation l Frame Aggregation, A-MPDU, and A-MSDU l Protection, Dynamic Bandwidth, and Channelization Wide RF Channel Bandwidths 802.11n defined 20 MHz- or 40 MHz-wide channels for wireless communication. 802.11ac added the use of 80 MHz- and 160 MHz-wide channels. In wireless communication, higher channel widths provide more throughput. In the Modulation and Rates section of this document, a comparison of the data rates achieved by using 80 MHz- and 160 MHz-wide channels is provided. The following figure shows the available spectrum in 5 GHz band in the US. Figure 1 Channels defined for 5 GHz band (US Regulations) showing 20, 40, 80, and 160 MHz Channels. In the US, Wi-Fi uses three blocks of spectrum in 5 GHz band: U-NII 1, U-NII 2, and U-NII 3. The U-NII 1 band is restricted to indoor operations, the U-NII 2 and U-NII 2 extended bands are for indoor and outdoor operations, and the U-NII 3/ISM band is intended for outdoor bridge products and may be used for indoor WLANs as well. 802.11ac Wave 1 allows for use of 80 MHz channels. In future, 802.11ac Wave 2 will allow use of 160 MHz channel width. As it will be difficult to find 160 MHz of contiguous spectrum, 802.11ac Wave 2 will allow two noncontiguous channels to be used together as 80 + 80 MHz channel. The 802.11ac standard does not operate in 2.4 GHz band and hence from the deployment standpoint all the best practice recommendations for 802.11n APs still apply to 2.4 GHz band. For more information, refer to
  10. 10. 12 | 802.11ac Features and Benefits Aruba 802.11ac Networks "Aruba 802.11n Networks Validated Reference Design” document available at:http://www.arubanetworks.com/vrd/80211nNetworksVRD/wwhelp/wwhimpl/js/html/wwhelp.htm Aruba recommends that customers do not use 40 MHz channels in the 2.4 GHz band due to the lack of available bandwidth and high chance of interference with legacy 802.11b/g networks. While it is possible to enable these channels, doing so will result in fewer overall channels and a decrease in throughput. OFDM Subcarriers Orthogonal Frequency-Division Multiplexing (OFDM) is the encoding scheme that is used in Wi-Fi transmissions. OFDM splits a single channel into very small subcarriers that can transport independent pieces of data as symbols. Each symbol represents some amount of data, which depends on the encoding scheme. The 802.11n standard only allowed for 40 MHz channel width, so you can only have 114 OFDM subcarriers. Now, as the 802.11ac standard allows for channel width of 80 MHz, you can have 234 usable data subcarriers and in future, 468 data subcarriers with 160 Mhz channel. This increase in channel width means that more data subcarriers are available to carry traffic. Each additional subcarrier can carry data over the channel, which increases the throughput. In the following figure, you can see the difference in the number of OFDM subcarriers across different 802.11 standards. The additional channel width is the primary reason for increased throughput with 802.11ac. Figure 2 OFDM Subcarriers Used in 802.11a, 802.11n, and 802.11ac Standard Channel Width Total Sub- carriers Usable Data Subcarriers 802.11a/802.11g 20 MHz 52 48 802.11n 20 MHz 56 52 802.11n 40 MHz 114 108 802.11ac 80 MHz 242 234 802.11ac 160 MHz 484 468 Table 4: OFDM data subcarriers with different 802.11 standards
  11. 11. Some of the subcarriers that do not carry data are called pilot carriers. These are used for the measurement of channel conditions like phase shift for each subcarrier and can also be used for synchronization to avoid intersymbol interference. This accounts for the difference in the number of total subcarriers and usable data subcarriers. More Spatial Streams Spatial Streams The concept of spatial streams of data is related to the ability to transmit and receive on multiple radio chains. More transmit and receive chains allow the AP to send independent streams of data. Multiple spatial streams enable the AP to transmit more data simultaneously. The data is split into multiple streams and transmitted over different radio chains. The following figure demonstrates the concept of multiple spatial streams of data. Figure 3 Spatial Streams Part of the merits of using Multiple Input Multiple Output (MIMO) and spatial streams is that APs can use multipath transmissions to their advantage. Single Input Single Output (SISO) systems used in legacy 802.11 standards see performance degradation due to multipath transmissions because multipaths may add to signal degradation. However, 802.11n and 802.11ac APs use multipath transmissions to significantly enhance performance. The delay in the propagation of paths at different rates allows MIMO and spatial streams to be received correctly at the other end of the transmission link. In a SISO system, that delay can cause interference. Multiple radio chains are needed to transmit and receive multiple spatial streams. Depending on the hardware, an AP or a client can transmit or receive spatial streams equal to the number of radio chains it has. However, it is common to have APs with more antennas than spatial streams. Understanding MIMO and MU-MIMO The MIMO technology, which was introduced in 802.11n standard, increases throughput by increasing the number of radio transmit and receive chains. The 802.11ac standard uses MIMO technology and allows for use of up to eight spatial streams. At present, with 802.11ac Wave 1, an AP or client can have up to four transmit and four receive chains. Currently, the 802.11ac-certified client devices available in the market support a maximum of three spatial streams. Figure 4 Comparison of SISO technology and MIMO technology Aruba 802.11ac Networks 802.11ac Features and Benefits | 13
  12. 12. 14 | 802.11ac Features and Benefits Aruba 802.11ac Networks The 802.11ac standard also introduced Multi-User MIMO (MU-MIMO). So far, in the 802.11n and 802.11ac Wave 1 standards, all the wireless communication is either point-to-point (that is, one-to-one) or broadcast (that is, one-to-all). 802.11ac Wave 2 will support MU-MIMO, where an AP by using its different streams can transmit data to multiple clients at the same time. Figure 5 Comparison of MIMO and MU-MIMO transmission MU-MIMO proposes that, instead of using multiple spatial streams between a given pair of devices, there should be capability to use spatial diversity to send multiple data streams between several devices at a given instant. The difficulty lies in coordinating between the various devices in a network – how do you discover which pairs of radio chains or devices support diverse paths; and how does a device know that another is transmitting, so it can safely transmit to its partner at the same instant? 802.11ac solves these problems by assuming that APs are different from client devices in that they are less space-, power-, and price-constrained, so they are likely to have more transmitting antennas than client devices. Therefore, since the number of spatially diverse paths depends on the number of radio chains, and the number of opportunities depends on the amount of traffic buffered for transmission, the AP is allowed to transmit to several clients simultaneously should it find an opportunity to do so. For example, a four-radio chain AP could simultaneously transmit two spatial streams each to two client devices, provided the conditions were favorable. This means that the transmissions to one client device should not cause excessive interference at the other client and the usual MIMO Spatial Division Multiplexing (SDM) conditions should prevail, where the streams between a given pair of devices are isolated. This downlink MU-MIMO (DL MU-MIMO) is the only configuration supported in 802.11ac. It precludes other forms such as uplink MU-MIMO. Only one AP or client can transmit at any instant, and while the AP can transmit to multiple clients simultaneously, clients can only transmit to the AP one by one. The following figure shows an example of an AP with four antennas using MU- MIMO to transmit simultaneously to four different clients. Figure 6 Downlink Multi-User MIMO Frame Sequences
  13. 13. The AP is also in a good position to monitor traffic for different clients and identify opportunities to exercise DL MU-MIMO. Space Time Block Coding, Maximum Ratio Combining, and Short Guard Interval Space Time Block Coding MIMO uses diversity techniques to improve performance. Between two communicating stations, one station can have more antennas than the other. If there are more transmit radio chains than receive chains, Space Time Block Coding (STBC) can be used to improve the signal-to-noise ratio (SNR) and the range for a given data rate. For STBC, the number of transmit chains must be greater than the number of spatial streams. Maximal Ratio Combining The operation of Maximal Ratio Combining (MRC) depends on the number of available receive radio chains. When there is more than one receive chain, the MRC technique combines the signals received on multiple chains. The signals can come from one or more transmit chains. When the signals are combined, the SNR is improved and the range for a given data rate is increased. Short Guard Interval The guard interval is the spacing between OFDM transmissions from or to a client. This interval prevents the frames that are taking a longer path from colliding with those in the subsequent transmissions that are taking a shorter path. It is the time that a receiver waits for all the transmissions to account for the delay spread of different transmit signals reaching the receiver. For example, think of this as an echo and how long the receiver will wait for the echo before considering the transmission complete. A shorter OFDM guard interval (from 800 ns to 400 ns) between frames means that transmissions can begin sooner in environments where the delay between frames is low. For more details about these features, refer to “802.11ac IN-DEPTH” white paper available at: http://www.arubanetworks.com/pdf/technology/whitepapers/WP_80211acInDepth.pdf Transmit Beamforming Transmit Beamforming (TxBF) in 802.11ac works on an explicit feedback to be sent from the beamformee to the beamformer regarding the current channel state. This information is used to modify amplitude and phase of signal so as to direct the energy towards the receiver. If correct weightings of amplitude and phase are chosen, the signal strength at the receive antennas is maximized in a local peak, which maximizes SNR and hence the sustainable link rate. TxBF can be thought of as directing a beam using phase shifts towards a particular receive antenna. Sounding frames are used in the 802.11ac standard to achieve explicit TxBF. Following points explain how it works: l A transmitter sends a known pattern of RF symbols from each antenna l The receiver constructs a matrix for how each of the receive antenna hears each transmit antenna l This matrix is then sent back to the transmitter, allowing it to invert the matrix and use the optimum amplitude-phase settings for best reception. With a single antenna receiver, this results in a local maximum for SNR for an effective beamforming. Aruba 802.11ac Networks 802.11ac Features and Benefits | 15
  14. 14. 16 | 802.11ac Features and Benefits Aruba 802.11ac Networks Figure 7 Implicit and Explicit Feedback for Beamforming The implicit beamforming technique is based on inferences of channel characteristics when frames are lost. The 802.11ac standard uses explicit TxBF, where beamformer transmits a sounding frame and the beamformee analyses how it receives the frame, compresses the results to a manageable size, and transmits them back to the beamformer. This provides accurate channel state information (CSI) and allows transmitter to direct its transmission accurately towards the receiver. 802.11ac uses sounding frames and the full sounding sequence comprises a set of special sounding frames sent by the transmitter (either the beamformer or the AP in case of DL MU-MIMO), and a set of compressed V matrix frames returned by the beamformee. Because multiple clients are involved in MU-MIMO, a special protocol ensures that they answer with feedback frames in sequence, following the reception of sounding frame. The protocol for generating CSI at the transmitter relies on sounding or null data packet (NDP) frames, together with announcement frames and response frames. First, the beamformer sends a null data packet announcement (NDPA) frame identifying the intended recipients and the format of the forthcoming sounding frame. This is followed by the sounding NDP frame itself, and the beamformee then responds with a beamforming report frame. The NDPA and NDP frames are quite simple. The NDPA identifies which stations should listen to the subsequent sounding frame, along with the dimensions of that frame, depending on the number of radio chains and spatial streams in use. The sounding frame itself is just a null data packet. After these exchanges, the information gathered is processed and used to construct a beamforming report, which is then used to perform TxBF. Modulation and Rates The 802.11ac amendment continues to extend the complexity of its modulation techniques. Building on the rates of up to 64 Quadrature Amplitude Modulation (QAM) of 802.11n, it now extends to 256-QAM. This means that each RF symbol represents one of the 256 possible combinations of amplitude (the signal power) versus phase (a shift from the phase of the reference signal). The following diagram illustrates how this complicates the task of encoding and decoding each symbol. There is very little room for error, as the receiver has to discriminate between 16 possible amplitude levels and 16 phase shift increments; but it increases the amount of information each symbol represents from 6 to 8 bits when comparing the top 802.11ac rate to the 802.11n rate.
  15. 15. Figure 8 Constellation Diagrams for 16-, 64-, and 256-QAM While the 256-QAM 5/6 modulation provides a higher raw-data top speed, the table of available physical layer (PHY) rates is very long, as with 802.11n, to account for various other options. The key determinants of PHY data rate are: 1. Channel width: As we discussed earlier, 802.11ac AP can be configured to use 20 MHz, 40 MHz, 80 MHz channel width. In future, the 802.11ac Wave 2 products will allow for 160 MHz channel width or noncontiguous 80 + 80 MHz channel width. 2. Modulation and coding: All the earlier options are still available, and are used if SNR is too low to sustain the highest rate. But in the modulation and coding scheme (MCS) table, the canon of 802.11n is extended to add 256-QAM options with coding of 3/4 and 5/6. 3. Guard interval: Unchanged from 802.11n, the long guard interval of 800 ns is mandatory while the short guard interval of 400 ns is an available option. The guard interval is the pause between transmitted RF symbols. It is necessary to avoid multipath reflections of one symbol from arriving late and interfering with the next symbol. Figure 9 802.11ac data rates with respect to channel width and spatial streams Majority of the client devices available today can support a maximum of three spatial streams. Aruba 802.11ac Networks 802.11ac Features and Benefits | 17
  16. 16. 18 | 802.11ac Features and Benefits Aruba 802.11ac Networks Client Capability 802.11n – 40 MHz Chan- nel 802.11ac – 40 MHz Channel 802.11ac – 80 MHz Channel 1x1 (Smart Phone) 150 Mbps 200 Mbps 433 Mbps 2x2 (Tablet, PC) 300 Mbps 400 Mbps 867 Mbps 3x3 (PC) 450 Mbps 600 Mbps 1300 Mbps Table 5: Comparison of 802.11n and 802.11ac data rates based on client capability As shown in the prior table, 256 QAM improves 802.11ac data rate when compared to 802.11n data rates at 40 Mhz channel width. The maximum 802.11ac Wave 1 data rates are obtained with 256 QAM modulation and 80 MHz channel width. Increased coding in terms of bits/sec per hertz of spectrum comes at a price. The required signal level for good reception increases with the complexity of modulation and the channel bandwidth. The following graph shows, for instance, that whereas -64 dBm was sufficient for the top rate (72 Mbps) of 802.11n in a 20 MHz channel, the requirement rises to - 59 dBm for the top rate (86 Mbps) of 802.11ac, single stream in a 20 MHz channel, and to -49 dBm for the top rate (866 Mbps) in a 160 MHz channel. Figure 10 Minimum RSSI requirements for different modulation types Error Correction Methods Like the 802.11n standard, 802.11ac supports two error correction methods: 1. Binary convolutional code (BCC) 2. Low-density parity check (LDPC) The BCC method is mandatory, while the LDPC method is optional. Though LDPC is a relatively new technique, it offers improvement over BCC and in some cases it can result in moving to the next higher-order modulation rate (on the prior graph), or alternatively, at the same modulation rate it can significantly reduce error packets. For more details about BCC and LDPC, refer to “802.11ac IN-DEPTH” white paper available at: http://www.arubanetworks.com/pdf/technology/whitepapers/WP_80211acInDepth.pdf Frame Aggregation, A-MPDU, and A-MSDU In addition to the enhancements discussed earlier, the 802.11ac standard includes enhancements to Frame Aggregation, Aggregated MAC Protocol Data Unit (A-MPDU), and Aggregated MAC Service Data Unit(A-MSDU). A client (or AP) must contend for the medium (a transmit opportunity on the air) with every frame it wishes to
  17. 17. transmit. This results in contention, collisions on the medium, and back-off delays that waste time, which could be better used to send traffic. The frame aggregation mechanism introduced in 802.11n, which reduces contention events, are also supported in the 802.11ac standard. With MAC-layer aggregation, a station with a number of frames to send can opt to combine them into an aggregate frame (MAC MPDU). The resulting frame contains lesser header overhead than that without aggregating, and because fewer, larger frames are sent, the contention time on the wireless medium is reduced. In the A-MSDU format, multiple frames from higher layers are combined and processed by the MAC layer as a single entity. Each original frame becomes a subframe within the aggregated MAC frame. Thus this method must be used for frames with the same source and destination, and only MSDUs of the same priority (access class as in 802.11e) can be aggregated. An alternative method, A-MPDU format, allows concatenation of MPDUs into an aggregate MAC frame. Each individual MPDU is encrypted and decrypted separately, and is separated by an A-MPDU delimiter, which is modified for 802.11ac to allow for longer frames. In 802.11ac, the A-MSDU limit is raised from 7,935 bytes to 11,426 bytes, and the maximum A-MPDU size from 65,535 bytes to 1,048,576 bytes. The following diagram shows the MAC frame aggregation of 802.11ac. Figure 11 MAC Frame Aggregation in 802.11ac A-MPDU must be used with the block-acknowledgment function introduced in 802.11n. This allows a single block acknowledgment frame to acknowledge a range of received data frames. It is possible to combine these techniques, that is combining a number of MSDUs and A-MSDUs in an A-MPDU. Theoretical studies have shown that this improves performance over either technique when used alone. However, most practical implementations to date concentrate on A-MPDU, which performs well in the presence of errors due to its selective retransmission ability. Power-Save Enhancements Many 802.11 devices are still battery-powered. Although other components of a smartphone, notably the display still tax the battery much more than the Wi-Fi subsystem, power-saving additions are still worthwhile. The new power-save enhancement is known as very high throughput transmit opportunity (VHT TXOP) power- save. It allows a client to switch off its radio circuit after it has seen the AP indicate that a transmit opportunity (TXOP) is intended for another client. This should be relatively uncontroversial, except that a TXOP can cover several frames; so the AP must ensure that after having allowed a client to doze at the beginning of a TXOP, it does not then transmit a frame for that client. Similarly, if a TXOP is truncated by the AP, it must remember that certain clients will still be dozing and not send new frames to them. Aruba 802.11ac Networks 802.11ac Features and Benefits | 19
  18. 18. 20 | 802.11ac Features and Benefits Aruba 802.11ac Networks To allow clients to quickly identify if a frame is addressed to them, a new field called partial association ID (partial AID) or Group ID for MU-MIMO is added to the preamble. If the partial AID field is not its own address, the client can doze for the remainder of the TXOP. One reason to introduce VHT TXOP power-save is that the frames are getting longer. 802.11ac has extended frame lengths and now allows for frames approaching 8 KB in length, and aggregated frames (A-MPDU) of 1 MB length. Some of this is accounted by the increased rates, so time on the medium will not be extended pro-rata. But video and large file transfers, two of the more important use cases, drive large number of long frames (possibly aggregated as A-MSDU or A-MPDU frames at the Wi-Fi layer); so it may well be worthwhile switching off a radio while large numbers of frames are being delivered to other clients. The other major power-saving feature of 802.11ac is its high data rates. Power consumption in 802.11 is heavily dependent on the time spent transmitting the data. The higher the rate, the shorter the transmission burst. The time spent receiving frames is also reduced by high rates, but not so significantly. Backward Compatibility Because 802.11ac includes new, higher-speed techniques, its transmissions are by definition not decodable by older 802.11 equipment. But it is important that an 802.11ac AP, adjacent to older APs, is a good neighbor. 802.11ac has a number of features for co-existence, but the main one is the extension of an 802.11n technique: A multipart RF header that uses 802.11a and 802.11n modulation. Non-802.11ac equipment can read these headers and identify that the channel will be occupied for a given time, and therefore can avoid transmitting simultaneously with the very high throughput frame. So 802.11ac is backward compatible with legacy 802.11 standards and can be deployed in mixed environment with legacy APs. Protection, Dynamic Bandwidth, and Channelization When an 80-MHz 802.11ac network operates in the neighborhood of an older AP, or a network that is only using a 20 MHz or 40 MHz channel, it must avoid transmitting simultaneously with a station in the neighboring network. The question here is as to how this can be achieved without permanently reducing its channel bandwidth. The solution lies in answering these three questions: 1. How can a station (AP or client) that wants to operate at 80 MHz, warn older stations to stay off the air while it is transmitting in 802.11ac mode, which they cannot decode? 2. How will the 802.11ac station know that the full channel is clear of other stations’ transmissions? 3. Finally, how can bandwidth usage be optimized if, for instance, an older station is transmitting in just 20 MHz of the 80-MHz 802.11ac channel? Figure 12 Dynamic Bandwidth Operation, 80 MHz Channel Sending a warning to other stations to stay off the air is achieved by Request to Send (RTS) frames. The 802.11ac station sends out multiple parallel RTS protection frames in each of its 20 MHz channel (out of the 80 MHz channel), at rates an 802.11a or 802.11n clients can understand. The multiple RTS frames use duplicate,
  19. 19. quadruplicate, or octuplicate transmission. Before sending RTS, it performs clear channel assessment (CCA) to make sure it cannot hear any transmissions in progress. On receiving the RTS frame, older stations know how long to wait for the 802.11ac transmission. Next, the recipient runs a CCA in each of the 20 MHz channels. The RTS frame format is extended so that the originator can indicate its channel options and replies with a Clear to Send (CTS) response to indicate whether it hears transmissions in progress from any neighboring network. If not, the originator transmits the data frame using the full bandwidth – 80 MHz in this case. However, if the recipient does find transmissions in progress on any secondary channel, it can still continue responding with CTS, while indicating which primary channels are clear (20 MHz or 40 MHz). Then, the originator can send its transmission using only the usable part of the 80 MHz channel. This may force a reduction in channel from 80 MHz to 40 MHz or even 20 MHz, but the frame will be transmitted using airtime that would otherwise be unused. This feature is called dynamic bandwidth operation. Dynamic bandwidth optimization is constrained by 802.11ac definitions of primary and secondary channels. For each channel, such as an 80 MHz channel, one 20 MHz channel (subchannel) is designated as primary. This is carried through from 802.11n, and in networks with a mix of 802.11ac and older clients, all management frames are transmitted in this channel so that all clients can receive them. The second part of the 40 MHz channel is called the secondary 20 MHz channel. And the 40 MHz of the wide channel that does not contain the primary 20 MHz channel is the secondary 40 MHz channel. Data transmissions can be in the primary 20 MHz channel, the 40 MHz channel including the primary 20 MHz channel, or the full 80 MHz channel, but not in other channel combinations. Figure 13 Dynamic bandwidth and Channelization in 802.11ac, 80 MHz Channel Finally, the introduction of wideband channels, especially the 80 + 80 MHz channels, requires some changes to the channel switch announcement (CSA) frame. CSA is used by an AP to inform its associated clients when it is about to switch channels after radar has been detected in the current channel. It was first introduced in 802.11h as part of Dynamic Frequency Selection (DFS). Otherwise, the operation of DFS remains unchanged with 802.11ac. Aruba 802.11ac Networks 802.11ac Features and Benefits | 21
  20. 20. Aruba 802.11ac Networks 802.11ac Planning and Deployment Guidelines | 23 Chapter 4 802.11ac Planning and Deployment Guidelines This chapter provides guidelines to plan and deploy 802.11ac WLAN network. In general, 802.11ac deployment can be divided into the following two categories: Greenfield:This is a deployment scenario where a network is being installed from scratch. There is no legacy network in place, which means you can design a network with future technology support in mind. A campus that does not have a wireless network today would be considered a Greenfield environment. Brownfield:This is a scenario where a legacy wireless network already exists and there is plan to deploy 802.11ac. Because there is a dependency on how the network can be designed, a phased approach is typically adopted to roll out new technology. A campus already having 802.11 a/b/g- or 802.11n-based wireless network, and requiring you to implement 802.11ac is an example for a mixed environment. Deployment recommendations might vary slightly based on the environment under consideration. If you are going through a refresh cycle to transition to 802.11ac network from legacy network, Aruba recommends consideration of the following points before doing a one-to-one replacement of legacy APs with 802.11ac APs: l If the existing network is a capacity-based design in 5 GHz band, then one-for-one AP replacement with 802.11ac AP is viable. l If the existing network was originally planned for legacy 802.11a/b/g or is an 802.11n network planned for 2.4 GHz based on coverage, then a network redesign is recommended. Redesigning includes a combination of both physical and virtual survey. Other factors to consider when planning for one-to-one replacement of legacy APs are: Original AP density: If the answer to any of the following questions is yes, then one- to-one replacement might not be a recommended best practice: l Is your current network planned for coverage as opposed to capacity? l Is there any coverage hole in your environment where you do not receive RF signals with current deployment? l Are there any known RF-related issues such as poor connectivity and low performance? l Do you want to provide seamless roaming experience to users? l Do you need location-based services? l Is there any architectural change in you facility like new walls or metal cabinets, which are resulting in poor Wi-Fi connection? Number of devices on the network: Number, type, capabilities, and mix (for example, single stream vs multiple stream, 802.11a/b/g or 802.11n or 802.11ac) of devices that are expected to be part of the network can be a good metric to identify how many APs you need in you network. If number of devices on your network increases, you will need to add more APs to support them, or otherwise there will be a drop in network performance and users will start complaining for poor service. Also, you need to ensure what type of devices you expect on your network. 802.11ac clients are much faster and take less airtime compared to legacy clients. Application type: You need to decide on what applications you want to support on your network. Enterprise applications like Microsoft Lync carry real-time voice and video traffic, which is delay-sensitive and requires thorough planning regarding AP placements. Depending on different applications you want to support on your network, identify how much bandwidth is required for each device. When you know the total number of devices on your network and the bandwidth required per device to support applications, you can plan on the number of clients associating per AP and total AP density required to cover the entire facility.
  21. 21. 24 | 802.11ac Planning and Deployment Guidelines Aruba 802.11ac Networks Although Aruba APs can support up to 255 client devices per radio, in general it is recommended to plan for 40 to 60 clients per radio so as to provide good user experience. ArubaOS firmware version 6.4 and later used on 7200 and 7000 Series controller supports AppRF, a deep packet inspection feature that allows you to classify and enforce policies on the applications running on your network. AppRF supports more than 1400 applications and allows network administrators to create policies for blocking or permitting applications depending on your network policy. You can also create bandwidth contracts to throttle traffic or apply Quality of Service (QoS) to prioritize application based on your use cases. Aruba Networks, Inc., supports Microsoft Lync Software-Defined Networking (SDN) API. This provides visibility into Microsoft Lync traffic and helps prioritize Microsoft Lync traffic with respect to other background traffic so that users can have high-quality voice and video calls. With SDN API, the Aruba Controller gets the real-time Microsoft Lync call quality metrics from the Microsoft Lync servers. This allows network adminstrators to quickly identify and troubleshoot issues related to Microsoft Lync voice and video calls. If any type of voice, UCC, or multicast applications are to be used over the Wi-Fi infrastructure, this will help drive the design criteria. After having understood the AP density requirements, the best practices and recommendations to deploy 802.11ac network using Aruba controllers and APs are provided in the following sections. This chapter covers the following sections: l Wired Network Considerations l RF Planning l Forwarding Mode Recommendations l Channel Width Selection l Capacity Planning Wired Network Considerations This section provides guidelines that will help you plan and design your wired network infrastructure to support the deployment of 802.11ac wireless network. AP Power Requirements An important consideration while choosing the wired access switch for powering the 802.11ac APs is the Power over Ethernet (PoE) capability. It is recommended to use 802.3at-capable (PoE+) switches at access layer to supply power to the APs. Although Aruba APs support full 802.11ac functionality with 802.3af (PoE) power source, the AP-220 Series operates with some reduced capabilities in 2.4 GHz band. 802.11ac-Capable AP Model 802.3af (PoE) 802.3at (PoE+) AP-224/ AP-225 5 GHz: 3x3:3 2.4 Ghz: 1x3:1 USB port: disabled Second Ethernet port: disabled 5 GHz: 3x3:3 2.4 GHz: 3x3:3 USB port: enabled Second Ethernet port: enabled AP-214 / AP-215 5 Ghz: 3x3:3 2.4 Ghz: 3x3:3 USB port: disabled Second Ethernet port: N/A 5 Ghz: 3x3:3 2.4 Ghz: 3x3:3 USB port: enabled Second Ethernet port: N/A AP-204 / AP-205 5G Hz: 2x2:2 2.4 GHz: 2x2:2 USB port: N/A Second Ethernet port: N/A 5 Ghz: 2x2:2 2.4 Ghz: 2x2:2 USB port: N/A Second Ethernet port: N/A Table 6: Capabilities of Aruba 802.11ac APs with respect to 802.3af and 802.3at power source
  22. 22. AP Uplink Considerations In theory, the dual band throughput of 802.11ac APs can exceed 1Gbps, as the maximum theoretical data rate in 5 GHz is 1.3 Gbps (802.11ac) and that in 2.4G Hz (802.11n) is 216 Mbps, assuming the recommended 20 MHz channel width for 2.4 GHz. We do not expect the actual throughput seen on the wired network to reach that limit in any 802.11ac Wave 1 deployment. Therefore, extending an additional Ethernet cable is not an absolute requirement today with the first generation 802.11ac deployment. However, in a Greenfield deployment where contractors are hired to extend cables to APs for the first time, it might be a good idea to think about the extending 2 x Ethernet cables per location to make the network future-proof. For an enterprise where wireless is the primary method of network access, this second Ethernet cable can be used today with AP- 220 Series for providing PoE redundancy. In such deployments, when the switch terminating eth0 port of AP fails, the AP can reboot and come up again using eth1 port terminating at a redundant switch. Figure 14 AP Uplink Consideration At the minimum, the cabling infrastructure in your network should be using Cat 5e cables. However if this is a Greenfield deployment and if you can afford to deploy Cat 6a cables, that will allow your network to be future- proof. Access Network Uplink Consideration Because 802.11ac is all about gigabit Wi-Fi, it is important that the supporting infrastructure is optimized to leverage all that 802.11ac APs have to offer. To support an increased throughput without making the switches at various layers (access, distribution, and core) a bottleneck, sizing the distribution network to provide sufficient end-to-end bandwidth for the given number of APs and devices as well as peak throughput is critical. The uplink recommendations for 802.11ac WLAN network are as follows: l Have a gigabit connectivity between AP and Access switch. l Uplink from access switch to the distribution switch should be 10 Gbps link. l If high availability is important to your network, have redundant 10 Gbps uplink between the access and distribution switches. l It is recommended to plan for a minimum of redundant 10 Gbps uplink from the controller. Link aggregation recommendations to support 802.11ac from the access layer to the core are a network best practice. The oversubscription offered is a common practice and really not a problem. Aruba 802.11ac Networks 802.11ac Planning and Deployment Guidelines | 25
  23. 23. 26 | 802.11ac Planning and Deployment Guidelines Aruba 802.11ac Networks Figure 15 Access Network Uplink Consideration Jumbo Frames With the advent of 802.11ac networks, the key factors for its improved performance over 802.11n are A- MSDU and A-MPDU, both of which aggregate services and MAC information. With an optimum aggregation level, an 802.11ac wireless frame is now a jumbo frame and is 4500 bytes or larger. Prior to the 802.11ac standard, the majority of the traffic fitted in a ‘normal’ 1500 byte Ethernet frame and no special handling was required on the wired network to achieve maximum aggregate performance. With the increased aggregation with 802.11ac, the underlying network needs to be able to support end-to-end jumbo frames; otherwise, the benefits of aggregation efficiency over the air will be lost due to fragmentation. So it is recommended to enable end-to-end jumbo frame support on your network to get the maximum 802.11ac performance. VLAN Design When you are planning for a VLAN design of your network, it is recommended to separate your wireless VLANs from wired VLANs, as this will eliminate unnecessary broadcast/multicast traffic in wireless VLANs and improve network performance. Figure 16 Wired and Wireless VLANs Wireless VLAN Design When you are planning a VLAN design for wireless clients, it is recommended to have a flat single VLAN design. Single VLAN configuration simplifies network design and works well on IPv4 and IPv6 networks especially in large campus design with thousands of users. It also simplifies network access configuration and hence makes network operation and maintenance much easier. In addition to single VLAN design, Aruba has an option to use VLAN pools. VLAN pool is a group of equal-sized VLANs that can be referenced as a single entity. A VLAN pool can be associated with an interface to allow for devices that are connecting via the interface to obtain an IP address from that pool of addresses. VLAN pools are used for networks where using a single VLAN option is not feasible due to IP address limitation. However, if you want IPv6 support on your network, it is not recommended to use VLAN pools. With IPv6, most clients use Stateless Address Auto Configuration (SLAAC) for address derivation, where the router announcements (RA) are sent as multicast packets to all clients. With Multiple VLANs in a VLAN pool and an IPv6 subnet associated with each VLAN in the pool, each client gets multiple RAs and can pick up any of the RAs
  24. 24. and derive an address from it. There is a very high probability that a client may pick an address in a VLAN that we did not associate it with. This breaks IPv6 connectivity. So Aruba recommends using a single flat VLAN for wireless clients. To optimize the wireless performance, it is recommended to use broadcast/multicast (BC/MC) optimization knobs of Aruba controller to prevent unnecessary broadcast/multicast traffic from occupying spectrum bandwidth. For more details, see the Broadcast/Multicast optimization section in Chapter 5: WLAN Optimizations. RF Planning When you are planning to deploy a WLAN network, it is important to understand how and where your APs will be mounted to have a seamless Wi-Fi experience. You should identify the attenuation and interference sources in you environment, which can degrade your network performance. Following section provides RF planning guidelines to deploy an 802.11ac WLAN network. AP Mounting Recommendations Indoor APs are typically deployed in either of the following methods: l Ceiling mount deployment l Wall mount deployment Aruba recommends against desk or cubicle mounts. These locations typically do not allow for a clear line-of- sight throughout the coverage area, which in turn can reduce WLAN performance. Ceiling Mount Deployment The majority of modern WLAN deployments are at the ceiling level. A ceiling deployment can occur at or below the level of the ceiling material. In general, it is not recommended to mount APs above any type of ceiling material, especially suspended or “false” ceilings. There are two reasons for this: First, many ceiling tiles contain materials or metallic backing that can greatly reduce signal quality. Second, the space above the ceiling is full of fixtures, air conditioning ducts, pipes, conduits, and other normal mechanical items. These items directly obstruct signal and can harm the user experience. Figure 17 Ceiling mounted Access Point Wall Deployment Wall deployments are not as common as ceiling deployments, but are often found in hotels and dormitory rooms. Walls are a common deployment location for large spaces such as lecture halls because reaching the ceiling is difficult. Wall deployments may also be preferable in areas with a hard ceiling where cabling cannot be run. If you are not using the AP-103Hor AP-205H, which was designed for wall mounting, consider the antenna pattern before you deploy wall-mounted APs. Aruba 802.11ac Networks 802.11ac Planning and Deployment Guidelines | 27
  25. 25. 28 | 802.11ac Planning and Deployment Guidelines Aruba 802.11ac Networks Figure 18 Wall Mounted Access Point Site Survey One of the important steps in RF planning is site survey analysis, which helps to identify AP placements to provide high-quality wireless experience throughout the facility. There are different types of site survey methods available such as virtual site survey, passive site survey, active site survey, and spectrum clearing site survey. A virtual site survey, which is generally done using softwares like Aruba’s VisualRF Plan, can be a good starting point to identify the coverage pattern. It can generate heat map showing RSSI values and can also help in generating bill of material (BoM) for your project. Although virtual site survey is a quick way to simulate AP placements and understand coverage patterns, it is recommended to conduct a physical site survey to validate the estimates of virtual site survey and verify the coverage and capacity of your network. For more details regarding wireless site survey, refer to the indoor site survey and planning VRD available at: http://community.arubanetworks.com/t5/Validated-Reference-Design/tkb-p/ArubaVDRs. When conducting site survey to plan for AP placements for a ubiquitous Wi-Fi coverage, it is important to remember that RF signals with higher frequency cover short distance compared to the low-frequency signals. You should plan your network in such a way that the 5 GHz band signals cover the area where you need to provide Wi-Fi to the users. If you plan the network based on 2.4 GHz band coverage, you might create a coverage hole as shown below. Figure 19 Comparison of 2.4 GHz and 5 GHz coverage pattern Aruba Recommendations for AP Placements AP placement recommendations for an enterprise network, which needs to support high-performing 802.11ac network along with real-time voice and video applications, are as follows: l Distance between two APs should be approximately 40 to 60 feet. l Minimum RSSI should be -65 dBm throughout the coverage area.
  26. 26. l SNR should be greater than 25 dB. l APs should be deployed in a honeycomb pattern as shown in the following diagram. This pattern ensures that distance is normalized along all directions to have the best coverage. Figure 20 Honeycomb Pattern AP Deployment The AP placement recommendations will vary if you are planning for ultra-high density environment such as conference halls, auditoriums, and public venues. For more information on these types of deployments, refer to “Very High Density 802.11ac Networks Validated Reference Design” guide available at: http://community.arubanetworks.com/t5/Aruba-Support-Documentation /tkbc- p/ArubaSupportDocumentation?_ga=1.65699885.224949537.1405570350 When you design an 802.11ac network using dual band APs in such a way that 5 GHz band signal covers the entire facility, it might create co-channel interference (CCI) in 2.4 GHz band. This is because 2.4 GHz signals have greater coverage range compared to 5 GHz signals. To avoid this scenario, you can disable the 2.4 GHz radio on some of the APs on your network as show in the following figure. Figure 21 Mitigating CCI in 2.4 GHz band Aruba 802.11ac Networks 802.11ac Planning and Deployment Guidelines | 29
  27. 27. 30 | 802.11ac Planning and Deployment Guidelines Aruba 802.11ac Networks In this figure, as 3 APs are enough to have a 2.4 GHz coverage, you can disable the 2.4 GHz radio on AP-4 to avoid co-channel interference. You can use the 2.4 GHz radio on AP-4 either as a dedicated spectrum monitor to collect spectrum analysis data or as a dedicated air monitor to perform wireless intrusion detection and wireless intrusion protection. Factors Attenuating Wireless Signals It is important to understand the physical environment where we are planning to deploy 802.11ac WLAN because different materials have different attenuation characteristics which can impact the wireless performance. The following table compares the attenuation caused in 2.4 Ghz and 5 Ghz bands due to walls, glass window, or other such things. Indoor Environment Attenuation in 2.4 GHz Attenuation in 5 GHz Fabric, blinds, ceiling tiles Approximately 1 dB Approximately 1.5 dB Interior drywall 3–4 dB 3–5 dB Cubicle wall 2–5 dB 4–9 dB Wood door (Hollow –Solid) 3–4 dB 6–7 dB Brick/concrete wall 6–18 dB 10–30 dB Glass/window (not tinted) 2–3 dB 6–8 dB Double-pane coated glass 13 dB 20 dB Steel/fire exit door 13–19 dB 25–32 dB Table 7: Comparison of Attenuation Losses in 2.4 GHz and 5 GHz band Wi-Fi and Non-Wi-Fi Interference Sources One of the common causes of degradation in wireless performance is interference. It can be Wi-Fi interference caused by neighboring APs or a non-Wi-Fi interference caused by a microwave lying in break room. You should conduct spectrum analysis to identify any potential Wi-Fi or non-Wi-Fi interference in your environment which can result in poor user experience. Some of the known interference sources are shown in the following table. Wi-Fi Interference Source Non-Wi-Fi Interference Source l Your APs (overdesigned) l Somebody else’s APs (neighbor) l Muncipal Wi-Fi Network l iPhone Personal Hotspots l Neighboring clients l Faulty clients l Blue-tooth (headset, keyboards, mouse, speaker) l Microwave Oven l Cordless phones, mouse l Very strong out-of-band source (GSM tower/DAS) l Baby monitor l WiMax (2.5 GHz) l ZigBee (802.15.4) l Video or security cameras Table 8: List of Wi-Fi and Non-Wi-Fi Interference Sources
  28. 28. Aruba APs can act as a dedicated spectrum analyzer which will scan all the Wi-Fi channel in regulatory domain or it can at as a hybrid spectrum analyzer where the AP will serve clients and simultaneously scan the channel on which it is serving clients. For more details about Spectrum Monitors, refer to “Aruba 802.11n Networks Validated Reference Design” document available at: http://community.arubanetworks.com/t5/Validated-Reference-Design/tkb- p/ArubaVDRs. Forwarding Mode Recommendations For campus AP deployment, Aruba supports three different forwarding mode — Tunnel Mode, Decrypt-Tunnel mode, and Bridge mode. In general, bridge mode is not recommended to be used in campus environments. This section provides information on the most common AP forwarding modes and the recommended mode for 802.11ac deployments. Tunnel Mode The bulk of today's deployments utilize tunnel mode as the de-facto AP forwarding mode, where the AP sends the 802.11 traffic back to the controller. One of the advantages of the tunnel mode is centralized encryption of control and data traffic. That is, in this mode, the control and data traffic between the AP and the mobility controller is encrypted, which increases network security. Figure 22 Tunnel Mode Tunnel mode is our preferred mode of operation and has met the requirements of Aruba customers. As discussed earlier, with frame aggregation techniques, 802.11ac frame is now a jumbo frame. Without jumbo frame support, Aruba controller and APs with service set identifiers (SSIDs) in tunnel mode do not participate in A-MSDU negotiations and hence there will be an impact on performance. To achieve high performance, it is always recommended to enable jumbo frames end-to-end, that is your switches and routers should also support jumbo frames. The forwarding mode does not affect the controllers' maximum AP limit and performance, for example a 7240 controller can handle 2048 campus APs operating in tunnel mode without any performance issues. Aruba 802.11ac Networks 802.11ac Planning and Deployment Guidelines | 31
  29. 29. 32 | 802.11ac Planning and Deployment Guidelines Aruba 802.11ac Networks Decrypt-Tunnel Mode When an AP uses decrypt-tunnel forwarding mode, it decrypts and decapsulates all 802.11 frames from a client and sends the 802.3 frames through the GRE tunnel to the controller, which then applies firewall policies to the user traffic. When the controller sends traffic to a client, the controller sends 802.3 traffic through the GRE tunnel to the AP, which then converts it to encrypted 802.11 and forwards to the client. In decrypt-tunnel mode, the encryption/decryption of traffic happens at the AP. The mobility controller still acts as the aggregation point for terminating data traffic. In this mode, the AP-Client pair can take full advantage of A- MSDU and A-MPDU aggregation on the WLAN radio side without requiring the wired network to transport the jumbo frames, because the AP is performing all assembly aggregation and de-aggregation locally. Figure 23 Decrypt-Tunnel Mode The performance of decrypt-tunnel mode is equivalent to tunnel mode with jumbo frames enabled; however, there is no centralized encryption because the user data traffic is decrypted by the AP and sent to the controller through a GRE tunnel. Channel Width Selection At present, 802.11ac Wave 1 products can be deployed to transmit in 20 MHz, 40 MHz, and 80 MHz channels in 5 GHz band. To get the maximum performance, 802.11ac APs should be deployed to use 80 MHz channel width. However, as discussed earlier, in the US there are only 5 available 80 MHz channel out of which 3 channels require DFS support to protect radar operation. We can design a network using the available five 80 Mhz channels in 5 GHz band using DFS channels support; however, it might be a problem if there is radar interference near your environment, because when an AP operating in DFS channel detects a radar signal, it will disconnect the clients and move to a non-DFS channel. This will affect the users connected on that AP and might also create a co-channel interference with the neighboring AP, thereby degrading the network performance. Selection of channel width depends on site environment and network requirements. Some ultra-high density networks would even prefer deploying APs with 20 Mhz channel width so as to have more channel to reuse throughout the network without causing Wi-Fi interference. You should also consider the clients' capabilities when planning for deploying APs with DFS channels to verify if all of your clients support DFS channels. Even if some clients support DFS channel, they may not actively probe on those channels and only learn of them through passive scanning. This can lead to roaming issues. It is recommended to perform roaming test using different clients to analyze their roaming pattern with DFS channels.
  30. 30. With 802.11ac standard, Federal Communications Commission (FCC) allowed the use of Channel 144. However, legacy and 802.11n clients do not support Channel 144 and hence they cannot associate to the AP if its primary channel is Channel 144. So make sure when you plan for 80 Mhz channel, avoid using channel 144 as primary channel. General guidelines for channel width selection is as follows: Channel Width Selection for Greenfield Deployments: When planning for Greenfield deployment, you can go with 80 Mhz channel width deployment; however, DFS channels need to be assessed on a case-by-case basis. Certain verticals like healthcare try to avoid deploying APs in the DFS channel to avoid radar-triggered channel shifts, given that mission-critical services like heart rate monitors and IV pumps are running on Wi-Fi. In case where use of DFS channels is not feasible either due to regulatory domain constraints or due to radar interference, it is recommended to use 40 MHz channel width so that more channels are available for reuse. Channel Width Selection for Brownfield Deployments: In a Brownfield deployment, where the customer is migrating from a legacy 802.11a/b/g/n AP to 802.11ac AP and there will be a mix of Wi-Fi technologies, you can utilize 80 MHz or 40 Mhz channels. If you are utilizing the wider 80 MHz channels, then you should perform interoperability tests with a sample set of your client devices to ensure that the legacy clients do not cause implementation issues. In such case, you would need to limit your network to 40 MHz channels until your clients are updated. This is more pronounced in environments such as universities, where the IT department does not have control over the devices that users bring in. For environments where IT has control over the device, it is recommended to update the client wireless chipset driver to the latest version and run some tests between 802.11n and 802.11ac APs when 802.11ac is deployed using 80 MHz channels. It is also recommended to deploy the new 802.11ac APs together in an area rather than a mix (salt and pepper) of legacy and 802.11ac APs. Capacity planning When planning for capacity, the most important things to consider are how many devices will access the network and what will be the type of client mix. Generally, people carry at least three devices – for example, a laptop, a tablet, and a smartphone. The number of devices per user also has ramifications in the design of VLANs and subnets. Expected number of active devices trying to access the network will be one of the metrics to calculate the required AP density. When calculating AP density for a capacity design, plan to have around 40 to 60 active devices per radio. Although APs can support 255 associated devices per radio, having less users will allow facilitation of bandwidth requirements and provides for high quality user experience. It is also important to select right devices to support your network requirements. Aruba Networks, Inc., have a wide portfolio of Controllers and APs that allows you to select the best combination of devices to meet your network requirements. For detailed information about WLAN products, refer to http://www.arubanetworks.com/products/. Active devices are the clients which are associated to the AP and actively sending and receiving data on the wireless network. Associated devices are clients that are just associated to the AP and might not be involved in active data transfer activity. As can be seen from the following figure, typically in a capacity-based design, you will have to deploy more APs compared to coverage-based design. In a capacity design, users are generally associated with high data rates and get better wireless experience. Aruba 802.11ac Networks 802.11ac Planning and Deployment Guidelines | 33
  31. 31. 34 | 802.11ac Planning and Deployment Guidelines Aruba 802.11ac Networks Figure 24 Capacity Planning Capacity planning along with Aruba’s unique features like Adaptive Radio Management and ClientMatch allows clients to associate at higher data rates. Parameter Recommendation AP forwarding mode Tunnel mode Distance between APs Neighboring APs should be 40 to 60 feet apart AP mounting Ceiling mount or wall mount Channel width recommendation 80 MHz channel will give maximum performance but will require DFS support. Consider using 40 MHz or 20 MHz channels in 5 Ghz band to have better channel separation. Number of devices per radio 40 to 60 active client devices Power It is recommended to use PoE+ enabled switches to power the APs. AP Uplink 1 Gpbs link between AP and access switch Access Switch Uplink 10 Gbps uplink for access switch terminating APs Controller Uplink At least 10 Gbps uplink with redundancy VLAN design Single Flat VLAN design is recommended along with the broadcast/multicast optimization configuration. Jumbo Frame support Enable end-to-end jumbo frame support. Ethernet cable At least Cat 5e cable is needed. Cat 6 would be preferred if cost is not an issue. Table 9: Summary of Aruba recommendations
  32. 32. Aruba 802.11ac Networks WLAN Optimizations | 35 Chapter 5 WLAN Optimizations This chapter provides guidelines and recommendations on some of the unique features supported by Aruba’s WLAN architecture to optimize WLAN network performance. We will provide recommendations for following topics: l Adaptive Radio Management (ARM) l ClientMatch (CM) l Broadcast/Multicast Optimization l Dynamic Multicast Optimization l Traffic Shaping l QoS Adaptive Radio Management (ARM) Radio Frequency (RF) spectrum is a limited and shared resource, and as many factors as possible must be controlled to provide an optimal user experience. ArubaOS supports Adaptive Radio Management (ARM) feature that allows WLAN infrastructure to make decisions about radio resources and client connections without manual intervention by network administrators or client-side software. Aruba APs or Air Monitors (AM) periodically scan the networks to gather information about the RF environment. This information is then fed to the ARM algorithm that optimizes the network and improves the user experience. ARM is a part of the base ArubaOS™ and is available on all Aruba Mobility Controllers and APs. One of the important functions of ARM is to dynamically select channel for the APs as a means to avoid Wi-Fi and non-Wi-Fi interference and to adjust transmit power so as to mitigate the issues of coverage hole and optimize network performance. Channel and Power Settings Initially, when 802.11n WLANs were introduced, network administrators had to manually build a channel and power plan based on onetime site survey. The following figure shows a typical 2.4 Ghz RF channel plan where the network engineer must manually change the power and channel on each AP. Remember that in the 2.4 GHz band, only three channels are practical for use in most regulatory domains. A similar plan exists in the 5 GHz band, but generally more channels are available.
  33. 33. 36 | WLAN Optimizations Aruba 802.11ac Networks Figure 25 Typical Channel Plan 20 MHz channel width After all the APs are configured, they will remain in this state until the administrator changes them manually. The problem with manual channel plans is that they were based on a snapshot in time of the RF environment. The presence of devices, walls, cubes, office doors that open and close, microwave ovens, and even the human body, all have an effect on the RF environment. This fluid environment generally cannot be tested and compensated for in a static channel and power plan. First of all, it is very time consuming to configure each and every AP on the network manually. Additionally, the static plan does not automatically work around AP failure and new sources of interference. If an AP in a particular area fails, the administrator will have to manually increase power on the surrounding APs to compensate for the RF “hole” until that AP can be replaced. If persistent interference makes a channel unusable, that AP must be configured with a new channel. New channels typically have a cascade effect and require that changes be made to other adjacent APs in the area, eventually propagating through the entire local wireless network. Consider the scenario shown in the following figure, when a wireless camera interferes with the AP's channel, the entire plan must be adjusted to compensate. Figure 26 Dynamic Channel Selection Using ARM to Avoid Interference At the most basic level, ARM allows the network to consider Wi-Fi and non-Wi-Fi interference and other APs before it configures power and channel settings for APs. APs and AMs continuously scan the environment. If an AP goes down, ARM automatically fills in the “RF hole.” ARM increases power on the surrounding APs until the original AP is restored. When the AP is restored, ARM sets the network to the new optimal setting. If an interfering device (Wi-Fi or non-Wi-Fi) appears on the network, such as a wireless camera that consumes a channel, ARM adjusts the AP channels appropriately.
  34. 34. The important thing here is that the Aruba WLAN controller learns networkwide information and takes decision dynamically to change channel and power of the APs to avoid interference and improve network performance. ClientMatch There is a better understanding of all the improvements that come with 802.11ac standard and how clients can get higher data rates. Even though clients can achieve high speeds, it is difficult to ensure that each client in a network has a good user experience especially when we have smartphones, tablets, and other clients that control their own connectivity and roaming decision. Prior to ClientMatch, clients were steered to the best AP only during the initial association. In case of any RF environment changes, for example if SNR or signal level of client falls below a certain level, the AP will not make any intelligent decision on steering the client to a better AP and will rely on clients to make its own decision. Similarly, during roaming scenario, some clients stick to an old AP even when it can hear another AP with better signal strength. This can result in poor connectivity and can bring down the performance of other associated clients on that AP. ClientMatch technology from Aruba Networks, Inc., is a patented, standards-based RF management technology that puts the WLAN infrastructure in control of client connectivity and roaming. Leveraging a system-level view of the network, ClientMatch monitors clients and automatically matches them to the right radio on the right AP, boosting the overall WLAN performance and delivering a consistent, predictable performance to every user and client, while eliminating the sticky client problem for good. ClientMatch is an ArubaOS function and no software changes are required on the client side to achieve this functionality. ClientMatch works with all clients, including all the latest 802.11ac clients across all operating systems. ClientMatch is supported on ArubaOS 6.3.0 and later firmware versions. ClientMatch leverages industry standards to accomplish its monitoring and control functions, including the 802.11k and the 802.11v standards. As a result, IT is assured of interoperability with no additional overhead. ClientMatch Capabilities ClientMatch has number of capabilities that enables it to connect the client to the best AP and improve the user experience. In general, here are some of the client/AP mismatch conditions that are managed by ClientMatch. Band Steering Dual band clients scan all the channels on both 2.4 GHz and 5 GHz radios and may attempt to connect to the basic service set identifier (BSSID) with the strongest signal or the BSSID that responds first to the client’s probe request. This sometimes results in a client connecting to an SSID in 2.4 GHz at lower PHY rates when it could connect to the same SSID in a clear 5 GHz channel at better PHY rates. In such scenarios, the ClientMatch band steers clients to the appropriate band. Figure 27 Band Steering Sticky Client Steering Once attached to an AP, many clients tend to stay attached – even when users begin to move away from the AP and WLAN signal weakens. As a result of this stickiness, performance for mobile users and clients often Aruba 802.11ac Networks WLAN Optimizations | 37
  35. 35. 38 | WLAN Optimizations Aruba 802.11ac Networks degrades, dragging down overall network throughput. ClientMatch intelligently steers such sticky clients to a better AP and improves user experience and overall network performance. Dynamic Load Balancing Dynamic Load Balancing enables APs and controllers to dynamically load-balance Wi-Fi clients to the APs within the same RF neighborhood on underutilized channels. This technique helps stationary and roaming clients in dense office environments, conference rooms, lecture halls, and environments that have high-bandwidth applications owing to client density being dynamically balanced among the APs in the same vicinity. ClientMatch performs dynamic load balancing and ensures that individual APs are not overtaxed and client performance is continually optimized, even in dense environments. All the features mentioned here work dynamically and improve client and network performance. Some of the benefits of ClientMatch are: l Faster network connections for individual clients, which translates to better overall performance for everyone. l Vastly improved performance for roaming smartphones, tablets, and laptops. l A standards-based solution that works with all client types, including 802.11a/b/g, 802.11n, and 802.11ac clients. l There is no need to purchase new clients or install new software. l Operates automatically, so there is nothing for IT to configure, monitor, or manage. l The network continuously optimizes client connections so overall network capacity and performance remains consistent. l Dramatically reduced help desk calls due to a better user experience. ClientMatch is enabled by default and supports band steering, sticky client steering, and dynamic load balancing features on AP-200 Series (802.11ac APs). The legacyArubaOS knobs to perform similar functions (band steering, client handoff assist, and spectrum load balancing) do not work with AP-200 Series. For more information on how ClientMatch configuration can be optimized for roaming, refer to the “RF and Roaming Optimization for Aruba 802.11ac Networks” VRD available at: http://community.arubanetworks.com/t5/Validated-Reference-Design/tkb-p/ArubaVDRs. Broadcast/Multicast (BC/MC) Optimization In the VLAN design section, we recommended using a single flat VLAN design for wireless users. In a high- density environment, this can create large broadcast domain. To control the unnecessary broadcast and multicast traffic from consuming airtime, Aruba recommends configuring the broadcast/multicast optimization knobs as discussed in the following table. Feature Default Value Recommended Value Comments Convert Broadcast ARP Requests to Unicast Enable Enable Helps to convert broadcast ARP and DHCP packets to unicast Drop Broadcast and Multicast Disable Enable Restricts all the broadcast and multicast traffic flooding into AP tunnels (“Convert Broadcast ARP to Unicast” feature must be enabled) Table 10: Recommendations for Broadcast/Multicast Optimization Knobs
  36. 36. AirGroup After you configure the broadcast/multicast optimization knobs, we drop the broadcast/multicast traffic in the air. However, in enterprise or campus deployments, multicast-based services like DLNA, MDNS, and other zero- configuration protocols are essential. To allow such services for AirPlay and Chromecast type of application, Aruba WLAN with AirGroup technology enables context-aware access to DLNA, Apple Bonjour, and other shared devices without constraining WLAN performance. When AirGroup is enabled, the controller maintains the list of the servers and clients that are using one of the multicast services. Each time a new client tries to access a service, or a server broadcasts the service, the controller stores it and proxy it on behalf of clients or servers. When you think about thousands of users in the campus environment and hundreds of servers, AirGroup can save significant bandwidth on wired and wireless side. Feature Default Value Recommended Value Comments AirGroup Disable Enable it if MDNS, DLNA or other zero-configuration services are needed. Allows AirPlay and Chromecast type of applications even if “drop broadcast and multicast” is enabled Table 11: AirGroup Recommendation Dynamic Multicast Optimization (DMO) AirGroup helps to allow and optimize multicast-based services like Airplay and Chromecast. However, in large enterprises or campus networks, there could be other type of multicast traffic that needs to be allowed. Many companies or universities have multicast video streams running in their network for business and educational purpose. There might be other custom applications that runs on multicast. To meet these requirements, Aruba controller provides knobs to optimize multicast traffic over the air. This section provides details about the following knobs: l Dynamic Multicast Optimization l Multicast Rate Optimization Dynamic Multicast Optimization The 802.11 standard states that multicast over WLAN must be transmitted at the lowest basic rate so that all the clients are able to decode it. The low transmission rate results in increased airtime utilization, and decreased overall throughput. Due to decrease in speed, it is advisable to transform multicast traffic to unicast when a few clients have subscribed to a multicast stream. Aruba 802.11ac Networks WLAN Optimizations | 39
  37. 37. 40 | WLAN Optimizations Aruba 802.11ac Networks Figure 28 Multicast Traffic Flow in WLAN With and Without Optimization The previous figure illustrates how Dynamic Multicast Optimization (DMO) parameter converts multicast packets to unicast and transmits it at a higher unicast rate over the air. In case of tunnel mode, the conversion is executed in the Aruba controller while in Decrypt-Tunnel mode, it is executed at the AP level. In Decrypt- tunnel mode, as conversion of multicast traffic to unicast is distributed across multiple APs, it is known as Distributed Dynamic Multicast Optimization (D-DMO). By default, DMO threshold has a default value of six clients. When threshold is reached, multicast traffic will be sent as is to other clients. The value of the DMO threshold should be high enough to match the expected number of clients on an AP. IGMP snooping or IGMP proxy needs to be enabled for DMO to work. IGMP refers to the Internet Group Management Protocol. Multicast stream should be prioritized by configuring uplink ACL and correct Wi-Fi Multimedia (WMM) parameter to match DSCP values. Multicast Rate Optimization Multicast rate optimization keeps track of the transmit rates sustainable for each associated client and uses the highest possible common rate for multicast transmission. For example, if all the clients connected to the virtual access point (VAP) are transmitting at a data rate of 24 Mbps or higher, multicast frames are transmitted at 24 Mbps, rather than the lowest basic rate, which ranges between 1 Mbps and 6 Mbps. Multicast Rate Optimization should be enabled along with DMO to optimize the multicast traffic when the DMO client threshold is hit.
  38. 38. Feature Default Value Recommended Value Comments Dynamic Multicast Optimization (DMO) Disable l Enable it if multicast streaming is needed. l Set DMO client threshold to 80. l Prioritize multicast stream using controller uplink access control list (ACL). l Converts multicast frames to unicast frames to deliver them at higher rates NOTE: l IGMP snooping or proxy needs to be enabled for DMO to work. Multicast Rate Optimization Disable Enable l Sends multicast frames at highest possible common rate l Enable it even if DMO is enabled. Table 12: Multicast Traffic Optimization Recommendation Depending on your network requirements, you will have to configure some or all of the following broadcast/multicast optimization knobs: l Convert Broadcast ARP Requests to Unicast l Drop Broadcast and Multicast l AirGroup l Dynamic Multicast Optimization (DMO) l Multicast Rate Optimization Traffic Shaping Wi-Fi uses a shared medium and is used by many different client types and applications. So, fair access to send data becomes critically important, especially during times of high contention amongst multiple clients. First, it is important that all clients receive access to that medium when they have data to transmit. At the same time, it is also important that high-speed clients can take advantage of their speed without being unduly slowed by legacy clients that unfairly consume airtime. Following traffic shaping policies can be applied to Aruba APs: l Default access: Traffic shaping is disabled, and client performance is dependent on MAC contention resolution. This might result in less-capable clients getting more time on the air than faster clients, thereby decreasing the aggregate network performance. l Fair access: Each client gets the same airtime, regardless of client capability and capacity. This option is useful in environments like a training facility or exam hall, where a mix of legacy, 802.11n ,and 802.11ac clients need equal amount of network resources, regardless of their capabilities. l Preferred access: In preferred access, more airtime is allocated to the clients with higher speeds – that is, 802.11ac clients will get more airtime compared to 802.11n and legacy clients. This mode gives the highest aggregate network performance but your legacy clients might get less performance. It is recommend to use fair access traffic shaping policy to provide equal airtime to each client irrespective of their 802.11 capabilities (Legacy vs. 802.11n vs. 802.11ac). Wi-Fi Multimedia and Quality of Service (QoS) Quality of service (QoS) is a set of packet markings and queuing mechanisms that prioritize classes of traffic through the network. Wi-Fi Multimedia (WMM) is based on the 802.11e amendment. It is a system for marking traffic as higher priority and adjusting the packet timers to allow delay-sensitive data to have precedence on Aruba 802.11ac Networks WLAN Optimizations | 41
  39. 39. 42 | WLAN Optimizations Aruba 802.11ac Networks the air. Streams that are commonly designated for special treatment include voice and video streams, where bandwidth, packet loss, jitter, and latency must all be controlled. End-to-End QoS For QoS and WMM to work effectively, they must be deployed end-to-end throughout the network. All components must recognize the packet marking and must react in the same way to ensure proper handling. Complete deployment of QoS ensures consistent delivery of data. With proper planning, high-quality voice and video can be achieved over the WLAN. The following figure shows how DSCP, 802.11p, and WMM marking is used in an Aruba deployment. Figure 29 QoS Segments The network uses WMM/802.11e mechanism on the wireless side, and DiffServ Code Point (DSCP) and 802.1p tagging mechanism on the wired side. WMM handles prioritization, queuing of packets, and servicing of queues. WMM also has additional power-save mechanisms to extend battery life. DSCP/802.1p tagging ensures appropriate delivery on the wired side of the network. To be effective, this tagging must be implemented throughout the network with the same values at all nodes. Aruba recommends you to enable WMM, if you are planning to support Voice/Video applications on your network. For detailed information about QoS over Aruba products and how we classify and prioritize traffic, refer to “Lync over Aruba Wi-Fi” validated reference design document available at: http://community.arubanetworks.com/t5/Validated-Reference-Design/tkb-p/ArubaVDRs. Feature Default Value Recommended Value Description Scanning Enable Enable l Enables AP to scan other channels Transmit Power 802.11a and 802.11g radio: Min 9/Max 127 Open Office: 5 GHz: Min 12/Max 15 2.4 GHz: Min 6/Max 9 Walled Office or Classroom: 5 GHz: Min 15/Max 18 2.4 GHz: Min 6/Max 9 l Sets the transmit power value NOTE: l The difference between minimum and maximum Tx power on the same radio should not be more than 6 dBm. l Tx power of 5 GHz radio should be 6 dBm higher than that of 2.4 GHz radio. Client Match Enable Enable l Optimizes user experience by steering clients to the best AP Table 13: WLAN Optimization Recommendations
  40. 40. Feature Default Value Recommended Value Description Convert Broadcast ARP Requests to Unicast Enable Enable l Helps to convert broadcast ARP and DHCP packets to unicast Drop Broadcast and Multicast Disable Enable l Restricts all the broadcast and multicast traffic flooding into AP tunnels (“Convert Broadcast ARP Requests to Unicast” feature must be enabled) AirGroup Disable Enable it if MDNS, DLNA or other zero-configuration services are needed. l Allows Airplay and ChromeCast type of applications even if “Drop Broadcast and Multicast” feature is enabled Dynamic Multicast Optimization (DMO) Disable l Enable it if multicast streaming is needed. l Set DMO client threshold to 80. l Prioritize multicast stream using controller uplink ACL. l Converts multicast frames to unicast frames to deliver them at higher rates l IGMP Snooping or Proxy feature needs to be enabled for DMO to work Multicast Rate Optimization Disable Enable l Sends multicast frames at the highest possible common rate l Enable it even if DMO is enabled Airtime Fairness Default Access Fair Access l Provides equal air time to all the clients WMM Disable Enable it if you want to prioritize voice/video traffic on your network. l Enables WMM capabilities to prioritize voice/video traffic Table 13: WLAN Optimization Recommendations Aruba 802.11ac Networks WLAN Optimizations | 43

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