The Hybrid Access Point Solution and new feature introduction The White Paper of Hybrid AP Technology Business AP

Transcription

1 The Hybrid Access Point Solution and new feature introduction The White Paper of Hybrid AP Technology Business AP Hybrid AP is benefits from a set of advanced wireless technologies that create its flexibility to adapt in various types of WLAN architectures that are most commonly deployed and allows for costs saving in the sense of total cost of ownership (TCO). This document is aimed primarily at helping network planners and sales engineers to understand the benefits brought by using Hybrid AP and the fundamental technology of Hybrid AP. However, professional services staff, system integrators, partners, and some customers may also find it useful. Customer Service Organization 05/12/2009

2 2 Hybrid Access Point Solution Overview During the past few years, deployment of wireless LAN (WLAN) is soaring in many of the business and education organizations as the laptops are becoming highly affordable. Furthermore, almost every notebook computer nowadays comes with build-in wireless client model. Wireless is the trend and mobile office is no longer an unreachable luxury solution. Wireless World Challenge Network facility maintenance is always a nightmare for the network administrator in the organization with large WLAN network. The first generation of usable, business-class APs was what we are now calling Fat, Smart, or Intelligent APs. These APs are designed to have everything onboard that is needed so that they can be connected to any Ethernet switch. These APs are not restricted to just supporting the wireless standards. Typically, they also support security and management features and, depending on the vendor, extra functionality to cope with fast roaming, for instance. To employ Fat AP over the medium/large size WLAN is absolutely not a great idea. Any slit change made over the wireless AP configuration or firmware upgrading, the network administrator has to configure each wireless AP one by one as no centralize management mechanism is employed. Unlike Hybrid AP, neither Stand Alone AP nor Wireless Switch does offer the flexibility from adapting capacity change or wireless LAN architecture change. Up front purchase costs and daily maintenance costs are hardly balanced out by using the Stand Alone AP and Wireless Switch solutions. As up front purchase costs of Stand Alone AP is comparably cheaper than those of Wireless Switch system, Fat AP is obviously a better solution if the organization is less demanding on WLAN capacity and the budget is limited. However, difficulties with maintenance become the major consideration of medium/big organizations running multiple wireless APs. All rights reserved 2009, ZyXEL Page 2

3 3 Hybrid Access Point Solution Various WLAN Network Architectures To understand the incentives for implementing the Hybrid APs and their operation in the network, it is useful to view the WLAN network architecture and the functions of the access points. Two types of WLAN network architectures are commonly deployed: Autonomous Architecture Centralized Architecture Note: This article uses the term Wireless Termination Point (WTP) to represent a generic AP and the term Access Controller (AC) to represent a generic WLAN control function implemented on a WLAN switch or stand alone wireless controller. Autonomous Architecture With the autonomous architecture, each of the WTPs can be independently managed as a separate network entity on the network. The WTPs completely terminate the traffic so that frames on the wired LAN are frames. The wireless access point in such architecture is often called a Fat AP or Thick AP. This is the most common solution for the smaller WLAN with few APs. Fat APs have commonly enhanced capacities such as Access Control List (ACLs), which filters the traffic from the specific WLAN client. Another significant capability of these devices is Quality of Service (QoS) function. For instance, traffic from the wireless stations may need to have a higher priority. You may need to insert an 802.1p or Differentiated Service Code Point (DSCP) for the traffic from the wireless stations. During the past few years, the popularity of centralized architectures with ACs and WTPs became more popular as it has provided network administrators with a structured control of multiple WTPs in the enterprise. All rights reserved 2009, ZyXEL Page 3

4 4 Hybrid Access Point Solution Centralized Architecture The centralized architecture involves a WLAN controller that is responsible for configuration, remote control and management of several WTPs. The WLAN is also known as the Access Controller (AC). The function is split between the WTP and the AC. The WLAN equipment manufacturers minimize the intelligence in the AP and centralize the intelligence of the network in the switch instead. Because the WTP in this model have a reduced function as compared to the autonomous architecture, they are also known as Thin APs or Lightweight APs. With this approach, relatively simple APs can share the features that enhance wireless communications in a cost-effective and efficient manner. As the thin APs do not implement much more than the standard, the extra processing power can be employed for providing optimum radio connectivity for wireless stations. Thin APs are often known as intelligent antennas that their primary job is to transmit and receive wireless traffic. They backward the wireless frames to a controller where the frames are processed before being switched to the wired LAN. In order to provide data security, Thin APs use a tunnel to backward the wireless traffic to the central controller. All rights reserved 2009, ZyXEL Page 4

5 5 Hybrid Access Point Solution Hybrid AP Solution What is Hybrid AP? Hybrid AP, known as the Hybrid Wireless Access Point, is a ZyXEL proprietary wireless access point technology capable of making wireless AP to switch between different roles within Autonomous Architecture and Centralized Architecture. With Hybrid AP technology, one single wireless access point can act as a Stand Alone AP (Fat AP), a Thin AP (Managed AP) or even an Access Controller (AC). All rights reserved 2009, ZyXEL Page 5

6 6 Hybrid Access Point Solution All rights reserved 2009, ZyXEL Page 6

7 7 Hybrid Access Point Solution ZyXEL Hybrid AP Triple-Mode Hybrid AP ZyXEL Hybrid AP technology is an All-In-One solution which offers 3 modes for users to choose from - Controller, Managed AP and Stand-Alone AP (e.g.nwa-3160, NWA-3163, NWA-3166, NWA-3500, and NWA-3550 series): Standalone AP (Fat AP) Managed AP (WTP) Access Controller (AC) Note: The default working mode of those AP products is stand-alone. Benefits of Hybrid AP There are many benefits of employing Hybrid AP technology: Simplify Installation and Daily Maintenance As AP management is centralized and configuration replication over different APs can be done by employing profile, managing multiple access points is as easy as managing a single AP. Flexibility from Budgeting and Future Expansion ZyXEL Hybrid AP technology is scalable and can easily adapt to different sizes of businesses. There is no need to build a costly centralized WLAN with stand-alone APs. With ZyXEL Hybrid AP technology, the customer can have WLAN controller and Access Point functionalities at the price of an access point. The same AP can simply be switched to controller mode as more Access Points are added. This can reduce the total cost of ownership (TCO) of a WLAN because of less expensive upgrades necessary for future technologies. Hybrid AP solution is ideal for any WLAN with initial scale from 3 to 24 APs. NWA-3160 series and NWA-3500 series Hybrid AP, supports access controller management mode and can manage another NWA-3160/3163/3166/3500/3550 APs. A Hybrid AP running as an Access Controller can manage up to 24 APs. This does not All rights reserved 2009, ZyXEL Page 7

8 8 Hybrid Access Point Solution include the Access Controller itself. When the Hybrid AP acts as an Access Controller, it can still manage its own wireless interface. Enterprise Class Design to Build Reliable Wi-Fi Network The communication between controller and managed AP is secured. All configurations are achieved through secured tunnel. As opposed to stand alone architecture, centralized management precludes the risk of configuration exposure or the risk of the AP being stolen since no configuration is actually stored on the managed AP. Control Protocol Employed by Hybrid AP (CAWAP) The CAPWAP is based on another standard named LWAPP. LWAPP Lightweight Access Point Protocol or LWAPP, same as CAWAP, is the name of a proprietary protocol that can control multiple wireless access points at once. This can reduce the amount of time spent on configuring, monitoring or troubleshooting a large network. The system will also allow network administrators to closely analyze the network. LWAPP was proposed by Airespace, as a standard protocol to provide interoperability among any brand of access point. Its purpose was to standardize "lightweight" access points with the Internet Engineering Task Force (IETF), but it was not approved as a standard. Airespace was purchased by Cisco Systems. Although this protocol has so far not been popular beyond the Airespace/Cisco product lines, it can also be found in analysis products from AirMagnet, who has recently implemented a software-based on this protocol to analyze Cisco wireless products. Note: Airespace was a networking hardware company founded in Cisco Systems acquired Airespace in CAPWAP The Control and Provisioning of Wireless Access Points (CAWAP) is the protocol defining the interface and protocol between an AP and its controlled WTP. The CAPWAP standard is another control protocol based on LWAPP. Over a year ago, the Internet Engineering Task Force (IETF) began a working group called CAPWAP the All rights reserved 2009, ZyXEL Page 8

9 9 Hybrid Access Point Solution Control and Provisioning of Wireless Access Points. The goal was to set a standard that could be used for "Thin APs" those wireless access points that would not only be centrally controlled, but would have most of their "smarts" residing on the central controller, usually a WLAN switch. Note: So far the CAPWAP protocol is still in draft stage. CAPWAP Functions The interface between the WTP and the AC is responsible for the following: RF Monitoring e.g. Radar detection, noise and interference detection, and measurement. RF Configuration e.g. for retransmission, channel selection, transmission power adjustment. WTP Discover and Select an AC AC Initiates Firmware Download to the WTP Upon Startup i.e. automatic loading and upgrading of WTP firmware for network wide consistency. When the firmware upgrade will be made? If the WTP s firmware is different from the firmware in the AC, AC sends its own firmware over to the WTP and upgrades it. Capabilities negotiation between the AC and the WTP The WTP provides details such as hardware, firmware, maximum number of radio, encryption capabilities, type of wireless radio (802.11b/g/a/n) support. Mutual authentication between the WTP and AC Configuration, status, statistics exchange between the WTP and the AC QoS tagging across the wire and wireless network Though CAPWAP does not define all the details, the AC conducts Radio Resource Management (RRM) and Rogue AP Detection based on configuration and monitoring the access points in its domain control. These functions vary according to vendor implementation. AC Discovery and Selection A WTP attempts to discover an AC to connect through broadcasting discovery request to the network domain, to which one or more AC can respond to Communication between the AC and WTP is through transport protocol User Data Protocol (UDP). The WTP determines which AC to connect to and then tries to All rights reserved 2009, ZyXEL Page 9

10 10 Hybrid Access Point Solution establish a secure session with the AC. What the other negotiation will be done between the AC and WTP: SSID Wireless Encryption Data Rate Wireless Channel Planning ZyXEL Specific Implementation: When a WTP sends discovery to the AC, you can configure the AC to accept the discovery automatically or manually. What is the purpose of accepting discovery message manually? The discovery request from the WTP is sent by broadcasting. As a result, you can never know which AC your WTP will subscribe to if there is more than one AC within the same subnet. WTP Configuration WTP configuration is used to push a specific configuration to the WTP and also to retrieve statistics from a WTP, for example: Amount of frames fragmented Amount of frames transmitted and received Number of retransmitted attempts and retransmitted failure count All rights reserved 2009, ZyXEL Page 10

11 11 Hybrid Access Point Solution Backup and Redundancy Support Backup In information technology, backup refers to making copies of data so that these additional copies may be used to restore the original after a data loss event. Redundancy This means having backup components which automatically "kick in" should one component fail. The term is most commonly used to describe computer-based systems designed to continue more or less fully operational with, perhaps, a reduction in throughput or an increase in response time in the event of some partial failure. In ZyXEL Hybrid AP series, the Access Controller working mode can be acted as two types, one being Primary Access Controller, and the other Secondary Access Controller. The Primary Access Controller will copy its configuration to the Secondary Primary Access Controller as backups. The managed APs can connect to Secondary Access Controller to continue the wireless service once Primary Access Controller is down (No power, internet disconnection, etc). Note: This feature has to work in the same device model and firmware V3.70 version. All rights reserved 2009, ZyXEL Page 11

12 12 Hybrid Access Point Solution Wireless Load Balancing Support Load balancing In computer networking, load balancing is a technique to spread work between two or more computers, network links, CPUs, hard drives, or other resources, in order to get optimal resource utilization, maximize throughput, and minimize response time. Using multiple components with load balancing, instead of a single component, may increase reliability through redundancy. The ZyXEL Hybrid AP series which support the wireless load balancing with two mechanisms. One is the connected station number, the other is the traffic level. Once one managed AP is overloaded, the client will try to connect to another unloaded managed AP for better stability and throughput performance. Note: This feature has to work in the same band, ESSID, security encryption and subnet. All rights reserved 2009, ZyXEL Page 12

13 13 Hybrid Access Point Solution Dynamic Channel Selection (DCS) Support The Dynamic Channel Selection (DCS) mechanism of Wireless technology determines whether a new channel between the AP and STAs within a particular basic service set (BSS) is needed; requests a channel signal quality measure to some of the plurality of stations by the AP; delivers a channel signal quality report back to the AP based on a received signal strength indication (RSSI) and a packet error rate (PER) of all channels detected by the stations within the BSS; selecting a new channel based on the channel quality report for use in communication between the AP and the plurality of stations. In ZyXEL Hybrid AP series, the APs will detect the sensitivity level (RSSI) in time intervals. Once sensitivity level achieves the setting rule, the channel will be changed, avoid wave interference with another AP and provide stable and good connection environment. All rights reserved 2009, ZyXEL Page 13

14 14 Hybrid Access Point Solution This article has provided the function and deployment of ZyXEL Hybrid AP by illustrating the architecture that relies on a centralized controller that is managing a group of wireless termination points (WTPs). It outlined some major aspect of the CAWAP control functions and the concerns occurring while implementing AC + WTP architecture. All rights reserved 2009, ZyXEL Page 14