SpectraLink NetLink Wireless Telephones Best Practices White Paper Wireless Telephone manuale d’uso

Deploying NetLink Wireless Telephones Best Practices White Paper Version 1.0 May 2004[...]

White Paper Page 1 1.0 Introduction Wi-Fi telephony is the convergence of wireless voice and data applications using a common Wi-Fi wireless LAN. Wi-Fi telephony bridges traditional te lecommunications, data communications, and mobile technologies. A Wi-Fi wireless telephone is a wirele ss LAN client device, using the same network technology as wir[...]

White Paper Page 2 2.1 Coverage One of the most critical issues in deploying NetLink Wireless Telephones is ensuring sufficien t wireless coverage. Often ent erprise Wi-Fi networks are designed on ly for data applications and may not provide adequate coverage for wirele ss telephone users. Quite often these networks are de signed to cover only area[...]

White Paper Page 3 voice is an application on the wireless LAN becau se the coverage area of the AP will be greatly reduced. I f a site requires config uring the APs to only negotiate at the h igher rates, the layout of the wireless LAN must account for the reduced coverage and additional A Ps will be required to ensure seamless overlapping coverag[...]

White Paper Page 4 and provides consistent coverage. 2.2.1 Si te S urveys Performing a site survey can minimize the po ssibility of dead spots. The AP equipment provider can usually perform a site survey. While many tools exist that allow customers to per form their own assessment, SpectraLink recommends that every site employ a pr ofessional site [...]

White Paper Page 5 2.3 Capacity The network capacity req uirements also factor into the number of APs required, although in most cases the coverage area is the prim ary factor. Data traffic is very bursty and sporadic , but data applications can tolerate network congestion with reduce d throughput and slower respon se times. On the other hand, voic[...]

White Paper Page 6 The maximum number of simult aneous telephone calls an AP can support is de termined by dividing the tot al available ba ndwidth by the percent age of bandwid th used for each individual call. Approximately 20- 40% of the AP bandwid th is reserved for channel n egotiation and association algor ithms, so 60-80% of the tot al avail[...]

White Paper Page 7 2.3.2 P ush-to-Talk Multic asting Considerations The push-to-talk (PTT) m ode of the NetLink i640 Wireless Te lephone uses SpectraLink’s proprietary SpectraLink Radio Protoco l (SRP) ADPCM encoding. If a PTT broadca st is active (i.e. a user presses the PTT button), the feature will use the bandwidth as indicated in th e table [...]

White Paper Page 8 User Calling Intensity Light Moderate Heavy Erlangs per User 0.10 0.15 0.20 Max Active Calls per AP Users Supported per AP (1% Blocking Probability) 1 1 1 1 2 2 2 2 3 4 3 3 4 8 6 4 5 13 9 7 6 19 13 10 7 25 17 13 8 31 21 16 9 37 25 19 10 44 30 22 11 51 34 26 12 58 39 29 Users Supported per Access Point Areas where more Wireless T [...]

White Paper Page 9 3.0 Networ k Infrastr uctur e Consider ations 3.1 Physic al Connections The NetLink Wireless Telephone infr astructure components should connect to the facility’s local are a network (LAN) using Ethernet switches, as opposed to Ethernet hubs, to provide adequat e bandwidth and limit traffic collision s. Ethernet switches should[...]

White Paper Page 10 Gateways, a separate TFTP server m ust be provided. Also, the NetLink SVP Server requires a separate TFTP se rver for software updat es. The NetLink Telephony Gateway cannot be used as a TFTP server for th e NetLink SVP Server code. NetL ink Telephony Gateways receive software updates only thr ough an FTP server.[...]

White Paper Page 11 4.0 Quality of Ser vice 4.1 SpectraLink Voice Pri ority (SVP) Quality of Service (QoS) is a means of guaranteeing a level of service that will result in a networ k connection of ad equate quality. Typically this results in providing d ifferent levels of service for d ifferent applications, depending on their req uirements. When [...]

White Paper Page 12 data transmission rate of 2 Mb/s. A NetLink SVP Server is requir ed for applications usin g an IP telephony server or using more than four NetLin k Telephony Gateways. A NetLink SVP Server can also be used with fo ur or f ewer NetLink Telephony Gateways to allow a maximum data transmission r ate of 11 Mb/s. A single NetLink SVP [...]

White Paper Page 13 5.0 Security 5.1 Security Concerns Security provisions are critical fo r any enterpr ise Wi-Fi network. Wireless technology does not prov id e any physical barrier to the network, since radio waves penetrate walls and can be monitored and accessed from outsid e a facility. The e xtent of security measure s utilized are typically[...]

White Paper Page 14 5.1.3 Em erging Security Standards Recognizing the need fo r stronger security st andards, the IEEE is developing the 802.11i standard, which is expected to be ratified in late 2004. The 802.11i st andard includes stronger en cryption, key management, and authentication mechanisms. An interim soluti on endorsed by the Wi-Fi Alli[...]

White Paper Page 15 the IP telephony protocol used on the telephony switch interface. The telephony switch vendor should be able to supply t he port numbers used by the protocol. The NetLink Wireless Telephones, Ne tLink Telephony Gateways, and NetLink SVP Server use TCP and UDP and other common IP protocols from time to time. These include DHCP, D[...]

White Paper Page 16 5.5 Virtual Private Networks (VPNs) Virtual Private Networks are secure d private network co nnections. VPNs typically employ some combination of en cryption, digital certificates, strong user authentication and access control to prov ide security to the traffic they carry. Th ey usually provide connectivity to many devices behi[...]

White Paper Page 17 6.0 NetLink W ireless T e lephones and Subnets Subnets are used to create a bo undary between network segments. Although these boundarie s are logical, they become somewhat of a physical boundary for mobile networ k devices moving throughout the enterprise. When a device wit h an es tablished IP data stream (such as with an acti[...]

White Paper Page 18 6.1 Subnets and NetLink Telephony Gateway Interfaces NetLink Wireless Teleph ones, NetLink Teleph ony Gateways, NetLink SVP Server(s), and the wireless APs must reside on the same subnet. One reason for this requirement is tha t the NetLink Wireless Te lephones use IP multicast messages to initialize the Wireless Telephone regis[...]