- 論壇徽章:
- 0
|
請教wireless
Wireless has become pervasive both in the workplace and for personal use. There are multiple wireless technologies supporting different standards, often using different radio frequencies, having different range characteristics, and supporting different requirements—creating a lot of interest, but plenty of confusion, too. We went to Charlie Giancarlo, senior vice president and general manager of the Cisco commercial line of business and an industry expert on wireless technologies, for some clarification on this hot new area of technology.
News@Cisco: Why is there so much interest in wireless?
Giancarlo: Companies are beginning to understand that wireless represents a real leap in productivity for business users. Now that laptop users can connect wirelessly to the Internet or to their corporate intranets from a broad range of locations, they can get meaningful work done when they're away from the office. At the same time, wireless devices of all kinds, including cell phones and PDAs [personal digital assistants], are able to provide online access for a variety of simple applications, such as checking e-mail, getting stock quotes, making airline reservations, and so on. According to a recent Gartner report, people are instinctively mobile, and I agree with that. It's really liberating to have wireless as an option in so many different situations now. The flexibility and cost savings that wireless offer are other reasons for its rapid growth. A business with a wireless network can quickly and easily move its network from a smaller facility to a larger one, or vice versa, without doing a lot of costly and time-consuming rewiring.
News@Cisco: Will wireless eventually replace wired networks?
Giancarlo: I don't see wireless replacing wired networks at any time. As valuable as wireless is, bandwidth limitations prevent it from being able to handle the heavy traffic demands of many larger businesses or demanding users. Today, a wireless access point is basically an 11 Mbps hub, although data transmission rates will keep increasing over time. The transfer of large files, or usage by a large number of users at the same time, can significantly slow down the performance of a wireless LAN [local-area network]. So while wireless is definitely the right choice when mobility is the priority, wired networks aren't going away, and for good reason.
News@Cisco: What are 802.11a and 802.11b?
Giancarlo: The IEEE 802.11 committee established a standard in 1997 defining the physical layer options for wireless transmission and MAC [Media Access Control] layer protocol, initially with a data rate of only 2 Mbps. Newer standards supporting much higher rates of data transmission for wireless LANs are known as 802.11a and 802.11b. Both 802.11a and 802.11b can deliver data at distances of 100 feet or more from a wireless access point. 802.11b was actually introduced first. It is being used worldwide and is growing very rapidly. 802.11b operates in the 2.4 GHz band and currently supports data rates up to 11 Mbps but should increase to 22-plus Mbps in the near future. 802.11a uses the 5 GHz band and will support data rates up to 54 Mbps over the next year or two, rising to potentially 100 Mbps in the future.
News@Cisco: Should companies that haven't implemented wireless yet wait for 802.11a?
Giancarlo: A similar question several years ago would have been whether to forego implementing 10 MB Ethernet while waiting for 100 MB Ethernet. The choice of when to implement a technology should be based on existing need and the application's effect on corporate productivity during its lifetime. 802.11a will not obsolete 802.11b. Both can coexist in the same campus. Vendors such as Cisco will create migration products and strategies for our customers to make use of existing infrastructure in conjunction with new technologies. We expect that 802.11b will become a standard feature in many computers over the next several years before 802.11a becomes mainstream. 802.11b will be very attractive to many companies, and those using it will realize immediate benefits. And they will certainly have a head start over companies that wait.
News@Cisco: How is 802.11b different from Bluetooth, HiperLAN2, and 3G?
Giancarlo: Bluetooth is generally limited to personal wireless solutions, because it has a very short range and lacks the speed (it operates at less than 1 Mbps), power, security, and manageability that businesses need and can already get with the 802.11 technologies. Examples of Bluetooth applications include wireless keyboard, mouse, cellular headset, etc. However, due to its limitations as well as a lack of availability, Microsoft recently announced that it won't be supporting Bluetooth in the next major version of Windows, so Bluetooth is a technology that still has some maturing to do. HiperLAN2 is similar to 802.11a but specifies the HiperLAN MAC rather than the 802.11 MAC, and is supported mainly in Europe. "3G" is shorthand for third-generation wireless, a new mobile, cellular communications technology that will provide higher-speed access to Internet-based services than current cellular (2G) technology. Expected applications for 3G include WAP [Wireless Application Protocol], SMS [short message service], paging, Web surfing, etc. While there has been some discussion of 4G technology, this is an undefined term and generally means the wireless technology that might be expected to supersede 3G. 802.11 has sometimes been referred to as a 4G technology.
News@Cisco: Why would an enterprise want to use 802.11b versus other technologies?
Giancarlo: There are three reasons. The first is that 802.11b is the most common wireless technology in use for high-speed data. It is standards-based, meaning that there is a framework in place to test and certify interoperability between major vendors. The second reason is that 802.11b can use up to 128-bit encryption, thus allowing very secure transmission of corporate data. Finally, 802.11b was developed specifically in response to the industry's need for wireless LAN products operating at an Ethernet-like data rate of 11 Mbps, a speed that makes it viable for enterprises and other large organizations. If a company requires LAN services in a mobility application, then 802.11 is the right technology.
News@Cisco: We keep hearing about something called WiFi. What is it and what does it do?
Giancarlo: The Wi-Fi logo is a registered trademark of the Wireless Ethernet Compatibility Alliance, a group founded by Cisco, 3Com, Intersil, Agere, Nokia, and Symbol and now supported by more than 60 leading companies. The use of the Wi-Fi logo designates that a member company's wireless LAN product has been independently tested and certified as meeting the group's standards for interoperability. Wi-Fi products are based on the IEEE 802.11b WLAN standard.
News@Cisco: How secure are wireless LANs?
Giancarlo: Cisco offers a truly secure network using our 128-bit encryption option with LEAP authentication, which is built into each Cisco Aironet access point and network interface card. Cisco and Microsoft collaborated on developing the first standards-based, enterprise-class security architecture for wireless networks. This security solution was based on the IEEE 802.1x draft standard for port-based network access control with necessary modifications to support 802.11, and is deployed in the Cisco Aironet wireless LAN products. The Cisco Aironet solution provides scalable, centralized security management and supports dynamic single-session, single-user encryption keys integrated with network logon—what enterprises need for hassle-free security management of large and midsize wireless deployments. For example, Microsoft has about 3,000 access points in its Redmond campus and satellite branch offices. Currently, about 7,000 employees are using wireless LAN cards in their laptops, a number that is expected to grow to 20,000 by the end of the year. Employees can now get high-speed access to the Internet and corporate intranet anywhere within the Microsoft campus—a capability that Microsoft believes will yield a 30-minute productivity gain per employee per day. Results like these are helping fuel the growing demand for wireless LANs. |
|
免費注冊
發(fā)表于 2003-02-26 12:10
