tailieunhanh - Voic 802.11e over phần 5

Đói để truyền dữ liệu tăng đã thúc đẩy một loạt các nhà nghiên cứu để tìm kiếm các cách để tăng tốc độ công nghệ của họ. OFDM có một cách tiếp cận chất lượng tương tự như multilink PPP: Khi một liên kết là không đủ, sử dụng một số song song. | 7 Security and Early analog cellular phone systems were vulnerable to eavesdropping. As a result the adoption of that technology was not as fast as it might have been had good security been implemented by service providers. must overcome any user anxieties regarding security on the network. Fears of eavesdropping and fraud can dampen consumer enthusiasm for the service. This chapter describes security measures for networks and provides an assessment of the difficulty of hacking or otherwise compromising the security of networks. Unlike wired systems which can be physically secured wireless networks are not confined to inside buildings but can be picked up as far as 1 000 feet outside of the premises with a laptop and a gain antenna. This makes WLANs inherently vulnerable to interception. Knowing this the committee added a first line of defense called Wireless Equivalency Protocol. WEP is an encryption protocol that is designed to provide the same level of security that wired cables provide. The standard provides both 40- and 128-bit really only 104-bit encryption at the link layer using the RC4 algorithm which the . government allows to be exported. Electronics retailer Best Buy Co. ran into trouble in mid-2002 when customers who had purchased WLAN cards from Best Buy installed the cards in their laptops before they left the parking lot. The customers noticed unencrypted WLAN traffic that contained customer information and possibly credit card numbers. The Best Buy case provides an example of why enterprises should at a minimum encrypt their WLAN traffic with WEP. By year-end 2002 it had been estimated that 30 of enterprises would have suffered serious security exposures from deploying WLANs without implementing the proper 97 98 Voice over security 1 . The task force is currently working on extensions that will help secure the WEP. According to the Wi-Fi Alliance formally the Wireless Ethernet Compatibility .