In 1985, the Computer Society of the IEEE started a project, called Project 802, to set standards to enable intercommunication among equipment from a variety of manufacturers. Project 802 is a way of specifying functions of the physical layer and the data link layer of major LAN protocols.
Chapter 13 introduces you to wired LANs: Ethernet. This chapter introduces wired local area networks. A wired LAN, viewed as a link, is mostly involved in the physical and data link layers. We have devoted the chapter to the discussion of Ethernet and its evolution, a dominant technology today.
The growth of the Internet, which I have been involved in, and the growth of mobile
telephone services, which NTT DoCoMo has been a leader in, have been peculiarly interlinked
and at the same time separate. The Internet is a lab experiment that broke free, and
finds itself in a world of its own contriving, which it often does not understand. The mobile
telephone world was developed for commercial purposes, and is in many respects the son of
its father, the wired telephone system.
WEP là từ viết tắt của Wired Equipvalent Privacy, nghĩa là bảo mật tương đương với mạng có dây (Wired LAN). Khái niệm này là một phần trong chuẩn IEEE 802.11. Theo Định nghĩa, WEP được thiết kế để đảm bảo tính bảo mật cho mạng không dây đạt mức độ như là mạng nối cáp truyền thống. Đối với mạng LAN (định nghĩa theo chuẩn IEEE 802.
Anatomy of slow download( cốt lõi của việc download chậm) .Tình huống: cả mạng download rất chậm.tiến hành: đặt wire lắng nghe toàn bộ đầu ra của mạng.phân thích: hình ảnh download dữ liệu về nên chiếm băng thông của mạng. we need to filter out of this http and tcp traffic.mặc định expert hiển thị tất cả các thông tin.nếu chỉ hiển thị error+ warn+ note thì ta sẽ có các thông tin
Welcome to the world of Cisco Certified Network Associate (CCNA) Wireless! As technology
continues to evolve, wireless technologies are finding their way to the forefront.
This clearly indicates the progression from a fixed wired type of connectivity to a more
fluid, mobile workforce that can work when, where, and how they want. Regardless of
your background, one of the primary goals of the new CCNA Wireless certification is to
introduce you to the Cisco Unified Wireless Network (CUWN).
một số công nghệ:
host và router gọi là các nút
các kênh truyền thông nối liền các nút lân cận gọi là các kết nối
các kết nối hữu tuyến (wired)
các kết nối vô tuyến (wireless)
gói dữ liệu trong lớp 2 gọi là frame, đóng gói datagram
The data link layer needs to pack bits into frames, so that each frame is distinguishable from another. Our postal system practices a type of framing. The simple act of inserting a letter into an envelope separates one piece of information from another; the envelope serves as the delimiter.
Put together a proposal for replacing hubs with switches at a branch office. Research at least two different solutions and develop a proposal. The project details are the following:
• The company has a branch location still using an Ethernet hub network. Congestion issues are getting to be a serious problem as more and more services are being added to the network. Currently each of the four floors has one or more hubs in a wiring closet supporting 30-35 computers except the ground floor, which has 65 computers.
• The four floors plug into an 8-port 10-Mbps switch that was added earlier...
Architecture of wireless LANs
In a wireless LAN (WLAN), the connection between the client and user exists through the use of a wireless medium such as Radio Frequency (RF) or Infrared (IR) communications. This allows the mobile user to stay connected to the network. The wireless connection is most usually accomplished by the user having a handheld terminal or a laptop computer that has an RF interface card installed inside the terminal or through the PC Card slot of the laptop. The client connection from the wired LAN to the user is made through an Access Point (AP) that can support...
In random access or contention methods, no station is superior to another station and none is assigned the control over another. No station permits, or does not permit, another station to send. At each instance, a station that has data to send uses a procedure defined by the protocol to make a decision on whether or not to send.
In this lab, the student will work with Ethernet cable drops that are attached to networking devices such as hubs and switches. This is to determine the characteristics of the devices and cabling and identify potential networking problems. Use some of the key capabilities of the Fluke LinkRunner, such as drop activity and ping, to perform the analysis.
As networks run faster and become more complex, infrastructure cabling and devices must operate to precise levels in a tighter performance window. As a result, nearly 80% of network problems stem from simple wiring and connection problems.
The generic cellular communication system, shown in Fig.l, is an
integrated network comprising a land base wire line telephone network and a
composite wired-wireless network. The land base network is the traditional
telephone system in which all telephone subscribers are connected to a
central switching network, commonly known as PSTN (Public Switching
Telephone Network). It is a digital switching system, providing: i)
Switching, ii) Billing, iii) 911 dialing, iv)l-800 and 1-900 calling features, v)...
1. Đối với phần điền vào chỗ trống: Xác định trước loại từ cần điền, và dự đoán thử nghĩa của từ đó. Cho ví dụ sau: I ____(1) re-wired the house so that Paul could reach all the ____(2). Ở câu này, nếu để ý, bạn có thể thấy ở chỗ trống thứ nhất, có thể dự đoán trước từ cần điền có thể là trạng từ, còn ở chỗ trống thứ hai, chắc chắn là danh từ. Trong ví dụ này, đáp án lần lượt là completely và switches. Việc xác định trước loại từ rất thuận tiện...
When the concept of a network without wires was first suggested more than two
decades ago, it sparked the imagination of scientists, product vendors, and users
around the globe eager for the convenience and flexibility of a free roaming connection.
Unfortunately, as the variety of wireless solutions began to emerge, anticipation
turned to disappointment.The first wave of solutions proved inadequate
for the networking, portability, and security needs of a changing IT environment.
This chapter discusses 802.11 security for customers currently investigating an enterprise wireless LAN
(WLAN) deployment. This chapter focuses on the most current enterprise security features that are
currently available for 802.11 wireless networks. For example, this guide focuses on methods such as
Wi-Fi Protected Access (WPA) and WPA2, and spends little time on Wired Equivalent Privacy (WEP).
Library of Congress Cataloging-in-Publication Data
Handbook of sensor networks : compact wireless and wired sensing systems / edited by Mohammad Ilyas and Imad Mahgoub. p. cm. Includes bibliographical references and index. ISBN 0-8493-1968-4 (alk. paper) 1. Sensor networks. 2. Wireless LANs. I. Ilyas, Mohammad, 1953- II. Mahgoub, Imad. TK7872.D48.H36 2004 004.6′8—dc22
campus network is a building or group of buildings that
connects to one network, called an enterprise network. Typically, one company
owns the entire network, including the wiring between buildings. This
local area network (LAN) typically uses Ethernet, Token Ring, Fiber Distributed
Data Interface (FDDI), or Asynchronous Transfer Mode (ATM)
The main challenge for network administrators is to make the campus
network run efficiently and effectively. To do this, they must understand
current campus networks as well as the new emerging campus networks....
An access point (AP) provides the connection between one or
more wireless client devices and a wired local area network
(LAN). The AP is usually connected to the LAN via a
Category-5 cable connection to a hub or switch. Client
devices communicate with the AP over the wireless link, giving
them access to all other devices through the hub or
switch, including a router on the other side of the hub, which
provides Internet access
Chuyển sang mã hóa WPA/WPA2-Enterprise
Các mạng Wi-Fi trong doanh nghiệp nào cũng cần sử dụng chế độ Enterprise của mã hóa WPA hoặc WPA2. Trong bài này, chúng tôi sẽ giới thiệu cho các bạn cách chuyển từ chế độ Personal (PSK) sang chế độ Enterprise (RADIUS). Chắc chắn nhiều người trong số bạn đọc đã biết, mã hóa Wired Equivalent Privacy (WEP) là một kiểu mã ngày nay không còn an toàn.