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 A+ Essentials (220-801) Cram Notes


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2.4 Explain common TCP and UDP ports, protocols, and their purpose

1. The ISP provides the information on the SMTP, and POP server addresses. You need to feed this information to the mail client while configuring to send and receive e-mail.

2. Given below are the basic commands that are used with FTP:

a. get to copy one file from the remote machine to the local machine

b. mget to copy multiple files from the remote machine to the local machine;

c. put to copy one file from the local machine to the remote machine

d. mput to copy multiple files from the local machine to the remote machine;

e. Ďpí is used to request help or information about the FTP commands, and ls is used to list directory contents.

3.  Remote Desktop Protocol (RDP)

a. The minimum requirement for setting up Remote Desktop host running RDP (Remote Desktop Protocol) is Windows XP Professional or later. The minimum requirements for the Client computer is Windows 9x or above. A Windows XP Home can act as client but not as a host. Note that the computer that offers the local resources to a remote user is called a host computer or simply the host. The computer that connects to the host computer is called a client computer or simply, client. The host computer runs remote desktop (RDP).

b. RDP servers are built into Windows operating systems; an RDP server for Linux also exists. By default, the server listens on TCP port 3389.

c. Remote Desktop uses Remote Desktop Protocol (RDP), which in turn uses port 3389. By configuring the router to forward traffic on port 3389 to the host computer running RDP, one should be able to access the host remotely. If the host computer is on a publicly accessible IP address, there is no need for port forwarding. Remote client can access the host directly using hostís public IP address. The port forwarding is usually configured on the router that communicates with the external network (Internet)

2.5 Compare and contrast wireless networking standards and encryption types

1. Wireless Networking

The generic standard that defines wireless LAN technologies is 802.11. Specifically, the following standards exist:

a. 802.11: applies to wireless LANs and provides 1 or 2 Mbps transmission in the 2.4 GHz band.

b. 802.11a: an extension to 802.11 that applies to wireless LANs and provides up to 54 Mbps in the 5GHz band. This higher frequency compared to 802.11b shortens the range of 802.11a networks. Because 802.11a and 802.11b utilize different frequencies, the two technologies are incompatible with each other.

c. 802.11b (initially referred to as 802.11 or Wi-Fi): an extension to 802.11 that applies to wireless LAN and provides up to 11 Mbps transmission in the 2.4 GHz band.

d. 802.11g: applies to wireless LANs and provides 20+ Mbps in the 2.4 GHz band.802.11g is backwards compatible with 802.11b.

e. 802.11n support data rates of over 100 Mbps. 802.11n also offers somewhat better range over earlier Wi-Fi standards due to its increased signal intensity. 802.11n equipment will be backward compatible with 802.11g gear.

2. The 802.11n high throughput (HT) standard defines three modes of operation: a legacy (non-HT) mode, a greenfield (HT-only) mode, and a mixed mode where HT protection mechanisms ensure that transmissions can be detected by both old 802.11a/g/b devices and new 802.11n devices.

3. In mixed mode, HT protection requires that 802.11n devices send a legacy preamble, followed by an HT preamble. The legacy preamble lets 802.11a/b/g devices to avoid transmitting over HT frames sent by 802.11n devices.

4. These HT protection mechanisms significantly reduce an 802.11n WLAN's throughput, but they are necessary to avoid collisions between older 802.11a/b/g devices and newer 802.11n devices. If you knew that no legacy devices were present, you could configure your access point (AP) to operate in greenfield (HT-only) mode, eliminating this overhead.

5. Bluetooth Class 3   supports speeds up to 1m at 2.4GHz (1mW power output max)

6. Bluetooth Class 2   supports speeds up to 10m at 2.4GHz (2.5mW power output max)

7. Bluetooth Class 1   supports speeds up to 100m at 2.4GHz (100mW power output max)

8.WPA, short for Wi-Fi Protected Access, is a Wi-Fi standard that was designed to improve upon the security features of WEP (Wired Equivalent Privacy). The technology is designed to work with existing Wi-Fi products that have been enabled with WEP.

9. To secure the router from unauthorized access you need to change the default login/password on a router soon after the router is installed. Secondly, ensure to set encryption such as WPA2 so that only authorized users will be able to access the wireless network

10. WEP, short for Wireless Equivalent Protection, is a security protocol designed to provide protection equivalent to wired LANs. WPA is an improved security protocol compared to WEP.

11. Infrared technology allows computing devices to communicate via short-range wireless signals. With infrared, computers can transfer files and other digital data bidirectionally. Infrared communications span very short distances. Place two infrared devices within a few feet (no more than 5 meters) of each other when networking them. Unlike Wi-Fi and Bluetooth technologies, infrared network signals cannot penetrate walls or other obstructions and work only in the direct "line of sight."

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