10/6 Notes Computer Networks, Wireless Networks

"Local Area Network"
LANs differ from WANs due to their high data transfer rate, local area of operation, do not need to lease telecommunication lines.

Ex. Ethernet, WiFi
TCP/IP protocol used.
Fiber optic cable used for high bandwidth.
LANs use spanning tree protocol to avoid loops and use VLANs to segregate traffic.
VLAN-a group of hosts with common requirements that communicate like they were attached to a broadcast domain-does not depend on location.


"Computer Network"
Group of interconnected computers
The Advanced Research Projects Agency (ARPA) funded the design of the "Advanced Research Projects Agency Network" (ARPANET) for the United States Department of Defense-first network of computers.

Networks are classified by the software that connects them (ex LAN).
Wireless LANs use infrared signals or radio waves to transmit.

Types of wired technologies:

Twisted-Pair Wire - used medium telecommunication.

Coaxial Cable – used for cable television systems, office buildings, and other worksites for local area networks.

Fiber Optics – These cables consist of one or more thin filaments of glass fiber wrapped in a protective layer. It transmits light which can travel over long distance and higher bandwidths.

Wireless Technologies

Terrestrial Microwave – Terrestrial microwaves use Earth-based transmitter and receiver. The equipment look similar to satellite dishes. Terrestrial microwaves use low-gigahertz range, which limits all communications to line-of-sight. Path between relay stations spaced approx. 30 miles apart. Microwave antennas are usually placed on top of buildings, towers, hills, and mountain peaks.

Communications Satellites

Cellular and PCS Systems

Wireless LANs

Bluetooth – A short range wireless technology. Operate at approx. 1Mbps with range from 10 to 100 meters. Bluetooth is an open wireless protocol for data exchange over short distances.

The Wireless Web – The wireless ex. cellular phones, pagers,PDAs.

Vary in size (LAN, SAN, WAN, VPN)

Internetwork-two or more networks linked.

Intranet-set of networks that use Internet Protocol

Extranet-limited to one network.

Network Components:

Network card, repeater,hubs,bridge.

*"A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model. Bridges do not promiscuously copy traffic to all ports, as hubs do, but learn which MAC addresses are reachable through specific ports. Once the bridge associates a port and an address, it will send traffic for that address only to that port. Bridges do send broadcasts to all ports except the one on which the broadcast was received."

Local ,remote, and wireless bridges.

Network switch

Router

"Management of RFID in Libraries"

The article covers the growing use of radio frequency identifiers in libraries. There are two types of RFID with several uses; the one used most by libraries is a short frequency version. RFIDs enable quick checkout-on the negative side, the frequency can easily be interfered with and librarians are wary about privacy concerns and staff "obsolescence."