Chapter 6--Data Communication

A computer network is a collection of computers that communicate with one another over transmission lines or wireless.
A local area network(LAN)- connects computers that reside in a single geographic location on the premises of the company that operates the LAN.
Wide area networks(WANs)- connect computers at different geographic locations.
An internet is a network of networks. The most famous internet is "the Internet"... which is the collection of networks that you can use send email or access a web site.
A protocol is a set of rules that two communicating devices follow. A switch is a special-purpose computer that receives and transmits messages on LAN.
Network interface card(NIC)- connects the devices circuitry to the cable. The computers, printers,switches,and other devices on LAN are connected using one of two media.
Connections between switches can use UTP cable, but if they carry a lot of traffic or are far apart UTP cable may be replaced by Optic fiber cables.
Bluetooth is designed for transmitting data over short distances, replacing cables.
Internet Service Provider(ISP)- three important functions:
1. provides you with legitimate Internet address
2. Serves as a gateway to the Internet
3. Pay for the internet.
DSL(Digital Subscriber Line)- operates on the same lines as voice telephones, but they operate so that their signals do not interfere with voice telephone service.
Cable modems provide high-speed data transmission using cable television lines
Narrowband lines typically have transmission speeds less than 56kbps. Broadband lines have speeds in excess of 256kbps.
A router is a special-purpose computer that moves network traffic from one node on a network to another.
Public switched data network(PSDN) network of computers and leased lines that is developed and maintained by a vendor that leases time on the network to other organizations.
A virtual private network(VPN) uses the internet to create the appearance of private point-to-point connections.
Tunnel- is a virtual, private pathway over a public or shared network from the VPN client to the VPN server.
Key-number used to encrypt the data.
Symmetric encryption-same key is used to encode and to decode
Asymmetric encryption-different keys are used
Firewall- a computing device that prevents unauthorized network access.
Packet-filtering firewall- examines each part of a message and determines whether to let that part pass.
Access control list(ACL)- encodes the rules stating which addresses are to be allowed and which are to be prohibited.
Presence- term that means you'll know who is on the system.