-a computer network is a collection of computers that communicate with one another over transmission lines or wireless. LAN connects computers through a single location while WAN connect computers at different locations
-LAN is a group of computers connected together on a single company site. Each device on a LAN has a hardware component called network interface card (NIC)
-most connections are made using unshielded twisted pair (UTP) cable. Twisting the wires substantially reduces the cross-wire signal interference that occurs when wires run parallel for long distances
-optical fiber cables are light rows that are reflected inside the glass core of the OFC. The core is surrounded by a cladding to contain the light signals. These cables use special connectors called ST and SC connectors
-most PCs today are equipped with an onboard NIC that supports what is called 10/100/1000 Ethernet
-Internet service providers (ISP) has three important functions
-provide users with a legitimate internet address
-serves as a gateway to the internet. ISP receives communication from your computer and passes them on to the internet
-ISPs pay for the internet. They collect money from their customers and pay access fees and other charges on your behalf
-modems convert digital data in the computer to a wavy analog signal
-there are different types of modems
-Digital subscriber line (DSL modem)
-Cable modems
-narrowband lines typically transmit speeds less than 56l, while broadband transmit in excess of 256k
-router is a special purpose computer that moves network traffic from one node on a network to another
-Public switched data network (PSDN) lease networks of computer and lines on time to other organizations
-encryption is the process of transforming clear text into coded, unintelligible text for security purposes. A key is a number used to encrypt data
-in symmetric encryption, the same key is used to encode and decode while in asymmetric encryption, different keys are used to encrypt and decode (public/private key)
-HTTPS data (internet) is encrypted using Secure Socket Layer (SSL), also known as transport layer security (TLS)
-firewall is a computing device that prevents unauthorized network access (it could be a computer or a program)
-a firewall has an access control list (ACL) which encodes the rules stating which addresses are to be allowed and which are to be prohibited.
-no computer should connect to the internet without firewall protection. Usually ISPs provide a firewall for its users
-each NIC is given an address at the factory, these addresses are considered your physical address, or MAC address
-logical addresses (IP address) are written as a series of dotted decimals which are used by the internet and other private networks
-there are two types of IP addresses. Public IP addresses are used on the internet while private IP addresses are used within private networks and internets
-when your computer is plugged in a LAN, the OS searches for a host program called Dynamic Host Configuration Protocol (DHCP). This program loans out a temporary IP address that the computer uses until it is disconnected from the LAN. DHCP can reuse the temporary IP if necessary
-Switch tables tell the switch where to send traffic to get it to its destination (LAN). Routing tables are the equivalent for routers
-the process of changing public IP addresses into private IP addresses, and the reverse, is called Network Address Translation (NAT)
-Changing a name into its IP address is called resolving a domain name. Top-level domains are the last letters in any domain name (com/org/net). Uniform resource locator (URL) is a combination of domain name plus its directory
-Voice over IP uses the TCP/IP to carry telephone voice conversations. Voice conversations are stored as bits, broken up into IP packets, and routed over the internet. Skype offer subscribers unrestricted telephone access using VoIP
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