Internet Connection Types• Connect to the Internet

through:– modem– local-area network – cable modem– Digital Subscriber Line

(DSL) connection. DSL is a very high-speed connection that uses the same wires as a regular telephone line.

More definitions of DSL…

• DSL ( Digital Subscriber Line ) is a method of high-speed data transfer over ordinary copper telephone lines. xDSL refers to different variations of DSL, such as ADSL, HDSL, SDSL and RADSL.

• *homework: find out what the above acronyms means!

GATEWAY

• A system (hardware-software combination) that links otherwise incompatible networks to communicate with one another.

• The term often refers to the server computer that links a LAN to the Internet.

Router• Central switching device in a packet-switched network that

directs and controls (routes) the flow of data.

• A traditional router routes packets within a single address • NAT router directs datagrams between different address

realms.

• NAT router sits on the border between two adress realms and performs such "transparent routing" by modifying addresses in IP headers, so that when packets enter another address realm they can be valid and routed properly.

• Routers are differentiated from data communications switches by the ability to perform higher-level functions necessary to the interconnection of different networks.

• NOW, What is NAT???

Network Address Translation

• NAT (Network Address Translation) is an IETF standard that enables LANs to use one set of private IP addresses for internal traffic an another set of IPs for external traffic.

• A NAT device makes all IP address translations where the LAN meets the WAN.

• NAT permits a large number of LAN users to share one external IP address,

• and adds some network security, since private IP address ranges are not routable outside the LAN.

NAT continued• The following 3 blocks of the IP address space have been

reserved by the Internet Assigned Numbers Authority (IANA) for private Intranets:

– 10.0.0.0 - 10.255.255.255 (class A, 10/8 prefix)

– 172.16.0.0 - 172.31.255.255 (class B range, 172.16/12 prefix)

– 192.168.0.0 - 192.168.255.255 (class C range, 192.168/16 prefix)

ETHERNET• Is an IEEE data communications protocol originally

developed for premises and local access networks (IEEE 802.3).

• It was originally developed for peer-to-peer communications using shared media over relatively short distances.

• Ethernet has been substantially improved over the years and now operates in a wide variety of settings. Ethernet is currently the most widely deployed LAN protocol in the world.

• Some of the newer variants of the standard include;Fast Ethernet - Ethernet at 100 Megabits per second.Gigabit Ethernet (Gig-E) - Ethernet at 1000 Megabits per second.

bandwidth• Is the amount of data that can be carried in a given

time period over a network.

• More technically, bandwidth is the width of the range of frequencies that an electronic signal occupies on a given transmission medium.

• In digital systems, bandwidth is usually expressed as – bps (bits per second), – Kbps (Kilobits/second or – Mbps (Megabits / second).

• In analog systems, it's the number of cycles of change per second, or hertz.

Homework!!!! You can do this in the lab

• Read the below sites:– http://computer.howstuffworks.com/wireless-network2.htm– http://www.webopedia.com/TERM/8/802_11.html– http://searchmobilecomputing.techtarget.com/sDefinition/

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