Networking Notes. Common Internet Speeds. Online Speed Test myspeed.visualware.com

Transcription

1 Networking Notes Common Internet Speeds Dial Up 56 kbs 1000kbs = 1 mbs (1 user capacity) DSL 1.5 mbs (1 channel 10 user capacity) T1 1.5 mbs (24 channel 500 user capacity) Scalable Ethernet (Adjustable between mbs) Ethernet 10 mbs T3 45 mbs 100 mbs (Download 10mb file in 10 seconds) 1000 mbs - Called gigabit Ethernet (Download 100 MB file in 10 seconds) Online Speed Test myspeed.visualware.com

2 Terms to know be able to explain what they do. LAN Local area Network WAN Wide area Network Protocol Network language. Two computers are able to communicate on a network if they have the same protocol installed. Some common protocols are NWLink, TCP/IP ISP Internet service provider. Provides access to the Internet Packet packet of 1 s and 0 s (ip address images code) IP address - The network address of your computer. Gateway Router to a larger network Router - 2 IP address. Internal & External. Acts as a gateway to the Internet Hub - Packet repeater. A packet received from any port is sent to all other ports even if that port does not contain the destination device. Therefore hubs create, a lot of unnecessary network traffic which can lead to congestion. Therefore, you can only have a maximum 4 hubs before a switch is needed. Switch Packet redirector. The switch looks at the destination IP and redirects to packet to the port which contains the destination device. Mac Address Physical address unique to each NIC This is a unique address stamped on every network device and is not shared by any other network device in the world. DNS Domain Name Server. The job of the DNS is to convert the common name such as google.com into the officially registered IP address such as DHCP Server Dynamically assigns IP addresses. This server gives an IP address to computers that request one. You can only have one DHCP server on a LAN network. CAT 5 or CAT 6 Ethernet cable containing 4 pairs of wire total of 8 wires) Straight thru same configuration and color on each end. (most common) Used between computer and hub, switch or routers. Crossover different connections at each end. Used for direct computer to computer connection. Mbps Megabits per second. http: - HyperText Transfer Protocol. Protocol used for most web pages. ftp: File Transfer Protocol. Protocol most commonly used to transfer entire files from one computer to another over the Internet.

3 Proxy Server Remote gateway. A proxy server can be used to force your packet to pass through a router at a remote location sometimes allowing you to bypass the LAN router s security settings, or making yourself anonymous. Port 80 http (Web Sites) Port 21 FTP Port Remote Desktop SSH (Secure Shell Use Putty Port 22) SSL Secure Socket Link (secure web sites) Port 443 Phishing DNS redirection attack Common Networking Commands cmd opens a command prompt ping sends a test packet to another computer ipconfig displays IP address, subnet mask and gateway of the computer you are using. /? displays help syntax /all displays more network info such as dns and mac address. /release releases the IP address of the computer /renew renews the IP address of the computer /flushdns flushes the local dns cache on the computer. Tracert traces a packet path thru various routers Net Send Send a text message to another computer

4 Simplified version of how the Internet works. Preconditions: A computer with a network card and TCP/IP protocol installed and configured. This computer is connected to a network which has a router and DHCP server. The router is connected to an Internet service provider, via a cable modem, DSL connection, or directly via fiber optic cable. Typical Scenario: Computer is turned on and requests an IP address from the DHCP server. (If no DHCP server is found the IP must be set manually.) The computer receives and IP address from the DHCP server along with other information such as DNS server IP, Gateway IP (Same as router internal IP) and Subnet mask IP. (In this example the computer s IP is ). Opening a command prompt and using the command > ipconfig will display this information. Additionally you can also type the command > ipconfig /all to reveal additional information about your computer network settings including the IPaddress of the DHCP server, any DNS servers, and the Physical MAC Address of the network card: 00-1C-C A8 (in this example)

5 A browser is opened and the user types: Packets are sent from your computer which contain a host of information such as the name IP address of your computer, the MAC address and the web site you typed. The DNS server database which contains the names of web sites and their assigned ip addresses translates the name (google.com) into its registered IP ( ). (This IP address was registered and paid for by Google. Anyone can register and name for about $10 a year using any Internet registrar service such as mydomain.com.) Once the packet knows it s destination IP it heads to the LAN gateway (a.k.a. Router) and is stripped of the original computer s IP and replaced with the router s external IP. A router s external IP can easily be obtained while using a computer inside the LAN and visiting ipchicken.com (In this example we will use the external IP of

6 The packet then is sent to the ISP and out to the Internet passing through numerous switches and routers until it reaches its destination IP (in this example google s server ). Google server receives the request and send packets back to the original router from which it came ( The LAN external router IP). The router remembers the computer from which the original request came and send the packet back the original IP ( ). Visual Representation LAN computer Computer is turned on and assigned an IP address by the DHCP server Request is made to open the web site. Packet is sent requesting the DNS server to translate the common name of google.com into its registered IP. LAN DHCP and DNS server The DNS server finds the registered IP in its database and adds this information to the packet and passes it on toward its destination. LAN Router The router can also act if the DHCP server. It contains an internal IP ( ) and an external IP ( ) The router replaces the internal IP on the packet with the external one and sends it on toward its destination IP at of at Google. ISP You packet then passes through your local ISP network which also has switches, routers and DNS servers. Your ISP then passes your packet to the Internet. Contains many routers and switches. Internet Google Router Google Switch Google Server Google server receives the request and sends packets back to the router from which it originated.