Networks Part 1: Naming NYU-Poly: HSWP Instructor: Mandy Galante

Networking = Sharing Info Humans communicate using 2 basic methods Speaking - in person, in a group, on the phone Writing - letter, , text message, notes on the board The methods have rules to make it work smoothly Speaking: Take turns, raise your hand, no yelling Writing: Addressing, salutation, punctuation. Network communications have rules too Rules for finding devices on the network Rules for making connections Rules for each type of info being shared M. Galante_CSAW HSWP 2014

Harry wants to send a message to Sally but they are not the only users of the cable. HarrySallyFrank JoanTom ?? ? ? Finding Devices in a Network What are the chances Harry’s message will actually get to Sally? M. Galante_CSAW HSWP 2014

Finding Devices in a Network Rule #1 – your device must be unique Devices can have more than one NIC... BUT each one must be unique MAC Address There must be an addressing system, a way of uniquely identifying computers and interfaces. VOCAB – An “interface” on a device is a component that acts as a door for connections. Examples: - a VGA port is an interface to the monitor - a USB port can be an interface to the printer - a NIC is a Network Interface Card M. Galante_CSAW HSWP 2014

MAC address Media Access Control Address = unique identifier for each networking device also known as the physical address of a device represented as 12 hexadecimal digits 00:24:E8:83:68:96 OR 00-C0-CA C A MAC address is like a SS # - not changeable, unique to you M. Galante_CSAW HSWP 2014

00C0CA2388C5 The first 6 digits of the MAC address represent the device manufacturer and is known as the OUI The manufacturer is responsible for uniquely assigning the last 6 digits to the device Organizational Unique Identifier (OUI) We can use the MAC address to look up who makes a device Example: 00-C0-CA = Alfa & 00:24:E8 = Dell M. Galante_CSAW HSWP 2014

With MAC addresses, we can uniquely identify each device or interface on the network. Finding Devices in a Network Alert – Mac Address can be spoofed! M. Galante_CSAW HSWP 2014

Finding Devices in a Network Rule #2 – you must “belong” to a network Joining a network provides you with lots of cool stuff: Access to shared files Access to devices like printers or scanners Access to Internet Service Providers When you join a network you become connected Great! How do I join?! Get an IP Address IP Address M. Galante_CSAW HSWP 2014

IP address Internet Protocol Address = TEMPORARY identifier for each interface Must be unique among the connected devices on that network also known as the logical address of a device An IP address is like an ID card - changeable - can belong to many organizations - unique within that organization M. Galante_CSAW HSWP 2014

IP Address There are two types of IP addresses IPv4 –the old kind, but it is still the most commonly used. The IPV4 format is 32 bits represented in 4 sections separated by dots. (Dotted decimal notation). Each section is called an octet and can hold a decimal number from 0 to 255. Example: IPv6 –the new kind, world is trying to convert slowly to this. The IPV6 format is 128 bits represented in 8 sections separated by colons. Each section can hold a hexadecimal number from 0000 to FFFF. Ex: 2001:0DB8:0000:0000:0008:8000:0000:417A M. Galante_CSAW HSWP 2014

Private An address series that can be used in many orgs Address can begin with: 10 or – or Must ‘piggyback’ on a public address to get to the Internet  this is called NAT (Network Address Translation) Public The addresses are unique in the entire world Must be used to go on the Internet There aren’t any more IPv4 public addresses IP v4 Address Can be Public or Private M. Galante_CSAW HSWP 2014

Getting an IP address You can get an IP address statically - add the IP address yourself to your device OR You can get an IP address dynamically - let a network server assign you an IP address - this is called DHCP (Dynamic Host Configuration Protocol) Every time your device joins a new network, it will get a new IP address. Home network - could be School network - could be Starbucks network - could be IMPORTANT!  IP and MAC addresses work together M. Galante_CSAW HSWP 2014

Find a device = ARP To send data a device must know BOTH the IP and the MAC address of the receiving device. ARP (Address Resolution Protocol) is a tool used by devices on the same network to find the MAC address associated with an IP address One device broadcasts an ARP request to all the devices on the network. It’s sort of like yelling to see if you can find someone. The device with the IP address responds with its MAC address. Let’s see an example: M. Galante_CSAW HSWP 2014

Sally Bob C0:43:1E:00:57:D3 Hey, everybody Who is ? I am!!! A1:FF:32:5A:EC:AA Ok – I’ll put that in my ARP table Internet addressPhysical address A1:FF:32:5A:EC:AA How ARP works

Finding Devices in a Network There is one naming method for computers that is “human readable” FQDN = Fully Qualified Domain Name format = host.yourdomain.top-leveldomain Top-level domain =.com.net.edu.gov.org (etc) Examples isis.poly.eduhelp.ubuntu.com A data packet is delivered by mapping a FQDN to it’s IP address and then to it’s MAC address. FQDN M. Galante_CSAW HSWP 2014

Activity #1 Finding your computer names M. Galante_CSAW Boot Camp 2013

Using the Terminal To open the terminal in Windows Start | cmd  Enter To open the terminal in MAC Spotlight | terminal  Enter M. Galante_CSAW Boot Camp 2013

TCP/IP tools Use handout to find out info about your own laptop Take a paper tag and use a pencil to fill in the info You will be using these terminal commands: CommandWhat info it provides ipconfig /allMAC addressIP address Computer name + Primary DNS Suffix = FQDN pingCan I successfully connect to a certain device? arp -aWhat is the MAC address of devices I previously have connected to? NslookupIP address of a FQDN M. Galante_CSAW HSWP 2014

Use of these materials is free with attribution. Questions or comments: M. Galante_CSAW HSWP 2014