Naming _ Addressing for the Internet Naming computers -named by IP by vivi07

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									Naming & Addressing for the Internet Naming computers -named by IP addresses -four numbers in the range of 0-255 -they are sets of octets b/c they're in binary -we use domains which uses natural language instead of numbers -computers find the IP address for a domain name from the Domain Name System - an IP addressbook computer -a computer needs to know IP address of the DNS server Naming Comps II -peole name comps by a domain name-hierarchical scheme that groups like comps .edu = all edu comps -.washington.edu - all comps at UW -ischool.washington.edu -www.ischool.washington.edu Domains -.edu, .com, .mil, .gov., .org., .net -top level domains Logical v. Physical -humans see a hierarchy of domains relating comps -comps see groups of four number IP adddresses Client/Server Structure -internet comps rely on client/server protocol: serveres provide services, clients use them -sample servers: email server, web server, ... -UW servers: dante, courses, www, student -frequently a server is actually many computers acting as one -DANTE is a group of 50 servers -Protocol - client packages a request and sends it ato a server; server sends a reply WWW -collection of servers & info they give access to -a WWW is a subset of all Internet comps -WWW is not the internet -server is web site comp and the client is the surfer's browser -many web server's domain names begin w/ www by tradition, but any name is OK -often multiple server names map to the same site Client Server interaction -web pages, client requests a page -server returns it -2 transmissions -servers serving servers that serve many clients -servers serve many clients; clients visit many servers HTTP -http:// is the protocol faculty.washington.edu = server -domain: edu -subdomain - washington -server: faculty -/daclem/LIS549sp08/index.html = pathname

-account: daclem -folder: LIS549sp08 -file: index.html Finding server & pathname finding the server 1. domin: edu 2. subdomain: washington 3. server courses -finding pathname: 4. account: wtcampus 5. directory: autumn -if there is a default, the browser goes there; if not it will get you a list of files Data Encapsulation Process -Remember the OSI layers -holds true for the destination and the source computers -puts the PDU (protocol data unit) from the layer above into its data field -adds a header to assist the receiving device's layer to perform its function -layers 2 -4 (Data link, network, transport) add identifiers (addresses) -on the destination side it is just the same but it goes in the reverse order -the source comp starts the app layer and works its way down to the physical layer and then sends it across to the destination computer Names for Data at Each Layer -OSI Model vs. TCP/IP Model -data is called a "frame" at the physical/datalink/network access layers -at the network/internet layer the data is called the "packet" -at the transport layer it is called a segment Identifiers for Each Layer -application Layer device names has some protocols -SFTP, SMTP, etc. -those protocols live at our software -Transport Layer - all the port numbers -firewall listens at different ports and says, "ok it's http, I'll send that through port 80 b/c I know that's where the web server lives" -if it's port 23 it's sftp -layer 4 port numbers - IDs application IP 16 bits 0 to 65535 -Port layers = doors in an apartment house -Port 80 - Oh the web server lives there -at the internet layer = transfer b/t networks - here the IP address is important -Layer 2 addresses - only local segment delivery -only w/in your network , now goes to particular machine -LANs - MAC address 48-bits 5C2E.1CD5.E3CF - hardware - burned in -Frame Relay - DLCI (0 to 1023) -ISDN - SPID 425...etc. INTRO: MAC and IP ADDRESS -MAC Address lives at Layer 2 ( the Data link layer) -Every NIC and Modem has one added by the manufacturer -also called burned in address and physical address -each unit, has a diff MAC -identifies nodes on the netwk -Six hexadecmial chars separated by colons: -e.g. - 00:00:A2:05:09:89 or 0000.A205.0989 -ethernet address - used to deliver in the local network

-must be unique on the LAN -half (first 24 bits / 6 HEX) - Mfr ID (OUI) -half (last 24 bits / 6 HEX) - unique serial number -hexadecimal system is base-6 number system MAC (MEdia Access Control) Address (Layer 2) - only the datalink layer (local) -identifies host but not where they are located (weakness) -analogies -street address on an envelope - only unique within a city -SSN - can be used in a classroom if everyone is present -but if someone is missing, nothing in the SSN helps us find them Why do we care? -WIFI and some security methods use MAC address to authenticate a device -can be found on bottom of laptop and many WIFI access points IP Address (Layer 3) -logical address assigned by administrator (software based?) -e.g. 201.105.45.195 -32 bits / 4 bytes / 4 octets -part identies the network -part identifies the host -must be unique on the entire internetwork -ip addressing scheme is used on the internet (TCP/IP) -why do we care? -allows data and traffic to move between networks -allows us to connect to and use the internet -analogy -we can identify the netowork (city/state) -we can identify the particular address (street address) Layer 2 & 3 Addresses -MAC address is used by Ethernet to deliver frames in local segment -IP Address identifies network (197.15.22.0/201.100.1010.0) and host -used to move packets from network -when traffic needs to leave a network it needs to end in "1" in final octet -each of these networks has a router port of network 1 -this router belongs to 2 different networks -2 networks communicate through a router -they both have ports in the same router -but the router but has ports on 2 different networks -router communicates between networks -passes data back and forth between networks and internet (TCP/IP) -Address Resolution Protocol (ARP) maps IP addresses to MAC addresses Layer 3 - IP Addressing -class c network - takes 3 octets to identify the network -each octet is 8 bits = takes 24 bits to identify the network -another type of notation to identify the "network" portion of the IP address -a netmask - allows PCs and routers "see" only the network portion of the IP address To Show PC Addresses -C:\ipconfig /all -"Host Name" -particular named computer on the network -physical address for the ethernet adapted wireless connection is the LAYER 2 MAC Address -remember that ist is a set of 6 digits Look at the IP Address - this shows layer 3

-you can also see the "subnet Mask" - set for 255.255.255.0 -shows us that this network has just got 3 octets to show the network name -can either be colons between the 6 sets of number in the MAC address or 4 digits could be paired w/ dots between them or hyphens between them Addresses in Data Frame -examining traffic on the internet that's going by in the bitstream -in order to pick out the addresses and headers as data flies by -Data link layer is Layer 2 -gives MAC addresses -Internet or IP layer is Layer 3 -gives IP addresses Internet Addressing Scheme -IP Address Example 10.2.2.3 -Look at Internet Addresses - 1st layer - the first octet (0-255) -255 branches on that first layer -each one of those choices has its own set of octet choices -256 x 256 x 256 x 256 combinations (4,294,967,296) Classful Addressing -Class A -octet - 1st one is for network - the last 3 are for host -can only have 128 networks (2 are reserved) -Class B - 2 octets represent network - last 2 represent host -Class C - 3octets - a lot of networks - few hotsts 16,384 possible netoworks -Class D - 4 octets - all host - lots of hosts IP Address Classes -Class -e.g. Business Size - large Class A for a multinational corp; Medium would be Class B - a College campus; Class C can be for a small business Layer 4: Port Numbers -Data transport Layer of OSI model -remember in the TCP/IP model -in the transport layer we have TCP (Transmission Control Protocol) -connection-oriented, reliable - TCP is like making a phone call -and the User Datagram Prtocol (UDP) - like a postcard -no software checking for segment delivery; fast, unreliable -we're looking at port numbers that is listening for particular operations in the application layer -TCP/IP Model Protocols Map -22 is FTP >>>> uses TCP -HTTP = 80 >>> uses TCP SMTP 25 >> uses UDP -DNS = 53 >>> uses UDP -TFTP = 69 >>> uses UDP Interace between Application and Transport Layers TCP and UDP Port Numbers -port number is like a door in an apartment building -numbers below 1024 are considered well-known port numbers -numbers above 1024 are dynamically assigned port numbers -registered port numbers are those registered for vendor-specific applications - most of these are above 1024

Port Number Example -Telnet Z is running at computer A with a particular IP address -software lives at port 1028 - it's a destination port How do we establish TCP? -we wrap it with layers - it has a new header -Layr 4 transport - tells you source port : 2352 and destination port - 80 (WWW - HTTP) -also has the Layer 3 layer - IP header - lgth, version, IP type, source IP address, destination IP address -Layer 2 layer - ethernet header - tells you the protocol type - the MAC address destination and the MAC address source -tells you timestamp and the length of the packets Envelope Analogy -Source name: Molly Jones Source layer 2 Address: 123 Main St Source Port Number: Apt 12 Source layer 3 Address: Tacoma, WA 98405 Same for destination


								
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