Chpt 3 Networking PDF

Chpt 3 Sunday, 10 November 2024 00:17 The basics of networking - General communication ○ Separated into synchronous and asynchronous § Synchronous communication □ Requires that both the sender and receiver are active at the same tim...

Chpt 3 Sunday, 10 November 2024 00:17 The basics of networking - General communication ○ Separated into synchronous and asynchronous § Synchronous communication □ Requires that both the sender and receiver are active at the same tim ® Telephone conversation, skype for example § Asynchronous communication □ Sending and receiving occurs at different times ® Post cards, emails and text messages are examples ◊ Written at one time and read at another § Synchronous messages can become asynchronous □ Answering machines and voice mail ○ Broadcast communications § Single reader and many receivers □ Radio and tv are examples of broadcast communications ○ Multicast § Many receivers, but the intended recipients aren't the whole populations □ Magazines with specific topics ○ Point-to-point communication § The opposite of broadcasting and multicasting § One specific sender and one specific reading ○ Broadcast vs point to point is different from synchronous vs asynchronous communication - The internet's communication properties ○ The internet supports point to point asynchronous communication ○ The internet links all computers together § Which then supports synchronous, multimedia and broadcasting communication ○ The internet becomes more effective the more computers are added to it - The client/server structure ○ A brief encounter § When you click on a web link your computer enters a client/server interac □ You are the client and the page is the server § "Client" is used whenever one computer (the client) gets services from another computer (the server) § The server answers your client request by sending the page to the client □ Completes the client/server request § Client/sever structure is quick and easy. One request is sent, one service is me ction s  □ You are the client and the page is the server § "Client" is used whenever one computer (the client) gets services from another computer (the server) § The server answers your client request by sending the page to the client □ Completes the client/server request § Client/sever structure is quick and easy. One request is sent, one service is received ○ Many brief relationships § The server can handle many clients at a time □ The server is busy with you only as longas it takes to perform a requ § Next time you click on another link the relationship starts again ○ Getting more connected § Software is added to make computers to implement the many forms of communications we use □ "client software" ® Software on the computers of the people communicating § Client software "slices up" signals coming from the computers microphone and bideo camera into pocket sized blockd and sends them to the other pa whos client reassembles the sound and image □ Cray □ Depends on fast and reliable internet - Appearing to stay connected ○ How do sites "stay connected" with users through multiple exchanges? § Two solutions: □ Cookies ® Small files stored on the clients computer by the server, and returned to the server with each page request. The file contain enough data from the server, such as a unique identifier, that can connect youto earlier interactions □ URL parameters ® Information added by a client to a URL when it connects to the server. ◊ https://www.google.com/search? q=memex+decive&sca_esv=09d50bc19946cdf1 ◊ Its the information after the "?" } In this example i searched for memex device in google § Client side/ server side □ Some things are done on each side ® Requesting travel dates by displaying a calendar is a client side activity ® Searching for flights that match the dates is a server-side activ The medium of the Message - The Name Game of Computer Addresses ○ Remember that the internet uses point-to-point communications (from one computer to another computer) § When something is sent point to point, the destination address is required s uest e arty ns it e e vity d  ® Searching for flights that match the dates is a server-side activ The medium of the Message - The Name Game of Computer Addresses ○ Remember that the internet uses point-to-point communications (from one computer to another computer) § When something is sent point to point, the destination address is required □ IP addresses ® Each computer connected to the internet is given a unique address (IP address or Internet Protocol address) ® IP Packet ◊ A computer communicates with another by sending an I Packet to its IP address. ◊ IP packet has the number of the ip its being sent to, and ip address it should be sent back to } It also has a sequence number and a payload – The payload is whats being sent w It can b one byte or thousands □ Routing and switching ® The internet is many switches and things that link everything together ◊ When an IP packet arrives at a switch, the switch decide which router will get the packet closest to its destination based on the IP Address, and forwards the packet on. } The transition from one router to another is called hop □ Many paths ® All routers and switches are connected to several others. They send packets to any of the neighbor routers ◊ If a router is down, the switch will use another router } Basically, IP packets can travel different routes ba to get to the same destination □ Trace route ® Because packets can take many routes, network engineers rec (and analyze) the routes they take. They use a tool called trace route. ◊ From the university of washinton to the swiss national technical university in Zurich a packet took 20 hops ® Local addresses start with 10 - Following protocol ○ The sending process uses transmission control protocol/internet protocol (TCP/ § TCP/IP postcard analogy □ Sending information over the internet is like sending a novel from ta to your publisher in New York City using only postards. ® First break up novel into small units so each unit fits on a post ® Then you number each postcard so you know where it belong the novel, and write the publishers address on each ® The postcards are sent from tahiti, but might not all take the s vity d IP d the es n da y can ased cord e /IP) ahiti tcard gs in same  □ Sending information over the internet is like sending a novel from ta to your publisher in New York City using only postards. ® First break up novel into small units so each unit fits on a post ® Then you number each postcard so you know where it belong the novel, and write the publishers address on each ® The postcards are sent from tahiti, but might not all take the s route ® Eventually the postcards reach the publisher, and the publishe uses the numbers to put together the novel ◊ An IP packet has limited space, like the postcard. So wha youre sending has to be broken down. ◊ At the destination they are reordered and put together § Packets are independent □ Means that the packets can go their own way (shoutout Gabriella HS ® They can take different routes if something f.eks. Is wrong wit one route ◊ Makes them more resilient - Far and near: WAN and LAN ○ The internet is a collection of Wide Area Network (WANs) § Networks designed to send information between two locations widely seperated and not directly connected ○ When computers are close enough to be linked by a single cable or pair of wires interconnection is referred to as Local Area Network (LAN) § Ethernet is the main technology for LANs. And is appropriate for connectin the computers in a lab or building ○ Ethernet, the setup § The Channel winds past a set of computers § Engineers "tap" the channel to connect a computer, allowing it to send a signal □ All computers connected to the channel can detect the signal, includ the senders. ® So the channel supports broadcast communication ○ Ethernet, party analogy § Tf § One person tells a story, if interrupted someone else will tell a story, if two people talk at the same time they both stop § (?) ○ Ethernet, the protocol § When a computer is sending signals on the channel, all the other compute will listen □ Unlike storytelling only one computer typically keeps the transmitte information. So this broadcast medium is being used for point to po communication § When a computer stops transmitting on a channel, another can start. If another is transmitting before the other one gets to start, the other one is quiet and waits again. Difference between ethernet and internet so far ahiti tcard gs in same er at SM) th s, the ng all ding o ers ed oint s  information. So this broadcast medium is being used for point to po communication § When a computer stops transmitting on a channel, another can start. If another is transmitting before the other one gets to start, the other one is quiet and waits again. ○ Difference between ethernet and internet so far § Internet uses point-to-point to get point-to-point communication □ Ethernet uses broadcasting to get point-to-point communication § With internet, many communictions can happen at the same time over different wires □ With ethernet only one communication can take place at a time because theres just one wire - Connecting your computer to the internet ○ Two basic methods today: § ISP and connection provided by a campus of enterprise network § Connections by ISP (internet service provider) □ Sells connections to the internet ® Examples are phone companies and cable companies □ How an ISP connection works: ® ISP company gives you a modem for your house ® Modem convert the bits a computer outputs into a form that i compatible with the carrier ® These signals are sent to the carriers business where they are converted (via another modem) into a form suitable for the se that connects to the internet. § Connection by LAN □ Uses local networks known as intranet □ These support communication within the organixation but also conn to the internet by gateway § Connections with wireless networks □ A variation of LAN connection ans is often referref to by its protocol name (802.11 "eight o two elleven") □ The router is connected to an ISPs modem connected to the interne and is capable of recieving and broadcastinf radio frequency (RF) sig □ The router relays intenret requests for the participating computers - Domains on the DNS ○ You use domain names to refer to computers rather than IP addresses ○ Hierarchy is handy § The domain name system (DNS) is the hierarchal structure that we use to name computers § "spiff.cs.washington.edu." □ "edu" ® "edu" is a top level domain name used by educational organizations □ All the computers in the university of washington are on the washin domain, within the edu domain □ In the computer science department, all the computers are part of t oint s is erver nect l et gnals ngton the  □ "edu" ® "edu" is a top level domain name used by educational organizations □ All the computers in the university of washington are on the washin domain, within the edu domain □ In the computer science department, all the computers are part of t cs domain, within the washington domain, within the edu (education domain □ Spiff is one of those computers in the cs domian § Peers □ Domains at the same level in the hierarchy are peers of each other ○ Top level domains § There were first only seven top-level domain names § Eventually there were two-letter country domains □ (.no) ○ A problem § The DNS servers have to figure out what numbers are what website (f.eks. § Given a domain name, the computer returns the address to your compute § Problem: there is no master list of domains on the internet □ So what if the DNS cant find the domain you're requesting? ○ Authorative name server § The authoritative name server (ANS) computer knows the domain that a website is in □ If a computer isnt on the list, its not in the domain, if it is, it knows th address § The DNS server asks the domain-ANS for the IP address, gets the answer, a ads it to its list [website: IP] ○ Start at the top § Begin by finding the IP address for the edu-ANS. It knows the IP addresses the ANS machines for all of its domain. Ask it for the IP address of si-ANS. T machine knows the IP addresses of all the computers in its domain. Ask fo the IP of airandscpave (example in book) ○ Root name servers § The computera that know the IP addreses for the top-level domain (TLD) □ EDU-ANS f.eks. ○ Caching § Isnt there a lot of traffic with the root servers? □ Whenever your computer recieves an IP address, it doesnt have to g again ® Slows down traffic a bit ® Saving ingormation for possible reuse soon is called caching ○ Redundancy § The use of. Multiple copies of informaiton (13 root servers, TLD lists in thi case) is called redundancy □ Reduncancy=repetition - DNS summary Internet Assigned Names Authority (IANA) ngton the n).) er he IP and s for That or get it  ○ Redundancy § The use of. Multiple copies of informaiton (13 root servers, TLD lists in thi case) is called redundancy □ Reduncancy=repetition - DNS summary ○ Internet Assigned Names Authority (IANA) § Takes care of the root name servers