네트워크 (이화여대 이미정) 썸네일형 리스트형 Network Class 6 1. User-server state : cookies many Web sites use cookies four components: 1) cookie header line of HTTP response message 2) cookie header line in next HTTP request message 3) cookie file kept on user's host, managed by user's browser 4) back-end database at Web site example : - Susan always access Internet from PC - visits specific e-commerce site for first time - when initial HTTP requests arr.. 더보기 Network Class 5 • Non-persistent HTTP 1. user enters URL (www.~) 2. HTTP client(browser) initiates TCP connection to HTTP server at www.~ on port 80 3. accept → HTTP client sends HTTP request message (containing URL) 4. HTTP server receives request message, forms response message 5. HTTP server closes TCP connection 6. HTTP client receives response message containing html file, displays html 7. Parsing html fil.. 더보기 Network Class 4 1. Client-server architecture • server - always-on host - permanent IP address - data centers for scaling • clients - communicate with server - may be intermittently connected - may have dynamic IP addresses 2. P2P architecture • no always-on server • peers request service from other peers, provide service in return to other peers - self scalability (new peers bring new service capacity, as well.. 더보기 Network Class 3 1. Four sources of packet delay 1) nodal processing • check bit errors • determine output link • typically < msec 2) queueing delay (variable) • time waiting at output link for transmission • depends on congestion level of router • L * a : 단위시간당 유입되는 traffic의 양 • L * a / R : traffic intensity • L : packet length • a : average packet arrival rate • R : link bandwidth 3) transmission delay • L/R •.. 더보기 Network class 2 1. Host : sends packets of data host sending function: • takes application message • breaks into smaller chunks, known as packets, of length L bits • transmits packet into access network at transmission rate R ‣ link transmission rate = link capacity = link bandwidth • packet transmission delay = L / R sec 2. Physical media • Type of links 1. guided media • twisted pair (copper) : e.g) Ethernet .. 더보기 Network class 1 1. What's the Internet • millions of connected computing devices • hosts = end systems • running network apps • communication links • fiber, copper, radio, satelite • transmission rate : bandwidth(Realizable bits per time unit) • Packet switches : forward packets • routers and switches • Internet : "network of networks" • interconnected ISPs • Protocols control sending, receiving of msgs • Inter.. 더보기 이전 1 다음
