ECE 550D Fundamentals of Computer Systems and Engineering Fall 2016 - - PowerPoint PPT Presentation
ECE 550D Fundamentals of Computer Systems and Engineering Fall 2016 Networking Basics Tyler Bletsch Duke University Slides are derived from work by Andrew Hilton (Duke) Networking How do computers communicate? Two computers connected
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Computer 1 66.220.152.32 Computer2 74.125.130.105 The Internet ISP 2 74.125.130.1 ISP 1 66.220.152.1
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Computer 1 66.220.152.32 ISP 1 66.220.152.1 Other Cust A 66.220.152.33 Other Cust B 66.220.152.34 ISP 4 98.139.183.1 ISP 5 ISP 6 129.42.60.1
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A C D z Dest Cost Rt A
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— v Dest Cost Rt A
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— x Dest Cost Rt A
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— w Dest Cost Rt A
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— 1 B t Dest Cost Rt A
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D 2 3 3 2 4 3 2 1 2 2
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A C D z Dest Cost Rt A
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— 1 B t Dest Cost Rt A
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D 2 3 3 2 4 3 2 1 2 2 2+1 via v 2+3 via x 2+1 via v
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A C D z Dest Cost Rt A
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D 2 3 3 2 4 3 2 1 2 2 no improvements
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A C D z Dest Cost Rt A
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t v Dest Cost Rt A
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t w Dest Cost Rt A
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D 2 3 3 2 4 3 2 1 2 2
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A C D z Dest Cost Rt A
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vw D
t v Dest Cost Rt A
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t w Dest Cost Rt A
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D 2 3 3 2 4 3 2 1 2 2
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A C D z Dest Cost Rt A
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vw D
t v Dest Cost Rt A
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z x Dest Cost Rt A
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t w Dest Cost Rt A
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v 1 B t Dest Cost Rt A
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D 2 3 3 2 4 3 2 1 2 2
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Use Abstraction… (and hierarchy)
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AS 1 AS 4 AS 2 AS 3
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Figure from DNS – Domain Name System, CS234, UC Irvine.
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cis.poly.edu gaia.cs.umass.edu
dns.poly.edu
authoritative DNS server dns.cs.umass.edu
Adapted from DNS – Domain Name System, CS234, UC Irvine.
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Does a simple HTTP request of google.com
// adapted from simple-client.c by Sean Walton and Macmillan Publishers // adapted by Tyler Bletsch for Duke University // This program will request http://google.com/ and print the first 1024 bytes of the response // Note: for simplicity, the google IP address is hard coded #include <stdlib.h> #include <stdio.h> #include <unistd.h> // needed for close #include <string.h> // needed for bzero #include <sys/socket.h> // needed for socket calls #include <resolv.h> // needed for socket type #include <arpa/inet.h> // needed for inet_aton #define PORT 80 #define SERVER_ADDR "172.217.1.14" // ^ this is google.com #define MAXBUF 1024 char request[] = "GET / HTTP/1.0\r\n\r\n"; int request_len = sizeof(request)-1; #define die(s) { perror(s); exit(1); } int main() { int sockfd; struct sockaddr_in dest; char buffer[MAXBUF]; /*---Open socket for streaming---*/ if ( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0 ) die("socket"); /*---Initialize server address/port struct---*/ bzero(&dest, sizeof(dest)); dest.sin_family = AF_INET; dest.sin_port = htons(PORT); if ( inet_aton(SERVER_ADDR, &dest.sin_addr) == 0 ) die(SERVER_ADDR); /*---Connect to server---*/ if (connect(sockfd, (struct sockaddr*)&dest, sizeof(dest)) != 0) die("connect"); /*---Send request---*/ send(sockfd, request, request_len, 0); /*---Get and print response---*/ bzero(buffer, MAXBUF); recv(sockfd, buffer, sizeof(buffer), 0); printf("%s", buffer); /*---Clean up---*/ close(sockfd); return 0; }
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