CS 152 Computer Architecture and Engineering Lecture 21 Networks and Routers 2006 11 9 John Lazzaro www cs berkeley edu lazzaro TAs Udam Saini and Jue Sun www inst eecs berkeley edu cs152 CS 152 L21 Networks and Routers UC Regents Fall 2006 UCB Last Time NAND Flash Idea Disk Replacement Presents memory to the CPU as a set of pages Chip remembers for 10 years Page format 2048 Bytes user data 64 Bytes meta data Note NOR Flash is another flash product for software code NOR Flash read interface is just like SRAM CS 152 L21 Networks and Routers NAND Flash has better cost bit UC Regents Fall 2006 UCB Last Time Making the Mac Mini G4 Size fixed by the form factor physical size of desktop DIMMS Laptop DRAM is smaller but too expensive for 499 price CS 152 L21 Networks and Routers UC Regents Fall 2006 UCB Why are networks different from buses Serial Data is sent bit by bit over one logical wire Network Network Primary Primary purpose purpose is is to to connect connect computers computers to to computers computers CS 152 L21 Networks and Routers USB USB FireWire FireWire Primary Primary purpose purpose is is to to connect connect devices devices to to a a computer computer UC Regents Fall 2006 UCB Today Networks Link layers Using physics to send bits from place to place Internet A network of networks Routing Inside the cloud CS 152 L21 Networks and Routers UC Regents Fall 2006 UCB Today Router Design Router architecture What s inside the box Forwarding engine How a router knows the next hop for a packet Switch fabric When buses are too slow replace it with a switch CS 152 L21 Networks and Routers UC Regents Fall 2006 UCB Networking bottom up Link two endpoints Q1 How far away are the endpoints Japan US undersea cable network Physical media optical fiber photonics Distance WiFi wireless mobility from hotel bed to bandwid access th Physical media unlicensed radio point influenc CS 152 L21 Networks and Routers UC Regents Fall 2006 UCB Networking bottom up Link two endpoints Q2 Initial investment cost for the link 1B USD A ship lays cable on ocean floor For The price expensive of the media WiFi much of laptop the price card the goes Unlicensed radio no fee to to base CS 152 L21 Networks and Routers UC Regents Fall 2006 UCB Networking bottom up Link two endpoints Q3 How is the link imperfect A steady bitstream circuit No Only bit flips per packets toone lose 10 000 000 000 000 sent Undersea failure is catastroph Solution ic Short Someone packets walks by spaced in and the time to network escape the stops CS 152 L21 Networks and Routers UC Regents Fall 2006 UCB Networking bottom up Link two endpoints Q4 How does link perform BW 640 ping irt1 ge1 1 tdc noc sony co jp Gb s CA JP Latenc PING irt1 ge1 1 tdc noc sony co jp 211 125 132 198 56 data bytes cable 64 bytes from 211 125 132 198 icmp seq 0 ttl 242 time 114 571 ms y round trip Compare Light speed in vacuum SFOTokyo 63ms In general risky to halve the round trip time RT for oneway latency paths are often different each direction BW In theory 801 11b offers 11 Mb s Users areIflucky 3 5 Mb s in Latency theretoissee no fading practice quite good CS 152 L21 Networks and Routers UC Regents Fall 2006 UCB There are dozens of link networks Protocol Complexity email WWW phone SMTP HTTP RTP TCP UDP IP The undersea CSMA async sonet cable the copper fiber radio hotel WiFi Diagram Credit Steve Deering and many Ethernet Wi Fi Link networ ks CS 152 L21 Networks and Routers UC Regents Fall 2006 UCB Web browsers do not know about link nets Protocol Complexity Applicatio ns Link networ ks CS 152 L21 Networks and Routers App authors email WWW phone do not want SMTP HTTP RTP to add TCP UDP support for N different IP network The types Ethernet Wi Fi undersea CSMA async sonet cable the copper fiber radio hotel WiFi Diagram Credit Steve Deering and many UC Regents Fall 2006 UCB The Internet A Network of Networks Protocol Complexity IP presents Internet email WWW phone link network Protocol IP errors losse SMTP HTTP RTP An s in an TCP UDP abstraction abstract for IP way not a applications link specific to target Ethernet Wi Fi Link way layer CSMA async sonet and for link is not networks to copper fiber radio expected support to be Diagram Credit Steve Deering Very simple perfect CS 152 L21 Networks and Routers UC Regents Fall 2006 UCB The Internet interconnects hosts IP4 IP4 number number for for this this computer computer 198 211 61 22 Every directly 198 211 61 22 connected host has a unique IP number Upper limit of 2 32 IP4 numbers some are reserved for other purposes Next generation IP 198 211 61 22 form 198 211 61 22 A A user friendly user friendly form of of IP6 limit 2 128 the the 32 bit 32 bit unsigned unsigned value value 3335732502 3335732502 CS 152 L21 Networks and Routers UC Regents Fall 2006 UCB Internet Sends Packets Between Hosts IP4 IP4 IP6 IP6 0etc etc How How the the destination destination the 1 should 2 3 should interpret interpret the 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 payload payload data data Version IHL Type of Service Total Length Identification Flags Fragment Offset Time to Live Protocol Header Checksum From Source Address Note From IP IP Note Could Could be be a a number lie To number Destination Addresslie To IP IP number number Payload data size implied by Total Length header field IHL IHL field field of of words words in in header header The The typical typical header header IHL IHL 5 5 words words is is shown shown Longer Longer headers headers code code add add extra extra CS 152 L21 Networks and Routers Bitfield Bitfield number number ss Heade Heade rr Data Data UC Regents Fall 2006 UCB Link networks transport IP packets ISO ISO Layer Layer Names IP Names IP packet packet Layer Layer 3 WiFi 3 WiFi and and Cable Cable Modem Modem packets packets Radio cable Layer Radio cable waveforms Layer 2 2 waveforms Layer Layer 1 1 801 11b WiFi packet IP Packet CS 152 L21 Networks and Routers For For this this hop hop IP IP packet packet sent sent inside inside of of a a wireless wireless Cable modem packet IP Packet For For this this hop hop IP IP packet packet sent sent inside inside of of a a cable cable modem modem DOCSIS DOCSIS UC Regents Fall 2006 UCB Link layers maximum packet size vary Maximum Maximum IP IP packet packet size size 64K 64K bytes bytes Maximum Maximum Transmission Transmission Unit Unit MTU MTU generalized generalized packet packet size of may size of link …
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