inst eecs berkeley edu cs61c CS61C Machine Structures Lecture 39 I O Networks 2004 12 01 Lecturer PSOE Dan Garcia www cs berkeley edu ddgarcia Clean to Zombie Bot in 4min USA Today and Avantegarde report that it took less than 4 min for an unprotected PC running XP SP1 to be compromised The Mac and Linux box were attacked but didn t fall www usatoday com money industries technology 2004 11 29 honeypot x htm CS61C L39 I O Networks 1 Garcia Fall 2004 UCB I O Review I O gives computers their 5 senses I O speed range is 12 5 million to one Processor speed means must synchronize with I O devices before use Polling works but expensive processor repeatedly queries devices Interrupts works more complex devices causes an exception causing OS to run and deal with the device I O control leads to Operating Systems CS61C L39 I O Networks 2 Garcia Fall 2004 UCB Peer Instruction A A faster CPU will result in faster I O 1 B Hardware designers handle mouse input 2 3 with interrupts since it is better than 4 polling in almost all cases 5 6 C Low level I O is actually quite simple as 7 it s really only reading and writing bytes 8 CS61C L39 I O Networks 3 ABC FFF FFT FTF FTT TFF TFT TTF TTT Garcia Fall 2004 UCB Peer Instruction Answer A Less sync data idle time B Because mouse has low I O rate polling often used C Concurrency device requirements vary TRUE FALSE FALSE A A faster CPU will result in faster I O 1 B Hardware designers handle mouse input 2 3 with interrupts since it is better than 4 polling in almost all cases 5 6 C Low level I O is actually quite simple as 7 it s really only reading and writing bytes 8 CS61C L39 I O Networks 4 ABC FFF FFT FTF FTT TFF TFT TTF TTT Garcia Fall 2004 UCB Buses in a PC connect a few devices 2002 Memory CPU bus Memory PCI Interface Data rates P4 Memory 400 MHz 8 bytes 3 2 GB s peak PCI Internal Backplane I O bus Ethernet SCSI Interface Interface Bus shared medium of communication that can connect to many devices Hierarchy SCSI External I O bus PCI 100 MHz 8 bytes wide 0 8 GB s peak SCSI Ultra4 160 MHz Wide 2 bytes 0 3 GB s peak 1 to 15 disks CS61C L39 I O Networks 5 Ethernet Local Gigabit Area Ethernet Network 0 125 GB s peak Garcia Fall 2004 UCB Shared vs Switched Based Networks Shared Media vs Switched in switched pairs point to point connections communicate at same time shared 1 at a time Shared Node Node Node Aggregate bandwidth BW in switched Node network is many times shared point to point faster since no arbitration simpler interface CS61C L39 I O Networks 6 Node Crossbar Switch Node Node Garcia Fall 2004 UCB Why Networks Originally sharing I O devices between computers e g printers Then Communicating between computers e g file transfer protocol Then Communicating between people e g email Then Communicating between networks of computers File sharing WWW CS61C L39 I O Networks 7 Garcia Fall 2004 UCB How Big is the Network 1999 30 Computers in 273 Soda 400 in inst cs berkeley edu 4 000 in eecs cs berkeley edu 50 000 in berkeley edu 5 000 000 in edu 46 000 000 in US com net edu mil us org 56 000 000 in the world Source Internet Software Consortium CS61C L39 I O Networks 8 Garcia Fall 2004 UCB Growth Rate 100 000 000 90 000 000 80 000 000 70 000 000 60 000 000 50 000 000 40 000 000 Internet Hosts 30 000 000 Ethernet Bandwidth 20 000 000 10 000 000 0 Jan 93 Apr 95 Jun 97 Aug 99 Source Internet Software Consortium http www isc org CS61C L39 I O Networks 9 1983 3 mb s 1990 10 mb s 1997 100 mb s 1999 1000 mb s 2004 10 Gig E to come Garcia Fall 2004 UCB What makes networks work links connecting switches to each other and to computers or devices Computer switch switch network interface switch ability to name the components and to route packets of information messages from a source to a destination Layering protocols and encapsulation as means of abstraction 61C big idea CS61C L39 I O Networks 10 Garcia Fall 2004 UCB Typical Types of Networks Local Area Network Ethernet Inside a building Up to 1 km peak Data Rate 10 Mbits sec 100 Mbits sec 1000 Mbits sec 1 25 12 5 125 MBytes s Run installed by network administrators Wide Area Network Across a continent 10km to 10000 km peak Data Rate 1 5 Mb s to 10000 Mb s Run installed by telecommunications companies Sprint UUNet MCI AT T Wireless Networks LAN CS61C L39 I O Networks 11 Garcia Fall 2004 UCB The Sprint U S Topology 2001 CS61C L39 I O Networks 12 Garcia Fall 2004 UCB ABCs of Networks 2 Computers Starting Point Send bits between 2 computers appln appln network interface device OS OS Queue First In First Out on each end Can send both ways Full Duplex Information sent called a message Note Messages also called packets CS61C L39 I O Networks 13 Garcia Fall 2004 UCB A Simple Example 2 Computers What is Message Format Similar idea to Instruction Format Fixed size Number bits Length 8 bit Data 32 x Length bits Header Trailer information to deliver message Payload data in message What can be in the data anything that you can represent as bits values chars commands addresses CS61C L39 I O Networks 14 Garcia Fall 2004 UCB Questions About Simple Example What if more than 2 computers want to communicate Need computer address field in packet to know which computer should receive it destination and to which computer it came from for reply source just like envelopes Dest Source Len Net ID Net ID CMD Address Data 8 bits 8 bits 8 bits 32xn bits Header Payload CS61C L39 I O Networks 15 Garcia Fall 2004 UCB ABCs many computers application application network interface device OS OS switches and routers interpret the header in order to deliver the packet source encodes and destination decodes content of the payload CS61C L39 I O Networks 16 Garcia Fall 2004 UCB Questions About Simple Example What if message is garbled in transit Add redundant information that is checked when message arrives to be sure it is OK 8 bit sum of other bytes called Check sum upon arrival compare check sum to sum of rest of information in message xor also popular Checksum Net ID Net ID Len Header CMD Address Data Payload Trailer Math 55 talks about what a Check sum is CS61C L39 I O Networks 17 Garcia Fall 2004 UCB Questions About Simple Example What if message never arrives Receiver tells sender when it arrives ack ala registered mail sender retries if waits too long Don t discard message until get ACK for …
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