inst eecs berkeley edu cs61c CS61C Machine Structures Lecture 38 I O Networks Lecturer PSOE Dan Garcia www cs berkeley edu ddgarcia Now Dual core processors Intel has found a way to achieve more performance out of their chips go parallel They ve introduced dual core technology i e 2 CPUs on a die This is similar to multiprocessing but on 1 die www intel com technology computing dual core CS61C L38 I O Netw orks 1 Garcia 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 L38 I O Netw orks 2 Garcia UCB Buses in a PC connect a few devices 2002 Memory CPU bus Memory PCI Interface Data rates P4 PCI Internal Backplane I O bus Ethernet SCSI Interface Interface Memory 400 MHz 8 bytes 3 2 GB s peak PCI 100 MHz 8 bytes wide 0 8 GB s peak Bus shared medium of communication that can connect to many devices Hierarchy SCSI External I O bus 1 to 15 disks Ethernet Local SCSI Ultra4 160 MHz Gigabit Area Wide 2 bytes Network Ethernet 0 3 GB s peak 0 125 GB s peak CS61C L38 I O Netw orks 3 Garcia 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 Crossbar Switch Aggregate bandwidth BW in switched Node network is many times shared point to point faster since no arbitration simpler interface CS61C L38 I O Netw orks 4 Node Node Node Garcia 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 L38 I O Netw orks 5 Garcia UCB How Big is the Network 2005 30 Computers in 273 Soda 525 in inst cs berkeley edu 6 400 in eecs cs berkeley edu 1999 50 000 in berkeley edu 9 000 000 in edu 217 000 000 in US net com edu arpa us mil org gov 318 000 000 in the world Source Internet Software Consortium www isc org CS61C L38 I O Netw orks 6 Garcia UCB Growth Rate Ethernet Bandwidth 1983 3 mb s 1990 10 mb s 1997 100 mb s 1999 1000 mb s 2006 10 Gig E to come en wikipedia org wiki 10 gigabit ethernet CS61C L38 I O Netw orks 7 Garcia 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 L38 I O Netw orks 8 Garcia 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 L38 I O Netw orks 9 Garcia UCB The Sprint U S Topology 2001 CS61C L38 I O Netw orks 10 Garcia UCB Upcoming Calendar Week 14 This week 15 Next week 16 Mon Wed Thu Lab I O Basics I O Networks I O Simulation Fri TA Casey I O Disks No Dan OH Performance I LAST CLASS Last Week Summary o Classes Review Sun aft HKN Review Evals CS61C L38 I O Netw orks 11 Performance II I O Networks TA Andy TBD FINAL EXAM SAT 05 14 12 30pm Garcia UCB Administrivia Remember Dan will be at the Faculty Retreat and not have OH tomorrow He WILL have OH today right after lecture CS61C L38 I O Netw orks 12 Garcia UCB ABCs of Networks 2 Computers Starting Point Send bits between 2 computers app app OS OS network interface device Queue First In First Out on each end Can send both ways Full Duplex One way information is called Half Duplex Information sent called a message Note Messages also called packets CS61C L38 I O Netw orks 13 Garcia 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 L38 I O Netw orks 14 Garcia 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 L38 I O Netw orks 15 Garcia UCB ABCs many computers application application OS OS network interface device switches and routers interpret the header in order to deliver the packet source encodes and destination decodes content of the payload CS61C L38 I O Netw orks 16 Garcia 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 L38 I O Netw orks 17 Garcia 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 ACKnowledgment Also if check sum fails don t send ACK Checksum Net ID Net ID Len Header CS61C L38 I O Netw orks 18 ACK INFO CMD Address Data Payload Trailer Garcia UCB Observations About Simple Example Simple questions such as those above lead to more complex procedures to send receive message and more complex message formats Protocol algorithm for properly sending and receiving messages packets CS61C L38 I O Netw orks 19 Garcia UCB Software Protocol to Send and Receive SW Send steps 1 Application copies data to OS buffer 2 OS calculates checksum starts timer 3 OS sends data to network interface HW and says start SW Receive steps 3 OS copies data from network interface HW to OS buffer 2 OS …
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