计算机结构与组成29-网络

CS61C L221 Performance ? UC Regents I/O Review I/O gives computers their 5 senses I/O speed range is 12.5-million to one Differences in processor and I/O speed ? synchronize with I/O devices before use Polling works, but expensive processor repeatedly queries devices Interrupts works, more complex device causes an exception, causing OS to run and deal with the device I/O control leads to Operating Systems Why Networks? Originally sharing I/O devices between computers ex: printers Then communicating between computers ex: file transfer protocol Then communicating between people ex: e-mail Then communicating between networks of computers ex: file sharing, www, … How Big is the Network (2006)? in 273 Soda in in eecs & cs . in in .edu (2005: ~9,000,000) in US (2005: ~217,000,000)(.net .com .edu .arpa .us .mil .org .gov) in the world (2005:~317,000,000) Growth Rate Shared vs. Switched Based Networks Shared vs. Switched: Switched: pairs (“point-to-point” connections) communicate at same time Shared: 1 at a time (CSMA/CD) Aggregate bandwidth (BW) in switched network ismany times shared: point-to-point faster since no arbitration, simpler interface What makes networks work? links connecting switches to each other and to computers or devices 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), ... The Sprint U.S. Topology (2001) Administrivia It’s the final countdown… <2 weeks left! Last Lecture and Course Surveys on Friday 12/08 Final Review Session on Sunday 12/10 Final Exam on Thursday 12/14 Project 3 grading this week Wednesday, Thursday, Friday Sign up for time slot online ABCs of Networks: 2 Compute