Hardware and Networking 
Class 2
LBSC 690
Information Technology
Agenda
•	Questions
•	History of Computing and Communication
•	What’s inside the Internet?
–	Computer processors
–	The storage hierarchy
–	Networking
–	Software
Very Brief History of Computing
•	Hardware:
–	Mechanical (adding machines)
–	Transistors & integrated circuits
–	Merge with consumer electronics
–	Re-emergence of compute intensive (“heavy metal”) web servers
•	Software: 
–	initial applications were military: (Numeric) computing gun angles and (Symbolic) Code-breaking
–	Network computing (e.g., java)
History of Networking and Services
•	Networking
–	From analog voice communications to digital convergence
–	Can no longer maintain the distinction between computing and communications
•	Services
–	From data processing to information processing (Vanevar Bush predicted this in 1948)
–	Interoperability essential in networked environment (big 4: URL, HTML, HTTP, MIME, + SMIL??) 

Timeline: Computing, Communication and Entertainemnt 
•	1960s - Mainframes, Transistor radios
–	IBM
•	1970s - Minicomputers
–	Digital Equipment (DEC)
•	1980s - Personal computers, LANs, CDs
–	Apple, Microsoft
•	1990s- Web, Internet, Cellular phones
–	Yahoo, AOL
•	2000s - Ecommerce? Wireless? MP3
–	Amazon, Ebay

Trends
•	Moore’s Law and related laws
–	processing capacity doubles every 18 months
–	disk capacity, networking speed, pixels on displays all increasing
–	miniturization (television camera and transmitter on an artificial insect) 
–	More information in more places: Ubiquitous information - wireless
•	Personalized services but loss of privacy
–	“de-massification” of mass media
Hardware Processing Cycle
•	Three basic parts
–	Input comes from somewhere
•	Keyboard, mouse, microphone, etc.
–	The system does something with it
•	Processor, memory, software, network
–	Output goes somewhere
•	Monitor, speaker, robot controls, etc.

Computer Hardware
•	Central Processing Unit (CPU)
–	Intel Pentium, Motorola Power PC, …
•	Internal communications “Bus”
–	PCI, ISA, …
•	Storage devices
–	Cache, RAM, hard drive, floppy disk, …
•	External communications
–	Modem, LAN, ...
Ways to Measure Speed
•	Speed can be expressed two ways:
–	How long to do something once?
•	Memory speed measured in access time
–	How many times can you do it in one second?
•	Processor speed measured in instructions per second
•	Convenient units are typically used
–	“10 microseconds” rather than “0.00001 seconds”
–	When comparing speeds, convert units first! 
•	Time and services
•	moderate priority -email
•	small lag - viewing TV program
•	real time interactive - telephone call

Converting Units
Speed

Unit	      Abbr	Fraction of a sec

second	      sec	1
millisecond    ms	1/1,000
microsecond  ms	1/1,000,000
nanosecond    ns	1/1,000,000,000
picosecond     ps	1/1,000,000,000,000
Size

Unit	Abbr	Bytes
bit		b	1/8
byte	B	1
kilobyte	kB	1,024
megabyte	MB	1,048,576
gigabyte	GB	1,073,741,824
terabyte	TB	1,099,511,627,776
CPU <-> Memory
•	The CPU is the fastest part of a computer
–	200 MHz Pentium = 100 MIPS
•	One operation every 10 ns
•	Cache memory is fast enough to keep up
–	10 ns L1 cache on chip, 32 kB (in a Pentium)
–	Soon, memory and CPU on one chip
•	RAM has more capacity but is slower
–	60 ns, typically at least16 MB
Types of Mass Storage
•	Fixed disk
–	May be partitioned into multiple volumes
•	In Windows, referred to as C:, D:, E:, …
•	In Unix, referred to as /software, /homes, /mail, …
•	Removable disks
–	3.5 inch floppy disk, zip drives
•	“Read-only” disks
–	CD-ROM, DVD-ROM
•	Sequential Storage 
–	Tapes store and access data sequentially
–	backups are important

The Disk Storage Hierarchy
•	The problem:
–	Fast memory devices are expensive
•	So large memory devices are slow!
–	But fast access to large memories is needed
•	The solution:
–	Keep what you need often in small (fast) places
•	Keep the rest in large (slow) places
–	Copy quickly between the two
How Disks Work
Memory <-> Disk
•	Hard disk is larger than RAM but much slower
–	10 ms access time and 2 GB is typical
•	1 hundred times larger than RAM
•	1 million times slower than the CPU!
•	The initial access is the slow part
–	Subsequent bytes sent at 17 MB/sec (60 ns/byte)
•	As virtual memory, makes RAM seem larger
–	But things slow down beyond physical RAM
System <-> Network
•	“The network is the computer”
–	Network file systems
•	Networks can be even slower than disks
–	12 ms each way to California using fiber optics
•	250 ms each way using a satellite
–	Sharing the circuit adds more delay
•	Two solutions
–	Use local disk to store some network data
•	Called “temporary Internet files” in Internet Explorer
–	Transfer files using FTP and then work locally
Communication Speeds
•	Traditional modems
–	Speed in kb/s (14.4, 28.8, 33.6, 56?)
–	Each byte (B) takes 10 bits (not 8!)
•	Cable modems
–	10 Mb/sec for data sent from cable company
–	Traditional modem for data sent by the user
•	T1
–	1.5 Mb/sec (1 medium quality video)
•	UMCP Campus backbone 
–	155Mb/s
•	Gigapop servers
System <-> User
•	People are usually the slowest component J
–	Fast typists produce 10 characters per second
–	Human perception time is about 100 ms
•	Batch processing lets machine run fast
–	Type everything in, then process it all at once
–	Very common when computing was expensive
•	Networks are sometimes slower than people 
–	Use a “type-ahead” buffer for congested periods
•	People do much better pattern recognition J

Networks
Some Network Vocabulary
•	Hosts
–	The computers that share the network
•	Communications
–	Like modems, with dedicated phone lines
•	Routing
–	Find a path from one host to another
•	Local Area Networks (LANs) (e.g., ethernet)
•	Wide Area Networks (WANs)
Packet Switching
•	Circuit switching vs. packet switching
•	Break long messages into short packets
–	Keeps one user from hogging a line
•	Route each packet separately
–	Number them for easy reconstruction
•	Request retransmission for lost packets
–	Unless the first packet is lost
•	Packet protocols
–	TCP/IP
Domain Names
•	IP addresses are 32 bit numbers
–	Part of every packet, designed for easy routing
•	People prefer to use names for things
–	Need to covert “domain names” to numbers
•	Each name server knows one level of names
–	WAM’s name server knows rac1, rac2, …
–	UMD’s name server knows wam, glue, ttclass, …
–	.edu name server knows umd, umbc, stanford, …
–	“Top level” name server knows .edu, .com, .mil, …
Types of Software
•	Application programs (e.g., Powerpoint)
–	What you normally think of as a “program”
•	Compilers and interpreters (e.g., Java)
–	Programs used to write other programs
•	Operating system (e.g., Windows 95)
–	Manages display, CPU, memory, disk, tape, …
•	Embedded program (e.g., a disk controller)
–	Permanent software inside some device
Hardware Summary
•	Speed, cost, and size (or distance) in CPUs:
–	You can easily get any 2, but not all 3
–	Computers use cache as a compromise strategy
•	The Internet includes LAN’s and WAN’s
–	Each contributes unique characteristics
•	Hardware and software work synergistically
–	Our focus will be on software and the Internet
–	But understand hardware abilities and limitations
•	Hardware is a commodity, will that happed to software?