Network technology
November 12, 1998
Topics
•Overview
•Telephone system
•Ethernet
•ATM
15-213
class24.ppt
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Understanding Computer Networks: A Deep Dive into Ethernet, ATM, and Protocols, Slides of Introduction to Computers
This document from a 1998 computer science class provides an overview of computer networks, focusing on ethernet and atm technologies. Students are introduced to the concept of abstraction in computer science and the importance of understanding underlying implementations. Packet communication, protocols, and performance measures, preparing students for later classes on compilers, operating systems, and networks.
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TopicsNovember 12, 1998Network technology
Overview
Telephone system
Ethernet
ATM
class24.ppt
CS 213 F’
class24.ppt
Course Theme
Abstraction is good, but don’t forget reality!
Earlier courses to date emphasize abstraction
Abstract data types
Asymptotic analysis
These abstractions have limits
Especially in the presence of bugs
Need to understand underlying implementations
Useful outcomes
- Able to tune program performance – Able to find and eliminate bugs efficiently Become more effective programmers
- Compilers, Operating Systems, Networks, Computer Architecture Prepare for later “systems” classes
CS 213 F’
class24.ppt
cdrom^ disk
Diskdisk
Computer system
Local/IO BusLocal/IO Bus
MemoryMemory
adaptoradaptorNetworkNetwork
controllercontrollerIDE diskIDE disk
adaptorVideoVideo DisplayDisplay adaptor
NetworkNetwork
and L1 cacheProcessorProcessor and L1 cache
controllercontrollerInterruptInterrupt
SCSI
SCSI busSCSI buscontrollercontrollerSCSI
controllercontrollerSerial portSerial port
controllercontrollerParallel portParallel port
controllercontrollerKeyboardKeyboardKeyboardKeyboard
MouseMouse
PrinterPrinter
ModemModem
Diskdisk
CS 213 F’
class24.ppt
Simple example
Starting Point: Want to send bits between 2 computers
FIFO queue on each end
Can send both ways (“full duplex”)
Name for standard group of bits sent: “packet”
Packet format and rules for communicating them (“protocol”)
Simple
request/response protocol and packet format:
data/address
1: here is the data word you asked for.0: please send the data word at “address”^ header
payload
CS 213 F’
class24.ppt
Generic network
h/w interfaceh/w interfaces/w interfaces/w interface
InterconnectInterconnect
h/w interfaceh/w interfaces/w interfaces/w interface
h/w interfaceh/w interfaces/w interfaces/w interface
link
link
link
host
host
host
protocol stack
interface cardadaptor/
kernel code
CS 213 F’
class24.ppt
Protocols
A
for communicating them across the network.protocol defines the format of packets and the rules
Different protocols provide different levels of service:
simple error correction (ethernet)
uniform name space, unreliable best-effort datagrams (host-host) (IP)
reliable byte streams (TCP)
unreliable best-effort datagrams (process-process) (UDP)
multimedia data retrieval (HTTP)
CS 213 F’
class24.ppt
TCP segment^ Encapsulation
header
TCP segment header
datadata datadata
Ethernet frame header
Ethernet frame header
IP datagram header
IP datagram header
TCP segment header
TCP segment header
datadata
IP datagram header
IP datagram header
TCP segment header
TCP segment header
datadata
Network interfaceIP TCP Application
CS 213 F’
class24.ppt
Protocol stacks
Repeaters/Bridges/Routers
Host A
Host B
Xmit raw bitsaccessrecovery, mediaFraming, ErrorCongestionFlow controlRouting
HTTP, emailTelnet, FTP,
IP
TCP/UDP
transportapplication
physicaldata linknetwork
transportapplication
physicaldata linknetwork
end user serviceReliable, efficient
physicaldata linknetwork
physicaldata linknetwork
10Base-TCSMA/CD
CS 213 F’
class24.ppt
Shared vs switched media
Shared media (e.g., Ethernet)
Switched media (e.g., ATM)
bb
cc
aa
dd
switch
aa
cc
bb
dd
aa
cc
bb
dd
bb
cc
aa
dd
switch
aa
cc
bb
dd
aa
cc
bb
dd
output ports
input ports
CS 213 F’
class24.ppt
Network performance measures
CS 213 F’
class24.ppt
Importance of Overhead (+ Latency)
Ethernet / SS10:
9 Mb/s BW,
secs ovhd
ATM
Synoptics
78 Mb/s BW,
secs ovhd.
NFS trace over 1 week: 95% msgs < 200 bytes
E t h e r n e t
ATM
Time (sec)
Overhead Transmission
7129
secs
9325
secs
Link
bandwidth
is
as
misleading
as
MIPS
CS 213 F’
class24.ppt
Basic network types
System area network
• (SAN)
- (^) 300 MB/s Cray T3E (^) same room (meters)
Local area network (LAN)
(kilometers)same bldg or campus
10 Mb/sEthernet
100 Mb/s Fast Ethernet
100 Mb/s FDDI
150 Mb/s OC-3 ATM
622 Mb/s OC-12 ATM
Metropolitan area network
• (MAN)
- (^) 800 Mb/s Gigabit Nectar (^) same city (10’s of kilometers)
Wide area network (WAN)
(1000’s of kilometers)nationwide or worldwide
telephone system
1.544 Mb/s T1 carrier
44.736 Mb/s T3 carrier
CS 213 F’
class24.ppt
Computer-to-computer calls
codeccodec
codeccodec
33 MB/scable or bus)digital (short
33 MB/scable or bus)digital (short
digital
digital
local loopanalog28.8 Kb/s
1.544 Mb/s (T1 carrier)
local loopanalog28.8 Kb/s
officelocal
officelocal
officetoll
home computerhome computer
home computerhome computer
V.34 modemV.34 modem
V.34 modemV.34 modem
CS 213 F’
class24.ppt
Modulating digital signals
to previous wave)(shifts are relative11: 3/4 shift left10: 1/2 shift left01: 1/4 shift left00 : no shiftmodulationphase modulationamplitudebinary signaling
sine wave carrier (1kHz-2kHz)