Lecture 1 - Introduction

Introduction
Abusayeed Saifullah
CS 5600 Computer Networks
These slides are adapted from Kurose and Ross
Goals of This Course
v 
Be familiar with
§  Fundamental network topics
§  Some advanced topics
§  State-of-the-art
v 
Implement the course concepts on networked
computers or embedded networked devices or
through standard simulators
Course Outline
Introduction to computer networks
v  Application layer
v  Transport layer
v  Network layer
v  Media Access Control (MAC) layer
v  Wireless networks
v  Basic security concepts
v 
Personnel
v 
Instructor
§  Dr. Abusayeed Saifullah
Personnel
v 
Instructor
§  Dr. Abusayeed Saifullah
§  Office: 335 Computer Science Building
§  Office hours
–  Tuesday 11:00am-12:00pm or by appointment
–  Feel free to stop by if you see I am in my office
v 
Teaching assistant
§  XXX XXX
•  office hours: TBD
Resources
v 
Textbook
§  Computer Networking: A Top-Down
Approach, 6/e; Kurose and Ross
v 
Reference books
§  Computer Networks; Tanenbaum
and Wetherall
§  Java Network Programming;
Elliotte Harold
§  Beej's Guide to Network Programming Using Internet Sockets
v 
Course website
§  http://web.mst.edu/~saifullaha/courses/cs5600.html
Coursework
Homework and literature study: 20%
v  Midterm: 25%
v  Final: 25%
v  Project: 25%
v  Class participation: 5%
v 
Literature study
General Network: SIGCOMM
v  Wireless: MobiCom
v  Theory: MobiHoc
v  Wireless sensor network: SenSys, IPSN, RTSS
v  Real-Time wireless: RTSS, RTAS
v 
Project
Group work: 3-4 students per group
v  Three options
v 
§  Each group can choose its own project à needs
instructor’s approval
§  Research project (requiring effort beyond the course
req.)
§  Instructor-assigned network protocol implementation
v 
Real implementation or in standard network
simulator (NS, QualNet, TOSSIM)
Expertise for Project
TinyOS, Contiki
v  NesC, C/C++, Java
v  Software Radio
v  QualNet, NS, TOSSIM
v  Socket Programming
v 
Questions?
Lecture Outline
our goal:
v  get feel and
terminology
v  more depth, detail
later in course
v  approach:
§  use Internet as
example
overview:
v 
v 
v 
v 
v 
v 
v 
v 
what s the Internet?
what s a protocol?
network edge; hosts, access net,
physical media
network core: packet/circuit
switching, Internet structure
performance: loss, delay,
throughput
security
protocol layers, service models
history
Roadmap
1.1 what is the Internet?
1.2 network edge
§  end systems, access networks, links
1.3 network core
§  packet switching, circuit switching, network structure
1.4 delay, loss, throughput in networks
1.5 protocol layers, service models
1.6 networks under attack: security
1.7 history
What is a Network?
An entity of interconnected
computers
v  Example
v 
§  Internet: the largest and the
most well-known network
§  Wireless LAN
§  3G Mobile
§  Wireless sensor network
v 
Driving applica,ons §  WWW, email, chat, videoconferencing, e-­‐commerce, audio/video streaming, VOIP, file sharing, monitoring, controlling, social networking Distributed Systems vs. Network
Distributed Systems vs. Network
A networked system can be either
centralized or distributed
v  Distributed system
v 
§  No centralized computation
§  Local computation
§  Scalable
•  Why?
•  Think why there are 50
states in USA
What s the Internet: nuts and bolts view
PC
server
v millions
wireless
laptop
smartphone
of connected
computing devices:
§  hosts = end systems
§  running network apps
v communication
wireless
links
wired
links
links
§  fiber, copper, radio,
satellite
§  transmission rate:
bandwidth
v Packet
router
switches: forward
packets (chunks of data)
§  routers and switches
mobile network
global ISP
home
network
institutional
network
regional ISP
Fun internet appliances
Web-enabled toaster +
weather forecaster
IP picture frame
http://www.ceiva.com/
Tweet-a-watt:
monitor energy use
Slingbox: watch,
control cable TV remotely
Internet
refrigerator
Internet phones
How does the Internet Look Like? Internet Protocol
v  Drives Internet traffic (see analogy with road traffic)
What’s a protocol?
human protocols:
v 
v 
v 
what s the time?
I have a question
introductions
… specific msgs sent
… specific actions taken
when msgs received, or
other events
network protocols:
v 
v 
machines rather than
humans
all communication activity
in Internet governed by
protocols
protocols define format, order
of msgs sent and received
among network entities,
and actions taken on msg
transmission, receipt
What s a protocol?
a human protocol and a computer network protocol:
Hi
TCP connection
request
Hi
TCP connection
response
Got the
time?
Get http://www.awl.com/kurose-ross
2:00
<file>
time
Protocol Standardization
v  Most widely used protocols are defined in standards
v  Why standard?
Internet Standardization Process
v  All standards of the Internet are published as RFC
(Request for Comments)
❍ 
❍ 
e.g., the SMTP protocol is specified in RFC821
but not all RFCs are Internet Standards
Internet Standardization Process
v  All standards of the Internet are published as RFC
(Request for Comments)
❍ 
❍ 
v 
e.g., the SMTP protocol is specified in RFC821
but not all RFCs are Internet Standards
A typical (but not the only) way of standardization:
❍ 
❍ 
❍ 
❍ 
Internet draft
RFC
draft standard (requires 2 working implementations)
Internet standard (declared by Internet Architecture
Board)
v  David Clark, 1992:
We reject: kings, presidents, and voting. We believe in:
rough consensus and running code.
Roadmap
1.1 what is the Internet?
1.2 network edge
§  end systems, access networks, links
1.3 network core
§  packet switching, circuit switching, network structure
1.4 delay, loss, throughput in networks
1.5 protocol layers, service models
1.6 networks under attack: security
1.7 history
A closer look at network structure:
v  network
§ 
§ 
v 
mobile network
hosts: clients and servers
servers often in data
centers
access networks, physical
media: wired, wireless
communication links
§ 
v 
edge:
global ISP
home
network
Shared or dedicated
network core:
§ interconnected routers
§ network of networks
institutional
network
regional ISP
Access net: digital subscriber line (DSL)
central office
DSL splitter
modem
voice, data transmitted
at different frequencies over
dedicated line to central office
telephone
network
DSLAM
ISP
DSL access
multiplexer
use existing telephone line to central office DSLAM
§  data over DSL phone line goes to Internet
§  voice over DSL phone line goes to telephone net
§  dedicated
v  < 2.5 Mbps upstream transmission rate (typically < 1 Mbps)
v  < 24 Mbps downstream transmission rate (typically < 10 Mbps)
v 
Access net: cable network
cable headend
…
cable splitter
modem
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Channels
frequency division multiplexing: different channels transmitted
in different frequency bands
Access net: cable network
cable headend
…
cable splitter
modem
data, TV transmitted at different
frequencies over shared cable
distribution network
v 
v 
CMTS
ISP
HFC: hybrid fiber coax
§  asymmetric: up to 30Mbps downstream transmission rate, 2
Mbps upstream transmission rate
network of cable, fiber attaches homes to ISP router
§  homes share access network to cable headend
§  unlike DSL, which has dedicated access to central office
Wireless access networks
v 
shared wireless access network connects end system to router
§  via base station aka access point
wide-area wireless access
wireless LANs:
§  within building (100 ft)
§  802.11b/g (WiFi): 11, 54 Mbps
transmission rate
§  provided by telco (cellular)
operator, 10 s km
§  between 1 and 10 Mbps
§  3G, 4G: LTE
to Internet
to Internet
Host: sends packets of data
host sending function:
v  takes application message
v  breaks into smaller
chunks, known as packets,
of length L bits
v  transmits packet into
access network at
transmission rate R
§  link transmission rate,
aka link capacity, aka
link bandwidth
packet
transmission
delay
=
two packets,
L bits each
2 1
R: link transmission rate
host
time needed to
transmit L-bit
packet into link
=
L (bits)
R (bits/sec)
Physical media
v 
bit: propagates between transmitter/receiver pairs
v 
physical link: what lies between transmitter & receiver
§  guided media: signals propagate in solid media: copper,
fiber, coax
§  unguided media: signals propagate freely, e.g., radio
Physical media: radio
v 
v 
v 
v 
signal carried in
electromagnetic spectrum
no physical wire
bidirectional
propagation environment
effects:
§  reflection
§  obstruction by objects
§  interference
radio link types:
v 
terrestrial microwave
§  e.g. up to 45 Mbps channels
v 
LAN (e.g., WiFi)
§  11Mbps, 54 Mbps
v 
wide-area (e.g., cellular)
§  3G cellular: ~ few Mbps
v 
satellite
§  Kbps to 45Mbps channel (or
multiple smaller channels)