Course Overview
Spring 2014
ECE/CS 372 Introduction to Computer Networks
Lecture 1
School of Electrical Engineering and Computer Science
Oregon State University
Credit for lecture slides to Professor Bechir Hamdaoui
Adapted from Jim Kurose & Keith Ross (original copyright)
Chapter 1, slide:
1
Lecture/Office/Lab Hours
 Course website


http://classes.engr.oregonstate.edu/eecs/spring2014/cs372-001/
Please write down this URL—all course material and information will be
provided thru this site
 Lectures

Tuesday, Thursday 12:00-1:20pm, 212 Kearney Hall
 Instructor

Stephen Redfield (redfiels@eecs.oregonstate.edu)

Office hours: TR 1:30-2:30pm @ Kelley Engineering Center Rm 2077
Chapter 1, slide:
2
Lecture/Office/Lab Hours
 Tamara AlShammari
 Location: KEC 2063
 Lab hours: to help you with your labs
 Hours TBD
Information can be found in course’s website
 MohammadJavad NoroozOliaee (MJ)
 Location: KEC 2063
 Office hours: to help you with your assignments
 Hours TBD
Information can be found in course’s website
Chapter 1, slide:
3
Prerequisite/Textbook
Prerequisite:
 CS or ECE 271 or an equivalent course
 Basic mathematical/probability skills
Textbook
 Textbook is Required
Computer Networking: A Top-Down Approach
Featuring the Internet, 6th Edition, Games F.
Kurose, Keith W. Ross
Chapter 1, slide:
4
Grading Policy
 Assignments: 15%



Each student must hand in one copy
5 assignments: approx. 1 every two weeks
Check, Check Minus, X Grading
 Labs: 20%


Each student must hand in one copy
4 labs: approx. 1 every two weeks
 Bonus pop quizzes: extra 2 to 10%

You need to get it completely right to receive an extra 1%
 One midterm exam: 30%
 Final exam: 35%
Chapter 1, slide:
5
Lectures & assignments
Objective
 Deep understanding of basic and fundamental
networking concepts, architectures, and philosophies
 IMPORTANT: this course is not about setting up your
router at home, or writing a twitter program!!
Approach: how to do well in this course
 Easy: attend ALL lectures and do ALL assignments
 Do your assignments individually (Don’t use Solutions)
 Do NOT miss any Bonus Quiz (i.e., do not miss class)
 Some HW problems will be solved in class: this gives
you the opportunity to clarify things further
Chapter 1, slide:
6
Labs
Objective
 Understand how Internet protocols work
 Force network protocols to perform certain actions
 Observe and analyze protocols’ behavior
Approach
 Software tool: Wireshark


Install on your Laptop
Do this EARLY so you can avoid problems with Lab 1
 Allows you to sniff and analyze traffic
sent/received from/by your end system: real
measurement of Internet traffic
 Lab 1 is posted and is due next Tuesday
Chapter 1, slide:
7
Break
 Online Course Available
 We’ll start after a 10-min break
Chapter 1, slide:
8
Chapter 1: Introduction
Our goal:
 learn basic network
terminologies
 more depth, detail
later in course
 approach:
 use Internet as
example
Acknowledgement: slides drawn heavily from Kurose & Ross
Chapter 1, slide:
9
Chapter 1: roadmap
1 What is the Internet?
2 Network edge
3 Network core
4 Internet structure and ISPs
5 Protocol layers, service models
6 Delay & loss in packet-switched networks
Chapter 1, slide: 10
What’s the Internet: a “service” view
 communication infrastructure
enables distributed apps:


Enables apps to communicate
Web, email, games, ecommerce, file sharing
 communication services
provided to apps:

Offers services
Chapter 1, slide: 11
What’s the Internet: “nuts and bolts” view
 hosts or end systems:
millions of connected
computing devices


e.g., Laptops, workstations
running network apps
router
server
mobile
local ISP
 routers & switches:
 forward packets (chunks of
data)
 communication links
 e.g., fiber, copper, radio,
satellite
workstation
regional ISP
company
network
Chapter 1, slide: 12
What’s the Internet: “nuts and bolts” view
 Internet standards
 IETF
(Internet Eng. Task Force)
• RFC: Request for comments

router
workstation
server
mobile
local ISP
IEEE: for links/hardware
E.g., Ethernet
regional ISP
 network protocols
 control sending/receiving of
messages
 e.g., TCP, IP, HTTP, FTP, PPP
company
network
Chapter 1, slide: 13
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
Chapter 1, slide: 14
What’s a protocol?
human protocols:
 “What’s the time?”
 “I have a question”
 introductions
… specific msgs sent
… specific actions taken
when msgs received,
or other events
network protocols:
 machines rather than
humans
 all communication
activity in Internet
governed by protocols
protocols define (1) format,
order of msgs sent and
received among network
entities, and (2) actions
taken on msg
transmission, receipt
Chapter 1, slide: 15
Chapter 1: roadmap
1 What is the Internet?
2 Network edge
3 Network core
4 Internet structure and ISPs
5 Protocol layers, service models
6 Delay & loss in packet-switched networks
Chapter 1, slide: 16
A closer look at network structure:
 network edge:
applications and
hosts
 network core:
routers
 network of
networks

 access networks,
physical media:
communication links
Chapter 1, slide: 17
The network edge: service models
 end systems (hosts):



run application programs
e.g. Web, email
at “edge of network”
 client/server model


client host requests, receives
service from always-on server
e.g. Web browser/server;
email client/server
 peer-to-peer model:


minimal (or no) use of
dedicated servers
e.g. Skype, BitTorrent, KaZaA
Chapter 1, slide: 18
Chapter 1: roadmap
1 What is the Internet?
2 Network edge
3 Network core
4 Internet structure and ISPs
5 Protocol layers, service models
6 Delay & loss in packet-switched networks
Chapter 1, slide: 19
The Network Core
 mesh of interconnected
routers
 the fundamental question:
how is data transferred
through net?
 circuit switching:
dedicated circuit per
call: telephone net
 packet-switching: data
sent thru net in
discrete “chunks”
Chapter 1, slide: 20
Network Core: Circuit Switching
End-end resources
reserved for “call”
 dedicated resources: no
sharing
 call setup required
 circuit-like (guaranteed)
performance
 same path for all chunks
Chapter 1, slide: 21
Network Core: Circuit Switching
network resources
(e.g., bandwidth)
divided into “pieces”
 allocated pieces per call
 no sharing
resource piece idle if
not used by owning call
Chapter 1, slide: 22
Network Core: Circuit Switching
 Two ways of dividing bandwidth into “pieces”
frequency division
 time division

Chapter 1, slide: 23
Circuit Switching: FDM and TDM
Example:
Freq. Division Multiplx. (FDM)
4 users
frequency
time
Time Division Multiplx. (TDM)
frequency
time
Chapter 1, slide: 24
Network Core: Packet Switching
100 Mb/s
Ethernet
A
B
C
1.5 Mb/s
each end-to-end data stream is divided into packets
 no dedication/reservation: all streams share resources
 no setup is required
 resources used as needed
 each packet uses full link bandwidth
 aggregate resource demand can exceed capacity
 no guarantee
Chapter 1, slide: 25
Network Core: statistical multiplexing
100 Mb/s
Ethernet
A
B
statistical multiplexing
C
1.5 Mb/s
queue of packets
waiting for output
link
D
E
Sequence of A & B packets does not have fixed pattern,
shared on demand  statistical multiplexing.
Whereas in TDM, each host gets same slot (periodically)
Chapter 1, slide: 26
Packet switching versus circuit switching
A
Circuit switching
B
B: has no
packets to send
A
2 Mb/s
• 2 circuits (use TDM)
• A reserves 1 circuit
• B reserves 1 circuit
Utilization = 50% only = 1 Mb/s
Packet switching
B
2 Mb/s
• statistical multiplex.
• B uses full link since
A is not using it
Utilization = 100% = 2 Mb/s
Chapter 1, slide: 27
Packet switching versus circuit switching
Packet-switching
 Resources
sharing
 Congestion
may lead to it
 Overhead
less overhead;
no connection setup
 Guarantee
Best-effort
no guarantee
Circuit-switching
dedicated
admission control
more overhead;
reserve resources 1st
provide guarantee
good for multimedia
Chapter 1, slide: 28
Numerical example
 How long does it take to send a file of 640,000
bits from host A to host B over a circuit-switched
network?


The link’s transmission rate = 0.64 Mbps
The link uses the following TDM scheme
• One frame per second
• 10 slots per frame (so we can accommodate up to 10 hosts)
0.5 sec to establish end-to-end circuit
Let’s work it out! You have few minutes!

 Solution:
 Bandwidth of circuit (in kbps)= .64x1000/10 = 64 kbps
 Time to send: 640 kbits/64 kbps + 0.5s = 10.5s
Chapter 1, slide: 29
ECE/CS 372 – Introduction to Computer
Networks
Lecture 2
Announcements:
 Please make sure to check the course’s website on a
regular basis
http://classes.engr.oregonstate.edu/eecs/spring2014/cs372-001/
 Unit Metrics – Let’s Sidestep the issue!
Credit for lecture slides to Professor Bechir Hamdaoui
Adapted from Jim Kurose & Keith Ross (original copyright)
Chapter 1, slide: 30
Packet switching versus circuit switching
Packet-switching
 Resources
sharing
 Congestion
may lead to it
 Overhead
less overhead;
no connection setup
 Guarantee
Best-effort
no guarantee
Circuit-switching
dedicated
admission control
more overhead;
reserve resources 1st
provide guarantee
good for multimedia
Chapter 1, slide: 31
Packet switching versus circuit switching
Packet switching allows more users to use network!
 3 Mb/s link
 each user:


1 Mb/s when “active”
active 1/3 of time
 circuit-switching:

N users
3 Mbps link
3 users
 packet switching:

With N=4 users, what are the chances that a user won’t get 1 Mb/s?
I.e., what is the prob. that more than 3 (strictly) users are active?

With N=5 users, what are the chances that a user won’t get 1 Mb/s?

With N=6 users, what are the chances that a user won’t get 1 Mb/s?
Chapter 1, slide: 32
Packet switching versus circuit switching
Board …
Chapter 1, slide: 33
ECE/CS 372 – Introduction to Computer
Networks
Lecture 3
Announcements:
 Assign 1 will be posted today and due in a week from
now.
Credit for lecture slides to Professor Bechir Hamdaoui
Adapted from Jim Kurose & Keith Ross (original copyright)
Chapter 1, slide: 34
Chapter 1: roadmap
1 What is the Internet?
2 Network edge
3 Network core
4 Internet structure and ISPs
5 Protocol layers, service models
6 Delay & loss in packet-switched networks
Chapter 1, slide: 35
Internet structure: network of networks
 roughly hierarchical: tier 1, tier 2, and tier 3
 at center: “tier-1” ISPs
 e.g., MCI, Sprint, AT&T, Cable and Wireless,
 national/international coverage
Tier-1
providers
interconnect
(peer)
privately
Tier 1 ISP
Tier 1 ISP
IXP
NAP
Network
Tier-1 providers
interconnects
also interconnect
handled
at publicatnetwork
Internet
Exchange
access points
Points
(NAPs)(IXP)
Tier 1 ISP
Chapter 1, slide: 36
Tier-1 ISP: e.g., Sprint
Sprint US backbone network
DS3 (45 Mbps)
OC3 (155 Mbps)
OC12 (622 Mbps)
OC48 (2.4 Gbps)
Seattle
Tacoma
Stockton
San Jose
Cheyenne
Kansas City
Chicago
Roachdale
New York
Pennsauken
Relay
Wash. DC
Anaheim
Atlanta
Fort Worth
Orlando
Chapter 1, slide: 37
Internet structure: network of networks
 “Tier-2” ISPs: smaller (often regional) ISPs
 Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs
Tier-2 ISP
Tier-2 ISP
Tier 1 ISP
Tier-2 ISP is
customer of
tier-1 provider
Tier 1 ISP
Tier-2 ISP
IXP
Tier 1 ISP
Tier-2 ISPs
also peer
privately with
each other,
interconnect
at IXP
Tier-2 ISP
Tier-2 ISP
Chapter 1, slide: 38
Internet structure: network of networks
 “Tier-3” ISPs and local ISPs
 last hop (“access”) network (closest to end systems)
local
ISP
Local and tier3 ISPs are
customers of
higher tier
ISPs
connecting
them to rest
of Internet
Tier 3
ISP
Tier-2 ISP
local
ISP
local
ISP
local
ISP
Tier-2 ISP
Tier 1 ISP
Tier 1 ISP
Tier-2 ISP
local
local
ISP
ISP
IXP
Tier 1 ISP
Tier-2 ISP
local
ISP
Tier-2 ISP
local
ISP
Chapter 1, slide: 39
Internet structure: network of networks
 a packet passes through many networks!
local
ISP
Tier 3
ISP
Tier-2 ISP
local
ISP
local
ISP
local
ISP
Tier-2 ISP
Tier 1 ISP
Tier 1 ISP
Tier-2 ISP
local
local
ISP
ISP
IXP
Tier 1 ISP
Tier-2 ISP
local
ISP
Tier-2 ISP
local
ISP
Chapter 1, slide: 40
Chapter 1: roadmap
1 What is the Internet?
2 Network edge
3 Network core
4 Internet structure and ISPs
5 Protocol layers, service models
6 Delay & loss in packet-switched networks
Chapter 1, slide: 41
Protocol “Layers”
Networks are complex!
 many “pieces”:
 hosts
 routers
 links of various
media
 applications
 protocols
 hardware,
software
Question:
Is there any hope of an
organizing structure of
network?
Chapter 1, slide: 42
Organization of air travel
ticket (purchase)
ticket (repurpose)
baggage (check)
baggage (claim)
gates (load)
gates (unload)
runway takeoff
runway landing
airplane routing
airplane routing
airplane routing
 a series of steps
Chapter 1, slide: 43
Layering of airline functionality
ticket (purchase)
ticket (complain)
ticket
baggage (check)
baggage (claim
baggage
gates (load)
gates (unload)
gate
runway (takeoff)
runway (land)
takeoff/landing
airplane routing
airplane routing
airplane routing
departure
airport
airplane routing
airplane routing
intermediate air-traffic
control centers
arrival
airport
Layers: each layer implements a service
 via its own internal-layer actions
 relying on services provided by layer below
Chapter 1, slide: 44
Why layering?
Dealing with complex systems:
 Easing assignment of tasks

identify relationship among pieces of complex
systems
 Easing maintenance, updating of system
change of implementation of layer’s service
transparent to rest of system
 e.g., change in gate procedure doesn’t affect
rest of system

Chapter 1, slide: 45
Internet protocol stack
 application: supporting network
applications

FTP, SMTP, HTTP
 transport: process-process data
transfer

TCP, UDP
 network: routing of datagrams from
source to destination

IP, routing protocols
 link: data transfer between
application
transport
network
link
physical
neighboring network elements

PPP, Ethernet
 physical: bits “on the wire”
Chapter 1, slide: 46
Encapsulation
source
message
segment
M
Ht
M
datagram Hn Ht
M
frame Hl Hn Ht
M
application
transport
network
link
physical
link
physical
switch
destination
M
Ht
M
Hn Ht
Hl Hn Ht
M
M
application
transport
network
link
physical
Hn Ht
Hl Hn Ht
M
M
network
link
physical
Hn Ht
M
router
Chapter 1, slide: 47
ISO/OSI Model: late 70’s
application
presentation
session
transport
application
transport
network
network
link
data link
physical
physical
7-layer ISO/OSI model
(OSI: open system interconnections)
5-layer Internet
Protocol Stack
Chapter 1, slide: 48
Chapter 1: roadmap
1 What is the Internet?
2 Network edge
3 Network core
4 Internet structure and ISPs
5 Protocol layers, service models
6 Delay & loss in packet-switched networks
Chapter 1, slide: 49
Sources of packet delay
 1. processing:
 check bit errors
 determine output link
 2. queueing
 time waiting at output
link for transmission
 depends on congestion
level of router
A
B
nodal
processing
queueing
Chapter 1, slide: 50
Sources of packet delay
4. Propagation delay:
3. Transmission delay:
 R=link bandwidth (bps)
 d = length of physical link
 L=packet length (bits)
 s = propagation speed in
medium (~2x108 m/sec)
 propagation delay = d/s
 trans. delay = L/R
Note: s and R are very different quantities!
transmission
A
propagation
B
nodal
processing
queueing
Chapter 1, slide: 51
Caravan analogy
100 km
ten-car
caravan
toll
booth
 Cars run at 100 km/hr (speed
of propagation)
 Booth takes 12 sec to service
a car (transmission time)
 Car ~ bit; caravan ~ packet
 Q: How long until caravan is
lined up before 2nd toll
booth?
100 km
toll
booth
 Time to “push” entire
caravan through toll booth
= 12*10 = 120 sec = 2 mns
 Time for last car to
propagate from 1st to 2nd
toll both:
=100km/(100km/hr)= 1 hr
 A: 1 hr 2 minutes
Chapter 1, slide: 52
Caravan analogy (more)
100 km
ten-car
caravan
toll
booth
 Cars now “propagate” at
1000 km/hr
 Toll booth now takes 1
min to service a car
 Q: Will cars arrive to
2nd booth before all
cars serviced at 1st
booth?
100 km
toll
booth
 Yes! After 7 min, 1st car
at 2nd booth and 8th car
still at 1st booth.
 1st bit of packet can
arrive at 2nd router
before packet is fully
transmitted at 1st router!
Chapter 1, slide: 53
Exercise 1
Packet length = L bits
Host A
trans. rate R = 1 Mbps
Host B
distance = 1 km, speed = 2x108m/s
Question:
 Which bit is being transmitted at the time the first bit
arrives at Host B for
Answer:
First bit arrives after
1/R + d/s = 1/106 + 103/(2x108) = 10-6 + 5x10-6 = 6x10-6 = 6 µsec
After 6 µsec
6 bits are already transmitted; so 7th bit is being transmitted
Chapter 1, slide: 54
Exercise 2
Transmission vs. propagation
L=100Bytes
Host A
Question:
trans. rate R = ?
Host B
distance = 2 km, speed = 2x108m/s
 At what rate (bandwidth) R would the propagation delay
equal the transmission delay of packet?
Answer:
 Propagation delay = 2x103 (m)/2x108 (m/s) = 10-5 sec
 Transmission delay = 100x8 (bits)/R
 Prop. delay = trans. delay => R=105x100x8 = 80 Mbps
Chapter 1, slide: 55
Exercise 3
Voice over IP
L=48 Bytes
a=64Kbps
Host A
trans. rate R = 1Mbps
Host B
delay_prop = 2msec
 Host A

converts analog to digital at a=64Kbps
groups bits into L=48Byte packets
sends packet to Host B as soon it gathers a packet

As soon as it receives the whole pckt, it converts it to analog


 Host B
 Question:

How much time elapses from the 1st bit of 1st packet is created
until the last bit of the 1st packet arrives at Host B?
Chapter 1, slide: 56
Exercise 3
Voice over IP
L=48 Bytes
a=64Kbps
Host A
trans. rate R = 1Mbps
delay_prop = 2msec
Host B
Answer:
 Time to gather 1st pkt: 48x8 (bits)/64x1000 (b/s) = 6 msec
 Time to push 1st pkt to link: 48x8 (bits)/1x106 (b/s) = 0.384 msec
 Time to propagate: 2 msec
 Total delay = 6 + 0.384 + 2 = 8.384 msec
Chapter 1, slide: 57
ECE/CS 372 – introduction to computer networks
Lecture 4
Announcements:
 Assign 1 is due next Tuesday
Credit for lecture slides to Professor Bechir Hamdaoui
Adapted from Jim Kurose & Keith Ross (original copyright)
Chapter 1, slide: 58
Nodal delay
d nodal  d proc  d queue  d trans  d prop
 dproc = processing delay
 typically a few microsecs or less
 dqueue = queuing delay
 depends on congestion
 dtrans = transmission delay
 = L/R, significant for low-speed links
 dprop = propagation delay
 a few microsecs to hundreds of msecs
Chapter 1, slide: 59
Queueing delay (more insight)
Packet arrival rate
= a packets/sec
Packet length
= L bits
queue
Link bandwidth
= R bits/sec
 Every second: aL bits arrive to queue
 Every second: R bits leave the router
 Question: what happens if aL > R ?
 Answer: queue will fill up, and packets will get dropped!!
aL/R is called traffic intensity
Chapter 1, slide: 60
Queueing delay: illustration
1 packet arrives
every L/R seconds
queue
Link bandwidth
= R bits/sec
Packet length L bits
Arrival rate: a = 1/(L/R) = R/L (packet/second)
Traffic intensity = aL/R = (R/L) (L/R) = 1
Average queueing delay = 0
(queue is initially empty)
Chapter 3, slide: 61
Queueing delay: illustration
N packet arrive simultaneously
every LN/R seconds
queue
Link bandwidth
= R bits/sec
Packet length L bits
Arrival rate: a = N/(LN/R) = R/L packet/second
Traffic intensity = aL/R = (R/L) (L/R) = 1
Average queueing delay (queue is empty is time 0) ?
{0 + L/R + 2L/R + … + (N-1)L/R}/N = L/(RN){1+2+…+(N-1)} =L(N-1)/(2R)
Note: traffic intensity is same as previous scenario, but queueing delay is different
Chapter 3, slide: 62
Queueing delay: behavior
Packet arrival rate
= a packets/sec
queue
Packet length
= L bits
Link bandwidth
= R bits/sec
 La/R ~ 0: avg. queueing delay small
 La/R -> 1: delays become large
 La/R > 1: more “work” than can be
serviced, average delay infinite!
(this is when a is random!)
Chapter 1, slide: 63
Packet-switching: store-and-forward
L
R
R
R
Entire packet must arrive at router before it can be
transmitted on next link: store and forward
 Takes L/R seconds to transmit (push out) packet of
L bits on to link of R bps
 delay = 3L/R (assuming zero propagation delay)
more on this next…
Chapter 1, slide: 64
Store-and-forward: illustration
 distance = d meters; speed of propagation = s m/sec
 transmission rate of link = R bits/s
L
d
R
 delay (one packet only)
= L/R + d/s
Example:
 d/s = 0.5 sec
 L = 10 Mbits
 R = 1 Mbps
 delay = 10.5 sec
L
d/2
d/2
R
R
 delay (one packet only)
= L/R + ½d/s + L/R + ½d/s
= 2L/R + d/s
Example:
 d/s = 0.5 sec
 L = 10 Mbits
 R = 1 Mbps
 delay = 20.5 sec
Chapter 1, slide: 65
Store-and-forward & queuing delay
 distance = d meters; speed of propagation = s m/sec
 transmission rate of link = R1 and R2 bits/s
 Consider sending two packets A and B back to back
d
L
R1
 Case 1: Assume R1 < R2
R2
 Case 2: Assume R1 > R2
Q: is there a queuing delay? how much is this delay?
Answer (queue is empty initially):
Time for last bit of 2nd pkt to arrive at router: d1= L/R1 + L/R1 + d/(2s)
Time for last bit of 1st pkt to leave router: d2= L/R1 + d/(2s) + L/R2
Queueing delay = d2 – d1 = L/R2 – L/R1 if positive, otherwise 0. Hence:
when R1 < R2, queueing delay = d2 – d1 = 0
when R1 > R2, queueing delay = d2 – d1 = L/R2 – L/R1
Chapter 1, slide:
66
Throughput analysis
Host A
L
R
R
R
Host B
 Suppose: Host A has huge file of size F bits to send to Host B
 File is split into N packets, each of length L bits (i.e., N=F/L)
 Ignore propagation delay for now
 Question 1: how long it takes to send the file?
A: (N+2)L/R = (F+2L)/R
 Question 2: what is the average throughput achieved
when sending the file?
A: NL/[(N+2)L/R]=NR/(N+2) = FR/(F+2L) = R/(1+2L/F)
Note: throughput = number of total bits sent / total time taken
Chapter 1, slide: 67
Throughput analysis
Host A
L
d/3
R
d/3
R
d/3
R
Host B
 Suppose: Host A has huge file of size F bits to send to Host B
 File is split into N packets, each of length L bits (i.e., N=F/L)
 Do NOT ignore propagation delay (assume prop. speed = s m/s)
 Question 1: how long it takes to send the file?
A: (N+2)L/R + d/s = (F+2L)/R + d/s
 Question 2: what is the average throughput achieved
when sending the file?
A: NL/[(N+2)L/R +d/s]=FR/[(N+2)L + dR/s] = FR/[F+2L+dR/s]
Chapter 1, slide: 68
Introduction: Summary
Covered a ton of material!
 Internet overview
 Network protocol
 Network edge, core, access network
 Packet-switching versus circuit-switching
 Internet/ISP structure
 layering and service models
 performance: delay and throughput analysis
Chapter 1, slide: 69