[SOLVED] CS algorithm Java dns FTP 1/5/21

1/5/21
UCLA CS 118 Winter 2021
Instructor: Giovanni Pau TAs:
Hunter Dellaverson Eric Newberry
Introduction
Chapter 1 Introduction
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Thanks and enjoy! JFK/KWR
All material copyright 1996-2016
J.F Kurose and K.W. Ross, All Rights Reserved
Computer Networking: A Top Down Approach
7th edition
Jim Kurose, Keith Ross Pearson/Addison Wesley April 2016
1-2
12
Chapter 1: introduction
Chapter goal:
Get feel, big picture, introduction to terminology
more depth, detail later in course
Overview/roadmap:
What is the Internet? What is a protocol?
Network edge: hosts, access network, physical media
Network core: packet/circuit switching, internet structure
Performance: loss, delay, throughput
Protocol layers, service models
Security
History
Introduction: 1-3
The Internet: a nuts and bolts view
Billions of connected computing devices:
hosts = end systems
running network apps at Internets edge
Packet switches: forward packets (chunks of data)
routers, switches Communication links
fiber, copper, radio, satellite transmission rate: bandwidth
Networks
collection of devices, routers, links: managed by an organization
mobile network
national or global ISP
home network
enterprise network
local or
regionIanl IStPernet
content provider network
datacenter network
Introduction: 1-4
34
1

The Internet: a services view
Whats a protocol?
Human protocols:
whats the time? I have a question introductions
Rules for:
specific messages sent specific actions taken
when message received, or other events
Infrastructure that provides services to applications:
Web, streaming video, multimedia teleconferencing, email, games, e- commerce, social media, inter- connected appliances,
provides programming interface to distributed applications:
hooks allowing sending/receiving apps to connect to, use Internet transport service
provides service options, analogous to postal service
mobile network
Network protocols:
computers (devices) rather than humans all communication activity in Internet
governed by protocols
Protocols define the format, order of messages sent and received among network entities, and actions taken
on message transmission, receipt
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Fun Internet-connected devices
Tweet-a-watt: monitor energy use
cars
scooters
Others?
Introduction: 1-5
bikes
Amazon Echo
IP picture frame
Slingbox: remote control cable TV
Pacemaker & Monitor
Web-enabled toaster + weather forecaster
Internet refrigerator
Security Camera
AR devices
Internet phones
Fitbit
Gaming devices
sensorized, bed mattress
The Internet: a nuts and bolts view
Internet: network of networks Interconnected ISPs
protocols are everywhere
control sending, receiving of
messages
e.g., HTTP (Web), streaming video,
Skype, TCP, IP, WiFi, 4G, Ethernet
Internet standards
RFC: Request for Comments
IETF: Internet Engineering Task Force
mobile network 4G
national or global ISP
Skype
IP
local or regional ISP
WiFi
Streaming video
home network
H T T P
Ethernet
enterprise network
content provider network
d a ne
TCP
Introduction: 1-6
tacent twork
e r
56
Skype
national or global ISP
Streaming video
datacenter network
Introduction: 1-7
local or regional ISP
home network
HTTP
enterprise network
content provider network
78
Introduction: 1-8
2

11
12
Whats a protocol?
A human protocol and a computer network protocol:
Chapter 1: roadmap
What is the Internet?
What is a protocol?
Network edge: hosts, access network, physical media
Network core: packet/circuit switching, internet structure
Performance: loss, delay, throughput
Security
Protocol layers, service models
History
Hi
Hi
Got the time? 2:00
TCP connection request
TCP connection response
GET http://gaia.cs.umass.edu/kurose_ross
time
Q: other human protocols?
9 10
A closer look at Internet structure
A closer look at Internet structure
Network edge:
hosts: clients and servers servers often in data centers
national or global ISP
Network edge:
hosts: clients and servers servers often in data centers
Access networks, physical media:
wired, wireless communication links
national or global ISP
mobile network
mobile network
home network
enterprise network
content provider network
datacenter network
Introduction: 1-11
home network
enterprise network
content provider network
datacenter network
Introduction: 1-12
local or regional ISP
local or regional ISP
Introduction: 1-9
Introduction: 1-10
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13
14
15
16
A closer look at Internet structure
Access networks and physical media
Network edge:
hosts: clients and servers servers often in data centers
Access networks, physical media:
wired, wireless communication links
Network core:
interconnected routers network of networks
national or global ISP
national or global ISP
Access networks: cable-based access
Access networks: cable-based access
cable modem
splitter
cable splitter modem
data, TV transmitted at different frequencies over shared cable distribution network
cable modem termination system
ISP
C
O VVVVVV N IIIIIIDDT DDDDDDAAR EEEEEETTO OOOOOOAAL
123456789 Channels
HFC: hybrid fiber coax
asymmetric: up to 40 Mbps 1.2 Gbps downstream transmission rate, 30-100 Mbps
frequency division multiplexing (FDM): different channels transmitted in different frequency bands
upstream transmission rate
network of cable, fiber attaches homes to ISP router
homes share access network to cable headend
cable headend
cable headend
CMTS
mobile network
Q: How to connect end systems to edge router?
mobile network
home network
enterprise network
content provider network
datacenter network
Introduction: 1-13
home network
enterprise network
content provider network
datacenter network
Introduction: 1-14
local or regional ISP

residential access nets
institutional access networks (school, company)
mobile access networks (WiFi, 4G/5G)
local or regional ISP

Introduction: 1-15
Introduction: 1-16
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Access networks: digital subscriber line (DSL)
central office
DSLAM
DSL access multiplexer
telephone network
DSL splitter modem
voice, data transmitted at different frequencies over dedicated line to central office
ISP
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
24-52 Mbps dedicated downstream transmission rate 3.5-16 Mbps dedicated upstream transmission rate
Introduction: 1-17
Access networks: home networks
Wireless and wired devices
often combined in single box
WiFi wireless access point (54, 450 Mbps)
to/from headend or central office
cable or DSL modem
router, firewall, NAT wired Ethernet (1 Gbps)
Introduction: 1-18
17 18
Wireless access networks
Shared wireless access network connects end system to router via base station aka access point
Wireless local area networks (WLANs)
typically within or around building (~100 ft)
802.11b/g/n (WiFi): 11, 54, 450 Mbps transmission rate
to Internet
Wide-area cellular access networks
provided by mobile, cellular network operator (10s km)
10s Mbps
4G cellular networks (5G coming)
to Internet
Introduction: 1-19
Access networks: enterprise networks
Ethernet switch
Enterprise link to ISP (Internet) institutional router
institutional mail, web servers
companies, universities, etc.
mix of wired, wireless link technologies, connecting a mix of switches
and routers (well cover differences shortly)
Ethernet: wired access at 100Mbps, 1Gbps, 10Gbps WiFi: wireless access points at 11, 54, 450 Mbps
Introduction: 1-20
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Access networks: data center networks
high-bandwidth links (10s to 100s Gbps) connect hundreds to thousands of servers together, and to Internet
Courtesy: Massachusetts Green High Performance Computing Center (mghpcc.org)
mobile network
national or global ISP
local or regional ISP
home network
enterprise network
content provider network
datacenter network
Introduction: 1-21
Host: sends packets of data
host sending function:
takes application message
breaks into smaller chunks, known as packets, of length L bits
transmits packet into access network at transmission rate R
two packets, L bits each
R: link transmission rate = L (bits)
21 link transmission rate, aka link host
capacity, aka link bandwidth
packet = transmission
delay
time needed to transmit L-bit packet into link
R (bits/sec)
Introduction: 1-22
Links: physical media
bit: propagates between transmitter/receiver pairs
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
Twisted pair (TP)
two insulated copper wires
Category5:100Mbps,1GbpsEthernet Category6:10GbpsEthernet
Introduction: 1-23
Links: physical media
Coaxial cable:
two concentric copper conductors bidirectional
broadband:
multiplefrequencychannelsoncable 100sMbpsperchannel
Fiber optic cable:
glass fiber carrying light pulses, each pulse a bit
high-speed operation:
high-speed point-to-point
transmission(10s-100sGbps) low error rate:
repeaters spaced far apart
immune to electromagnetic noise
Introduction: 1-24
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Links: physical media
Wireless radio
signal carried in various bands in electromagnetic spectrum
no physical wire
broadcast, half-duplex (sender to receiver)
propagation environment effects:
reflection
obstruction by objects Interference/noise
Radio link types:
Wireless LAN (WiFi)
10-100s Mbps; 10s of meters
wide-area (e.g., 4G cellular) 10s Mbps over ~10 Km
Bluetooth: cable replacement short distances, limited rates
terrestrial microwave
point-to-point; 45 Mbps channels
satellite
up to 45 Mbps per channel 270 msec end-end delay
Introduction: 1-25
Chapter 1: roadmap
What is the Internet?
What is a protocol?
Network edge: hosts, access network, physical media
Network core: packet/circuit switching, internet structure
Performance: loss, delay, throughput
Security
Protocol layers, service models
History
Introduction: 1-26
25 26
The network core
mesh of interconnected routers
packet-switching: hosts break application-layer messages into packets
network forwards packets from one router to the next, across links on path from source to destination
mobile network
national or global ISP
local or regional ISP
home network
enterprise network
content provider network
datacenter network
Introduction: 1-27
Two key network-core functions
routing algorithm
Forwarding:
aka switching local action:
move arriving packets from routers input link to appropriate router output link
1 32
Routing:
global action: determine source- destination paths taken by packets
routing algorithms
Introduction: 1-28
llocall forward header value
0100 0101 0111 1001
diing tablle output link
3 2 2 1
destination address in arriving packets header
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routing
Introduction: 1-29
forwarding
forwarding
Introduction: 1-30
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Packet-switching: store-and-forward
L bits
per packet
source 3 2 1 destination R bps R bps
packet transmission delay: takes L/R seconds to transmit (push out) L-bit packet into link at R bps
storeandforward:entirepacketmust arriveat router before it can be transmitted on next link
One-hop numerical example:
L = 10 Kbits
R = 100 Mbps
one-hop transmission delay
= 0.1 msec
Introduction: 1-31
Packet-switching: queueing
R=100Mb/s
A
B
R=1.5Mb/s
C
D
E
queue of packets waiting for transmission over output link
Queueing occurs when work arrives faster than it can be serviced:
Introduction: 1-32
31 32
8

Packet-switching: queueing
R=100Mb/s
A
B
R=1.5Mb/s
C
D
E
queue of packets waiting for transmission over output link
Packet queuing and loss: if arrival rate (in bps) to link exceeds transmission rate (bps) of link for some period of time:
packets will queue, waiting to be transmitted on output link packets can be dropped (lost) if memory (buffer) in router fills up
Introduction: 1-33
Alternative to packet switching: circuit switching
end-end resources allocated to, reserved for call between source and destination
in diagram, each link has four circuits. call gets 2nd circuit in top link and 1st
circuit in right link. dedicated resources: no sharing
circuit-like (guaranteed) performance circuit segment idle if not used by call (no
sharing)
commonly used in traditional telephone networks
* Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive
Introduction: 1-34
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Circuit switching: FDM and TDM
Frequency Division Multiplexing (FDM)
optical, electromagnetic frequencies divided into (narrow) frequency bands
each call allocated its own band, can transmit at max rate of that narrow band
Time Division Multiplexing (TDM)
time divided into slots
each call allocated periodic slot(s), can transmit at maximum rate of (wider) frequency band (only) during its time slot(s)
4 users
time
time
Introduction: 1-35
Packet switching versus circuit switching
example:
1 Gb/s link each user:
100 Mb/s when active active 10% of time
N
users
1 Gbps link
Q: how many users can use this network under circuit-switching and packet switching? circuit-switching: 10 users
packet switching: with 35 users, probability > 10 active at same time is less than .0004 *
Q: how did we get value 0.0004? A: HW problem (for those with
* Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive
course in probability only)
Introduction: 1-36
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9
..
frequency frequency

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Packet switching versus circuit switching
Is packet switching a slam dunk winner?
great for bursty data sometimes has data to send, but at other times not resource sharing
simpler, no call setup
excessive congestion possible: packet delay and loss due to buffer overflow protocols needed for reliable data transfer, congestion control
Q: How to provide circuit-like behavior with packet-switching?
Its complicated. Well study various techniques that try to make packet
switching as circuit-like as possible.
Q: human analogies of reserved resources (circuit switching) versus on-demand allocation (packet switching)?
Introduction: 1-37
Internet structure: a network of networks
hosts connect to Internet via access Internet Service Providers (ISPs)
access ISPs in turn must be interconnected
so that any two hosts (anywhere!) can send packets to each other
resulting network of networks is very complex
evolution driven by economics, national policies
mobile network
national or global ISP
local or regional ISP
home network
enterprise network
content provider network
datacenter network
Lets take a stepwise approach to describe current Internet structure
Internet structure: a network of networks
Question: given millions of access ISPs, how to connect them together?
access net
access net
access net
access net
access net
access net
access net
access net
access net
access net
access net
access net
access net
access net
access net
access net
Introduction: 1-39
Internet structure: a network of networks
Question: given millions of access ISPs, how to connect them together?
access net
access net
access net
access net
access net
access net
access net
access net
access net
connecting each access ISP to
access net
access net
each other directly doesnt scale:
2
O(N ) connections.
access net
access net
access net
access
access net net
Introduction: 1-40
39 40
10

41
42
43
44
Internet structure: a network of networks
Option: connect each access ISP to one global transit ISP? Customer and provider ISPs have economic agreement.
Internet structure: a network of networks
But if one global ISP is viable business, there will be competitors .
access net
access net
access net
access net
access net
access
net access
access access net net
access net
want to be connected
access net
ISP A ISP C
access net
access net
access net
Internet exchange point
access net
access net
access net
ISP B
access net
access net
access net
access net
access net
ISP A ISP C
access net
access net
access net
access net
ISP A ISP C
access net
access net
global ISP
access net
access net
access net
access net

access net
access net
peering link
access net
access net
regional ISP
access net
access net
IXP
ISP B
access net
access net
access net
access net
access net
access net
access net
IXP
access net
access net
access net
access net
access net
access net
Internet structure: a network of networks
Internet structure: a network of networks
But if one global ISP is viable business, there will be competitors . who will
and regional networks may arise to connect access nets to ISPs
access net
access net
access net
IXP
access net
IXP
access
net access
access net
access net
access net
access net
ISP B
access net
access net
access net
Introduction: 1-41
Introduction: 1-42
Introduction: 1-43
Introduction: 1-44
net net
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Internet structure: a network of networks
and content provider networks (e.g., Google, Microsoft, Akamai) may run their own network, to bring services, content close to end users
access net
access net
access net
access net
access net
access net
access net
ISP A ISP C
access net
IXP
access net
access net
Content provider network
ISP B
IXP
regional ISP
access net
access net
access net
access net
access
access net net
Introduction: 1-45
Internet structure: a network of networks
Tier 1 ISP Tier 1 ISP Google
IXP
Regional ISP
access access access access ISP ISP ISP ISP
IXP
Regional ISP
access access access
ISP ISP ISP ISP
IXP
At center: small # of well-connected large networks
tier-1 commercial ISPs (e.g., Level 3, Sprint, AT&T, NTT), national & international coverage content provider networks (e.g., Google, Facebook): private network that connects its
data centers to Internet, often bypassing tier-1, regional ISPs
Introduction: 1-46
access
45 46
Chapter 1: roadmap
What is the Internet?
What is a protocol?
Network edge: hosts, access network, physical media
Network core: packet/circuit switching, internet structure
Performance: loss, delay, throughput
Security
Protocol layers, service models
History
Introduction: 1-47
How do packet delay and loss occur?
packets queue in router buffers, waiting for turn for transmission
queue length grows when arrival rate to link (temporarily) exceeds output link
capacity
packet loss occurs when memory to hold queued packets fills up
packet being transmitted (transmission delay) A
B
packets in buffers (queueing delay)
free (available) buffers: arriving packets dropped (loss) if no free buffers
Introduction: 1-48
47 48
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49
50
51
52
Packet delay: four sources
transmission
A propagation B nodal
dnodal = dproc + dqueue + dtrans + dprop
Packet delay: four sources
processing queueing
nodal
dproc: nodal processing check bit errors
determine output link typically < microsecsdqueue: queueing delay time waiting at output link fortransmission depends on congestion level ofdtrans: transmission delay: L: packet length (bits) R: link transmission rate (bps) dtrans = L/Rdprop: propagation delay: d: length of physical link s: propagation speed (~2×108 m/sec) dprop = d/sIntroduction: 1-50Caravan analogy100 km ten-car caravan toll booth(aka 10-bit packet) (aka link) car ~ bit; caravan ~ packet; tollservice ~ link transmission toll booth takes 12 sec to service car (bit transmission time) propagate at 100 km/hr Q: How long until caravan is lined up before 2nd toll booth?100 kmCaravan analogyten-car caravan (aka 10-bit packet)100 km (aka router)100 kmrouterdtrans and dprop very differenttoll booth time to push entire caravanthrough toll booth onto highway = 12*10 = 120 sec time for last car to propagate from 1st to 2nd toll both: 100km/(100km/hr) = 1 hrtoll boothtoll booth A: 62 minutes suppose cars now propagate at 1000 km/hr and suppose toll booth now takes one min to service a car Q: Will cars arrive to 2nd booth before all cars serviced at first booth?A: Yes! after 7 min, first car arrives at second booth; three cars still at first boothIntroduction: 1-52toll boothIntroduction: 1-49Introduction: 1-51A Btransmissionpropagation processing queueingdnodal = dproc + dqueue + dtrans + dprop1/5/2113 1/5/21 Packet queueing delay (revisited) a: average packet arrival rate L: packet length (bits) R: link bandwidth (bit transmission rate)L . a : arrival rate of bits traffic R service rate of bits intensityLa/R ~ 0: avg. queueing delay small La/R -> 1: avg. queueing delay large La/R > 1: more work arriving is
more than can be serviced average delay infinite!
traffic intensity = La/R 1 La/R ~ 0
La/R -> 1
Introduction: 1-53
Real Internet delays and routes
what do real Internet delay & loss look like?
traceroute program: provides delay measurement from source to router along end-end Internet path towards destination. For all i:
sends three packets that will reach router i on path towards destination (with time-to-live field value of i)
router i will return packets to sender
sender measures time interval between transmission and reply
3 probes 3 probes
3 probes
Introduction: 1-54
53 54
Real Internet delays and routes
traceroute: gaia.cs.umass.edu to www.eurecom.fr 3 delay measurements from
gaia.cs.umass.edu to cs-gw.cs.umass.edu
3 delay measurements
to border1-rt-fa5-1-0.gw.umass.edu
1 cs-gw (128.119.240.254) 1 ms 1 ms 2 ms
2 border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145) 1 ms 1 ms 2 ms
3 cht-vbns.gw.umass.edu (128.119.3.130) 6 ms 5 ms 5 ms
4 jn1-at1-0-0-19.wor.vbns.net (204.147.132.129) 16 ms 11 ms 13 ms
5 jn1-so7-0-0-0.wae.vbns.net (204.147.136.136) 21 ms 18 ms 18 ms
6 abilene-vbns.abilene.ucaid.edu (198.32.11.9) 22 ms 18 ms 22 ms
7 nycm-wash.abilene.ucaid.edu (198.32.8.46) 22 ms 22 ms 22 ms
8 62.40.103.253 (62.40.103.253) 104 ms 109 ms 106 ms
9 de2-1.de1.de.geant.net (62.40.96.129) 109 ms 102 ms 104 ms
10 de.fr1.fr.geant.net (62.40.96.50) 113 ms 121 ms 114 ms
11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms
12 nio-n2.cssi.renater.fr (193.51.206.13) 111 ms 114 ms 116 ms
13 nice.cssi.renater.fr (195.220.98.102) 123 ms 125 ms 124 ms
14 r3t2-nice.cssi.renater.fr (195.220.98.110) 126 ms 126 ms 124 ms
15 eurecom-valbonne.r3t2.ft.net (193.48.50.54) 135 ms 128 ms 133 ms 16 194.214.211.25 (194.214.211.25) 126 ms 128 ms 126 ms
17 ***
18 ***
19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms
* Do some traceroutes from exotic countries at www.traceroute.org
trans-oceanic link looks like delays
decrease! Why?
* means no response (probe lost, router not replying)
Introduction: 1-55
Packet loss
queue (aka buffer) preceding link in buffer has finite capacity
packet arriving to full queue dropped (aka lost)
lost packet may be retransmitted by previous node, by source end system, or not at all
A
B
buffer
(waiting area) packet being transmitted
packet arriving to full buffer is lost
* Check out the Java applet for an interactive animation (on publishers website) of queuing and loss
Introduction: 1-56
55 56
14
average queueing delay

Throughput
throughput: rate (bits/time unit) at which bits are being sent from sender to receiver
instantaneous: rate at given point in time average: rate over longer period of time
plinipkectahpatccitayn carry pilpinekthcapt accaintycarry
server sends bits server, with
R fbluitids/aset crate Rflubiditas/tsreacte sc
(fluid) into pipe file of F bits
(Rs bits/sec)
(Rc bits/sec)
to send to client
Introduction: 1-57
Throughput
Rs < Rc What is average end-end throughput? Rs bits/secRs > Rc What is average end-end throughput? Rc bits/sec
bottleneck link
link on end-end path that constrains end-end throughput
Rc bits/sec
Rs bits/sec
Introduction: 1-58
57
58
Throughput: network scenario
Chapter 1: roadmap
What is the Internet?
What is a protocol?
Network edge: hosts, access network, physical media
Network core: packet/circuit switching, internet structure
Performance: loss, delay, throughput
Security
Protocol layers, service models
History
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Rs
Rs
Rc
Rc
R
Rs
Rc

per-connection end- end throughput: min(Rc,Rs,R/10)
in practice: Rc or Rs is often bottleneck
* Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/
59
60
10 connections (fairly) share backbone bottleneck link R bits/sec
Introduction: 1-59
Introduction: 1-60
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Network security
Internet not originally designed with (much) security in mind
original vision: a group of mutually trusting users attached to a transparent networkJ
Internet protocol designers playing catch-up
security considerations in all layers! We now need to think about:
how bad guys can attack computer networks
how we can defend networks against attacks
how to design architectures that are immune to attacks
Introduction: 1-61
Network security
Internet not originally designed with (much) security in mind
original vision: a group of mutually trusting users attached to a transparent networkJ
Internet protocol designers playing catch-up
security considerations in all layers! We now need to think about:
how bad guys can attack computer networks
how we can defend networks against attacks
how to design architectures that are immune to attacks
Introduction: 1-62
61 62
Bad guys: packet interception
packet sniffing:
broadcast media (shared Ethernet, wireless)
promiscuous network interface reads/records all packets (e.g.,
including passwords!) passing by
AC
src:B dest:A payload
B
Wireshark software used for our end-of-chapter labs is a (free) packet-sniffer
Introduction: 1-63
Bad guys: fake identity
IP spoofing: injection of packet with false source address
AC
src:B dest:A payload
B
Introduction: 1-64
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67
68
Bad guys: denial of service
Denial of Service (DoS): attackers make resources (server, bandwidth) unavailable to legitimate traffic by overwhelming resource with bogus traffic
Lines of defense:
1. select target
2. break into hosts around the network (see botnet)
3. send packets to target from compromised hosts
hardware assist in traditional Internet
confidentiality: via encryption
integrity checks: digital signatures prevent/detect tampering access restrictions: password-protected VPNs
Chapter 1: roadmap

What is the Internet? What is a protocol?
Network edge: hosts, access network, physical media
Network core: packet/circuit switching, internet structure Performance: loss, delay, throughput Security
Protocol layers, service models
History
Networks are complex, with many pieces:
hosts
routers
links of various media applications protocols
hardware, software
Question: is there any hope of organizing structure of network?
and/or our discussion of networks?
target
firewalls: specialized middleboxes in access and core networks:
off-by-default: filter incoming packets to restrict senders, receivers, applications
Introduction: 1-65
detecting/reacting to DOS attacks
lots more on security (throughout, Chapter 8)
Protocol layers and reference models
Introduction: 1-66
Introduction: 1-67
Introduction: 1-68
authentication: proving you are who you say you are
cellular networks provides hardware identity via SIM card; no such
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Example: organization of air travel
end-to-end transfer of person plus baggage
ticket (purchase) baggage (check) gates (load) runway takeoff airplane routing
ticket (complain) baggage (claim) gates (unload) runway landing airplane routing
airplane routing
How would you define/discuss the system of airline travel?
a series of steps, involving many services
Introduction: 1-69
Example: organization of air travel
ticket (purchase)
baggage (check)
gates (load)
runway takeoff
ticketing service
baggage service
gate service
runway service
ticket (complain)
baggage (claim)
gates (unload)
runway landing
airplane routing
aroiruptlianngesreoruvticineg
airplane routing
layers: each layer implements a service via its own internal-layer actions
relying on services provided by layer below
Introduction: 1-70
Why layering?
Approach to designing/discussing complex systems:
explicit structure allows identification, relationship of systems pieces
layered reference model for discussion
modularization eases maintenance, updating of system
change in layers service implementation: transparent to rest of system
e.g., change in gate procedure doesnt affect rest of system
Introduction: 1-71
Layered Internet protocol stack
application: supporting network applications HTTP, IMAP, SMTP, DNS
transport: process-process data transfer TCP, UDP
network: routing of datagrams from source to destination
IP, routing protocols
link: data transfer between neighboring network elements
Ethernet, 802.11 (WiFi), PPP physical: bits on the wire
application
ttrranssporrtt
network
link
physical
Introduction: 1-72
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Services, Layering and Encapsulation
application
transport
network
link
physical
M
Application exchanges messages to implement some application service using services of transport layer
Ht M
Transport-layer protocol transfers M (e.g., reliably) from one process to another, using services of network layer
transport-layer protocol encapsulates application-layer message, M, with transport layer-layer header Ht to create a transport-layer segment
Ht used by transport layer protocol to implement its service
source
destination
Introduction: 1-73
application
transport
network
link
physical
Services, Layering and Encapsulation
application
transport
network
link
physical
application
transport
network
link
physical
source
M
Ht M
Transport-layer protocol transfers M (e.g., reliably) from one process to another, using services of network layer
HnHt M
Network-layer protocol transfers transport-layer segment [Ht | M] from one host to another, using link layer services
network-layer protocol encapsulates transport-layer segment [Ht | M] with network layer-layer header Hn to create a network-layer datagram
Hn used by network layer protocol to destination implement its service
Introduction: 1-74
73 74
Services, Layering and Encapsulation
application
transport
network
link
physical
application
transport
network
link
physical
source
M
Ht M
HnHt M
Network-layer protocol transfers transport-layer segment [Ht | M] from one host to another, using link layer services
Hl Hn Ht M
Link-layer protocol transfers datagram [Hn| [Ht |M] from host to neighboring host, using network-layer services
link-layer protocol encapsulates network datagram [Hn| [Ht |M], with link-layer header Hl to create a link-layer frame
destination
Introduction: 1-75
Services, Layering and Encapsulation
application
transport
network
link
physical
application
transport
network
link
physical
message segment datagram frame
M
Ht M
Hn Ht M Hl Hn Ht M
M Ht M Hn Ht M HlHnHt M
source
destination
Introduction: 1-76
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source
Encapsulation: an end-end view
application
transport
network
link
physical
message M segment Ht M datagram Hn Ht M frame Hl Hn Ht M
link
physical
destination
Hn Ht M HlHnHt M
switch
Ht M
router
network
Hn
link physical
application
transport
network
link
physical
M Ht M HnHt M Hl Hn Ht M
Introduction: 1-77
Chapter 1: roadmap
What is the Internet?
What is a protocol?
Network edge: hosts, access network, physical media
Network core: packet/circuit switching, internet structure
Performance: loss, delay, throughput
Security
Protocol layers, service models
History
Introduction: 1-78
Internet history
1961-1972: Early packet-switching principles
1961: Kleinrock queueing theory shows effectiveness of packet-switching
1964: Baran packet-switching in military nets
1967: ARPAnet conceived by Advanced Research Projects Agency
1969: first ARPAnet node operational
1972:
ARPAnet public demo
NCP (Network Control Protocol)
first host-host protocol first e-mail program
ARPAnet has 15 nodes
Internet history
1972-1980: Internetworking, new and proprietary networks
1970: ALOHAnet satellite network in Hawaii
1974: Cerf and Kahn architecture for interconnecting networks
1976: Ethernet at Xerox PARC late70s: proprietary
architectures: DECnet, SNA, XNA 1979: ARPAnet has 200 nodes
Cerf and Kahns internetworking principles:
minimalism, autonomy no internal changes required to interconnect networks
best-effort service model
stateless routing
decentralized control
define todays Internet architecture
Introduction: 1-80
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Internet history
1980-1990: new protocols, a proliferation of networks
1983: deployment of TCP/IP
1982: smtp e-mail protocol
defined
1983: DNS defined for name- to-IP-address translation
1985: ftp protocol defined
1988: TCP congestion control
new national networks: CSnet, BITnet, NSFnet, Minitel
100,000 hosts connected to confederation of networks
Introduction: 1-81
Internet history
1990, 2000s: commercialization, the Web, new applications
early 1990s: ARPAnet decommissioned
1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995)
early 1990s: Web
hypertext [Bush 1945, Nelson 1960s] HTML, HTTP: Berners-Lee
1994: Mosaic, later Netscape
late 1990s: commercialization of the Web
late 1990s 2000s:
more killer apps: instant messaging, P2P file sharing
network security to forefront est. 50 million host, 100 million+
users
backbone links running at Gbps
Introduction: 1-82
Internet history
2005-present: scale, SDN, mobility, cloud
aggressive deployment of broadband home access (10-100s Mbps)
2008: software-defined networking (SDN)
increasing ubiquity of high-speed wireless access: 4G/5G, WiFi
service providers (Google, FB, Microsoft) create their own networks
bypass commercial Internet to connect close to end user, providing instantaneous access to social media, search, video content,
enterprises run their services in cloud (e.g., Amazon Web Services, Microsoft Azure)
rise of smartphones: more mobile than fixed devices on Internet (2017)
~18B devices attached to Internet (2017)
Introduction: 1-83
Chapter 1: summary
Weve covered a ton of material!
Internet overview
whats a protocol?
network edge, access network, core
packet-switching versus circuit- switching
Internet structure
performance: loss, delay, throughput
layering, service models
security
history
You now have:
context, overview, vocabulary, feel of networking
more depth, detail, and fun to follow!
Introduction: 1-84
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Additional Chapter 1 slides
Introduction: 1-85
ISO/OSI reference model
Two layers not found in Internet protocol stack!
presentation: allow applications to interpret meaning of data, e.g., encryption, compression, machine-specific conventions
session: synchronization, checkpointing, recovery of data exchange
Internet stack missing these layers! these services, if needed, must be
implemented in application needed?
The seven layer OSI/ISO reference model
application
presentation
session
transport
network
link
physical
Introduction: 1-86
85 86
Wireshark
packet analyzer
packet capture (pcap)
application (www browser, email client)
Transport (TCP/UDP)
Network (IP)
application
OS
copy of all
Ethernet frames sent/received
Link (Ethernet)
Physical
Introduction: 1-87
87
22