程序代写代做代考 dns C html game FTP algorithm Chapter 1 Introduction

Chapter 1 Introduction
Computer Networking: A Top-Down Approach
8th edition
Jim Kurose, Keith Ross Pearson, 2020
Introduction: 1-1

Chapter 1: introduction
Chapter goal: Overview/roadmap:
§Get “feel,” “big picture,” introduction to terminology
• more depth, detail later in course
§ Approach:
• use Internet as example
§ 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: 1-2

The Internet: a “nuts and bolts” view
Billions of connected computing devices:
§ hosts = end systems
§ running network apps at Internet’s “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
local or
home network
enterprise network
regional ISP Internet
content provider network
datacenter network
Introduction: 1-3

“Fun” Internet-connected devices
Pacemaker & Monitor
sensorized, bed mattress
Amazon Echo
Internet refrigerator
Security Camera
Internet phones
IP picture frame
Slingbox: remote control cable TV
Tweet-a-watt: monitor energy use
Web-enabled toaster + weather forecaster
AR devices
Others?
Fitbit
Introduction: 1-4

The Internet: a “nuts and bolts” view
§ Internet: “network of networks” • Interconnected ISPs
§ protocols are everywhere
• control sending, receiving of
• 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
messages
Skype
Ethernet
enterprise network
IP
local or regional ISP
Streaming video
datacenter network
TCP
home network
HTTP
content provider network
WiFi
Introduction: 1-5

The Internet: a “service” view
§ Infrastructure that provides services to applications:
mobile network
• Web, streaming video, multimedia teleconferencing, email, games, e- commerce, social media, inter- connected appliances, …
national or global ISP
Streaming video
datacenter network
Skype § provides programming interface
local or regional ISP
to distributed applications:
• “hooks” allowing sending/receiving
apps to “connect” to, use Internet transport service
• provides service options, analogous to postal service
home network
HTTP
enterprise network
content provider network
Introduction: 1-6

What’s a protocol?
Human protocols:
§ “what’s the time?” § “I have a question” § introductions
… specific messages sent
… specific actions taken when message received, or other events
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 msg transmission, receipt
Introduction: 1-7

What’s a protocol?
A human protocol and a computer network protocol:
Hi
Hi
Got the time?
2:00
TCP connection request
TCP connection response
GET http://gaia.cs.umass.edu/kurose_ross
Q: other human protocols?
time
Introduction: 1-8

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: 1-9

A closer look at Internet structure
Network edge:
§hosts: clients and servers §servers often in data centers
national or global ISP
mobile network
local or regional ISP
home network
enterprise network
content provider network
datacenter network
Introduction: 1-10

A closer look at Internet structure
mobile network
Network edge:
§hosts: clients and servers §servers often in data centers
Access networks, physical media:
§wired, wireless communication links
national or global ISP
local or regional ISP
home network
enterprise network
content provider network
datacenter network
Introduction: 1-11

A closer look at Internet structure
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
mobile network
local or regional ISP
home network
enterprise network
content provider network
datacenter network
Introduction: 1-12

Access networks and physical media
Q: How to connect end systems to edge router?
§ residential access networks
§ institutional access networks (school,
company)
§ mobile access networks (WiFi, 4G/5G)
What to look for:
§ transmission rate (bits per second) of access network?
§ shared or dedicated access among users?
mobile network
national or global ISP
local or regional ISP
home network
enterprise network
content provider network
datacenter network
Introduction: 1-13

Access networks: cable-based access
cable headend
…
cable splitter
modem
O VVVVVV N IIIIIIDDT DDDDDDAAR EEEEEETTO OOOOOOAAL
123456789 Channels
C
frequency division multiplexing (FDM): different channels transmitted in different frequency bands
Introduction: 1-14

Access networks: cable-based access
cable splitter
modem
data, TV transmitted at different frequencies over shared cable
distribution network
cable headend
…
CMTS
cable modem termination system
ISP
§ HFC: hybrid fiber coax
• asymmetric: up to 40 Mbps – 1.2 Gbps downstream transmission rate, 30-100 Mbps
upstream transmission rate
§ network of cable, fiber attaches homes to ISP router • homes share access network to cable headend
Introduction: 1-15

Access networks: digital subscriber line (DSL)
central office
DSLAM
DSL access multiplexer
telephone network
DSL splitte modem
ISP
r
voice, data transmitted at different frequencies over dedicated line to central office
§ 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: 1-16

Access networks: fiber to the home (FTTH)
optical splitter
central office
optical network terminator(ONT)
optical fibers
optical line terminator (OLT)
ISP
§ simple in principle
• an optical fiber path is run from the central office (CO) to the home, giving access
rates in the Gbps range
• fiber could run direct from the CO to each home, but more often is split close to the home and only from the splitter are there customer-specific fibers
• terminators at each end convert optical and electrical signals to connect with
other gear
Introduction: 1-17

Access networks: home networks
wireless devices
often combined in single box
WiFi wireless access point
to/from headend or central office
cable or DSL modem or ONT
router, firewall, NAT wired Ethernet
Introduction: 1-18

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)
§ 802.11a/b/g/n/ac/ax (WiFi): 10 Mbps – 10 Gbps
to Internet
Wide-area cellular access networks
§ provided by mobile, cellular network operator (10’s km)
§ 10’s 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 (we’ll cover differences shortly)
§ Ethernet: wired access at 100Mbps, 1Gbps, 10Gbps § WiFi: wireless access points at various speeds
Introduction: 1-20

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
21
• link transmission rate, aka link host capacity, aka link bandwidth
packet = transmission
delay
time needed to transmit L-bit packet into link
R: link transmission rate = L (bits)
R (bits/sec)
Introduction: 1-21

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: 1-22

Links: physical media
Coaxial cable:
§ two concentric copper conductors
§ bidirectional
§ broadband:
• multiple frequency channels on cable
• 100’s Mbps per channel
Fiber optic cable:
§ glass fiber carrying light pulses, each pulse a bit
§ high-speed operation:
• high-speed point-to-point
transmission (10’s-100’s Gbps) § low error rate:
• repeaters spaced far apart
• immune to electromagnetic noise
Introduction: 1-23

Links: physical media
Wireless radio
§signal carried in electromagnetic spectrum
§no physical “wire” §broadcast and “half-duplex”
(sender to receiver)
§propagation environment effects:
• reflection
• obstruction by objects • interference
Radio link types:
§terrestrial microwave • upto45Mbpschannels
§ Wireless LAN (WiFi)
• Up to 100’s Mbps or more
§ wide-area (e.g., cellular) • 4G cellular: ~ 10’s Mbps
§ satellite
• up to 45 Mbps per channel
• 270 msec end-end delay
• geosynchronous versus low- earth-orbit
Introduction: 1-24

The network core
§mesh of interconnected routers
§packet-switching: hosts break application-layer messages into packets
• forward packets from one router to the next, across links on path from source to destination
• each packet transmitted at full link capacity
mobile network
national or global ISP
local or regional ISP
home network
enterprise network
content provider network
datacenter network
Introduction: 1-26

Packet-switching: store-and-forward
L bits
per packet
source 3 2 1 destination R bps R bps
§ Transmission delay: takes L/R seconds to transmit (push out) L-bit packet into link at R bps
§ Store and forward: entire packet must arrive at router before it can be transmitted on next link
§ End-end delay: 2L/R (above), assuming zero propagation delay (more on delay shortly)
One-hop numerical example:
§L = 10 Kbits
§R = 100 Mbps
§ one-hop transmission delay = 0.1 msec
Introduction: 1-27

Packet-switching: queueing delay, loss
R = 100 Mb/s
C
D
E
A
B
R = 1.5 Mb/s queue of packets
waiting for output link
Packet queuing and loss: if arrival rate (in bps) to link exceeds transmission rate (bps) of link for a 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: 1-28

Two key network-core functions
routing algorithm
llocall forwardiing tablle
header value
output link
0100
0101
0111
1001
3 2 2 1
Forwarding:
§local action: move arriving
packets from router’s input link to appropriate routeroutputlink
Routing:
§ global action: determine source- destination paths taken by packets
§ routing algorithms
1 3 2
destination address in arriving packet’s header
Introduction: 1-29
0111

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
Introduction: 1-30

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, but only during its time slot(s)
4 users
time
time
Introduction: 1-31
frequency
frequency

Packet switching versus circuit switching
packet switching allows more users to use network!
Example:
§ 1 Gb/s link
§ each user:
• 100 Mb/s when “active” • active 10% of time
§circuit-switching: 10 users
§packet switching: with 35 users, probability > 10 active at same time is less than .0004 *
N
users
1 Gbps link
* Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive
Introduction: 1-32
Q: how did we get value 0.0004? Q: what happens if > 35 users ?
…..

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?
• bandwidth guarantees traditionally used for audio/video applications
Q: human analogies of reserved resources (circuit switching) versus on-demand allocation (packet switching)?
Introduction: 1-33

Internet structure: a “network of networks”
§ Hosts connect to Internet via access Internet Service Providers (ISPs)
• residential, enterprise (company, university, commercial) ISPs
§ Access ISPs in turn must be interconnected
• so that any two hosts can send packets to each other
§ Resulting network of networks is very complex
• evolution was driven by economics and national policies
§ Let’s take a stepwise approach to describe current Internet structure
Introduction: 1-34

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: 1-35
…
…
…
…
…
…

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
connecting each access ISP to each other directly doesn’t scale: O(N2) connections.
access net
access net
access net
access net
access net
access net
access
access net net
Introduction: 1-36
…
…
…
…
…
…
…
…
…
…
…

Internet structure: a “network of networks”
Option: connect each access ISP to one global transit ISP? Customer and provider ISPs have economic agreement.
access net
access net
access net
access net
access net
access net
access net
access net
access net
access net
global ISP
access net
access net
access net
access net
access net
access net
Introduction: 1-37
…
…
…
…
…
…

Internet structure: a “network of networks”
But if one global ISP is viable business, there will be competitors ….
access net
ISP A
access net
access net
access net
access net
access net
access net
access net
ISP B
access net
access net
access net
ISP C
access net
access net
access net
access net
access net
Introduction: 1-38
…
…
…
…
…
…

Internet structure: a “network of networks”
But if one global ISP is viable business, there will be competitors …. who will
want to be connected
access net
ISP A
access net
access net
Internet exchange point
access net
access net
access net
access net
IXP
access net
IXP
ISP B
access net
access net
access net
ISP C
access net
access net
peering link
access net
access net
access net
Introduction: 1-39
…
…
…
…
…
…

Internet structure: a “network of networks”
… and regional networks may arise to connect access nets to ISPs
access net
ISP A
access net
access net
access net
access net
access net
access net
IXP
access net
IXP
ISP B
access net
access net
access net
ISP C
access net
access net
access
access net net
regional ISP
access net
Introduction: 1-40
…
…
…
…
…
…

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
ISP A
access net
access net
access net
access net
access net
access net
IXP
access net
Content provider network
IXP ISP B
access net
access net
access net
ISP C
access net
regional ISP
access net
access net
access
access net net
Introduction: 1-41
…
…
…
…
…
…

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
access
Introduction: 1-42

How do packet loss and delay occur?
packets queue in router buffers
§ packets queue, wait for turn
§ arrival rate to link (temporarily) exceeds output link capacity: packet loss
A B
packets in buffers (queueing delay)
free (available) buffers: arriving packets dropped (loss) if no free buffers
packet being transmitted (transmission delay)
Introduction: 1-44

Packet delay: four sources
transmission
A B
dnodal = dproc + dqueue + dtrans + dprop
propagation
dproc: nodal processing § check bit errors
§ determine output link § typically < msec dqueue: queueing delay § time waiting at output link for transmission § depends on congestion level of router nodal processing queueing Introduction: 1-45 Packet delay: four sources transmission A B dnodal = dproc + dqueue + dtrans + dprop propagation nodal processing queueing dtrans: transmission delay: § L: packet length (bits) § R: link transmission rate (bps) §dtrans = L/R dprop: propagation delay: § d: length of physical link § s: propagation speed (~2x108 m/sec) §dprop = d/s * Check out the online interactive exercises: http://gaia.cs.umass.edu/kurose_ross Introduction: 1-46 dtrans and dprop very different Caravan analogy 100 km (aka 10-bit packet) (aka router) §cars“propagate”at 100km/hr § toll booth takes 12 sec to service car (bit transmission time) § car ~ bit; caravan ~ packet § Q: How long until caravan is lined up before 2nd toll booth? 100 km §timeto“push”entirecaravan through toll booth onto highway = 12*10 = 120 sec § time for last car to propagate from 1st to 2nd toll both: 100km/(100km/hr) = 1 hr § A: 62 minutes ten-car caravan toll booth toll booth Introduction: 1-47 Caravan analogy 100 km (aka 10-bit packet) (aka router) 100 km ten-car caravan toll booth toll booth § 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 booth Introduction: 1-48 Packet queueing delay (revisited) §R: link bandwidth (bps) §L: packet length (bits) §a: average packet arrival rate §La/R ~ 0: avg. queueing delay small §La/R -> 1: avg. queueing delay large
§La/R > 1: more “work” is arriving than can be serviced – average delay infinite!
traffic intensity = La/R 1 La/R ~ 0
La/R -> 1
Introduction: 1-49
average queueing delay

“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: 1-50

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
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
3 delay measurements
to border1-rt-fa5-1-0.gw.umass.edu
* means no response (probe lost, router not replying)
trans-oceanic link
Introduction: 1-51

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
Introduction: 1-52

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
server sends bits server, with
sc
(fluid) into pipe file of F bits
(Rs bits/sec)
(Rc bits/sec)
to send to client
link capacity
pipe that can carry
link capacity pipe that can carry
R bits/sec fluid at rate
R bits/sec fluid at rate
Introduction: 1-53

Throughput
Rs < Rc What is average end-end throughput? Rs bits/sec Rc bits/sec Rs > Rc What is average end-end throughput?
Rs bits/sec
Rc bits/sec
bottleneck link
link on end-end path that constrains end-end throughput
Introduction: 1-54

Throughput: network scenario
Rs
Rc
Rs
§ per-connection end- end throughput: min(Rc,Rs,R/10)
§ in practice: Rc or Rs is often bottleneck
Rs
R Rc
Rc
10 connections (fairly) share backbone bottleneck link R bits/sec
* Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/
Introduction: 1-55

Network security
§field of network security:
• how bad guys can attack computer networks
• how we can defend networks against attacks
• how to design architectures that are immune to attacks
§Internet not originally designed with (much) security in mind
• original vision: “a group of mutually trusting users attached to a transparent network”J
• Internet protocol designers playing “catch-up”
• security considerations in all layers!
Introduction: 1-57

Bad guys: malware
§ malware can get in host from:
• virus: self-replicating infection by receiving/executing object
(e.g., e-mail attachment)
• worm: self-replicating infection by passively receiving object that gets itself executed
§ spyware malware can record keystrokes, web sites visited, upload info to collection site
§ infected host can be enrolled in botnet, used for spam or distributed denial of service (DDoS) attacks
Introduction: 1-58

Bad guys: denial of service
Denial of Service (DoS): attackers make resources (server, bandwidth) unavailable to legitimate traffic by overwhelming resource with bogus traffic
1. select target
2. break into hosts around the network (see botnet)
3. send packets to target from compromised hosts
target
Introduction: 1-59

Bad guys: packet interception
packet “sniffing”:
§broadcast media (shared Ethernet, wireless)
§promiscuous network interface reads/records all packets (e.g.,
including passwords!) passing by
A
C
src:B
dest:A
payload
B
Wireshark software used in this course is a (free) packet-sniffer
Introduction: 1-60

Bad guys: fake identity
IP spoofing: send packet with false source address
A
C
src:B
dest:A
payload
B
… lots more on security (throughout, Chapter 8)
Introduction: 1-61

Protocol “layers” and reference models
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?
…. or at least our
discussion of networks? Introduction: 1-63

Example: organization of air travel
ticket (purchase) baggage (check) gates (load) runway takeoff airplane routing
ticket (complain) baggage (claim) gates (unload) runway landing airplane routing
airplane routing
airline travel: a series of steps, involving many services
Introduction: 1-64

Example: organization of air travel
ticket (purchase)
baggage (check)
gates (load)
runway takeoff
airplane routing
ticketing service
baggage service
gate service
runway service
aroiruptlianngesreoruvticineg
ticket (complain)
baggage (claim)
gates (unload)
runway landing
airplane routing
layers: each layer implements a service §via its own internal-layer actions
§relying on services provided by layer below
Q: describe in words the service provided in each layer above
Introduction: 1-65

Why layering?
dealing with complex systems:
§ explicit structure allows identification, relationship of complex system’s pieces
• layered reference model for discussion
§ modularization eases maintenance, updating of system
• change in layer’s service implementation: transparent to rest of system
• e.g., change in gate procedure doesn’t affect rest of system
§ layering considered harmful?
§ layering in other complex systems?
Introduction: 1-66

Internet protocol stack
§application: supporting network applications • IMAP, SMTP, HTTP
§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
transport
network
link
physical
Introduction: 1-67

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: 1-68

datagram frame
Hn
Ht
M
source
Encapsulation
application
transport
network
link
physical
M
M
message segment
Hl
Hn
Ht
M
link
physical
network
switch
destination
application
transport
network
link
physical
M
M
Hn
Ht
M
link
Hl
Hn
Ht
M
Hn
Ht
M
physical
Ht
Hn
Ht
M
router
Hl
Hn
Ht
M
Ht
Introduction: 1-69

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
Introduction: 1-71

Internet history
1972-1980: Internetworking, new and proprietary nets
§1970: ALOHAnet satellite network in Hawaii
§1974: Cerf and Kahn – architecture for interconnecting networks
§1976: Ethernet at Xerox PARC §late70’s: proprietary architectures:
DECnet, SNA, XNA
§late 70’s: switching fixed length packets (ATM precursor)
§1979: ARPAnet has 200 nodes
Cerf and Kahn’s internetworking principles:
§ minimalism, autonomy – no internal changes required to interconnect networks
§ best-effort service model
§ stateless routing
§ decentralized control
define today’s Internet architecture
Introduction: 1-72

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: 1-73

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 1960’s] • 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: 1-74

Internet history
2005-present: more new applications, Internet is “everywhere”
§ ~18B devices attached to Internet (2017) • rise of smartphones (iPhone: 2007)
§ aggressive deployment of broadband access
§ increasing ubiquity of high-speed wireless access: 4G/5G, WiFi
§ emergence of online social networks:
• Facebook: ~ 2.5 billion users
§ service providers (Google, FB, Microsoft) create their own networks • bypass commercial Internet to connect “close” to end user, providing
“instantaneous” access to search, video content, …
§ enterprises run their services in “cloud” (e.g., Amazon Web Services, Microsoft Azure)
Introduction: 1-75

Chapter 1: summary
We’ve covered a “ton” of material!
§ Internet overview
§ what’s 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: 1-76

Additional Chapter 1 slides
Introduction: 1-77

Wireshark
application (www browser,
email client)
packet analyzer
application OS
Transport (TCP/UDP)
Network (IP)
Link (Ethernet)
Physical
packet capture (pcap)
copy of all Ethernet frames sent/received
Introduction: 1-78

Related Posts