8/20/2019 DCCN First Chapter_1_V6.1
1/101
Introduction 1-1
Mohammad kaleem, PhD
Data Communication andComputer Networks
(DCCN)Course Information
Spring 2016
EEE
-
314
8/20/2019 DCCN First Chapter_1_V6.1
2/101
Introduction 1-2Introduction 1-2
Computer Networking: A
Top Down Approach6th edition Jim Kurose, Keith RossAddison-WesleyMarch 2012
Data
Communicationand Computer
Networks
8/20/2019 DCCN First Chapter_1_V6.1
3/101
Dr. Mohammad kaleem
Asst. Prof. NUST (E&ME) 2002 ---- Feb2014
IT Consultant BT England 1999 ---- 2002
Network Engineer Silicon Software Tech. Ltd. 1998 ---1999
Hard ware Engineer GHS Technology Ltd. 1995---1997 PhD in Nano-photonics
MSEng in Telecommunication and ComputerNetworks England UK
BEng(Hons) in Electrical Electronics andInformation System Engineering England UK
Introduction 2-3
8/20/2019 DCCN First Chapter_1_V6.1
4/101
Introduction
Prerequisites: EEE 343 Computer Organization
EEE Introduction to Communication
Textbook:
Computer Networking, J. Kurose and K. Ross, 6thed. Pearson, 2012
Reference Books:
Data Communications and Networking, Behrouz
A. Forouzan, 4th ed.2003. Data and Computer Communications, William
Stallings,8th ed. Prentice Hall, 2007
Computer Networks, Andrew S. TanenbaumIntroduction 2-4
8/20/2019 DCCN First Chapter_1_V6.1
5/101
Assessment Plan
Introduction 2-5
Theory Quizz
(4)
15%
Homework assignments 10%
2 Sessional exams (in class, 60-80
minutes each, 10%+15%)
25%
Terminal exam (3 hours) 50%
Total (theory) 100%
Lab work Lab
repot
(12)
25%
2 Lab sessionals 25%
Lab project and terminal exam 50%
Total (lab) 100%
8/20/2019 DCCN First Chapter_1_V6.1
6/101
Introduction 1-6
Course Objectives
Focus is on the principles, architectures ,protocols and fundamental techniques related to
computer networks
Goal is to cover core and advanced topics in
depth along with introduction to Network
Modeling, Simulation and Analysis
Lots of interesting topics to cover
Feedback if you would like to discuss some other
technology or any related topic
8/20/2019 DCCN First Chapter_1_V6.1
7/101Introduction 1-7
Course Contents
Introduction: Internet Architecture, End-to-End principle and Internet
design, Physical Layer Technologies Applications and Transport: HTTP, FTP, DNS, SMTP, Overlay Networks
and Peer-to-Peer (P2P) Systems, P2P File Sharing, Transport Services(TCP and UDP)
IP Routing: IP Addressing, Overview of Internet Protocols (e.g. IP, ARP,RARP, ICMP), Distance Vector, Link-State (OSPF), BGP, Multicastrouting.
Congestion Control: Open-loop (Policing and Shaping), Closed-loop(TCP congestion control algorithms - Reno, Tahoe, Vegas); NetworkAssisted – ECN; Active Queue Management (RED).
Internet QoS: QoS Schedulers (WFQ, DRR, PQ), IP QoS
Architectures, IntServ and RSVP, DiffServ, Router Design for IP QoS,Policy-based QoS Management.
8/20/2019 DCCN First Chapter_1_V6.1
8/101Introduction 1-8
Course Contents Traffic Engineering: Principles of IP Traffic Engineering, MPLS, ..
Multimedia Networking: Multimedia Applications, Protocols forMultimedia Support, RTP, RTCP, RTSP, ..
Virtualization: Cloud Computing, SDN, Open Flow, ..
Network Management: Network management framework, SNMP,ASN
Network Security: Cryptography, Symmetric Key Algorithms, PublicKey Algorithms, Digital Signatures, Management of Public Keys,Communication Security, IPSec, Firewalls, VPNs, AuthenticationProtocols
Network Modeling, Simulation and Analysis: System Performance
Evaluation, Traffic Analysis and Optimization, Queuing Theory,Simulation Modeling and Analysis (Network Simulators : ns-3,OMNET, NCTNns)
8/20/2019 DCCN First Chapter_1_V6.1
9/101Introduction 1-9
A Communications Model
Source generates data to be transmitted
Transmitter Converts data into transmittable signals
Transmission System Carries data
Receiver Converts received signal into data
Destination Takes incoming data
8/20/2019 DCCN First Chapter_1_V6.1
10/101
Introduction 1-10
Simplified Communications Model
- Diagram
8/20/2019 DCCN First Chapter_1_V6.1
11/101
Introduction 1-11
Key Communications Tasks
Transmission System Utilization Interfacing
Signal Generation
Synchronization
Exchange Management Error detection and correction
Addressing and routing
Recovery
Message formatting
Security
Network ManagementSuppose we have a digital transmission system
with bandwidth of 4MHz. Let us attempt to transmit
a sequence of alternating 1s and 0s as the square
wave. What data rate can be achieved? Assume f =
1MHz (cycle/sec). Repeat if f = 2MHz (cycle/sec).
8/20/2019 DCCN First Chapter_1_V6.1
12/101
Introduction 1-12
Simplified Data Communications
Model
8/20/2019 DCCN First Chapter_1_V6.1
13/101
Introduction 1-13
Networking
Point to point communication not usuallypractical
Devices are too far apart
Large set of devices would need impracticalnumber of connections
Solution is a communications network
8/20/2019 DCCN First Chapter_1_V6.1
14/101
Introduction 1-14
Simplified Network Model
8/20/2019 DCCN First Chapter_1_V6.1
15/101
Introduction
Chapter 1: introduction
our goal: get “feel” and
terminology
more depth, detail
later in course approach:
use Internet asexample
overview : 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
1-15
8/20/2019 DCCN First Chapter_1_V6.1
16/101
Introduction
Chapter 1: roadmap
1.1 Internet1.2 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: security1.7 history
1-16
8/20/2019 DCCN First Chapter_1_V6.1
17/101
Introduction
What’s the Internet: “nuts and bolts” view
millions of connectedcomputing devices:
hosts = end systems
running network apps
communication links fiber, copper, radio,
satellite transmission rate:
bandwidth
Packet switches: forwardpackets (chunks of data)
routers and switches
wiredlinks
wirelesslinks
router
mobile network
global ISP
regional ISP
homenetwork
institutionalnetwork
smartphone
PCserver
wirelesslaptop
1-17
8/20/2019 DCCN First Chapter_1_V6.1
18/101
Introduction
“Fun” internet appliances
IP picture frame
http://www.ceiva.com/
Web-enabled toaster +
weather forecaster
Internet phonesInternet
refrigerator
Slingbox: watch,
control cable TV remotely
1-18
Tweet-a-watt:
monitor energy use
8/20/2019 DCCN First Chapter_1_V6.1
19/101
Introduction
Internet: “network of networks” Interconnected ISPs
protocols control sending,receiving of msgs e.g., TCP, IP, HTTP, Skype, 802.11
Internet standards RFC: Request for comments
IETF: Internet Engineering TaskForce
What’s the Internet: “nuts and bolts” view
mobile network
global ISP
regional ISP
homenetwork
institutionalnetwork
1-19
Q: Given the following information, find the
minimum bandwidth required for the path:
FDM Multiplexing
Five devices, each requiring 4000 Hz.200 Hz guard band for each device.
8/20/2019 DCCN First Chapter_1_V6.1
20/101
What’s the Internet: a service view
Infrastructure that providesservices to applications: Web, VoIP, email, games, e-
commerce, TV/IP, social
nets, … (Distributed bynature..)
provides programminginterface to apps
hooks that allow sendingand receiving app programsto “connect” to Internet
provides service options,analogous to postal service
mobile network
global ISP
regional ISP
homenetwork
institutionalnetwork
Introduction 1-20
8/20/2019 DCCN First Chapter_1_V6.1
21/101
Introduction
What’s a protocol?
human protocols: “what’s the time?”
“I have a question”
introductions
… specific msgs sent
… specific actions takenwhen msgs received, orother events
network protocols: machines rather than
humans
all communication activityin Internet governed by
protocols
protocols define format , order
of msgs sent and received among network entities,
and actions taken on msg
transmission, receipt
1-21
8/20/2019 DCCN First Chapter_1_V6.1
22/101
Introduction
a human protocol and a computer network protocol:
Q: other human protocols?
Hi
Hi
Got the
time?
2:00
TCP connectionresponse
Get http://www.awl.com/kurose-ross
time
TCP connectionrequest
What’s a protocol?
1-22
8/20/2019 DCCN First Chapter_1_V6.1
23/101
Introduction
Chapter 1: 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: security1.7 history
1-23
8/20/2019 DCCN First Chapter_1_V6.1
24/101
Introduction
A closer look at network structure:
network edge: hosts: clients and servers
servers often in datacenters
access networks, physicalmedia: wired, wirelesscommunication links
network core: interconnected routers
network of networks
mobile network
global ISP
regional ISP
home
network
institutionalnetwork
1-24
8/20/2019 DCCN First Chapter_1_V6.1
25/101
Introduction
Access networks and physical media
Q: How to connect endsystems to edge router? residential access nets
institutional accessnetworks (school,company)
mobile access networks
keep in mind: bandwidth (bits per second)
of access network?
shared or dedicated?
1-25
8/20/2019 DCCN First Chapter_1_V6.1
26/101
Introduction
Access net: digital subscriber line (DSL)
central office
ISP
telephonenetwork
DSLAM
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
< 2.5 Mbps upstream transmission rate (typically < 1 Mbps)
< 24 Mbps downstream transmission rate (typically < 10 Mbps)
DSLmodem
splitter
DSL accessmultiplexer
1-26
8/20/2019 DCCN First Chapter_1_V6.1
27/101
Introduction
Access net: cable network
cablemodem
splitter
…
cable headend
Channels
V
I
D
E
O
V
I
D
E
O
V
I
D
E
O
V
I
D
E
O
V
I
D
E
O
V
I
D
E
O
D
A
T
A
D
A
T
A
C
O
N
T
R
O
L
1 2 3 4 5 6 7 8 9
frequency division multiplexing: different channels transmittedin different frequency bands
1-27
8/20/2019 DCCN First Chapter_1_V6.1
28/101
Introduction
data, TV transmitted at differentfrequencies over shared cable
distribution network
cablemodem
splitter
…
cable headend
CMTS
ISP
cable modemtermination system
HFC: hybrid fiber coax
asymmetric: up to 30Mbps downstream transmission rate, 2Mbps 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
Access net: cable network
1-28
8/20/2019 DCCN First Chapter_1_V6.1
29/101
Introduction
Access net: home network
to/from headend orcentral office
cable or DSL modem
router, firewall, NAT
wired Ethernet (100 Mbps)
wireless accesspoint (54 Mbps)
wireless
devices
often combinedin single box
1-29
8/20/2019 DCCN First Chapter_1_V6.1
30/101
Introduction
Enterprise access networks (Ethernet)
typically used in companies, universities, etc 10 Mbps, 100Mbps, 1Gbps, 10Gbps transmission rates
today, end systems typically connect into Ethernet switch
Ethernetswitch
institutional mail,web servers
institutional router
institutional link toISP (Internet)
1-30
8/20/2019 DCCN First Chapter_1_V6.1
31/101
Introduction
Wireless access networks
shared wireless access network connects end system to router via base station aka “access point”
wireless LANs: within building (100 ft)
802.11b/g (WiFi): 11, 54 Mbpstransmission rate
wide-area wireless access provided by telco (cellular)
operator, 10’s km
between 1 and 10 Mbps 3G, 4G: LTE
to Internet
to Internet
1-31
If a periodic signal is decomposed into five sine waves with frequencies of
100, 300, 500, 700,and 900 Hz, what is the bandwidth? Draw the spectrum,assuming all components have a maxi-mum amplitude of 10 V.
8/20/2019 DCCN First Chapter_1_V6.1
32/101
Host: sends packets of data
host sending function:
takes application message
breaks into smallerchunks, known as packets,of length L bits
transmits packet intoaccess network attransmission rate R
link transmission rate,aka link capacity, aka
link bandwidth
R: link transmission ratehost
12
two packets,
L bits each
packettransmission
delay
time needed totransmit L-bit
packet into link
L (bits)
R (bits/sec)= =
1-32
An image is 800x600 pix els with 3 bytes/pixel .
Assume the image is uncompressed. How
long does it take to transmit it:
over a 56-kbps modem channel?
over a 1-Mbps cable modem?over a 10-Mbps Ethernet?
8/20/2019 DCCN First Chapter_1_V6.1
33/101
Introduction
Physical media
bit: propagates betweentransmitter/receiver pairs
physical link: what liesbetween 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 copperwires Category 5: 100 Mbps, 1
Gpbs Ethernet
Category 6: 10Gbps
1-33
8/20/2019 DCCN First Chapter_1_V6.1
34/101
Introduction
Physical media: coax, fiber
coaxial cable: two concentric copper
conductors
bidirectional
broadband: multiple channels on cable
HFC
fiber optic cable: glass fiber carrying light
pulses, each pulse a bit
high-speed operation: high-speed point-to-point
transmission (e.g., 10’s-100’sGpbs transmission rate)
low error rate: repeaters spaced far apart
immune to electromagnetic
noise
1-34
8/20/2019 DCCN First Chapter_1_V6.1
35/101
Introduction 1-35
Optical Fiber
8/20/2019 DCCN First Chapter_1_V6.1
36/101
Introduction 1-36
Optical Fiber Transmission Modes
8/20/2019 DCCN First Chapter_1_V6.1
37/101
Introduction
Physical media: radio
signal carried inelectromagnetic spectrum
no physical “wire”
bidirectional
propagation environment
effects: reflection
obstruction by objects
interference
radio link types: terrestrial microwave
e.g. up to 45 Mbps channels
LAN (e.g., WiFi) 11Mbps, 54 Mbps
wide-area (e.g., cellular) 3G cellular: ~ few Mbps
satellite Kbps to 45Mbps channel (or
multiple smaller channels)
270 msec end-end delay geosynchronous versus low
altitude
1-37
A client-server system uses a satellite network, with the satellite at a height of 15,000 km.
What is the best-case delay in response to a request?
8/20/2019 DCCN First Chapter_1_V6.1
38/101
Introduction
Chapter 1: 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: security1.7 history
1-38A digital signal has a bit rate of 2000 bps. What is the duration of each bit (bit interval)?
8/20/2019 DCCN First Chapter_1_V6.1
39/101
Introduction
mesh of interconnectedrouters
packet-switching: hostsbreak application-layer
messages into packets forward packets from one
router to the next, acrosslinks on path from sourceto destination
each packet transmitted atfull link capacity
The network core
1-39
A signal has a spectrum with frequencies between 1000 and 2000 Hz (bandwidth of 1000 Hz).
A medium can pass frequencies from 3000 to 4000 Hz (a bandwidth of 1000 Hz). Can this
signal faithfully pass through this medium?
8/20/2019 DCCN First Chapter_1_V6.1
40/101
Introduction
Packet-switching: store-and-forward
takes L/R seconds totransmit (push out) L-bitpacket into link at R bps
store and forward: entirepacket must arrive at routerbefore it can be transmittedon next link
one-hop numerical example:
L = 7.5 Mbits
R = 1.5 Mbps
one-hop transmissiondelay = 5 sec
more on delay shortly …
1-40
sourceR bps
destination123
L bitsper packet
R bps
end-end delay = 2L/R (assumingzero propagation delay)
8/20/2019 DCCN First Chapter_1_V6.1
41/101
Introduction
Packet Switching: queueing delay, loss
A
B
CR = 100 Mb/s
R = 1.5 Mb/sD
Equeue of packetswaiting for output link
1-41
queuing and loss: If arrival rate (in bits) to link exceeds transmission rate of
link for a period of time: packets will queue, wait to be transmitted on link
packets can be dropped (lost) if memory (buffer) fills up
8/20/2019 DCCN First Chapter_1_V6.1
42/101
Network Layer 4-42
Two key network-core functions
forwarding : move packets fromrouter’s input to appropriaterouter output
routing: determines source-destination route taken bypackets routing algorithms
routing algorithm
local forwarding table
header value output link
0100
01010111
1001
3
22
1
1
23
dest address in arriving
packet’s header
8/20/2019 DCCN First Chapter_1_V6.1
43/101
Introduction
Alternative core: circuit switching
end-end resources allocatedto, reserved for “call”between source & dest:
In diagram, each link has fourcircuits.
call gets 2nd circuit in toplink and 1st circuit in rightlink.
dedicated resources: no sharing
circuit-like (guaranteed)performance
circuit segment idle if not usedby call (no sharing)
Commonly used in traditional
telephone networks 1-43
8/20/2019 DCCN First Chapter_1_V6.1
44/101
Introduction
Circuit switching: FDM versus TDM
FDM
frequency
timeTDM
frequency
time
4 users
Example:
1-44
8/20/2019 DCCN First Chapter_1_V6.1
45/101
Introduction
Packet switching versus circuit switching
example:
1 Mb/s link
each user:
• 100 kb/s when “active”
• active 10% of time
circuit-switching: 10 users
packet switching: with 35 users, probability >
10 active at same time is lessthan .0004 *
packet switching allows more users to use network!
Nusers
1 Mbps link
Q: how did we get value 0.0004?
Q: what happens if > 35 users ?
1-45* Check out the online interactive exercises for more examples
8/20/2019 DCCN First Chapter_1_V6.1
46/101
Introduction
great for bursty data
resource sharing
simpler, no call setup
excessive congestion possible: packet delay and loss
protocols needed for reliable data transfer, congestioncontrol
Q: How to provide circuit-like behavior?
bandwidth guarantees needed for audio/video apps
still an unsolved problem (chapter 7)
is packet switching a “slam dunk winner?”
Q: human analogies of reserved resources (circuit switching)
versus on-demand allocation (packet-switching)?
Packet switching versus circuit switching
1-46
I k f k
8/20/2019 DCCN First Chapter_1_V6.1
47/101
Internet structure: network of networks
End systems connect to Internet via access ISPs (Internet
Service Providers) Residential, company and university 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 Internetstructure
I k f k
8/20/2019 DCCN First Chapter_1_V6.1
48/101
Internet structure: network of networks
Question: given millions of access ISPs, how to connect them
together?
accessnet
access
net
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnetaccess
net
accessnet
I k f k
8/20/2019 DCCN First Chapter_1_V6.1
49/101
Internet structure: network of networks
Option: connect each access ISP to every other access ISP?
accessnet
access
net
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnetaccess
net
accessnet
connecting each access ISP
to each other directly
I t t t t t k f t k
8/20/2019 DCCN First Chapter_1_V6.1
50/101
Internet structure: network of networks
accessnet
access
net
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnetaccess
net
accessnet
Option: connect each access ISP to a global transit ISP? Customer
and provider ISPs have economic agreement.
global
ISP
I t t t t t k f t k
8/20/2019 DCCN First Chapter_1_V6.1
51/101
Internet structure: network of networks
accessnet
access
net
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnetaccess
net
accessnet
But if one global ISP is viable business, there will be competitors
….
ISP B
ISP A
ISP C
I t t t t t k f t k
8/20/2019 DCCN First Chapter_1_V6.1
52/101
Internet structure: network of networks
accessnet
access
net
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnetaccess
net
accessnet
But if one global ISP is viable business, there will be competitors
…. which must be interconnected
ISP B
ISP A
ISP C
IXP
IXP
peering link
Internet exchange point
I t t t t t k f t k
8/20/2019 DCCN First Chapter_1_V6.1
53/101
Internet structure: network of networks
accessnet
access
net
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnetaccess
net
accessnet
… and regional networks may arise to connect access nets to
ISPS
ISP B
ISP A
ISP C
IXP
IXP
regional net
I t t t t t k f t k
8/20/2019 DCCN First Chapter_1_V6.1
54/101
Internet structure: network of networks
accessnet
access
net
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnet
accessnetaccess
net
accessnet
… and content provider networks (e.g., Google, Microsoft,Akamai ) may run their own network, to bring services, contentclose to end users
ISP B
ISP A
ISP B
IXP
IXP
regional net
Content provider network
Internet structure: network of networks
8/20/2019 DCCN First Chapter_1_V6.1
55/101
Introduction
Internet structure: network of networks
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 network (e.g, Google): private network that connects
it data centers to Internet, often bypassing tier-1, regional ISPs 1-55
access
ISP
access
ISP
access
ISP
access
ISP
access
ISP
access
ISP
access
ISP
access
ISP
Regional ISP Regional ISP
IXP IXP
Tier 1 ISP Tier 1 ISP Google
IXP
8/20/2019 DCCN First Chapter_1_V6.1
56/101
Introduction 1-56
COMSATS Institute of Information Technology, Islamabad CampusAssignment – 1 Spring 2016
Class: Marks:
Write a short report which shows the Internet layout plan of
COMSATS, Institute of Information technology.The Layout plan should also discuss the bandwidth distribution
to different departments and the back bone Internet provider
(ISPs).
Note:
Copied or plagiarized assignments will result in a zero grade.
Submission Date: 10-03-2016
8/20/2019 DCCN First Chapter_1_V6.1
57/101
Introduction
Tier-1 ISP: e.g., Sprint
…
to/from customers
peering
to/from backbone
…
… … …
POP: point-of-presence
1-57
8/20/2019 DCCN First Chapter_1_V6.1
58/101
Introduction
Chapter 1: 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: security1.7 history
1-58
H d l d d l ?
8/20/2019 DCCN First Chapter_1_V6.1
59/101
Introduction
How do loss and delay occur?
packets queue in router buffers packet arrival rate to link (temporarily) exceeds output link
capacity
packets queue, wait for turn
A
B
packet being transmitted (delay)
packets queueing (delay)
free (available) buffers: arriving packets
dropped (loss) if no free buffers
1-59
F f k d l
8/20/2019 DCCN First Chapter_1_V6.1
60/101
Introduction
Four sources of packet delay
d proc
: nodal processing check bit errors
determine output link
typically < msec
A
B
propagation
transmission
nodal
processing queueing
d queue
: queueing delay time waiting at output link
for transmission
depends on congestionlevel of router
d nodal = d proc + d queue + d trans + d prop
1-60
8/20/2019 DCCN First Chapter_1_V6.1
61/101
Introduction 1-61
Subject Projects
Software Define NetworksSystem on Chip
Network on Chip
Lab on Chip
OFDM based Supper Channel for DWDMLink performance Analysis of an Optical DWDM (QAM/QPSK).
Investigation of Foure Wave Mixing in Ultra Dense WDM Networks
Birefringence Effects in Multimode Fiber Transmission Systems
Implementation of Multimedia over IPV6
F f k t d l
8/20/2019 DCCN First Chapter_1_V6.1
62/101
Introduction
d trans: transmission delay:
L: packet length (bits) R: link bandwidth (bps)
d trans = L/R
d prop: propagation delay:
d : length of physical link s: propagation speed in medium
(~2x108 m/sec)
d prop = d /sd trans and d propvery different
Four sources of packet delay
propagation
nodal
processing queueing
d nodal = d proc + d queue + d trans + d prop
1-62
A
B
transmission
* Check out the Java applet for an interactive animation on trans vs. prop delay
Caravan analogy
8/20/2019 DCCN First Chapter_1_V6.1
63/101
Introduction
Caravan analogy
cars “propagate” at100 km/hr
toll booth takes 12 sec toservice car (bit transmissiontime)
car~bit; caravan ~ packet Q: How long until caravan is
lined up before 2nd tollbooth?
time to “push” entirecaravan through tollbooth onto highway =12*10 = 120 sec
time for last car topropagate from 1st to2nd toll both:100km/(100km/hr)= 1hr
A: 62 minutes
toll
booth
toll
booth
ten-car
caravan
100 km 100 km
1-63
Caravan analogy (more)
8/20/2019 DCCN First Chapter_1_V6.1
64/101
Introduction
Caravan analogy (more)
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, 1st car arrives at second booth; threecars still at 1st booth.
toll
booth
toll
booth
ten-car
caravan
100 km 100 km
1-64
Q d l ( d)
8/20/2019 DCCN First Chapter_1_V6.1
65/101
Introduction
R: link bandwidth (bps)
L: packet length (bits)
a: average packet arrivalrate
traffic intensity= La/R
La/R ~ 0: avg. queueing delay small
La/R -> 1: avg. queueing delay large La/R > 1: more “work ” arriving
than can be serviced, average delay infinite!
a v
e r a g e
q u e u e i n g
d e l a y
La/R ~ 0
Queueing delay (revisited)
La/R -> 1
1-65
* Check out the Java applet for an interactive animation on queuing and loss
“R l” I d l d
8/20/2019 DCCN First Chapter_1_V6.1
66/101
Introduction
“Real” Internet delays and routes
what do “real” Internet delay & loss look like?
traceroute program: provides delaymeasurement 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 router i will return packets to sender
sender times interval between transmission and reply.
3 probes
3 probes
3 probes
1-66
“R l” I t t d l t
8/20/2019 DCCN First Chapter_1_V6.1
67/101
Introduction
Real Internet delays, routes
1 cs-gw (128.119.240.254) 1 ms 1 ms 2 ms2 border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145) 1 ms 1 ms 2 ms3 cht-vbns.gw.umass.edu (128.119.3.130) 6 ms 5 ms 5 ms4 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 ms6 abilene-vbns.abilene.ucaid.edu (198.32.11.9) 22 ms 18 ms 22 ms7 nycm-wash.abilene.ucaid.edu (198.32.8.46) 22 ms 22 ms 22 ms8 62.40.103.253 (62.40.103.253) 104 ms 109 ms 106 ms9 de2-1.de1.de.geant.net (62.40.96.129) 109 ms 102 ms 104 ms10 de.fr1.fr.geant.net (62.40.96.50) 113 ms 121 ms 114 ms11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms12 nio-n2.cssi.renater.fr (193.51.206.13) 111 ms 114 ms 116 ms13 nice.cssi.renater.fr (195.220.98.102) 123 ms 125 ms 124 ms14 r3t2-nice.cssi.renater.fr (195.220.98.110) 126 ms 126 ms 124 ms15 eurecom-valbonne.r3t2.ft.net (193.48.50.54) 135 ms 128 ms 133 ms16 194.214.211.25 (194.214.211.25) 126 ms 128 ms 126 ms17 * * *18 * * *
19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms
traceroute: gaia.cs.umass.edu to www.eurecom.fr
3 delay measurements from
gaia.cs.umass.edu to cs-gw.cs.umass.edu
* means no response (probe lost, router not replying)
trans-oceanic
link
1-67* Do some traceroutes from exotic countries at www.traceroute.org
P k l
8/20/2019 DCCN First Chapter_1_V6.1
68/101
Introduction
Packet loss
queue (aka buffer) preceding link in buffer has finitecapacity
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
packet being transmitted
packet arriving to
full buffer is lost
buffer
(waiting area)
1-68* Check out the Java applet for an interactive animation on queuing and loss
Th h
8/20/2019 DCCN First Chapter_1_V6.1
69/101
Introduction
Throughput
throughput: rate (bits/time unit) at which bitstransferred between sender/receiver instantaneous: rate at given point in time
average: rate over longer period of time
server, withfile of F bits
to send to client
link capacityRs bits/sec
link capacityRc bits/sec
server sends bits(fluid) into pipe
pipe that can carryfluid at rateRs bits/sec)
pipe that can carryfluid at rateRc bits/sec)
1-69
Th h tSuppose a MP3 file = 32Million bits, the
Server has the transmission rate of Rs= 2Mbp
8/20/2019 DCCN First Chapter_1_V6.1
70/101
Introduction
Throughput
Rs < Rc What is average end-end throughput?
Rs bits/sec Rc bits/sec
Rs > Rc What is average end-end throughput?
link on end-end path that constrains end-end throughput
bottleneck link
Rs bits/sec Rc bits/sec
1-70
You have an access link of Rc=1Mbps.
The time needed to transmit the file =
Throughput: Internet scenario
8/20/2019 DCCN First Chapter_1_V6.1
71/101
Introduction
Throughput: Internet scenario
10 connections (fairly) share
backbone bottleneck link R bits/sec
Rs
Rs
Rs
Rc
Rc
Rc
R
per-connection end-end throughput:min(Rc,Rs,R/10)
in practice: Rc or Rsis often bottleneck
1-71
8/20/2019 DCCN First Chapter_1_V6.1
72/101
Introduction
Chapter 1: 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: security1.7 history
1-72
P t l “l ”
8/20/2019 DCCN First Chapter_1_V6.1
73/101
Introduction
Protocol layers
Networks are complex,with many “ pieces” :
hosts
routers
links of variousmedia
applications
protocols
hardware,software
Question:is there any hope of
organizing structure ofnetwork?
…. or at least our
discussion of networks?
1-73
O i i f i l
8/20/2019 DCCN First Chapter_1_V6.1
74/101
Introduction
Organization of air travel
a series of steps
ticket (purchase)
baggage (check)
gates (load)
runway takeoff
airplane routing
ticket (complain)
baggage (claim)
gates (unload)
runway landing
airplane routing
airplane routing
1-74
Layering of airline functionality
8/20/2019 DCCN First Chapter_1_V6.1
75/101
Introduction
ticket (purchase)
baggage (check)
gates (load)
runway (takeoff)
airplane routing
departure
airportarrival
airport
intermediate air-traffic
control centers
airplane routing airplane routing
ticket (complain)
baggage (claim
gates (unload)
runway (land)
airplane routing
ticket
baggage
gate
takeoff/landing
airplane routing
Layering of airline functionality
layers: each layer implements a service
via its own internal-layer actions
relying on services provided by layer below
1-75
Wh l ?
8/20/2019 DCCN First Chapter_1_V6.1
76/101
Introduction
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 ofsystem change of implementation of layer’s service
transparent to rest of system
e.g., change in gate procedure doesn
’t affect rest ofsystem
layering considered harmful?
1-76
TCP/IP Protocol Architecture
8/20/2019 DCCN First Chapter_1_V6.1
77/101
Introduction 1-77
TCP/IP Protocol Architecture
Developed by the US Defense Advanced ResearchProject Agency (DARPA) for its packet switchednetwork (ARPANET)
Used by the global Internet
No official model but a working one. Application layer Host to host or transport layer
Internet layer
Network access layer
Physical layer
Physical Layer
8/20/2019 DCCN First Chapter_1_V6.1
78/101
Introduction 1-78
Physical Layer
Physical interface between data transmission device(e.g. computer) and transmission medium ornetwork
Characteristics of transmission medium
Signal levels Data rates
etc.
Network Access Layer
8/20/2019 DCCN First Chapter_1_V6.1
79/101
Introduction 1-79
Network Access Layer
Exchange of data between end system and network Destination address provision
Invoking services like priority
Internet Layer (IP)
8/20/2019 DCCN First Chapter_1_V6.1
80/101
Introduction 1-80
Internet Layer (IP)
Systems may be attached to different networks Routing functions across multiple networks
Implemented in end systems and routers
Transport Layer (TCP)
8/20/2019 DCCN First Chapter_1_V6.1
81/101
Introduction 1-81
Transport Layer (TCP)
Reliable delivery of data Ordering of delivery
Application Layer
8/20/2019 DCCN First Chapter_1_V6.1
82/101
Introduction 1-82
Application Layer
Support for user applications
e.g. http, SMTP
TCP/IP Protocol Architecture
8/20/2019 DCCN First Chapter_1_V6.1
83/101
Introduction 1-83
TCP/IP Protocol Architecture
Model
OSI Model
8/20/2019 DCCN First Chapter_1_V6.1
84/101
Introduction 1-84
OSI Model
Open Systems Interconnection Developed by the International Organization
for Standardization (ISO)
Seven layers
A theoretical system delivered too late! TCP/IP is the de facto standard
Internet protocol stack
8/20/2019 DCCN First Chapter_1_V6.1
85/101
Introduction
Internet protocol stack
application: supporting networkapplications FTP, SMTP, HTTP
transport: process-process datatransfer
TCP, UDP network: routing of datagrams
from source to destination IP, routing protocols
link: data transfer betweenneighboring network elements Ethernet, 802.111 (WiFi), PPP
physical: bits “on the wire”
application
transport
network
link
physical
1-85
ISO/OSI reference model
8/20/2019 DCCN First Chapter_1_V6.1
86/101
Introduction
ISO/OSI reference model
presentation: allow applicationsto interpret meaning of data,e.g., encryption, compression,machine-specific conventions
session: synchronization,checkpointing, recovery of dataexchange
Internet stack “missing” theselayers! these services, if needed, must be
implemented in application
needed?
application
presentation
session
transport
network
link
physical
1-86
OSI v TCP/IP
8/20/2019 DCCN First Chapter_1_V6.1
87/101
Introduction 1-87
OSI v TCP/IP
source
Encapsulation
8/20/2019 DCCN First Chapter_1_V6.1
88/101
Introduction
application
transport
network
linkphysical
HtHn M
segment Ht
datagram
destination
application
transport
network
link
physical
HtHnHl M
HtHn M
Ht M
M
network
link
physical
link
physical
HtHnHl M
HtHn M
HtHn M
HtHnHl M
router
switch
Encapsulationmessage M
Ht M
Hn
frame
1-88
Cha ter 1: r adma
8/20/2019 DCCN First Chapter_1_V6.1
89/101
Introduction
Chapter 1: 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: security1.7 history
1-89
Network security
8/20/2019 DCCN First Chapter_1_V6.1
90/101
Introduction
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 toattacks
Internet not originally designed with (much)security in mind original vision: “a group of mutually trusting users
attached to a transparent network ”
Internet protocol designers playing“catch-up
”
security considerations in all layers!
1-90
Bad guys: put malware into hosts via Internet
8/20/2019 DCCN First Chapter_1_V6.1
91/101
Introduction
Bad guys: put malware into hosts via Internet
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 forspam. DoS attacks
1-91
Bad guys: attack server, network infrastructure
8/20/2019 DCCN First Chapter_1_V6.1
92/101
Introduction
target
Denial of Service (DoS): attackers make resources
(server, bandwidth) unavailable to legitimate trafficby overwhelming resource with bogus traffic
1. select target
2. break into hosts aroundthe network (see botnet)
3. send packets to target from
compromised hosts
g y ,
1-92
Bad guys can sniff packets
8/20/2019 DCCN First Chapter_1_V6.1
93/101
Introduction
Bad guys can sniff packets
packet“ sniffing
” : broadcast media (shared ethernet, wireless)
promiscuous network interface reads/records all packets(e.g., including passwords!) passing by
A
B
C
src:B dest:A payload
wireshark software used for end-of-chapter labs is a
(free) packet-sniffer
1-93
Bad guys can use fake addresses
8/20/2019 DCCN First Chapter_1_V6.1
94/101
Introduction
Bad guys can use fake addresses
IP spoofing: send packet with false source address
A
B
C
src:B dest:A payload
1-94
… lots more on security (throughout, Chapter 8)
Chapter 1: roadmap
8/20/2019 DCCN First Chapter_1_V6.1
95/101
Introduction
Chapter 1: 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: security1.7 history
1-95
Internet history
8/20/2019 DCCN First Chapter_1_V6.1
96/101
Introduction
y
1961: Kleinrock -queueing theory showseffectiveness of packet-switching
1964: Baran - packet-switching in military nets
1967: ARPAnetconceived by AdvancedResearch Projects
Agency 1969: first ARPAnet
node operational
1972:
ARPAnet public demo
NCP (Network ControlProtocol) first host-host
protocol first e-mail program
ARPAnet has 15 nodes
1961-1972: Early packet-switching principles
1-96
Internet history
8/20/2019 DCCN First Chapter_1_V6.1
97/101
Introduction
1970: ALOHAnet satellitenetwork in Hawaii
1974: Cerf and Kahn -architecture for interconnecting
networks 1976: Ethernet at Xerox PARC
late70’s: proprietaryarchitectures: DECnet, SNA,XNA
late 70’s: switching fixed lengthpackets (ATM precursor)
1979: ARPAnet has 200 nodes
Cerf and Kahn’sinternetworking principles: minimalism, autonomy - no
internal changes required tointerconnect networks
best effort service model
stateless routers
decentralized control
define today’s Internetarchitecture
1972-1980: Internetworking, new and proprietary nets
y
1-97
8/20/2019 DCCN First Chapter_1_V6.1
98/101
Internet history
8/20/2019 DCCN First Chapter_1_V6.1
99/101
Introduction
early 1990’s: ARPAnetdecommissioned
1991: NSF lifts restrictions oncommercial use of NSFnet
(decommissioned, 1995)early 1990s: Web
hypertext [Bush 1945,Nelson 1960’s]
HTML, HTTP: Berners-Lee
1994: Mosaic, later Netscape
late 1990’s:commercialization of the Web
late 1990’s – 2000’s:
more killer apps: instantmessaging, P2P file sharing
network security to
forefront est. 50 million host, 100
million+ users
backbone links running atGbps
1990, 2000’s: commercialization, the Web, new apps
y
1-99
Internet history
8/20/2019 DCCN First Chapter_1_V6.1
100/101
Introduction
2005-present
~750 million hosts Smartphones and tablets
Aggressive deployment of broadband access
Increasing ubiquity of high-speed wireless access
Emergence of online social networks: Facebook: soon one billion users
Service providers (Google, Microsoft) create their ownnetworks
Bypass Internet, providing “instantaneous” access
to search, emai, etc. E-commerce, universities, enterprises running their
services in “cloud” (eg, Amazon EC2)
y
1-100
Introduction: summary
8/20/2019 DCCN First Chapter_1_V6.1
101/101
y
covered a“ ton
” of material!
Internet overview
what’s a protocol? network edge, core, access
network
packet-switching versuscircuit-switching
Internet structure
performance: loss, delay,throughput
layering, service models
security
history
you now have: context, overview, “feel”
of networking
more depth, detail tofollow!
Top Related