Cn Chp1 [Compatibility Mode]

8/9/2019 Cn Chp1 [Compatibility Mode]

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Computer NetworksComputer Networks

[email protected]@iust.ac.ir OrientationOrientation 11--11

Orientation


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Chapter 1: OrientationChapter 1: Orientation

1.0 Why Networking

1.1 What isthe Internet?

1.2 Network Structure

Network edge

Network core


Network access and physical media

1.3 Internet structure and ISPs

1.4 Delay & loss in packet-switched networks

1.5 Protocol layers, service models1.6 History


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Distributed Software Application (will be discussed): WEB, email, 3-tier appl., Database Directory

Resource Sharing

Why Networking !Why Networking !


File, Software, Data, (Network File System, FileTransfer, )

CPU, Memory, Peripherals,

Communication Email, Chat, TV, Radio, Video Conference, Telephone, . Virtual Terminal (Remote Login)


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Platform (OS + Hardware)

Application Program Interface (API)

Application Software

Platform Services

Graphics

Data Interchange

Application Agent

Application SoftwareApplication Software


Platform (OS + Hardware)


Applicationprocess

Applicationprocess

Inter-process Communication

Data Management User Interface

Software Engineering

Communication Services


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Distributed Applications or Network Application:Distributed Applications or Network Application:

Client/ServerClient/Server

Application Software (Client Part)

Networking Software & HardwareNetworking Software & Hardware

Application Software (Server Part)

Client (user) Agent Server Agent

Application Program Interface (API) Application Program Interface (API)Syste

Applicat

ion

++


CommunicationCommunicationNetworkNetwork

Client Agents Examples: Internet Explorer + http,

Opera + http MSs Outlook + SMTP,Netscapes Messenger +SMTP, Eudora + SMTP

next slide


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Application

process

Client/Server ApplicationsClient/Server Applications

Application Program Interface (API) Application Program Interface (API)

Networking Software & HardwareNetworking Software & Hardware

Application Process(Client Side)

Application Process(Server Side)



Server Agents Examples: Internet Information

Sever + http,Appachi + http

SQL query engines + http

Communication SoftwareExamples: TCP, UDP; IP


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ApplicationSoftware

Presentation

User Interface

Layered Application ModelLayered Application Model

Client Part


Data (Database Access)Server Parts


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Presentation: The client agent remains focused on

presenting information to or receiving input from

the user. User Interface: Users access to the application

Client PartClient Part


.

configured by user. It is build on the top of the

user interface control.

Dynamic User Interface:

Customizing the look (example: www.cstore.com

Customizing the content ( examples: my.yahoo.com ,

www.exite.com )


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Business Rules (Application Logic)

Units of processing or algorithms that representsconcept of importance to the organization using

database.

Server PartsServer Parts


Data (Database Access) Logic to connect to database; access/manipulate data held

within databases.


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User Interface

Presentation Business(Application Logic)

Layered Application:Layered Application:

33--Tier Client/Server ModelTier Client/Server Model

Run by Client AgentRuns by Application

Server Agent


Database

Client Workstation(rich client)

Data

(Data Access andStorage)


Mobile ClientWorkstation(thin client)

User Interface

Presentation

Data Server

Runs by DatabaseServer Agent

Run by Client Agent

user


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Logical Tiers vs Physical TiersLogical Tiers vs Physical Tiers

Application Model

Logical Tiers Presentation User Interface

Presentation ClientWorkstationUser Interface


Data

Physical Tiers

Client workstation Application server

Data Base

us ness(Application Logic)

pp ca onServer

Data

(Database Access)Database


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Chapter 1 OutlineChapter 1 Outline

1.0 Why Networking


1.2 Network Structure

Network edge

Network core


Network access and physical media1.3 Internet structure and ISPs




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Local ISP (LAN)Local ISP (LAN)

hub

Server

Client

LAN Switch

Client

Remote Access ServerModem pools

TelephoneLines

Router

External Link

Servers

modem

modem


Client

PrinterClient

modem

modem External LinkRouter


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internet: network of networksinternet: network of networks

modem

modem

local ISProuter

servermodem

regional ISP

links


companynetwork

mobile station

workstationlocal ISP

Base Station


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InternetInternet

millions of connected computing devices:

hosts, end-systems

PCs workstations, servers,

Personal Data Assistances, phones,

running network apps


commun ca on n s fiber, copper, radio, satellite

transmission rate = bandwidth

routers: forward packets Networking Hardware and Software

Protocols, Hubs, LAN Switches, Repeaters,


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protocolscontrol sending, receiving ofmessages e.g., TCP, IP, HTTP, FTP, PPP,

Internet:network of networks loosely hierarchical

InternetInternet


public Internet versus private intranet Internet standards (IAB)

RFC: Request for comments

IETF: Internet Engineering Task Force


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Examples? Search Engines (Google)

Email (Hotmail) Shopping (Amazon)

Auctions eBa

Internet ServicesInternet Services


Chat (AOL)

Goals? Fast service (low latency)

Service all users (scalability)

Always available (fault tolerance)


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the Internetthe Internetintranet

routerfirewall

intranetintranet


Intranet: access is denied from outside

A private corporate network consisting of hosts, routers,and networks that use TCP/IP technology. An intranet mayor may not connect to the global Internet.


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Company 1Company 3

extranetextranet


Extranet: an internet of networkseach of which is belong to

individual company or organization

Company 2


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IP addressing: ICANNIP addressing: ICANN

Q: How does an ISP get block of addressesand Names?

A: ICANN: (Internet Corporation ForAssigned Names and Numbers) The organization that took over the IANA


u es a er os e s ea .

IANA: (Internet Assigned Number Authority)Essentially one individual (Jon Postel). IANAwas originally responsible for assigning IPaddresses and the constants used in TCP/IPprotocols. Replaced by ICANN in 1999.


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IP addressing: ICANNIP addressing: ICANN

ICANN coordinates the assignment of

identifiers that must be globally unique forthe Internet to function.


manages DNS assigns domain names, resolves disputes

assigns default port numbers

sets protocol parameter


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(i)(i) NORDUnet Stockholm, Sweden

(k)(k) RIPE London, UK

(m)(m) WIDE Tokyo, Japan

(a)(a) NSI Herndon, VA(c)(c) PSInet Herndon, VA

(d)(d) U Maryland College Park, MD(g)(g) DISA Vienna, VA

(h)(h) ARL Aberdeen, MD(j)(j) NSI (TBD) Herndon, VA

DNS Root ServersDNS Root Servers


(b)(b) USC-ISI Marina del Rey, CA(l)(l) ICANN Marina del Rey, CA

(e)(e) NASA Mt View, CA(f)(f) Internet Software C. Palo Alto, CA


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communication

infrastructureenables

distributed applications: Web, email, games,

e-commerce, database.,

modem

modem

local ISPregional ISP

Whats the Internet: a service viewWhats the Internet: a service view


i e s aring

communication services

provided to apps:

connectionless connection-oriented

companynetwork


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Chapter 1: OutlineChapter 1: Outline

1.0 Why Networking1.1 What isthe Internet?

1.2 Network StructureNetwork edgeNetwork core


e wor access an p ys ca me a

1.3 Internet structure and ISPs1.4 Delay & loss in packet-switched networks1.5 Protocol layers, service models

1.6 History


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Network StructureNetwork Structure

network edge:

applications andhosts

:

modem

modem



routers

access networks,physical media: communication links companynetwork


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The network edge:The network edge:

end systems (hosts): run application programs

e.g. Web, email

at edge of network

client/server model

modem

modem



,

service from always-on server e.g. Web browser/server;

email client/server

peer-peer model: minimal (or no) use of

dedicated servers

e.g. Gnutella, KaZaA

companynetwork


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ClientClient--ServerServer

Application Software

modem

modem

1. Client-ServerClient Side Software

Client SideSoftware

Peer Side


2. Peer-to-Peer ! (chapter 2)

Server Side

SoftwarePeer Side

S TS T


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Server TypesServer Types

Web server

File Server (example: Network File System)

Database Server

Application Server


Groupware Server Software Server

Object Server

Proxy Server DNS Server


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Network edge: connectionNetwork edge: connection--oriented serviceoriented service

Goal:data transfer

between end systems handshaking:setup

(prepare for) data

TCP service [RFC 793]

reliable, in-orderbyte-stream data transfer loss: acknowledgements


set up statein two

communicating hosts

TCP - Transmission

Control Protocol Internets connection-

oriented service

flow control: sender wont overwhelm

receiver

congestion control: senders slow down sending

rate when networkcongested

N k d i l iN k d i l i


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Network edge: connectionless serviceNetwork edge: connectionless service

Goal:data transfer

between end systems same as before!

UDP - User Datagram

Apps using TCP:

HTTP (Web), FTP (filetransfer), Telnet(remote login), SMTP


Internetsconnectionless service

unreliable data

transfer no flow control

no congestion control

Apps using UDP: streaming media,

teleconferencing, DNS,Internet telephony

Ch t 1 O tliCh t 1 O tli


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1.0 Why Networking


1.2 Network StructureNetwork edge

Network core





Th N t k CTh N t k C


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The Network CoreThe Network Core

mesh of interconnectedrouters

thefundamentalquestion: how is datatransferred throu h net?

modem

modem



circuit switching:dedicated circuit percall: telephone net

packet-switching: datasent thru net indiscrete chunks

companynetwork

N t k C Ci it S it hiN t k C Ci it S it hi


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Network Core: Circuit SwitchingNetwork Core: Circuit Switching

End-end resources

reserved for call link bandwidth, switch

capacity

modem

modem



e icate resources:no sharing

circuit-like(guaranteed)

performance call setup required

companynetwork

Net ork Core: Circ it S itchingNet ork Core: Circ it S itching


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Network Core: Circuit SwitchingNetwork Core: Circuit Switching

network resources(e.g., bandwidth)

divided into pieces pieces allocated to calls

dividing link bandwidthinto pieces

frequency division time division


not used by owning call(no sharing)

Packet Switching: Statistical MultiplexingPacket Switching: Statistical Multiplexing


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Packet Switching: Statistical MultiplexingPacket Switching: Statistical Multiplexing

A

B

C10 MbsEthernet

1.5 Mbs

statistical multiplexing

queue of packetswaiting for output

emptybuffer


Sequence of A & B packets does not havefixed pattern statistical multiplexing.

In TDM each host gets same slot in revolvingTDM frame.

D E

n

Packet switching versus circuit switchingPacket switching versus circuit switching


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Packet switching allows more users to use network!

User: 1

Switch


Each user: sends 100 kbps when active

is activep=10% of time

1 Mbps link

User:N

Circuit-Switch 10 simultaneous users


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Packet Switching UsersPacket Switching Users


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Packet Switching UsersPacket Switching Users

Switch supports 35 simultaneous users(connections) Up to 10 users be active: no queue, packet

switching has almost the same delayperformance as circuit switching.

More than 10 users be active: out ut ueue


begin to grow and the connections experiencequeuing delay.

Because the probability of having 11 or moresimultaneous active users is 0.0017,almost thesame delay performance as circuit switching.

Packet switching allows more than 3 times thenumber of users.



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Great for bursty data resource sharing

simpler no call setup

Excessive congestion:


protocols needed for reliable data transfer,

congestion control Q: How to provide circuit-like behavior?

bandwidth guarantees needed for audio/videoapplications. still an unsolved problem (chapter 6)

PacketPacket--switching: storeswitching: store--andand--forwardforward


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PacketPacket switching: storeswitching: store andand forwardforward

Takes L/R seconds totransmit (push out)acket of L bits on to

Example: L = 7.5 Mbits; message

R R R

L


link or R bps Entire packet must

arrive at router beforeit can be transmittedon next link: store andforward

delay = 3L/R

R = 1.5 Mbps; linkbandwidth

message transmission

time = L/R = 5 sec delay = 3L/R = 15 sec

Packet Switching: Message SegmentingPacket Switching: Message Segmenting


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Packet Switching: Message SegmentingPacket Switching: Message Segmenting

Now break up the messageinto 5000 packets

Each packet 1,500 bits

1 msec to transmit


pipelining:each linkworks in parallel

Delay reduced from 15

sec to 5.002 sec

PacketPacket--switched networks: forwardingswitched networks: forwarding


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gg

Goal:move packets through routers from source todestination well study several path selection (i.e. routing)algorithms

(chapter 4) datagram network:

destination address in packet determines next hop


routes may change during session

virtual circuit network: each packet carries tag (virtual circuit ID), tag

determines next hop

fixed path determined at call setup time, remains fixedthru call

routers maintain per-call state

Network TaxonomyNetwork Taxonomy


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Network TaxonomyNetwork Taxonomy

Telecommunicationnetworks

Circuit-switchednetworks

Packet-switchednetworks


FDM TDMNetworkswith VCs

DatagramNetworks

Datagram network is noteither connection-orientedor connectionless. Internet provides both connection-oriented (TCP)

and connectionless services (UDP) to applications.



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1.0 Why Networking



Network core





Access networks and physical mediaAccess networks and physical media


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p yp y

Q: How to connection endsystems to edge router?

residential access nets

institutionalinstitutional accessnetworks (school,

modem

modem



mobile access networks

Keep in mind: bandwidth (bits per

second) of accessnetwork?

shared or dedicated?

companynetwork

Residential access: point to point accessResidential access: point to point access


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p pp p

Dialup via modem

up to 56Kbps direct access to

router (often less) Cant surf and phone at same

time: cant be always onmodem

modem


ADSL: asymmetric digital subscriber line up to 1 Mbps upstream (today typically < 256 kbps)

up to 8 Mbps downstream (today typically < 1 Mbps)

FDM: 50 kHz - 1 MHz for downstream4 kHz - 50 kHz for upstream

0 kHz - 4 kHz for ordinary telephone

Residential access: cable modemsResidential access: cable modems


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HFC: hybrid fiber coax

asymmetric: up to 10Mbps upstream, 1 Mbpsdownstream

network of cable and fiber attaches homes to


router

shared access to router among home

issues: congestion, dimensioning

deployment: available via cable companies, e.g.,MediaOne

Residential access: cable modemsResidential access: cable modems


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Diagram: http://www.cabledatacomnews.com/cmic/diagram.html

Cable Network Architecture: OverviewCable Network Architecture: Overview


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T icall 500 to 5 000 homes


home

cable headend

cable distributionnetwork (simplified)



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home

cable headend

cable distributionnetwork (simplified)



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server(s)


home

cable headend

cable distributionnetwork



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V

IDEO

V

IDEO

V

IDEO

V

IDEO

V

IDEO

V

IDEO

DATA

DATA

CON

TROL

1 2 3 4 5 6 7 8 9

FDM:


home

cable headend

cable distributionnetwork

anne s

Company access: local area networksCompany access: local area networks


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company/univ local areanetwork (LAN) connects

end system to edge router Ethernet:

shared or dedicated link modem

modem


connects end systemand router

10 Mbs, 100Mbps,Gigabit Ethernet

deployment: institutions,home LANs happening now

LANs: chapter 5

Wireless access networksWireless access networks


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shared wirelessaccessnetwork connects endsystem to router via base station access

point

wireless LANs:

base

router


802.11b (WiFi): 11 Mbps

wider-area wireless access provided by telco operator 3G ~ 384 kbps

Will it happen?? WAP/GPRS in Europe

(IranCell)

mobilestations (hosts)

Home networksHome networks


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Typical home network components: ADSL or cable modem

router/firewall/NAT

Ethernet wireless access point

(Network Address Translation) A technology that

allows hosts with private addresses to communicate

with an outside network such as the global Internet.

router/Firewall/NAT


wireless access point

wirelesslaptops

cable modem

to/fromInternet

Ethernet (switched)

Physical (Transmission) MediaPhysical (Transmission) Media--LinkLink


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Physical Media (link) : what lies between transmitter & receiver.


Twisted PairTwisted Pair


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Twisted Pair (TP) Unshielded/Shielded

UTP/STP Category 3: traditional

phone wires, 10 MbpsEthernet

Category 5 TP: 100MbpsEthernet


Physical Media: coax, fiberPhysical Media: coax, fiber


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Coaxial cable: two concentric copper

conductors

bidirectional baseband:

Fiber optic cable: glass fiber carrying light

pulses, each pulse a bit

high-speed operation: high-speed point-to-point

transmission (e.g., 5 Gps)


legacy Ethernet broadband:

multiple channel on cable

HFC

low error rate: repeatersspaced far apart ; immuneto electromagnetic noise


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Links: Delay and BandwidthLinks: Delay and Bandwidth


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Delay Latency for propagating data along the link

Corresponds to the length of the link Typically measured in seconds

Bandwidth (Capacity)


Amount of data sent (or received) per unit time Corresponds to the capacity of the link Typically measured in bits per second

Bandwidth(Bps)

Delay

(sec)

delay x bandwidth(bit)



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1.0 Why Networking



Network core





Tier DefinitionTier Definition--Tier 1Tier 1


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Tier 1 providers make settlement-free interconnectionarrangements with other Tier 1 providers, in which the two

networks agree to carry each other's traffic (so-called"peering" with one another) at no cost.


Tier 1, and in general all other ISPs directly or indirectly paythe Tier 1s for access to their networks.

Tier 1 providers own the physical medium over which

information is carried, as well as the network equipmentwhich manages that information.

Tier 1 IPv4 ISPsTier 1 IPv4 ISPs


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The following are believed to be the only Tier 1 ISPsworldwide:1. AOL Transit Data Network (ATDN)-AS 1668

2. AT&T -AS 7018 (not 2685, 2686, 2687, 2688 or 7132)3. Global Crossing (GX)-AS 3549

4. Level 3-AS 3356


5. Verizon Business (UUnet)-AS 701 (not 702, 703 or 19262)

6. Nippon Telegraph and Telephone Corp. (NTT)-AS 29147. Qwest-AS 209

8. SAVVIS (Cable & Wireless America)-AS 35619. Sprint Nextel Corporation-AS 1239

In the Internet, an autonomous system (AS)is a collection of IPnetworks and routers under the control of one entity (or sometimesmore) that presents a common routing policy to the Internet. See RFC1930 for additional detail on this updated definition.

UUNET US backbone network


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TierTier--1 ISPs Interconnection1 ISPs Interconnection


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9

11

22

Topology: Full MeshData Rates: 622Mbps, 2.5-10Gbps

NAPs

NAPs

NAPs

High Speed Link from Telecom Companies

1. NSF 1988 ,T12. ANS 1993 ,T3


33

4

NAPs

NAPs

NAP:NetworkAccessPoint

TierTier--2 ISPs2 ISPs

Tier DefinitionTier Definition--Tier 2, 3Tier 2, 3


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There is no formal interconnection hierarchy,lower-tier companies are divided into two

categories: Tier 2 - A network who peers with other networks, but

still pays for transit to reach some portion of the


Internet.

Tier 3 - A network who solely purchases transit fromother networks to reach the Internet.

Many of Tier 2 and 3 companies are very large Internetproviders, but since they purchase IP transit from othernetworks they are not considered Tier 1.


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TierTier--1 ISP: e.g., UUNET1 ISP: e.g., UUNET


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Internet structure: network of networksInternet structure: network of networks


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roughly hierarchical

at center: tier-1 ISPs (e.g., UUNet, BBN/Genuity,

Sprint, AT&T), national/international coverage treat each other as equals


Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

Tier-1providersinterconnect(peer)

privately

NAP

er- prov ers

also interconnectat public networkaccess points(NAPs)


Tier 2 ISPs: smaller (often regional) ISPs


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Tier-2 ISPs: smaller (often regional) ISPs Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs

Tier-2 ISPs also

peer privately witheach other,interconnect at NAP


Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

NAP

Tier-2 ISPTier-2 ISP

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP pays

tier-1 ISP forconnectivity torest of Internet tier-2 ISP iscustomerof

tier-1 provider

Tier-2 ISP



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Tier-3 ISPs and local ISPs last hop (access) network (closest to end systems)


localISPlocal

ISPlocalISP

local

ISP Tier 3ISPLocal and tier-3 ISPs are

InternetInternetConnectionConnection


Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

NAP

Tier-2 ISP Tier-2 ISP

Tier-2 ISP

localISP

localISP

localISP

localISP

customerso

higher tierISPsconnectingthem to restof Internet

Providers (ICPs)Providers (ICPs)

For local ISPsFor local ISPs

End to End CommunicationEnd to End Communication


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AccessISPAccess

ISPAccess

ISP

Access

ISP Tier 3ISP

a packet passes through many networks!


Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

NAP

Tier-2 ISP Tier-2 ISP

Tier-2 ISP

AccessISP

AccessISP

AccessISP

AccessISP



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1.0 Why Networking



Network core





1.5 Protocol layers, service models

1.6 History

How do loss and delay occur?How do loss and delay occur?


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packets queuein router buffers packet arrival rate to link exceeds output link capacity

packets queue, wait for turn

packet being transmitted (delay)


A

Bpackets queue (delay)

free (available) buffers: arriving packetsdropped (loss) if no free buffers

Four sources of packet delayFour sources of packet delay


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1. nodal processing: check bit errors

determine output link

2. queueing time waiting at output

link for transmission depends on congestion

level of router


A

B

propagation

transmission

nodalprocessing queue

Delay in packetDelay in packet--switched networksswitched networks


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3. Transmission delay: R=link bandwidth (bps)

L=number of bits in

packet (bits) time to send bits into

link =L/R

4. Propagation delay: d= length of physical link

s = propagation speed in

medium (~2x108

m/sec) propagation delay = d/s


A

B

propagation

transmission

nodalprocessing queue

different quantities!

bit length: s/R [m]

packet length: Ls/R [m]

Caravan analogyCaravan analogy


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22331010

11


car=bit

caravan = packet

cars speed (km/hr) = propagation speed (m/sec)

service rate at toll booth (car/sec) = bandwidth

(bit/sec)

Caravan Analogy (cont.)Caravan Analogy (cont.)


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cars speed = 120 km/hr = 2km/min

toll booth takes 12 sec to service a car ( car/sec)1

22331010

11

4km


Q: How long until caravan is lined up before 2nd toll booth? Time to push entire caravan through toll booth onto

highway = 12*10 = 120sec = 2min

Time for last car to propagate from 1st to 2nd toll both:120km/(120km/hr)= 1 hr

A: 62 minutes

Caravan Analogy (cont.)Caravan Analogy (cont.)


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cars s eed = 1200 km/hr = 20km/min

22331010

1177

99 88


Q: Will cars arrive to 2nd booth before all cars serviced at 1stbooth?

After (1+6) min, 1st car at 2nd booth and 3 cars still at 1stbooth.

1st bit of packet can arrive at 2nd router before packet isfully transmitted at 1st router!

toll booth takes 1min to service a car ( 1 car/min)

Bit LengthBit Length


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bit length = s/R Packet length = Ls/R

s = propagation speed of energy in the link (medium)[m/sec]

R = link bandwidth [bps] L = number of bits in packet [bits]


Example : s= 200m/s;

R=10Mbps [Tbit =0.1 s];L= 500 Byte = 2000 bit

20m

linksource destination

Propagation direction

2

000

1

999

1234

202000 m

Nodal delayNodal delay


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dproc = processing delay typically a few msecs or less

proptransqueueprocnodal ddddd +++=


queue

depends on congestion dtrans = transmission delay

= L/R, significant for low-speed links

dprop = propagation delay a few microsecs to hundreds of msecs

Queuing delay (revisited)Queuing delay (revisited)


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R=link bandwidth (bps)

L=packet length (bits)

a=average packetarrival rate

gequeuingdelay


traffic intensity = La/R

La/R ~ 0: average queuing delay small

La/R > 1: delays become large La/R > 1: more work arriving than can be

serviced, average delay infinite!

La/RAvera

1

Real Internet delays and routesReal Internet delays and routes


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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 ion path

towards destination


router iwill return packets to sender

sender times interval between transmission and reply.

3 probes

3 probes

3 probes

Real Internet delays and routesReal Internet delays and routes


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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 ms5 jn1-so7-0-0-0.wae.vbns.net (204.147.136.136) 21 ms 18 ms 18 ms

traceroute: gaia.cs.umass.edu to www.eurecom.frThree delay measements fromgaia.cs.umass.edu to cs-gw.cs.umass.edu


- . . . . . .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 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 ms

15 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

* means no reponse (probe lost, router not replying)

trans-oceanic

link

Packet LossPacket Loss


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queue (aka buffer) preceding link in buffer hasfinite capacity

when packet arrives to full queue, packet isdropped (aka lost)


node, by source end system, or not retransmittedat all



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1.0 Why Networking



Network core






1.6 History

Network ModelsNetwork Models


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The network model isdefined in 3-D space.

App. Software (User) Plane: Data Communication.

Control Plane:

App. Software (User) Plane:Data Communication. We study this part only!


Connection setup and

connection Maintenance, Resources access control and

access level control.

Management Plane:

Measurement andmanagement of networkperformance.

App. SoftwareApp. Software(User)(User)PlanePlane

Figure: Network Model.

Layering: A hierarchical PartitioningLayering: A hierarchical Partitioning

of Networksof Networks


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Networks are complex!

many elements:

Hosts, Routers,

Question:

Is there any hope oforganizingstructure ofnetwork?


,

Application Software, Control and

Management Software,

Communication,

Hardware.

Or at least our discussionof networks?

Why layering?Why layering?


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Dealing with complex systems: explicit structure allows identification,

relationship of complex systems pieces layered reference model for discussion

modularization eases maintenance u datin o


system

change of implementation of layers servicetransparent to rest of system

e.g., change in gate procedure doesnt affect

rest of system layering considered harmful?

Whats a protocol?Whats a protocol?human protocols:

h t th ti ?

network protocols:

hi th th


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whats the time? I have a question

introductions

specific msgs sent

machines rather thanhumans

all communication

activity in Internetgoverned by protocols


when msgs received,or other events

format, orderof msgs sent and

received amongnetwork entities, and

actionstaken on msgtransmission,reception.

Protocols (stack)Protocols (stack)


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Distributed Systems relies on communicatingelements.

Communicating elements follow a set of rules,syntax and semantics, i.e. Protocol.


A protocol governs the co-operation of two remoteparties (elements), or

Two elements, remote to each other, do together a taskusing a predefined rules, syntax, and semantics.

Protocol Stack: It is a set of protocols, designedto govern entire network.

Internet Layering Model and ProtocolsInternet Layering Model and Protocols

Applicati n: supp rtin netw rk


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Application: supporting networkapplications FTP, SMTP, HTTP

Transport: host-host data transfer TCP, UDP

Network: routin of data rams

application

transport


from source to destination IP, routing protocols

Link: data transfer betweenneighboring network elements

PPP, Ethernet Physical: Putting bits on the wire

network

link

physical

Layers and AddressesLayers and Addresses

Application Layer


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Application Layer domain name e.g. www.iust.ac.ir

Transport Layer

the identity of the application in thedestination host Port number: 2 bytes e.g. 80

application

transport


Network Layer

the network identity of the destination host IP address: 4 bytes for IPv4 e.g. 202.156.1.78

Link Layer the identity of network interface card MAC address (physical address): 6 bytes e.g. 00-04-23-5E-6A-93

network

link

physical

OSI model vs TCP/IP modelOSI model vs TCP/IP model


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application

transport

application

transport

applicationpresentation

Session

transport


Open Systems Interconnection model(International Standard Organization-ISO, UN)

network

link

physical

network

networkinterface

network

Link

physical

Layering and DataLayering and Data

Each layer takes data from above


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Each layer takes data from above adds header information to create new data unit

passes new data unit to layer below

Source process Destination process


PDUs: frame, datagram (packet), segment, message

pp ca on

transportnetworklink

physical

pp ca on


physical

segmentdatagram

frame

MHtHnHl Tl

MHtHnMHt

MHtHnHl Tl

MHtHnMHt

Layering and ProtocolLayering and Protocol

Appl. Soft. Appl. Soft.


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App. Layer Protocols

(ftp, http, SMTP, )Transport Layer

Protocol (TCP, UDP)

application

transport

application

transport


Network Layer

Protocols (IP, OSPF, RSVP)

Link LayerProtocols (Ethernet, FDDI, )

network

link

physical

network

link

physicalPhysical Layer

Protocols (Ethernet, FDDI, )

Physical Communication Channel

Protocol layering and dataProtocol layering and data


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Message App. Process

applicationHa Message

App. Process decides to senda message to its counterpart

App. Layer adds its header,sends the message to transport layer


Httransport

Ht Ht Ht

network

Transport layer breaks down

the message into several parts,add its header to each partAnd makes segments.It sends one-by-one segmentsto network layer

Protocol Data UnitsProtocol Data Units

Appl Soft Appl Soft[tps] [HTTPops/s]


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message[mes/sec]

Segment[seg/sec]

application

transport

Appl. Soft.

application

transport

Appl. Soft.[tps], [HTTPops/s],[NFS IOPS]

l/sec


a agram[Packet/sec]

Frame[frame/sec]

network

link

physical

network

link

physical

1st layer PDU(physical frame)

[bps]

Physical Communication Channel

[Baud], [Hz]Baud=c

hangesinsigna

NetworkNetwork BandwidthBandwidth,, ThroughputThroughputandand GoodputGoodput

ApplicationLayer TransportLayer NetworkLayer LinkLayer Physicallayer


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ppLayer pLayer Layer Layer ylayer

BandwidthThroughput

Goodput

Tps,HTTPops/s,

Segmant/s Packet/s Frame/s Bit/s

Bandwidth: The rate at which the data units can be


.

Throughput: The rate at which the data units aredelivered(transferred).

It is a function of load.

Its upper-band is Bandwidth.

Goodput: The rate at which the usefuldata units aredelivered (transferred).

Its upper-band is the Throughput.

Throughput, Goodput vs LoadThroughput, Goodput vs Load


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Goodput

Throughput


Example: Network Layer GoodputExample: Network Layer Goodput


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Goodput:

[sec]durationtimerecieving

[bit]packetperlengthpayloadreplica)recieved-packetsrecievedsbGoodput

=

(]/[


Efficiency:

link.congestion-noandpacket,corupted-nopacket,loss-no:ofconditioningoodputgoodputOptimum

[bps]goodputoptimum

[bps]goodputEfficiency

=

= 100

Protocols/ServicesProtocols/Services


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application

transport

Application Program

Services End-to-Endprotocols


network

link

physical

Data TransportServices Hop-to-Hop

protocols

From Application ViewpointFrom Application Viewpoint


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Application SoftwareApp. Softwareapplication

Controlledby App. Soft.



Communication Software & HardwarePlatform (OS + Hardware)

transportnetwork

linkphysical

Controlledby OS

Layering: Physical CommunicationLayering: Physical Communication

application

data


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modemnetwork

linkphysical

applicationtransportnetwork

link

physical

Host A Router R


application


physical

modem


linkphysical

application

transportnetwork

linkphysical

data

Host B

Layering: Logical CommunicationLayering: Logical Communication--11

Each layer:

application


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Each layer:

distributed

entitiesimplementlayer functions

modem networklink

physical

transportnetwork

link

physical


t each node

entitiesperformactions,

exchangemessages withpeers


linkphysical

modem

application

transportnetwork

linkphysical

application


physical

Layering: LogicalLayering: Logical CommunicationCommunication

E g : transport

application

data


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E.g.: transport take data from app

add addressing,

reliability checkinfo to formdata ram

modem networklink

physical

transportnetwork

link

physical

transport

ack


send datagram to

peer wait for peer to

ack receipt

analogy: post

office


linkphysical

modem

application

transportnetwork

linkphysical

application


physical

ata

data

transport

TCP/IP protocol stackTCP/IP protocol stack

ftp: file transfer protocolhttp; hypertext transfer protocol

icmp: Internet control message protocolospf: open shortest path first protocolrsvp: resource reservation protocol


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mime

ftp http smtp telnet snmp tftp rtp dns

domain nameservice

real time pr.trival filetransfer pr.

simple networkmanagement pr.

Smtp: simple mail transfer protocolMime: multipurose Internet mail extensionstelnet=virtual terminal

rsvp resource reservat on protocoligmp: Internet group management protocol


Transmission Control Pr. (TCP) User Datagram Pr. (UDP)

icmp ospfrsvp igmp

Ethernet, token ring, FDDI, ATM, Frame relay, SNA, X25

arp rarpInternet Protocol (IP)

arp: address resolution protocolrarp: reverse address resolution protocol


1 0 Why Networking


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1.0 Why Networking


1.2 Network StructureNetwork edgeNetwork core



1.3 Internet structure and ISPs1.4 Delay & loss in packet-switched networks


1.6 History

Internet Host CountInternet Host Count


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Internet Systems Consortium, Inc. (ISC) is a nonprofit

corporation dedicated to supporting the infrastructure of the universalconnected self-organizing Internet and

has autonomy to participates by developing and maintaining coreproduction quality software, protocols, and operations.

Internet Standard: RFCsInternet Standard: RFCs


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mbers


Introduction Year

RFCNu

Internet HistoryInternet History

1961-1972: Early packet-switching principles


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1961: Kleinrock - queueingtheory shows

effectiveness of packet-switching

1972:

ARPAnet

demonstrated publicly NCP (Network Control


- -

switching in military nets 1967: ARPAnet conceived

by Advanced ResearchProjects Agency

1969: first ARPAnetnode operational

ro oco rs os -

host protocol first e-mail program

ARPAnet has 15

nodes


1972-1980: Internetworking, new and proprietary nets


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1970: ALOHAnet satellitenetwork in Hawaii

1973: Metcalfes PhD thesisproposes Ethernet

1974: Cerf and Kahn -

Cerf and Kahnsinternetworking principles:

minimalism, autonomy -no internal changesrequired to


architecture for

interconnecting networks late70s: proprietary

architectures: DECnet, SNA,XNA

late 70s: switching fixedlength packets (ATMprecursor)

1979: ARPAnet has 200 nodes

interconnect networks

best effort servicemodel

stateless routers

decentralized control

define todays Internetarchitecture


1980-1990: new protocols, a proliferation of networks


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1983: deployment ofTCP/IP

1982: SMTP e-mailprotocol defined

new national networks:Csnet, BITnet,

NSFnet, Minitel 100,000 hosts


1983: DNS defined

for name-to-IP-address translation

1985: FTP protocol

defined 1988: TCP congestion

control

connected to

confederation ofnetworks


1990, 2000s: commercialization, the Web, new apps


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Early 1990s: ARPAnetdecommissioned

1991: NSF lifts restrictions oncommercial use of NSFnet(decommissioned, 1995)

Late 1990s 2000s: more killer apps: instant

messaging, peer2peerfile sharing (e.g.,


early 1990s: Web

hypertext [Bush 1945, Nelson1960s]

HTML, HTTP: Berners-Lee

1994: Mosaic, later Netscape

late 1990s:commercialization of the Web

network security toforefront est. 50 million host, 100

million+ users

backbone links runningat Gbps

References & LinksReferences & Links

Complimentary Hyperlinks


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Complimentary Hyperlinks This part provides hyperlinks to interesting

(and hopefully useful) computer-networkingresources. Most of these resources provide


chapter 1. If you're asked to write a paperpertaining to a specialized topic in computernetworking, these resources should serve as agood starting point for your research.

References and Hyperlinks

ComplimentaryComplimentary Hyperlinks 1Hyperlinks 1

IEEE History Center


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IEEE History Centerhttp://www.ieee.org/organizations/history_center/oral_histories/comsoc_oh.html.

Oral Histories that have been collected to commemorate the50th Anniversary of the IEEE Communications Society. Anumber of interesting interviews with pioneers in the field.


International Engineering Consortium: Web ProForumTutorials http://www.iec.org/online/tutorials/ More than 150 tutorials on communications and networking

topics, with a focus on cutting edge technology. The tutorialsvary in terms of their technical depth, but many areoutstanding, and all are extremely well-written and veryreadable. This is the first place we look when looking for an on-line survey or tutorial.

Broadband: Bringing home the bits

Complimentary Hyperlinks 2Complimentary Hyperlinks 2


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Broadband Bringing home the bitshttp://www.nap.edu/html/broadband Extensive report on the importance and future of

residential broadband access from the Computer ScienceAnd Telecommunications Board, National ResearchCouncil, January 2002


Webopedia http://www.pcwebopaedia.com/ Online dictionary for computer and Internet technology

Internet Economicshttp://china.si.umich.edu/telecom/net-economics.html Comprehensive index for resources relating to Internet

economics, including regulation and pricing.

traceroute.org http://www.traceroute.org/ As discussed in Section 1 6 Traceroute provides routes and packet



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As discussed in Section 1.6, Traceroute provides routes and packetdelays between pairs of hosts in the Internet. This site gives you directaccess to hundreds of source hosts from which you can trace routes toarbitrary destination hosts. Choose a country, a source host in that

country, and any destination host -- then see how the packets weavetheir way through the Internet.

htt : www.iet .or


The IETF is an open international community concerned with the

development and operation of the Internet and its architecture. The

IETF was formally established by the Internet Architecture Board(IAB), http://www.isi.edu/iab, in 1986. The IETF meets three times ayear; much of its ongoing work is conducted via mailing lists by workinggroups. Typically, based upon previous IETF proceedings, workinggroups will convene at meetings to discuss the work of the IETFworking groups. The IETF is administered by the Internet Society,http://www.isoc.org/, whose Web site contains lots of high-quality,Internet-related material.

Henning Schulzrinne's Internet Technical



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gResourceshttp://www.cs.columbia.edu/~hgs/internet Henning Schulzrinne has an extensive - although notalways current - index of online resources for the

Internet.


The Association for Computing Machinery (ACM)http://www.acm.org/ A major international professional society that has

technical conferences, magazines, and journals in thenetworking area. The ACM Special Interest Group inData Communications (SIGCOMM),http://www.acm.org/sigcomm, is the group within thisbody whose efforts are most closely related tonetworking

The Institute of Electrical and Electronics Engineers (IEEE)http:// i /



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http://www.ieee.org/ The other major international professional society that has technical

conferences, magazines, and journals in the networking area. The IEEE

Communications Society, http://www.comsoc.org/, and the IEEEComputer Society, http://www.computer.org/, are the groups withinthis body whose efforts are most closely related to networking.

[email protected]@iust.ac.ir OrientationOrientation11--120120

e ome ro ect ttp: set at ome.ss . er e ey.e u As discussed in Section 1.2, the SETI@home project is a scientific

experiment that uses Internet-connected computers to search forextraterrestrial intelligence. You can download the SETI programdirectly from this site.

Nerds 2.0.1 A Brief History of the Internethttp://www.pbs.org/opb/nerds2.0.1 This is the Web site for the highly entertaining and informative PBSvideo on the history of the Internet. The PBS video, Triumph of the

Nerds, about the history of personal computers, is also recommended.

Leonard Kleinrock's Personal History of the Internethttp://www lk cs ucla edu/LK/Inet/birth html



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http://www.lk.cs.ucla.edu/LK/Inet/birth.html Professor Leonard Kleinrock made numerous important contributions to

Internet technology and to the field of computer networking. This page

provides his own interesting and highly entertaining description of theearly history of the Internet.

The DSL Forum htt ://www.dslforum.org/


DSL Forum is a consortium of nearly 250 leading industry players

covering telecommunications, equipment, computing, networking and

service provider companies. The site is rich in information aboutdevelopments in digital subscriber loop and broadband access to thehome.

Cable-modems.org http://www.cable-modems.org/ This site has many tutorials on cable modems, hybrid fiber-coax, and

related topics. Also includes reviews of cable modem products.



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A note on Internet Request for Comments (RFCs): Copiesof Internet RFCs are maintained at multiple sites. The RFC

URLs below all point into the RFC archive at the InformationSciences Institute (ISI), maintained the the RFC Editor ofthe Internet Society (the body that oversees the RFCs).


er s es nc u e p www. aqs.org r c,http://www.pasteur.fr/other/computer/RFC (located in

France), and http://www.csl.sony.co.jp/rfc/ (located inJapan).

Internet RFCs can be updated or obsoleted by later RFCs.We encourage you to check the sites listed above for themost up-to-date information. The RFC search facility at ISI,http://www.rfc-editor.org/rfcsearch.html, will allow you tosearch for an RFC and show updates to that RFC.

References and Hyperlinks 1References and Hyperlinks 1

[@Home 1998] @Home, "Frequently Asked


123/136

[ ] , q yQuestions," http://www.home.com/qa.html.

[Abramson 1970] N. Abramson, "The AlohaSystem--Another Alternative for Computer"


,Computer Conference, AFIPS Conference, p. 37,

1970. [ADSL 1998] ADSL Forum, "ADSL Tutorial,"

http://www.adsl.com/adsl_tutorial.html

[Almanac 1998] Computer Industry Almanac,http://www.c-i-a.com/


[AT&T Apps 1998] AT&T, "Killer Apps,"htt // tt /t h l /f t d t /b i i / t


124/136

http://www.att.com/technology/forstudents/brainspin/networks/killerapps.html

[AT&T Bandwidth 1999] AT&T, "Bandwidth: The Need forSpeed,"http://www.att.com/technology/forstudents/brainspin/netw


or s an w game. m [AT&T Optics 1999] AT&T, "What are fiber optics?,"

http://www.att.com/technology/forstudents/brainspin/fiberoptics/

[Baran 1964] P. Baran, "On Distributed CommunicationNetworks," IEEE Transactions on Communication Systems,

Mar. 1964. Rand Corporation Technical report with the sametitle (Memorandum RM-3420-PR, 1964).http://www.rand.org/publications/RM/RM3420/


[Berners-Lee 1989] T. Berners-Lee, CERN, "InformationManagement: A Proposal " Mar 1989 May 1990


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Management: A Proposal," Mar. 1989, May 1990.http://www.w3.org/History/1989/proposal.html

[Bertsekas 1991] D. Bertsekas and R. Gallagher, DataNetworks, 2nd Ed. , Prentice Hall, Englewood Cliffs, NJ,1991.


[Bush 1945] V. Bush, "As We May Think," T e At anticMonthly, July 1945.

http://www.theatlantic.com/unbound/flashbks/computer/bushf.htm

[Cable 1998] Cable Data News, "Overview of Cable ModemTechnology and Services," 1998.

http://www.cabledatacomnews.com/cmic/cmic1.html


[Cerf 1974] V. Cerf and R. Kahn, "A Protocol for PacketNetwork Interconnection " IEEE Transactions on


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Network Interconnection, IEEE Transactions onCommunications Technology, Vol. COM-22, No. 5, pp. 627-641.

[Cisco LAN 1998] Cisco Systems Inc., "Designing SwitchedLAN Internetworks,"http://www.cisco.com/univercd/cc/td/doc/cisintwk/idg4/nd


. tm [Clark 1988] D. Clark, " The Design Philosophy of the

DARPA Internet Protocols, Proceedings of ACMSIGCOMM'88, (Stanford, CA), Aug. 1988, Vol. 18, No. 4,http://www.acm.org/sigcomm/ccr/archive/1995/jan95/ccr-9501-clark.html

[Cusumano 1998] M.A. Cusumano and D.B. Toffle, Competing

on Internet Time: Lessons from Netscape and its Battlewith Microsoft, Free Press, 1998


[Daigle 1991] J. N. Daigle, Queuing Theory forTelecommunications Addison Wesley Reading MA 1991


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Telecommunications, Addison-Wesley, Reading, MA, 1991. [DEC 1990] Digital Equipment Corporation, "In Memoriam: J.

C. R. Licklider 1915-1990," SRC Research Report 61, Aug.1990. http://gatekeeper.dec.com/pub/DEC/SRC/research-reports/abstracts/src-rr-061.html


[Dertouzos 1999] M. Dertouzos, "The Future of Computing,"Scientific American, August 1999, pp.52-55.

[Fraser 1983] A. G. Fraser, "Towards a Universal DataTransport System," IEEE Journal on Selected Areas inCommunications, Vol. SAC-1, No 5, pp. 803-816.


[Fraser 1993] A. G. Fraser (1993). "Early Experiments withAsynchronous Time Division Networks " IEEE Network


128/136

Asynchronous Time Division Networks, IEEE NetworkMagazine, Vol. 7, No. 1, pp. 12-27.

[Goodman 1997] D. Goodman (Chair), The Evolution ofUntethered Communications, National Academy Press,Washington DC, Dec. 1997.


p www.nap.e u rea ngroom oo s evo u on n ex. ml

[Green 1992] P. Green, Fiber Optics Networks, PrenticeHall, 1992

[Greenberg 1997] I. Greenberg, "The Future of the LivingRoom."

http://www.cnet.com/Content/Features/Dlife/Living/index.html


[Haynal 1999] R. Haynal, "Internet Backbones,"http://navigators.com/isp.html


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p g p [Huston 1999a] G. Huston, "Interconnection, Peering, and

Settlements - Part I," The Internet Protocol Journal, Vol. 2, No. 1,

(June 1999). http://www.cisco.com/warp/public/759/ipj_2-1/ipj_2-1_ps1.html [Huston 1999b] G. Huston, "Interconnecting, Peering, and

- "


, , . , .(June 1999). http://www.cisco.com/warp/public/759/ipj_2-2/ipj_2-2_ps1.html

[Iren 1999] S. Iren, P. Amer, P. Conrad, "The Transport Layer:Tutorial and Survey," ACM Computing Surveys, Vol 31, No 4, (Dec1999). http://www.cis.udel.edu/~amer/PEL/survey/

[Jacobson 1988] V. Jacobson, "Congestion Avoidance and Control,"Proceedings of ACM SIGCOMM '88, pp. (Stanford, CA, Aug. 1988),

314-329, ftp://ftp.ee.lbl.gov/papers/congavoid.ps.Z


[Kegel 1999] Dan Kegel's ISDN Page,http://alumni.caltech.edu/~dank/isdn/


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[Kleinrock 1961] L. Kleinrock, "Information Flow in LargeCommunication Networks," RLE Quarterly Progress Report, July

1961. [Kleinrock 1964] L. Kleinrock, 1964 Communication Nets:

Stochastic Message Flow and Delay, McGraw-Hill, NY, NY, 1964.


. , , . , ,New York, 1975.

[Kleinrock 1976] L. Kleinrock, Queuing Systems, Vol. 2, John Wiley,New York, 1976. [Kleinrock 1998] L. Kleinrock, "The Birth of the Internet,"

http://www.lk.cs.ucla.edu/LK/Inet/birth.html [Leiner 1998] B. Leiner, V. Cerf, D. Clark, R. Kahn, L. Kleinrock, D.

Lynch, J. Postel, L. Roberts, and S. Woolf, "A Brief History of the

Internet," http://www.isoc.org/internet/history/brief.html [List 1999] "The List: The Definitive ISP Buyer's Guide,"

http://thelist.internet.com/


[Lucky 1997] R. Lucky, "New Communication Services -What Do People Want?", Proceedings of the IEEE, Oct.


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p g1997, pp 1536-1543.

[Metcalfe 1976] R. M. Metcalfe and D. R. Boggs. "Ethernet:Distributed Packet Switching for Local Computer Networks,"Communications of the Association for Computing Machinery,Vol. 19, No. 7, (July 1976), pp. 395 - 404.


ttp: www.acm.org c ass cs apr [Mills 1998] S. Mills, "TV set-tops set to take off," CNET

News.com, Oct. 1998. http://news.cnet.com/news/0-1006-200-334433.html [NAS 1995] National Academy of Sciences, The

Unpredictable Certainty: Information InfrastructureThrough 2000, National Academy of Sciences Press, 1995.

http://www.nap.edu/readingroom/books/unpredictable/chap4.html


[Network 1996] Network Wizards, "Internet DomainSurvey", July 1996, http://www.nw.com/zone/WWW-


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u y , Ju y 99 , p //www. w. m/z /WWW9607/report.html

[Network 1999] Network Wizards, "Internet DomainSurvey," Jan. 1999, http://www.isc.org/ds/ [Pacific Bell 1998] Pacific Bell, "ISDN Users Guide,"


http://www.pacbell.com/Products_Services/Residential/ISDNuserguide/0,1078,20,00.html

[Perkins 1994] A. Perkins, "Networking with Bob Metcalfe,"The Red Herring Magazine, Nov. 1994.http://www.herring.com/mag/issue15/bob.html

[Quittner 1998] J. Quittner, M. Slatalla, Speeding the Net:

The Inside Story of Netscape and How it ChallengedMicrosoft, Atlantic Monthly Press, 1998.


[Ramaswami 1998] R. Ramaswami, K. Sivarajan, Optical Networks:A Practical Perspective, Morgan Kaufman Publishers, 1998[RFC 001] S C k "H t S ft " RFC 001 (th fi t


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[RFC 001] S. Crocker, "Host Software," RFC 001 (the very firstRFC!).

[RFC 793] J. Postel, "Transmission Control Protocol," RFC 793,Sept. 1981. http://www.rfc-editor.org/rfc/rfc793.txt [RFC 801] J. Postel, "NCP/TCP Transition Plan," RFC 801 Nov. 1981.


. - . . [RFC 1034] P. V. Mockapetris, "Domain Names--Concepts and

Facilities," RFC 1034, Nov. 1987. http://www.rfc-editor.org/rfc/rfc1034.txt [Roberts 1967] L. Roberts, T. Merril, "Toward a Cooperative

Network of Time-Shared Computers," AFIPS Fall Conference, Oct.1966.

[Ross 1995] K. W. Ross, Multiservice Loss Models for Broadband

Telecommunication Networks, Springer, Berlin, 1995. [Segaller 1998] S. Segaller, Nerds 2.0.1, A Brief History of the

Internet, TV Books, New York, 1998.


[Thinplanet 2000] Thinplanet homepage,http://www.thinplanet.com/


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[Turner 1986] J. Turner, "New Directions in Communications

(or Which Way to the Information Age?)," Proceedings ofthe Zrich Seminar on Digital Communication, (Zurich,Switzerland, Mar. 1986), pp. 25-32,.


e or e e onsor um, eHistory of the World Wide Web," 1995.

http://www.w3.org/History.html [Wakeman 1992] Ian Wakeman, Jon Crowcroft, Zheng

Wang, and Dejan Sirovica, "Layering Considered Harmful,"IEEE Network, Jan. 1992, p. 20-24.

References and Hyperlinks 13

[Waung 1998] W. Waung, "Wireless Mobile DataNetworking The CDPD Approach," Wireless Data Forum,1998


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1998.http://www2.wirelessdata.org/public/whatis/whatis.html

[Wireless 1998] Wireless Data Forum, "CDPD SystemSpecification Release 1.1," 1998.http://www2.wirelessdata.org/public/specification/index.ht


m [Wood 1999] L. Wood, "Lloyds Satellites Constellations,"

http://www.ee.surrey.ac.uk/Personal/L.Wood/constellations/iridium.html [Ziff-Davis 1998] Ziff-Davis Publishing, "Ted Nelson:

Hypertext pioneer," 1998.http://www.zdnet.com/zdtv/screensavers_story/0,3656,212

7396-2102293,00.html 2000-2001 by Addison WesleyLongmanA division of Pearson Education.

Home WorkHome Work-- Chapters1Chapters1

Computer Networking3edition .


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