iap 01- introduction to internet architecture and protocols

8/8/2019 IAP 01- Introduction to Internet Architecture and Protocols

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CS-3302-3 & IT-5302-3

Internet Architecture and Protocols

Punjab University College of Information Technology,

University of the Punjab, Pakistan.

Lecture 01, 02

Introduction and Basic Concepts


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CS-3302-3 & IT5302-3 Internet Architecture and Protocols 2

Lecture 01 - Objectives

Introduction Course Objectives, Outline and Grading Policies

What is the Internet?

Nuts and Bolts View

Service Oriented View

Network Edge

Network Core Circuit Switched Networks

Packet Switched Networks

Datagram Virtual Circuits

Network Access and Physical Media


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Introduction

PUCITLeading the Nation in Knowledge

Management Technology Class Introduction

Resource Person Introduction

Knowledge Management (KM)

The Art of Creating Value from Intangible Assets

Knowledge Internees Knowledge Engineers

Knowledge Mentors


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KM Principles

Explore yourself Know your skills

Know your values

Know your achievements Know your environment

Discover your strength

Weaknesses

Opportunities

Threats

Sharing Knowledge is Wisdom, HidingKnowledge is a Curse


5/67CS-3302-3 & IT5302-3 Internet Architecture and Protocols 5

Course Objectives

To understand the design philosophy of the Internetand its basic architectural components.

To provide in-depth knowledge of major Internet

technologies. To understand the components of Internet service

provider and its role in Internet architecture.

To strengthen the concepts of TCP/IP ProtocolSuite.

To provide comprehensive knowledge andimplementation of routing protocols.

To realize the need of Quality of Service basedcommunication and to understand various QoStechniques.

To introduce the basic concepts of real timecommunications.


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What is the Internet?

A Nuts and Bolts Description End systems

Communication Links, Bandwidth

Routers, Packet ISPs

Protocols, TCP/IP

Internet Standards, RFCs

A service Description

Distributed Applications

Connection Oriented Reliable Service

Connectionless Unreliable Service

What is a protocol?


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Describing the Internet

Two ways to describe the Internet Nuts and Bolts View

The basic hardware and software components

Service Oriented View

The networking infrastructure that provides

services to distributed applications


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Nuts and Bolts View of the Internet

Hosts or End Systems Computing Devices such as PCs, PDAs (Personal

Digital Assistants), TVs, servers, mobile

computers, automobiles, etc. connected to theInternet are called hosts or end systems.


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Communication links End systems are connected together by communication

links.

Communication links are made up of different types ofmedia, including twisted pair, coaxial cable, fiber optics,

and radio spectrum.

Bandwidth Different links can transmit data at different rates.

The link transmission rate is often called the bandwidth

(i.e, the width of the band) of the link which is measured

in bits per second (bps).


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Routers End systems are not directly connected to each

other via a single communication link.

They are indirectly connected to each through

intermediate switching devices known as

routers.

A router receives chunk of information from one

of its incoming communication link and

forwards it to one of its outgoing communication

link.


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Packets The chunk of information is called packet.

Route or Path

The path that the packet takes from the sending end

system, through a series of communication links and

routers, to the receiving end system is known as a route

or path.

Packet switching

The Internet uses a technique known as packet switching

that allows multiple communicating end systems to share

a path, or parts of path at the same time.


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Internet Service Providers (ISPs) End systems access the Internet through the

Internet Service Providers (ISPs).

The different ISPs provide a variety of differenttypes of network access to the end systems,

including 56Kbps dial up modem access, cable

modem or DSL, high speed LAN access, andwireless access.


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Protocols End systems, routers, and other pieces of the

Internet, run protocols that control the sending

and receiving of information within the Internet.

TCP (Transmission Control Protocol) and IP

(Internet protocol) are two of the most important

protocols in the Internet. The Internets principal protocols are collectively

known as TCP/IP Protocol Suite.


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Intranets There are many private networks, such as many

corporate and government networks, whose

hosts cannot exchange messages with hostsoutside of the private network (unless the

messages pass through so-called firewalls,

which restrict the flow of messages to and fromthe network).

These private networks are often referred to as

intranets, as they use the same types of hosts,routers, links, and protocols as the public

Internet.


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Internet Standards At the technical and development level, the Internet is

made possible through creation, testing, and

implementation of Internet Standards.

These standards are developed by Internet Engineering

Task Force (IETF).

RFCs The IETF standards documents are called RFCs (Request

for comments).

RFCs started out as general request for comments (hence

the name) to resolve architecture problems of the Internet. They define protocols such as TCP, IP, HTTP, SMTP.


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Some Pieces of the Internet

companynetwork

local ISP

regional ISP

router workstation

servermobile


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Service Oriented View of the Internet

Distributed Applications The Internet allows distributed applications

running on its end systems to exchange data

with each other. These applications include remote login,

electronic mail, web surfing, instant messaging,

audio and video streaming, Internet telephony,distributed games, peer-to-peer (P2P) file

sharing, and much more.

Communication Services Connection oriented reliable service

Connectionless unreliable service


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Service Oriented View of the Internet

Internet Provides two services to its distributedapplications: Connection Oriented Reliable Service

It guarantees that data transmitted from asender to a receiver will eventually bedelivered to the receiver in order and in itsentirety.

Connectionless Unreliable Service It does not make any guarantees about

eventual delivery. Note: Distributed applications makes use of one or the

other (but not both) of these two services.

Thus, Internet is an infrastructure in which newapplications are being constantly invented and

deployed.

h i l?


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What is a Protocol?

A Human Analogy Assalam u Alaikum

Whats the time?

In human protocols specific messages are

sent, and specific actions are taken in

response to messages received, or other

events.

Network protocols

All activity in the Internet that involves two or

more communicating remote entities is governed

by a protocol.

Wh i l?


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What is a protocol?

A human protocol and a computer network protocol

Hi

Hi

Got thetime?

2:00

TCP connectionreq

TCP connectionresponse

time

Gethttp://www.awl.com/kurose-ross

Wh i P l?


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What is a Protocol?

A Protocol is a set of rules and regulations thatgoverns the exchange of information between twoor more entities.

It takes two (or more) communicating entitiesrunning the same protocol in order to accomplish atask.

All communication activity in Internet governed by

protocols. A protocol defines the format, order of messages

exchanged between two or more communicating

entities, as well as the actions taken on thetransmission and/or receipt of a message or otherevent.

N t S fi


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Net Surfing

Some Good Hyperlinks: http://www.ietf.org

http://www.iab.org

http://www.w3.org

http://www.ieee.org

http://www.acm.org

http://www.acm.org/sigcomm

http://www.computer.org

http://www.comsoc.org

A Cl L k t N t k St t


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A Closer Look at Network Structure

Network Edge: applications and hosts

Network Core:

routers

network of networks

Access networks, physical media: Residential, company and mobile access

Twisted Pair, Coaxial, Fiber Optics, Radio

Channels communication links

N t k Ed


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Network Edge

end systems (hosts): run application programs

e.g. Web, email

at edge of network

client/server model

client host requests,receives service from

always-on server e.g. Web browser/server;email client/server

peer-peer model:

minimal (or no) use ofdedicated servers

e.g. Gnutella, KaZaA

N t k Ed


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Network Edge

End Systems, Clients and Servers In Computer Networking, computers connected

to the Internet are referred to as End Systems,as they sit at the edge of the Internet.

End Systems = Hosts

Hosts are subdivided into two categories: Clientand Servers

Client/Server Applications A client program is a program running on one

end system that requests and receives a servicefrom a server program running on another endsystem.

Client/Server Internet applications are, by

definition, distributed applications.

Net ork Edge


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Network Edge

Peer to Peer Applications In peer to peer application, the program running

in a peer (users machine) acts as a client when

it requests a file from another peer; and theprogram acts as a server when it sends a file to

another peer.

Examples are peer-to-peer file sharingapplications like Napster, KaZaA etc.

Network Edge


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Network Edge

Connection Oriented Service Reliable Data Transfer

Using acknowledgements & retransmissions

Flow Control

sender wont overwhelm receiver

Congestion Control

senders slow down sending rate when

network congested

TCP

Applications using TCP are:

HTTP (Web), FTP (file transfer), Telnet (remote

login), SMTP (email)

Network Edge


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Network Edge

Connectionless Service Unreliable Data Transfer

no flow control

no congestion control

Fast

connectionless

UDP

Applications using UDP are:

multimedia, videoconferencing, DNS, Internet

telephony

TCP vs UDP


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TCP vs. UDP

Unreliable Protocol Connectionless

Much faster than TCP

No acknowledgement

waits

No proper sequencing

of data units

Suitable for

applications where

speed matters morethan reliability

Reliable Protocol Connection Oriented

Performs three ways

handshake

Provision for error

detection and

retransmission Most applications use

TCP for reliable and

guaranteedtransmission

The Network Core


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The Network Core

Mesh of interconnectedRouters

The fundamental question:

how is data transferredthrough network?

circuit switching dedicated circuit per

call: telephone net

packet-switching data sent through net

in discrete chunks

Network Core


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Network Core

Long distance transmission is typicallydone over a network of switched nodes

Nodes not concerned with content of data

End devices are stations

Computer, terminal, phone, etc.

A collection of nodes and connections is acommunications network

Data routed by being switched from node to

node

Node to node links usually multiplexed

Simple Switched Network


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Simple Switched Network

Network Core: Circuit Switching


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Network Core: Circuit Switching

End-to-end resourcesreserved for call

link bandwidth, switch

capacity dedicated resources: no

sharing

circuit-like (guaranteed)performance

call setup required

Network Core Circuit Switching


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Switched circuits allow data connectionsthat can be initiated when needed and

terminated when communication is

complete Circuit switched network - a network in

which a dedicated circuit is established

between sender and receiver and all data

passes over this circuit.

The telephone system is a commonexample.

The connection is dedicated until one party

or another terminates the connection.

Circuit Switching


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Circuit Switching



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Dedicated communication path betweentwo stations

Three phases (Establish, Transfer, Disconnect)

Inefficient (for data traffic) Channel capacity dedicated for duration of

connection

Much of the time a data connection is idle If no data, capacity wasted

Set up (connection) takes time

Once connected, transfer is transparent Circuit switching designed for voice

Constant Data rate (Both ends must operate at the same rate)

Network Core - Circuit Switching


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Multiplexing in Circuit Switched Networks Multiplexing is a technique, in which a single

transmission medium is being shared among

multiple users. Types of Multiplexing

Frequency Division Multiplexing FDM

Time Division Multiplexing TDM

Circuit Switching: FDM and TDM


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Circuit Switching: FDM and TDM

Example: 4 users

FDM

Frequency

time

TDM

Frequency

time

Synchronous TDM


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Synchronous TDM

Synchronous TDM with empty time slots


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Synchronous TDM with empty time slots

Statistical TDM or Asynchronous TDM


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Statistical TDM or Asynchronous TDM

Network Core: Packet Switching


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g

Packet switched network A network in which data is transmitted in the

form of packets Multiple users share network resources

No dedicated bandwidth is allocated

No resources are reserved, resources used asneeded

Each packet uses full link bandwidth Good for bursty traffic, simpler, no call setup Packets queued and transmitted as fast as

possible Packets are accepted even when network isbusy, which causes the delivery to slow down

Packet Switching: Statistical Multiplexing


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g p g

A

B

C10 Mb/sEthernet

1.5 Mb/s

D E

statistical multiplexing

queue of packetswaiting for output

link

Sequence of A & B packets does not have fixed

pattern s t a t is t ica l m u l t ip lex in g .

Network Core: Packet Switching


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g

The goal of packet switching is tomove packets through routers from

source to destination Packets sent one at a time to the network

Two approaches are used:

Datagram Approach

Virtual Circuits Approach


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Packet Switching - Datagram


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g g

Datagram Approach: Each packet is treated independently

No reference to packets that have gone before

Each node chooses next node on path usingdestination address

Packets with same destination address may notfollow same route

Packets may arrive out of sequence, may be lost

It is up to receiver to re-order packets andrecover from lost packets

No Call setup

For an exchange of a few packets, datagramquicker

Analogy: driving, asking directions



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g g

The Internet is a Datagram network Datagram network is not either connection-

oriented or connectionless.

Internet provides both connection-oriented(TCP) and connectionless services (UDP) to

applications.

Datagram Networks


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A datagram network is not either aconnectionless or a connection orientednetwork.

It can provide connectionless service tosome of its applications and connection-oriented service to other applications.

Example The Internet, which is a datagram network,

provides both connectionless (UDP) and

connection oriented (TCP) services to itsapplications

Networks with Virtual Circuits are,however, always connection-oriented.



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Packet Switching Virtual Circuits


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Virtual Circuit Approach: Virtual circuit packet switched network create

a logical path through the subnet

Call request and call accept packets establish avirtual connection

Virtual route remains fixed through the call.

All packets from one connection follow thispath.

Each packet contains a virtual circuit identifier

instead of destination address to determinesthe next hop

Not a dedicated path

No routing decisions required for each packet

Switching Technique Virtual Circuit


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Preplanned route established before packets sent All packets follow same route

Similar to circuit in circuit-switching network Hence virtual circuit

Each packet has virtual circuit identifier Nodes on route know where to direct packets

No routing decisions

Not dedicated path, as in circuit switching Packet still buffered at node and queued for output

Routing decision made on before that virtual circuit

Network may provide services related to virtualcircuit Sequencing and error control

Packets should transit more rapidly

If node fails, all virtual circuits through node lost

Virtual Circuit Networks


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A virtual circuit (VC) consists of: A path between the source and destination hosts Virtual circuit numbers, one number for each

link along the path

Entries in the virtual circuit VC-numbertranslation tables in each packet switch alongthe path.

Example Consider host A requests that the network

establish a VC between itself and host B.

Suppose the network chooses the path andassigns the VC numbers on three links asfollows:

Path: A --------- Switch1 --------- Switch2 --------- B

VC #: 12 22 32



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A simple virtual circuit network

Switch 1 Switch 2

Switch 3 Switch 4

A B

211

3 3

2



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VC-number Translation Table

Incoming

Interface

Incoming

VC#

Outgoing

Interface

Outgoing

VC#

1 12 2 22

2 63 1 18

3 7 2 17

1 97 3 87

Why a packet doesnt just keep the same VC number on eachof the link along its route?



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Why a packet doesnt just keep the same VCnumber on each of the link along its route? First, by replacing the number from link to link, the length

of the VC field is reduced.

Second, by permitting a different VC number for each linkalong the path of the VC, a network management functionis simplified.

i.e. with multiple VC numbers, each link in the path

can choose a VC number independently of what theother links in the path choose.

If a common number were required for all the linksalong the path, the switches would have to exchangeand process a substantial number of messages to agreeon the VC number to be used

Switches in the VC maintain the state information(create entries in translation tables) for the ongoingconnections.


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Circuit Switching vs. Virtual Circuits


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Path A dedicated path isestablished between two

devices for the duration

of session. Reserved Resources

The link (multiplexed /

not multiplexed) that

makes the path are

dedicated, and cannot

be used by other

connections constant data rates.

Route No dedicated path isestablished. Only a

route is defined. Each

switch creates an entryin its routing table for

the duration of virtual

circuit

Shared Links The link that makes a

route can be shard by

other connections

Features of Circuit and Packet Switching


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Feature CircuitSwitching

Packet Switching

Data sent as packets? No Yes

Packets follow same route? N/A Yes (VC), No (Datagram)

Resources reserved in network? Yes No

Data send can have variable latency

(response time)

No Yes

Connection made? Yes VC: Yes, Datagram: No

State info stored at network nodes? N/A VC: Yes, Datagram: No

Addressing info needed? only when call

is set up

VC: virtual circuit

numberDatagram: destination

Address

Network Taxonomy


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Telecommunication

networks

Circuit-switched

networks

FDM TDM

Packet-switched

networks

Networks

with VCs

Datagram

Networks

Network Access


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Network Access: The physical link that connects an end system to itsEdge Router, which is the first router on a path fromthe end system to any other distant end system.

Classification of Network Access: Residential Access

Connecting a home end system to an edge router

Dial-up modems, DSL, HFC system

Company Access

Switched Ethernet LANs

Mobile Access

Wireless LAN (802.11b) Wide Area Wireless Access Networks (GPRS, 3G,

WAP)

Note: these categories are not hard and fast


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Internet Addressing SchemesIP Add i S h


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IP Addressing Scheme Dotted decimal Notation, Use hierarchal Address Space

IANA (Internet Assigned Number Authority)

IPv4 and IPv6

MAC addresses 48 bits Unique addresses, Use flat Address Space

IEEE assigned vendor ID (first 24 bits)

Vendor serial numbers (last 24 bits)

Why two addressing mechanisms are used?

Significance of using a MAC address \ Burnt InAddress Communication over a LAN

Identifying Destination Network Extracting destination network address from destination

IP address.

Food for thought!


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Internet vs. internet Difference between:

internet, intranet and extranet

Data sensitive traffic vs. Delay sensitivetraffic

LAN vs. WAN Beyond theoretical definitions

Why Circuit Switching is not appropriate for

data traffic?

ReferencesC t N t ki A T D A h


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Computer Networking; A Top Down ApproachFeaturing the Internet 3rd Edition: Chapter 1, Jim Kurose and Keith Ross

Data and Computer Communications

7th Edition, William Stallings

Data Communications and Networking 3rd Edition, Behrouz A. Forouzan

Data Communications and Computer Networks Curt M. White

Computer Networks 4th Edition, by Andrew S. Tanenbaum

Note: Slides are adapted from the companion web sites ofreferenced books.

iap 01- introduction to internet architecture and protocols

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