Iap lecture 1

Internet Architecture and Protocols

Instructor: Engr. Musfara Farooqui

University of Education Township Lahore

Lecture # 01

Introduction and Basic Concepts

University of Education Township Lahore 2

Course Objectives

To understand the design philosophy of the Internet and 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 Protocol Suite. To provide comprehensive knowledge and implementation of

routing protocols. To realize the need of Quality of Service based

communication and to understand various QoS techniques. To introduce the basic concepts of real time communications.


Lecture - Objectives Introduction 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


Lecture 1: 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?University of Education Township Lahore 5

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


7

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 the Internet are called hosts or end systems


8


Communication links End systems are connected together by communication

links. Communication links are made up of different types of

media, 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).


9


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.


10


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.


11


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

Service Providers (ISPs). The different ISPs provide a variety of different types of

network access to the end systems, including 56Kbps dial up modem access, cable modem or DSL, high speed LAN access, and wireless access.


12


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 Internet’s principal protocols are collectively known as TCP/IP Protocol Suite.


13


Intranets There are many private networks, such as many corporate

and government networks, whose hosts cannot exchange messages with hosts outside of the private network (unless the messages pass through so-called firewalls, which restrict the flow of messages to and from the 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.


14


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


15

Some Pieces of the Internet

companynetwork

local ISP

regional ISP

router workstationserver

mobile


16

Lecture 2: 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


17

Service Oriented View of the Internet

Internet Provides two services to its distributed applications: Connection Oriented Reliable Service• It guarantees that data transmitted from a sender to a

receiver will eventually be delivered to the receiver in order and in its entirety.

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 new applications

are being constantly invented and deployed.


18

Connection Oriented Service

Reliable Data Transfer• Using acknowledgements & retransmissions

Flow Control• sender won’t overwhelm receiver

Congestion Control• senders “slow down sending rate” when network

congestedTCP• Applications using TCP are:–HTTP (Web), FTP (file transfer), Telnet (remote

login), SMTP (email)


19

Connectionless Service

Unreliable Data Transfer• no flow control• no congestion control

Fast• connectionless

UDP• Applications using UDP are:–multimedia, videoconferencing, DNS, Internet

telephony


20

TCP vs. UDP

TCP Reliable Protocol Connection Oriented Performs three ways

handshake Provision for error detection

and retransmission Most applications use TCP

for reliable and guaranteed transmission

UDP Unreliable Protocol Connectionless Much faster than TCP No acknowledgement waits No proper sequencing of

data units Suitable for applications

where speed matters more than reliability


21

What is a Protocol?

A Human Analogy “Assalam u Alaikum” “What’s 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.


22

What is a protocol?

• A human protocol and a computer network protocol

Hi

Hi

Got thetime?

2:00

TCP connection req

TCP connectionresponse

<file>

time


23

What is a Protocol?…

A Protocol is a set of rules and regulations that governs the exchange of information between two or more entities.

It takes two (or more) communicating entities running the same protocol in order to accomplish a task.

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 the transmission and/or receipt of a message or other event.


24

The Network Core Mesh of interconnected Routers The fundamental question: how

is data transferred through network? circuit switching• dedicated circuit per call:

telephone net packet-switching• data sent through net in

discrete “chunks”


25

Network Core

Long distance transmission is typically done 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 a communications

network Data routed by being switched from node to node Node to node links usually multiplexed


26

Network Core: Circuit Switching

End-to-end resources reserved for “call”

link bandwidth, switch capacity dedicated resources: no sharing circuit-like (guaranteed) performance call setup required


27

Network Core – Circuit Switching

Switched circuits allow data connections that 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 common example.

The connection is dedicated until one party or another terminates the connection.


28

Circuit Switching


29

Network Core – Circuit Switching

Dedicated communication path between two 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)


30

Network Core - Circuit Switching

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


31

Circuit Switching: FDM and TDM


32University of Education Township Lahore

Output Stream generated by a synchronous time division multiplexer

33

Multiplexer transmission stream with one input device transmitting data.


34

Two stations out of four transmitting via a statistical multiplexer


35

Network Core: Packet Switching

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 as needed 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 is busy, which

causes the delivery to slow down


36

Packet Switching: Statistical Multiplexing

• Sequence of A & B packets does not have fixed pattern statistical multiplexing

A

B

C10 Mb/sEthernet

1.5 Mb/s

D E

statistical multiplexing

queue of packetswaiting for output

link


37

Network Core: Packet Switching

The goal of packet switching is to move 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


38

Packets Forwarding

Two broad classes of packet switched networks are: Datagram Networks• Any network that forwards the packet according to the

destination address is called a datagram network• The routers in the Internet forwards packets according

to host destination addresses; hence the Internet is a datagram network.

Virtual Circuit Networks• Any network that forwards the packet according to the

virtual circuit identifier is called a virtual circuit network• Examples are X.25, Frame Relay, ATM technologies


39

Packet Switching - Datagram Datagram Approach:

Each packet is treated independently No reference to packets that have gone before Each node chooses next node on path using destination

address Packets with same destination address may not follow

same route Packets may arrive out of sequence, may be lost It is up to receiver to re-order packets and recover from lost

packets No Call setup For an exchange of a few packets, datagram quicker Analogy: driving, asking directions


40

Packet Switching - Datagram

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.


41

Datagram Networks

A datagram network is not either a connectionless or a connection oriented network.

It can provide connectionless service to some 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 its applications

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


42

Packet Switching - Datagram


43

Packet Switching: Datagram Approach


44

Packet Switching – Virtual Circuits

Virtual Circuit Approach: Virtual circuit packet switched network create a logical

path through the subnet Call request and call accept packets establish a virtual

connection Virtual route remains fixed through the call. All packets from one connection follow this path. Each packet contains a virtual circuit identifier instead of

destination address to determines the next hop Not a dedicated path No routing decisions required for each packet


45

Switching Technique – Virtual Circuit 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 virtual circuit Sequencing and error control

Packets should transit more rapidly If node fails, all virtual circuits through node lost


46

Packet Switching: VC Approach


47

Circuit Switching vs. Virtual Circuits

CS Path

A dedicated path is established 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

VC

Route No dedicated path is

established. Only a route is defined. Each switch creates an entry in its routing table for the duration of virtual circuit

Shared Links The link that makes a route

can be shard by other connections


48

Network Taxonomy


49

Network Access Network Access:

The physical link that connects an end system to its Edge Router, which is the first router on a path from the 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


Physical Media

Twisted Pair Cable– UTP Cat 5

Coaxial Cable– Baseband and Broadband Cable

Fiber Optics– Multimode and single mode

Terrestrial Radio Channels– Local Area Radio Channels (Wireless LANs)– Wide Area Radio Channels (WAP, I-mode, 3G)

Satellite Radio Channels– Geostationary Satellites (36000 km)– Low Altitude Satellites


References Computer Networking; A Top Down Approach Featuring 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 of referenced books.

•


Iap lecture 1

Documents

Transcript of Iap lecture 1