CSC461-CN-Lecture-2-Jan-16-2013

BITS Pilani Pilani | Dubai | Goa | Hyderabad

Computer Networks Lecture-3, January 16, 2013

Rahul Banerjee, PhD (CSE)

Professor, Department of Computer Science & Information Systems

E-mail: [email protected]

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

Types of applications and services benefitting from networking Interconnecting Networks for forming Internetworks Architecture of the Internet What is the Internet today?

–  The Internet and the World-Wide Web –  Who decides about the Internet?

Of The Internet, Intranet and Extranet Protocols, Layers, Interfaces, Logical / Virtual Communication

& Services Of Network Architectures & Network Reference Models Select References to the literature Summary

Interaction Points

Types of Applica.ons benefi2ng from Networking

•  Types of applications & services: –  hard real-time applications & services, –  soft real-time applications & services, –  non-real-time / best-effort / delay-tolerant

applications / services •  Examples of each kind of applications and

services •  About the significance of application-driven and

economics-constrained nature of network system design approaches

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How do things work over the Internet?

•  Example-‐1: A web request and its response •  Example-‐2: A desk-‐top video-‐call •  Example-‐3: A Video-‐on-‐Demand over the Internet •  Example-‐4: An Email exchange over the Internet •  Example-‐5: Virtual Private Network services over the Internet

•  Example-‐6: Public cloud-‐based services over the Internet


An Example of a Computer Network

Another Form of Ethernet LAN

6 (c) Dr. Rahul Banerjee, BITS, Pilani, India

The Shared Ethernet hub

Personal Computer

Network Printer

Worksta.on

Worksta.on

Laptop Computer

Worksta.on

Tablet PC

(c) Dr. Rahul Banerjee, BITS Pilani, INDIA 7

Local Area Internetwork / Intranet •  Traditionally, a Campus Internetwork is a campus-wide

internetwork of individual LANs which may be geographically spread over the part or whole of a single campus. This sometimes called campus intranet.

•  In common practice, the entire campus internetwork including its communication subnet is wholly owned by a single organization or institution.

•  Usually, the campus internetworks use LAN technology; however, it is possible to use WAN technology, when so desirable.

•  The latter may be desirable in some cases when the campus is very large and comprises of a vast set of buildings spread over it. Protocols used in both of these cases at the lower layers, are, generally, different. 16/01/13

(c) Dr. Rahul Banerjee, BITS, Pilani, India 8

Some Terms Related to Networks

•  Channel <application-level logical / virtual communication path>

•  Services: Functionalities provided by a layer / protocol / entity

•  Interfaces: Peer-to-Peer / Layer-to-Layer / entity-to-entity

•  Service Access Points: defined addresses / ports through which data / parameters are passed

•  Tunneling <Encapsulation & Decapsulation>


Network Elements of a Node •  A typical network node has following

hardware elements of relevance, at the least: – Processor (CPU) with / without registers / caches – Optional External Cache(s) – RAM (Main Memory) – ROM / PROM / EPROM / EEPROM / EAPROM – Optional Secondary / Tertiary Memory / Storage

(Flash, Disk, MBM etc.) – Network Adapter / Network Interface Controller – Slots / Ports for connectivity to other node(s) – Power-provisioning – Bus / Lines (Control, Address, Data, Power)

Elements of a Network Interface Controller / Network Adapter

•  A Network Adapter / Interface Controller Unit / Chip / Dongle often comprises of the following elements: –  Host bus / line / link –  Control Status Registers (often called CSR or simply even as Control

Registers) •  logically readable / writable by the CPU

–  --à often, a copy of the contents of the CSR is located in some pre-specified location in memory making it simple for CPU to perform R/W operations, as per need

»  --à Actual writing to the NIC’s CSR is done by the Device Driver though –  Bus Interface Unit –  Internal storage (buffer included) –  Transceivers for transmission and reception at the physical level

•  Data Transfer Methods: DMA (no worry for the CPU) or Programmed I/O (PIO) based Data Transfer (CPU needs to work herein) from the memory of the host node to the NIC / Adapter

A Diagramma.c View of NIC

h^p://www.plxtech.com/images/about/news/images/image042505.gif

h^p://commons.wikimedia.org/wiki/File:Ethernet_NIC_100Mbit_PCI.jpg

h^p://www.dansdata.com/images/gigabit/gbcard440.jpg

h^p://www.altera.co.jp/products/ip/ampp/morethanip/images/m-‐m.p-‐10g_etherpcs_fig1.gif

Examples of Ethernet Adapters

Source: h^p://www.altera.co.jp/products/ip/ampp/morethanip/images/m-‐m.p-‐10g_etherpcs_fig1.gif (c)


Based on IEEE documents with instructional modifications Copyright: IEEE Inc., N.Y.

The IEEE 802.x Architecture and Specifications revisited

Operation of a Bridge with Two LANs


Source Destination

S

H

H H H

H H

H

Hub

What is an Internetwork?

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(c) Dr. Rahul Banerjee, BITS Pilani, INDIA 16

Of the Internet, Intranet and Extranet

•  The Global Public Internetwork: The Internet •  The Wholly Owned / Private Internetwork:

Intranet •  The Hybrid Internetwork-- private networks /

internetworks connected through the Internet: Extranet

In the early stages of development, technologies used for the internetworks of all type were essentially the same, except probably at the lowest level.

This situation is rapidly changing.

16/01/13


Architecture of the Internet •  Originally, it was a point-to-

point WAN. •  Original architecture that led

to ARPANET has evolved over the years that have passed by.

•  It is loosely hierarchical. •  Currently, Internet

architecture is largely governed by the IAB of the ISoc.

•  Has many sub-organs which facilitate evolution and coordinated maintenance of the Internet.

•  IESG steers the ISoc in a general way the engineering issues are resolved.

•  IETF workgroups do the ground work and by a democratic process helps community in building up engineering solutions through IETF drafts and standards (RFCs) etc.


What is the Internet today? •  Wide Area Network of variety of networks •  Global •  Public •  Not transparent, as yet •  Hybrid topology but largely hierarchical •  No single controller •  Internet Society (ISoc) oversees, assists ---

does not control •  QoS, Security continue to have issues – partly at

least •  Web, mail, commerce, education, entertainment,

sharing continue to dominate its application space


Project BITS-Connect 2.0


Project BITS-Connect 2.0 The Immersive Tele-presence Rooms •  This is how an

18-seater immersive tele-presence room looks like at all the Indian campuses.

•  Chancellor’s office is equipped with one two-‐seater system

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A Bus Topology based Computer Network

SHARED BUS

(c) Dr. Rahul Banerjee, BITS-Pilani, INDIA

N1 N2 N3 N4

22

A Ring Topology based Computer Network

C

C

C

C

C


23

A Ring Topology based Computer Network

C

C

C

C

C


24

A Tree Topology based Computer Network

NC1 NC2

NC11

NR

NC21

NC22

NC12


25

A Star Topology based Computer Network

C

C

C

Switch


S

N1

N2

N3

N4


Summary of Network Topologies •  Bus Topology

–  Shared –  Switched

•  Tree Topology •  Ring Topology

–  Single –  Double

•  Star Topology •  Irregular Topology •  Complete Topology

Network Architecture & Reference Models

•  Architecture versus Reference Model: A simplistic perspective: – Architecture: It may be seen as a detailed

generic blueprint with unambiguous definitions of services, interfaces, organization and defined protocols that helps in design and implementation of a set of relevant protocol stack / suite based network / internetwork

– Reference Model: It is the same as the architecture minus the specifically defined readily usable protocols.

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Network Architectures & Reference Models

•  Examples: –  TCP/IP Architecture &

TCP/IP Reference Model

–  OSI Reference Model & OSI Architecture

–  ATM Reference Model & ATM Architecture

–  Our own Hypothetical Reference Model (slide-5)

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LLC Sub-layer

MAC Sub-layer

Physical layer

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Data Link Layer

Physical Layer

Transport Layer

Network Layer

Applica9on Layer

Presenta9on Layer

Session Layer

The ISO OSI Reference Model

(c) Dr. Rahul Banerjee, BITS-‐Pilani, INDIA

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The ISO OSI Reference Model


Copyright: Dr. Rahul Banerjee BITS, Pilani (India) 31

Data Link Layer

Physical Layer

Transport Layer

Network Layer

Applica9on Layer

A Hypothetical Network Reference Model for Easy Conceptual Understanding

Layer-‐5

Layer-‐4

Layer-3

Layer-2

Layer-1

Often on the NIC card or chip

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A Simplified Network Reference Model <for Instruction>

Host-1 Host-2

Application Layer Application Layer

Upper Layer-‐to-‐ Lower Layer Interface Upper Layer-‐to-‐ Lower Layer Interface



Same Layer -to- Same Layer Virtual Communication Interface




Same Layer -to- Same Layer Physical Communication Interface



A Few More Networking Terms •  Repeaters / Repeater Hubs / Shared Hubs: where usually Physical

layer / level exist with L1-protocol data unit (raw bits) regeneration and onward transmission

•  Managed Hubs / Layer-2 Switching Hubs: where Physical and Data Link layers / levels exist with ability to handle and deliver Layer-2-protocol data unit (frame)

•  Bridges: where Physical and Data Link layers / levels exist with L2-protocol data unit (frame) processing and forwarding

•  Switches: where Physical and Data Link and / or Network (sometimes even higher) layers / levels exist with Layer-2 and / or Layer-3-protocol data unit (frame / packet) processing, switched routing / forwarding

•  Routers: where Physical and Data Link and Network layers / levels exist with L3-protocol data unit (packet) processing, routing and forwarding

•  Gateways: where two or more different networks meet and may require protocol / message translation capabilities

•  Clouds: abstraction of node connectivity in the networking context <details hidden>

References •  Larry L. Peterson & Bruce S. Davie: Computer Networks: A Systems Approach,

Fifth Edition, Morgan Kaufmann / Elsevier, New Delhi, 2011. <System design approach>

•  S. Keshav: Computer Networking: An Engineering Approach, Pearson Education, New Delhi, 1997.

•  A. S. Tanenbaum: Computer Networks, Fifth Edition, Pearson Education, New Delhi, 2012. <Conceptual Approach>

•  Y. Zheng and S. Akhtar: Networks for Computer Scientists and Engineers, Oxford University Press, New York, 2002. <Structural approach>

•  A. Leon Garcia and I. Widjaja: Communication Networks: Fundamental Concepts and Key Architectures, Second Edition, Tata McGraw-Hill, New Delhi, 2004.

•  Mohammed G. Gouda: Elements of Network Protocol Design, Wiley Student Edition, John Wiley & Sons (Pte.) Ltd., Singapore, 2004.

•  Thomas G. Robertazzi: Computer Networks and Systems: Queuing Theory and Performance Evaluation, Third Edition, Springer-Verlag, New York, 2000. <Analytical approach>

© Dr. Rahul Banerjee, BITS, Pilani (India) 16/01/13 (c) Dr. Rahul Banerjee, BITS Pilani, INDIA 34

Summary •  Intranet: Completely private network of networks

•  Wireline •  Wireless

– Fixed – Mobile

•  Hybrid •  The Internet: Global public network of networks

•  Wireline •  Wireless

– Fixed – Mobile

•  Hybrid •  Extranet: Intranets interconnected via the Internet

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Concluding remarks •  Networking support of some kind is already inside most of the opera.ng systems we use today in variety of forms on Notebooks, Laptops, Worksta.ons and Servers. All Smart-‐phones and several set-‐top boxes support it too.

•  Subsequent lectures shall introduce you to the following topics:

•  Internetworks •  Network Architectures •  Performance •  Quality of Service •  Reliability •  Security


References •  Larry L. Peterson & Bruce S. Davie: Computer Networks: A Systems Approach,

Fifth Edition, Morgan Kaufmann / Elsevier, New Delhi, 2011. <System design approach>

•  S. Keshav: Computer Networking: An Engineering Approach, Pearson Education, New Delhi, 1997.

•  A. S. Tanenbaum: Computer Networks, Fifth Edition, Pearson Education, New Delhi, 2012. <Conceptual Approach>

•  Y. Zheng and S. Akhtar: Networks for Computer Scientists and Engineers, Oxford University Press, New York, 2002. <Structural approach>

•  A. Leon Garcia and I. Widjaja: Communication Networks: Fundamental Concepts and Key Architectures, Second Edition, Tata McGraw-Hill, New Delhi, 2004.

•  Mohammed G. Gouda: Elements of Network Protocol Design, Wiley Student Edition, John Wiley & Sons (Pte.) Ltd., Singapore, 2004.

•  Thomas G. Robertazzi: Computer Networks and Systems: Queuing Theory and Performance Evaluation, Third Edition, Springer-Verlag, New York, 2000. <Analytical approach>

© Dr. Rahul Banerjee, BITS, Pilani (India) 16/01/13 (c) Dr. Rahul Banerjee, BITS Pilani, INDIA 37


An Example of a Computer Network

BITS Pilani Pilani | Dubai | Goa | Hyderabad

Rahul Banerjee

Thank you for your kind attention!

CSC461-CN-Lecture-2-Jan-16-2013

Documents

john wiley

protocol data unit

rahul brahul anerjee

network protocol design

network architectures

oxford university press

lower layer interface

time applications