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: rahul@pilani.bits-pilani.ac.in

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

Laptop Computer

Worksta.on

Tablet PC

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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

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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

What is an Internetwork?

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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.

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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

A Bus Topology based Computer Network

SHARED BUS

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

N1 N2 N3 N4

A Ring Topology based Computer Network

A Tree Topology based Computer Network

NC1 NC2

A Star Topology based Computer Network

Switch

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

Data Link Layer

Physical Layer

Transport Layer

Network Layer

Applica9on Layer

Presenta9on Layer

Session Layer

The ISO OSI Reference Model

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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

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>

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