csc461-cn-lecture-2-jan-16-2013
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Bits LEcture slidesTRANSCRIPT
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
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An Example of a Computer Network
Another Form of Ethernet LAN
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The Shared Ethernet hub
Personal Computer
Network Printer
Worksta.on
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>
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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)
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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
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Source Destination
S
H
H H H
H H
H
Hub
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.
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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
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
Project BITS-Connect 2.0
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
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
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N1 N2 N3 N4
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A Ring Topology based Computer Network
C
C
C
C
C
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A Ring Topology based Computer Network
C
C
C
C
C
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A Tree Topology based Computer Network
NC1 NC2
NC11
NR
NC21
NC22
NC12
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A Star Topology based Computer Network
C
C
C
Switch
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S
N1
N2
N3
N4
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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
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The ISO OSI Reference Model
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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
Upper Layer-‐to-‐ Lower Layer Interface Upper Layer-‐to-‐ Lower Layer Interface
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 Virtual Communication Interface
Same Layer -to- Same Layer Virtual Communication Interface
Same Layer -to- Same Layer Virtual Communication Interface
Same Layer -to- Same Layer Physical Communication Interface
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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>
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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
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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>
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An Example of a Computer Network
BITS Pilani Pilani | Dubai | Goa | Hyderabad
Rahul Banerjee
Thank you for your kind attention!