CSEN 503 Introduction to Communication Networks 1-1 Mervat AbuElkheir Hana Medhat Ayman Dayf ** Slides are attributed to J. F. Kurose
People and Resources 1-2 Course Name Introduction to Communication Networks My Email TAs Textbooks mervat.abuelkheir@guc.edu.eg Hana Medhat Ayman Dayf Computer Networking, A Top-Down Approach Featuring the Internet, James F. Kurose & Keith W. Ross, ISBN 0-321-26976-4 Slide contents are copyrighted to: 1996-2010, J.F Kurose and K.W. Ross, All Rights Reserved
Assessment 1-3 Project 20% Final Exam 40% Quiz 20% Midterm Exam 20%
Course Outline 1-4 Internet Datacenters and Clouds Internet of Things Introduction Network Delays Application Layer Transport Layer Network Layer Data Link Layer Datacenters Introduction to Cloud Computing ISM and Virtualization Introduction to the IoT Tagging, Sensing, Actuating Sensor Networks
Important Note 1-5 These slides are not meant to be comprehensive lecture notes! They are only remarks and pointers. The material presented here is not sufficient for studying for the course Your main sources for studying are: the text and your own lecture notes
Introduction: Roadmap 1-6 1.1 What is the Internet? 1.2 Network edge end systems, access networks, links 1.3 Network core circuit switching, packet switching, network structure 1.4 Delay, loss and throughput in packet-switched networks 1.5 Protocol layers, service models
What s the Internet: nuts and bolts view 1-7 millions of connected computing devices: hosts = end systems running network apps communication links fiber, copper, radio, satellite transmission rate = bandwidth Mobile network Global ISP Home network Regional ISP Institutional network PC server wireless laptop cellular handheld access points wired links routers: forward packets (chunks of data) router
Cool internet appliances 1-8 Web-enabled toaster + weather forecaster IP picture frame http://www.ceiva.com/ World s smallest web server http://www-ccs.cs.umass.edu/~shri/ipic.html Internet phones
1-9 Cool internet appliances
What s the Internet: nuts and bolts view 1-10 protocols control sending, receiving of msgs e.g., TCP, IP, HTTP, Skype, Ethernet Internet: network of networks loosely hierarchical public Internet versus private intranet Internet standards RFC: Request for comments IETF: Internet Engineering Task Force Mobile network Global ISP Home network Regional ISP Institutional network
What s a protocol? 1-11 Let's create a protocol! What do you do when you use an ATM machine?
What s a protocol? 1-12 human protocols: what s the time? I have a question introductions specific msgs sent specific actions taken when msgs received, or other events network protocols: machines rather than humans all communication activity in Internet is governed by protocols protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt
What s a protocol? 1-13 a human protocol and a computer network protocol: Hi Hi Got the time? 2:00 time TCP connection request TCP connection response Get http://www.awl.com/kurose-ross <file>
1-14 What s the Internet: a service view Communication infrastructure enables distributed applications: Web, VoIP, email, games, e- commerce, file sharing Communication services provided to apps: reliable data delivery from source to destination best effort (unreliable) data delivery
Network Edge - End systems, - access networks, - links
A closer look at network structure: 1-16 Network edge: applications and hosts Access networks, physical media: wired, wireless communication links Network core: interconnected routers network of networks
The network edge: 1-17 end systems (hosts): run application programs e.g. Web, email at edge of network peer-peer client/server model: client host requests, receives service from always-on server e.g. Web browser/server; email client/server client/server peer-peer model: minimal (or no) use of dedicated servers e.g. Skype, BitTorrent
Access networks and physical media 1-18 Q: How to connect end systems to edge router? residential access nets institutional access networks (school, company) mobile access networks Keep in mind: bandwidth (bits per second) of access network? shared or dedicated?
Examples of Access Networks 1-16 1-19 Dial-up modem Digital Subscriber Line (DSL) Cable Internet Ethernet Wireless Networks
Chapter 1: roadmap 1-20 1.1 What is the Internet? 1.2 Network edge end systems, access networks, links 1.3 Network core circuit switching, packet switching, network structure 1.4 Delay, loss and throughput in packet-switched networks 1.5 Protocol layers, service models
The Network Core 1-21 mesh of interconnected routers How is data transferred through net? circuit switching: dedicated circuit per call: telephone net packet-switching: data sent thru net in discrete chunks
Network Core: Circuit Switching 1-22 End-end resources reserved for call link bandwidth, switch capacity dedicated resources: no sharing circuit-like (guaranteed) performance call setup required
Network Core: Circuit Switching 1-23 network resources (e.g., bandwidth) divided into pieces pieces allocated to calls resource piece is idle if not used by owning call (no sharing) Piece: frequency division time division
Network Core: Circuit Switching 1-24 Images source: http://lastdaystudy.com/cse-it/data-communication/2-physical-layer/107/
Network Core: Packet Switching 1-25 each end-end data stream is divided into packets user A, B packets share network resources each packet uses full link bandwidth resources used as needed Bandwidth division into pieces Dedicated allocation Resource reservation resource contention: aggregate resource demand can exceed amount available congestion: packets queue, wait for link use store and forward: packets move one hop at a time Node receives complete packet before forwarding
Packet-switching: store-and-forward 1-26 L R R R takes L/R seconds to transmit (push out) packet of L bits on to link at R bps store and forward: entire packet must arrive at router before it can be transmitted on next link delay = 3L/R (assuming zero propagation delay) Example: L = 7.5 Mbits R = 1.5 Mbps transmission delay = 15 sec more on delay shortly
Packet Switching: Statistical Multiplexing 1-27 A 100 Mb/s Ethernet statistical multiplexing C B queue of packets waiting for output link 1.5 Mb/s D E Sequence of A & B packets does not have fixed pattern, bandwidth shared on demand statistical multiplexing
Packet switching versus circuit switching 1-28 packet switching great for bursty data resource sharing simpler, no call setup excessive congestion: packet delay and loss protocols needed for reliable data transfer, congestion control Q: How to provide circuit-like behavior? bandwidth guarantees needed for audio/video apps still an unsolved problem (Free Reading: chapter 7)
Internet structure: network of networks 1-29 roughly hierarchical at center: tier-1 ISPs (e.g., Verizon, Sprint, AT&T, Cable and Wireless), national/international coverage treat each other as equals fully connected Tier-1 providers interconnect (peer) privately Tier 1 ISP Tier 1 ISP Tier 1 ISP
1-30 Tier 1 Networks
Internet structure: network of networks 1-31 Tier-2 ISPs: smaller (often regional) ISPs Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs Tier-2 ISP pays tier- 1 ISP for connectivity to rest of Internet tier-2 ISP is customer of tier-1 provider Tier-2 ISP Tier-2 ISP Tier 1 ISP Tier 1 ISP Tier 1 ISP Tier-2 ISPs also peer privately with each other Tier-2 ISP Tier-2 ISP Tier-2 ISP
Internet structure: network of networks 1-32 Tier-3 ISPs and local ISPs last hop ( access ) network (closest to end systems) Local and tier- 3 ISPs are customers of higher tier ISPs connecting them to rest of Internet local ISP local ISP Tier 3 ISP Tier-2 ISP Tier 1 ISP Tier-2 ISP local ISP local ISP Tier 1 ISP local ISP Tier-2 ISP Tier 1 ISP Tier-2 ISP local ISP local ISP Tier-2 ISP local ISP
Internet structure: network of networks 1-33 a packet passes through many networks! local ISP Tier 3 ISP Tier-2 ISP local ISP Tier 1 ISP local ISP Tier-2 ISP local ISP local ISP Tier 1 ISP Tier-2 ISP local ISP Tier 1 ISP Tier-2 ISP local ISP Tier-2 ISP local ISP
Next Time 1-34 1.1 What is the Internet? 1.2 Network edge end systems, access networks, links 1.3 Network core circuit switching, packet switching, network structure 1.4 Delay, loss and throughput in packet-switched networks 1.5 Protocol layers, service models