CS412 Computer Networks

CS412 Computer Networks

CS 313 Introduction to Computer Networking & Telecommunication Introduction Part II Chi-Cheng Lin, Winona State University Topics Introduction Metric Units Network Hardware Network Software Reference Models Example Networks Standards and Standards

Organizations 2 Network Hardware By transmission technology Broadcast links smaller, geographically localized networks Point-to-point links larger networks

By scale PAN LAN MAN WAN 3 Point-to-Point Networks Many connections between pairs of machines Intermediate machines (called routers) might have to be visited by a short message (called packet) from source to destination more than one path is

possible Routing algorithms are important Routing: process of finding a path from a source to the destination(s) in the network 4 Broadcast Network A single communication channel shared by all machines on the network Packets sent by any machine are received by all the others

Address field of packet: whom it is intended Intended receiver processes packet Others (should) ignore Examples Classic Ethernet Wireless networks 5 Broadcast Network

Message transmission Unicast: one sends, one receives Broadcasting: one sends, all receive Multicasting: one sends, a group receives How? 6 Classification by Scale 7

Personal Area Network (PAN) Communications over the range of a person Examples Bluetooth RFID 8 Local Area Network (LAN)

Private-owned Networks Within/nearby a single building Wireless LANs Example: WiFi (IEEE 802.11) Wireless and wired LANs. (a) 802.11 (b) Switched Ethernet 9 LAN Wired LAN characteristics

Restricted in size Worst-case transmission time bounded and known in advance Helps designing network protocols Transmission technology High Speed/capacity: 100 Mbps - 10 Gbps Low Delay: microseconds, nanoseconds Errors: very few 10 LAN Topologies Topology the way in which a network is laid out

Point-to-point Example: Switched Ethernet Virtual LANs Single linear cable Broadcasting Example: Classic Ethernet 11 Home Network = LAN? Network of home appliances

Issues Consumer considerations Cost Scalability Security Connection Wired, wireless, power-line? etc. 12 LAN - Channel Allocation Needed by wireless networks and

wired broadcast networks as all computers share one communication pathway Static channel allocation Divide up time into discrete intervals Run a round robin algorithm Allow each machine to broadcast only when its time slot comes up Problem: Wasting channel capacity 13 LAN - Channel Allocation

Dynamic channel allocation Centralized A central entity determines who goes next Decentralize No central entity Each machine decides for itself to transmit or not Algorithms needed to resolve potential chaos It does work! 14 Metropolitan Area Network

(MAN) Covers city Examples Cable TV network IEEE 802.16 high-speed wireless Internet access (WiMAX) 15 Metropolitan Area Networks A metropolitan area network based

on cable TV. 16 Wide Area Network (WAN) Country or continent Components Host (end system) Machine running user (application) programs Communication subnet (subnet) Connecting hosts Carrying messages from host to host

Note that subnet used here simply means communication subnet, not the subnet in the Internet addressing 17 WAN Example 18 WAN - Subnet Components Transmission lines Move bits between machines

Switching elements Specialized computers that connect two or more transmission lines Determine out going line for incoming data ROUTER 19 WAN - Hosts and Subnet H1

R1 R2 R3 R5 R4 R6 H2 : Host : Router

20 WAN - Architecture Contains numerous cables or telephone lines Each cable connects a pair of routers Two routers must communicate indirectly if they are not connected by a cable There might be more than one route between two hosts and it might change from time to time E.g., Route from H1 to H2

21 WAN - Architecture An intermediate router in a WAN Receives a packet in its entirety Queues the packet until required output line is free Forwards the packet Subnet using the principle above is called

Store-and-forward or packet-switched subnet 22 Other WANs Satellite systems Each computer has an antenna to send/receive data Inherently broadcast all computers can hear output from satellite

Cellular telephone network 23 Internetwork What is internetwork? A collection of interconnected networks "Internet" and "internet" internet: internetwork Internet: the worldwide internetwork using

TCP/IP protocol suite The Big Picture http://navigators.com/internet_architecture.html Problem: Communication between networks with different SW/HW Solution: Gateways Machines connect different, incompatible networks Connection and translation 24

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