Chi-Cheng Lin, Winona State University CS 313 Introduction to Computer Networking & Telecommunication Introduction – Part II

2 Topics l Introduction l Metric Units l Network Hardware l Network Software l Reference Models l Example Networks l Standards and Standards Organizations

3 Network Hardware l By transmission technology  Broadcast links  smaller, geographically localized networks  Point-to-point links  larger networks l By scale  PAN  LAN  MAN  WAN

4 Point-to-Point Networks l Many connections between pairs of machines l 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 l Routing algorithms are important  Routing: process of finding a path from a source to the destination(s) in the network

5 Broadcast Network l A single communication channel shared by all machines on the network l 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 l Examples  Classic Ethernet  Wireless networks

6 Broadcast Network l Message transmission  Unicast: one sends, one receives  Broadcasting: one sends, all receive  Multicasting: one sends, a group receives l How?

7 Classification by Scale

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

9 Local Area Network (LAN) l Private-owned Networks l Within/nearby a single building l Wireless LANs  Example: WiFi (IEEE ) Wireless and wired LANs. (a) (b) Switched Ethernet

10 LAN l 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

11 LAN Topologies l Topology – the way in which a network is laid out l Point-to-point  Example: Switched Ethernet l Virtual LANs l Single linear cable  Broadcasting  Example: Classic Ethernet

12 Home Network = LAN? l Network of home appliances l Issues  Consumer considerations  Cost  Scalability  Security  Connection  Wired, wireless, power-line?  … etc.

13 LAN - Channel Allocation l Needed by wireless networks and wired broadcast networks as all computers share one communication pathway l 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

14 LAN - Channel Allocation l 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!

15 Metropolitan Area Network (MAN) l Covers city l Examples  Cable TV network  IEEE high-speed wireless Internet access (WiMAX)

16 Metropolitan Area Networks l A metropolitan area network based on cable TV.

17 Wide Area Network (WAN) l Country or continent l 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

18 WAN Example

19 WAN - Subnet Components l Transmission lines  Move bits between machines l Switching elements  Specialized computers that connect two or more transmission lines  Determine out going line for incoming data  ROUTER

20 WAN - Hosts and Subnet : Host : Router H1 H2 R1R2 R3R4 R5 R6

21 WAN - Architecture l Contains numerous cables or telephone lines l Each cable connects a pair of routers l Two routers must communicate indirectly if they are not connected by a cable l 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

22 WAN - Architecture l An intermediate router in a WAN  Receives a packet in its entirety  Queues the packet until required output line is free  Forwards the packet l Subnet using the principle above is called  Store-and-forward or packet-switched subnet

23 Other WANs l Satellite systems  Each computer has an antenna to send/receive data  Inherently broadcast – all computers can hear output from satellite l Cellular telephone network

24 Internetwork l What is internetwork?  A collection of interconnected networks l "Internet" and "internet"  internet: internetwork  Internet: the worldwide internetwork using TCP/IP protocol suite  The “Big Picture” l Problem: Communication between networks with different SW/HW  Solution: Gateways  Machines connect different, incompatible networks  Connection and translation