1. Networking Basics: A Review Carey Williamson iCORE Chair and Professor Department of Computer Science University of Calgary

2. Copyright © 2005 Department of Computer Science CPSC 641 Winter 20112 Communications Networks Historically, there have been two different philosophies guiding the design, operation, and evolution of communication networks –the “telco” view (i.e., telecommunications networks to support voice telephony and other emerging services, such as fax, data, location, etc.) –the “data networking” view (i.e., the Internet) While the two approaches share some similar goals and challenges (e.g., scale, geography, heterogeneity), they often have quite different underlying assumptions

3. Copyright © 2005 Department of Computer Science CPSC 641 Winter 20113 Telco Networks (1 of 2) About 100 years old Circuit-switched network Designed for transmission of human voice Twisted pair copper wire for residential access –“cheap”, adequate bandwidth, easy to handle... Aggregation of multiple calls at toll office for multiplexing/demultiplexing using TDM Low bandwidth required per call (e.g., 64 Kbps) Fixed bandwidth required per call

4. Copyright © 2005 Department of Computer Science CPSC 641 Winter 20114 Telco Networks (2 of 2) Call routing and circuit allocation decided once per call at time of call arrival End to end path allocation, with dedicated circuit (reserved bandwidth) per active call All bits travel same path; stay in same order Call state information crucial in network switches Busy signal if no path possible (blocking <= 2%) Billing model based on time used (in minutes) Single class of service; high reliability (99.99%) New services: faxes, modems, mobility,...

5. Copyright © 2005 Department of Computer Science CPSC 641 Winter 20115 The Internet (1 of 2) About 30 years old Packet-switched network Variable size packets permitted Designed for transmission of data Wide range of access technologies Wide range of user and application behaviour Bursty, variable bandwidth required per call Aggregation of traffic at routers/switches Transmission links shared on stat mux basis

6. Copyright © 2005 Department of Computer Science CPSC 641 Winter 20116 The Internet (2 of 2) Connection-less network layer protocol (IP) “Best effort” datagram delivery model Packet routing decided on a per packet basis No end to end path allocation; no reserved bandwidth per active call Packets can travel any path; packets can be delayed, lost, duplicated, re-ordered Minimal state info in network switches Single class of service Billing model? (hours? pkts? bytes? bandwidth?)

7. Copyright © 2005 Department of Computer Science CPSC 641 Winter 20117 Asynchronous Transfer Mode (1of2) About 20 years old Packet-switched network Small fixed-size packets (53 bytes) Designed for integrated services (voice, video, data, imaging, interactivity,…) High speed network technologies (optical) Wide range of user and application behaviour Bursty, variable bandwidth required per call Aggregation of traffic at switches Transmission links shared on a stat mux basis

8. Copyright © 2005 Department of Computer Science CPSC 641 Winter 20118 ATM (2 of 2) Connection-oriented Allocates a virtual channel (VC) per active call End to end path allocation determined at time of call arrival; reserved bandwidth per active call All packets travel same path (order preserved) Crucial state info in ATM switches Multiple classes of service (priority levels) Offers end to end QOS guarantees (SLAs) Billing model? (cells? bandwidth? time?)

9. Copyright © 2005 Department of Computer Science CPSC 641 Winter 20119 Internet Protocol Stack Application: supporting network applications and end-user services –FTP, SMTP, HTTP, DNS, NTP Transport: end to end data transfer –TCP, UDP Network: routing of datagrams from source to destination –IPv4, IPv6, BGP, RIP, routing protocols Data Link: hop by hop frames, channel access, flow/error control –PPP, Ethernet, IEEE 802.11b Physical: raw transmission of bits Application Transport Network Data Link Physical 001101011...

10. Copyright © 2005 Department of Computer Science CPSC 641 Winter 201110 Internet Protocol Stack Application Transport Network Data Link Physical Application Transport Network Data Link Physical Core Network

11. Copyright © 2005 Department of Computer Science CPSC 641 Winter 201111 Internet Protocol Stack Application Transport Network Data Link Physical Application Transport Network Data Link Physical Application Transport Network Data Link Physical Router

12. Copyright © 2005 Department of Computer Science CPSC 641 Winter 201112 Internet Protocol Stack Application Transport Network Data Link Physical Application Transport Network Data Link Physical Application Transport Network Data Link Physical Switch