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

2 Communications Networks r Historically, there have been two different philosophies guiding the design, operation, and evolution of communication networks m the “telco” view (i.e., telecommunications networks to support voice telephony and other emerging services) m the “data networking” view (i.e., the Internet) r While the two approaches share some similar goals and challenges (e.g., scale, geography, heterogeneity), they often have quite different underlying assumptions

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

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

5 The Internet (1 of 2) r About 30 years old r Packet-switched network r Variable size packets permitted r Designed for transmission of data r Wide range of access technologies r Wide range of user and application behaviour r Bursty, variable bandwidth required per call r Aggregation of traffic at routers/switches r Transmission links are shared on a statistical multiplexing basis

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

7 Asynchronous Transfer Mode (1of2) r About 20 years old r Packet-switched network r Small fixed-size packets (53 bytes) r Designed for integrated services (voice, video, data, imaging, interactivity,…) r High speed network technologies (optical) r Wide range of user and application behaviour r Bursty, variable bandwidth required per call r Aggregation of traffic at switches r Transmission links are shared on a statistical multiplexing basis

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

9 Internet Protocol Stack r Application: supporting network applications and end-user services m FTP, SMTP, HTTP, DNS, NTP r Transport: end to end data transfer m TCP, UDP r Network: routing of datagrams from source to destination m IPv4, IPv6, BGP, RIP, routing protocols r Data Link: hop by hop frames, channel access, flow/error control m PPP, Ethernet, IEEE b r Physical: raw transmission of bits Application Transport Network Data Link Physical

10 Internet Protocol Stack Application Transport Network Data Link Physical Application Transport Network Data Link Physical Core Network

11 Internet Protocol Stack Application Transport Network Data Link Physical Application Transport Network Data Link Physical Application Transport Network Data Link Physical Router

12 Internet Protocol Stack Application Transport Network Data Link Physical Application Transport Network Data Link Physical Application Transport Network Data Link Physical Switch