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Networking Basics: A Review

Networking Basics: A Review

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Networking Basics: A Review

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

  2. 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 CPSC 641 Winter 2011

  3. 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 CPSC 641 Winter 2011

  4. 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, ... CPSC 641 Winter 2011

  5. 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 CPSC 641 Winter 2011

  6. 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?) CPSC 641 Winter 2011

  7. 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 CPSC 641 Winter 2011

  8. 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?) CPSC 641 Winter 2011

  9. 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 Internet Protocol Stack 001101011... CPSC 641 Winter 2011

  10. Application Transport Network Data Link Physical Application Transport Network Data Link Physical Internet Protocol Stack Core Network CPSC 641 Winter 2011

  11. Application Transport Network Data Link Physical Application Transport Network Data Link Physical Application Transport Network Data Link Physical Internet Protocol Stack Router CPSC 641 Winter 2011

  12. Application Transport Network Data Link Physical Application Transport Network Data Link Physical Application Transport Network Data Link Physical Internet Protocol Stack Switch CPSC 641 Winter 2011