Transcript bonus slides - University of Calgary

Networking Basics: A Review
Carey Williamson
iCORE Professor
Department of Computer Science
University of Calgary
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Communications Networks
r Historically, there have been two different
philosophies guiding the design, operation,
and evolution of communication networks
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the “telco” view (i.e., telecommunications
networks to support voice telephony and other
emerging services)
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
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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
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“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
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Telco Networks (2 of 2)
r Call routing and circuit allocation decided once
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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 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, ...
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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
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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
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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?)
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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,
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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 are shared on a statistical
multiplexing basis
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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
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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?)
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Internet Protocol Stack
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Application: supporting network
applications and end-user services
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Transport: end to end data transfer
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IPv4, IPv6, BGP, RIP, routing protocols
Data Link: hop by hop frames,
channel access, flow/error control
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TCP, UDP
Network: routing of datagrams
from source to destination
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FTP, SMTP, HTTP, DNS, NTP
PPP, Ethernet, IEEE 802.11b
Application
Transport
Network
Data Link
Physical
001101011...
Physical: raw transmission of bits
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Internet Protocol Stack
Application
Application
Transport
Transport
Network
Network
Data Link
Data Link
Physical
Core
Network
Physical
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Internet Protocol Stack
Application
Application
Application
Transport
Transport
Transport
Network
Network
Network
Data Link
Data Link
Data Link
Physical
Physical
Physical
Router
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Internet Protocol Stack
Application
Application
Application
Transport
Switch
Transport
Transport
Network
Network
Network
Data Link
Data Link
Data Link
Physical
Physical
Physical
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